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What's New in Bazel 7.0

Brentley Jones
Brentley Jones, Developer Evangelist @ BuildBuddy

Bazel 7.0 includes over 3,700 changes since 6.0. It's the latest major release, following the release of 6.0 in December of last year, and it's Bazel's fourth LTS release.

Since there were so many changes, many of them quite impactful, I felt I needed to review them all and provide a nice summary for y'all.

While I reviewed every change, I didn't understand every change 😅. I just wanted to mention that, since this isn't an exhaustive list of changes, but it is a lot of changes I felt were relevant to a large portion of the community. Also, this year I've included changes that appeared in the Bazel 6 minor releases (e.g. Bazel 6.1). While you might already be on a version greater than 6.0, you might not know about all of the neat changes that made it into these "minor" releases.

Similar to Bazel 6.0's changes, the end result was quite big, so I've included a table of contents to allow easy navigation to the changes that interest you the most:

Command-line flag changes​

Bazel's LTS strategy allows for breaking changes between major versions. In particular, it allows for command-line flags to be removed, renamed, made to do nothing, or have their default values changed. In the following sections I collected all such flag changes I could find.

Renamed​

  • [6.1.0] --experimental_strict_conflict_checks to --incompatible_strict_conflict_checks (77f82f4)
  • [6.2.0] --experimental_remote_grpc_log to --remote_grpc_log (2715120)
  • [6.3.0] --experimental_credential_helper to --credential_helper (0573eee)
  • [6.3.0] --experimental_credential_helper_cache_duration to --credential_helper_cache_duration (0573eee)
  • [6.3.0] --experimental_credential_helper_timeout to --credential_helper_timeout (0573eee)
  • --experimental_allow_unresolved_symlinks --allow_unresolved_symlinks (215f698)
  • --experimental_heuristically_drop_nodes to --heuristically_drop_nodes (e8a69f5)
  • --experimental_remote_build_event_upload to --remote_build_event_upload (fb16e8c)
  • --experimental_remote_cache_compression to --remote_cache_compression (0cdd409)
  • --experimental_remote_download_regex to --remote_download_regex (6d04d38)
  • --experimental_repository_disable_download to --repository_disable_download (4c7baa2)
  • --experimental_sandbox_memory_limit to --experimental_sandbox_memory_limit_mb (09a07a4)
  • --experimental_worker_multiplex to --worker_multiplex (4ad970d)

Default values changed​

  • [6.3.0] --experimental_credential_helper_timeout=10s (5a71d9b)
  • [6.4.0] --experimental_cc_implementation_deps=true (05787f3)
  • --android_fixed_resource_neverlinking=true (253e986)
  • --enable_bzlmod=true (30d033c)
  • --experimental_build_transitive_python_runfiles=false (2f9c7d6)
  • --experimental_exec_configuration_distinguisher=off (94d8bd3)
  • --experimental_link_static_libraries_once=true (1456361)
  • --experimental_merged_skyframe_analysis_execution=true (1b729a5)
  • --experimental_output_directory_naming_scheme=diff_against_dynamic_baseline (81d12db)
  • --experimental_sandbox_async_tree_delete_idle_threads=4 (d169556)
  • --incompatible_allow_tags_propagation=true (d0625f5)
  • --incompatible_check_sharding_support=true (d6257ee)
  • --incompatible_disallow_java_import_exports=true (b740189)
  • --incompatible_enable_android_toolchain_resolution=true (05bea52)
  • --incompatible_enable_cc_toolchain_resolution=true (1be55d8)
  • --incompatible_exclusive_test_sandboxed=true (23580aa)
  • --incompatible_fail_on_unknown_attributes=true (5f4a0b2)
  • --incompatible_legacy_local_fallback=false (0f75c57)
  • --incompatible_remote_use_new_exit_code_for_lost_inputs=true (c77790f)
  • --incompatible_sandbox_hermetic_tmp=true (fe85936)
  • --incompatible_merge_fixed_and_default_shell_env=true (8c191d8)
  • --incompatible_multi_release_deploy_jars=true (36998c5)
  • --incompatible_strict_conflict_checks=true (53035bf)
  • --incompatible_use_host_features=true (93f2216)
  • --incompatible_visibility_private_attributes_at_definition=true (0656103)
  • --lockfile_mode=update (8ba6618)
  • --java_language_version="" (f23440b)
  • --remote_build_event_upload=minimal (bfdff54)
  • --remote_download_outputs=toplevel (9c96529)
  • --watchos_cpus=x86_64 (0205bf7)
  • --dynamic_local_strategy now includes standalone when --experimental_local_lockfree_output is set (40cf855)
  • Removed --experimental_inmemory_jdeps_files and --experimental_inmemory_dotd_files from the expansion of --remote_download_minimal and --remote_download_toplevel (0d9e477)
  • Removed --nobuild_runfile_links from the expansion of --remote_download_minimal (24ba4fa)

Undeprecated​

Surprisingly, a flag was undeprecated in Bazel 7.0:

  • --allowed_local_actions_regex (a1dcaea)

No-op​

These flags now do nothing, but still exist to allow for migration off of them:

  • [6.2.0] --use_workers_with_dexbuilder (765c0eb)
  • [6.3.0] --experimental_use_fork_join_pool (30cf799)
  • --action_cache_store_output_metadata (ec6ce5b)
  • --android_databinding_use_androidx (6a19449)
  • --android_databinding_use_v3_4_args (6a19449)
  • --collapse_duplicate_defines (68a4780)
  • --experimental_allow_android_library_deps_without_srcs (2c16f3f)
  • --experimental_android_databinding_v2 (6a19449)
  • --experimental_collect_local_action_metrics (549254e)
  • --experimental_collect_local_sandbox_action_metrics (549254e)
  • --experimental_enable_aspect_hints (86d4f48)
  • --experimental_genquery_use_graphless_query (b7678af)
  • --experimental_parse_headers_skipped_if_corresponding_srcs_found (d4625cf)
  • --experimental_require_availability_info (c02d128)
  • --experimental_sandboxfs_map_symlink_targets (217fafe)
  • --experimental_worker_as_resource (660f441)
  • --high_priority_workers (8e359e7)
  • --legacy_bazel_java_test (08d3187)
  • --incompatible_auto_configure_host_platform (f95df42, 51396c3)
  • --incompatible_disallow_symlink_file_to_dir (8d375a9)
  • --incompatible_generated_protos_in_virtual_imports (3efaa32)
  • --incompatible_remote_build_event_upload_respect_no_cache (fe97f20)
  • --incompatible_remote_results_ignore_disk (c88f374)
  • --incompatible_remove_rule_name_parameter (fcf6b79)
  • --incompatible_require_javaplugininfo_in_javacommon (192702c)
  • --target_platform_fallback (51396c3)
  • --use_top_level_targets_for_symlinks (32df891)

Removed​

  • --android_include_proguard_location_references (bbf11ed)
  • --apple_bitcode (37b8e1b)
  • --apple_compiler (1acdfc4)
  • --apple_enable_auto_dsym_dbg (40ef6d3)
  • --apple_grte_top (fb4106b)
  • --compress_in_memory_genquery_results (554f309)
  • --debug_print_action_contexts (737830a)
  • --distinct_host_configuration (9c01a5a)
  • --deduplicate_depsets (53ca28c)
  • --dynamic_worker_strategy (2ca7c18)
  • --experimental_allow_top_level_aspects_parameters (6b2ff30)
  • --experimental_analysis_test_call (b747a4f)
  • --experimental_android_local_test_binary_resources (6122700)
  • --experimental_apple_mandatory_minimum_version (dbd9e18)
  • --experimental_async_execution (6b2ff30)
  • --experimental_availability_info_exempt (6b2ff30)
  • --experimental_build_setting_api (d72760b)
  • --experimental_cc_shared_library_debug (92e16da)
  • --experimental_cpp_compile_argv_ignore_param_file (b34ea66)
  • --experimental_enable_objc_cc_deps (51f45c4)
  • --experimental_enable_target_export_check (1456361)
  • --experimental_execution_graph_log (8ab9c6e)
  • --experimental_execution_graph_log_cached (6b204c0)
  • --experimental_execution_graph_log_missed (6b204c0)
  • --experimental_execution_log_spawn_metrics (c0f2e14)
  • --experimental_dynamic_execution_cpu_limited (6b2ff30)
  • --experimental_dynamic_skip_first_build (6b2ff30)
  • --experimental_includes_attribute_subpackage_traversal (1961b09)
  • --experimental_java_proto_library_default_has_services (0c8b3ed)
  • --experimental_keep_config_nodes_on_analysis_discard (6b2ff30)
  • --experimental_lazy_template_expansion (61c31d2)
  • --experimental_local_memory_estimate (6b2ff30)
  • --experimental_multi_cpu (6b2ff30)
  • --experimental_multi_threaded_digest (6b2ff30)
  • --experimental_persistent_javac (7fe8fa2)
  • --experimental_prioritize_local_actions (e45b8d4)
  • --experimental_replay_action_out_err (6b2ff30)
  • --experimental_repository_cache_urls_as_default_canonical_id (a6f8923)
  • --experimental_repository_hash_file (176b07f)
  • --experimental_sandboxfs_path (217fafe)
  • --experimental_shortened_obj_file_path (6b2ff30)
  • --experimental_show_artifacts (bdcd311)
  • --experimental_skip_runfiles_manifests (2dc7375)
  • --experimental_skyframe_include_scanning (205091e)
  • --experimental_skymeld_ui (681a0c1)
  • --experimental_supports_info_crosstool_configuration (1ebfb7d)
  • --experimental_use_sh_binary_stub_script (f2d82c6)
  • --experimental_verify_repository_rules (176b07f)
  • --incompatible_avoid_conflict_dlls (e1eef7c)
  • --incompatible_disallow_legacy_javainfo (606dac7)
  • --incompatible_disable_cc_configuration_make_variables (20528af)
  • --incompatible_disable_cc_toolchain_label_from_crosstool_proto (20528af)
  • --incompatible_disable_crosstool_file (20528af)
  • --incompatible_disable_depset_in_cc_user_flags (20528af)
  • --incompatible_disable_expand_if_all_available_in_flag_set (ff37230)
  • --incompatible_disable_legacy_cpp_toolchain_skylark_api (20528af)
  • --incompatible_disable_legacy_flags_cc_toolchain_api (20528af)
  • --incompatible_disable_managed_directories (20528af)
  • --incompatible_disable_runtimes_filegroups (20528af)
  • --incompatible_display_source_file_location (8c24877)
  • --incompatible_disable_sysroot_from_configuration (20528af)
  • --incompatible_disable_tools_defaults_package (20528af)
  • --incompatible_disable_third_party_license_checking (ae40562)
  • --incompatible_dont_emit_static_libgcc (20528af)
  • --incompatible_enable_legacy_cpp_toolchain_skylark_api (20528af)
  • --incompatible_force_strict_header_check_from_starlark (3f36464)
  • --incompatible_genquery_use_graphless_query (58a44d4)
  • --incompatible_linkopts_in_user_link_flags (20528af)
  • --incompatible_load_cc_rules_from_bzl (65b5640)
  • --incompatible_provide_cc_toolchain_info_from_cc_toolchain_suite (20528af)
  • --incompatible_remove_cpu_and_compiler_attributes_from_cc_toolchain (0567176)
  • --incompatible_require_feature_configuration_for_pic (20528af)
  • --incompatible_use_platforms_repo_for_constraints (a7f7df3)
  • --legacy_spawn_scheduler (f2c11f7)
  • --print_workspace_in_output_paths_if_needed (f2c11f7)
  • --remove_all_convenience_symlinks (002bd04)
  • --resource_autosense (c6ba553)
  • --show_warnings (53b0081)
  • --toolchain_resolution_override (60a3c5b)
  • --tvos_simulator_version (f2c11f7)
  • --tvos_simulator_device (f2c11f7)
  • --use_single_jar_apk_builder (669c8aa)
  • --use_workers_with_dexbuilder (f2c11f7)
  • --watchos_simulator_version (f2c11f7)
  • --watchos_simulator_device (f2c11f7)

Remote​

One of Bazel's most powerful features is its ability to use remote caching and remote execution. Numerous improvements and fixes to Bazel's remote capabilities made it into Bazel since 6.0.

Below are some changes that weren't tied to any specific remote feature (e.g. gRPC connections):

  • [6.2.0] Added the --remote_retry_max_delay flag, which allows remote retry max delay to be user configurable. (060fea5)
  • [6.3.0] Added the --experimental_circuit_breaker_strategy, --experimental_remote_failure_rate_threshold, and --experimental_remote_failure_window_interval flags, which causes Bazel to stop using the remote cache or remote execution after a certain rate of failures. (5575ff2, 10fb5f6)
  • [6.4.0] The digest_function field is now set as part of all relevant gRPC requests. (0a8380b)
  • [6.4.0] The stack trace is now included in all gRPC errors when --verbose_failures is set. (454f11d)
  • [6.4.0] SSL BAD_DECRYPT errors are now retried. (fb38c3a)
  • Optimized fetching of ServerCapabilities. (35642f4, 0d36c6b)
  • exec_properties is now used when remote_execution_properties is empty. (6f24fa5)

Remote caching (RBC)​

Using a remote cache is one of the most popular ways of speeding up a Bazel build. Thankfully these changes make using a remote cache both more performant and more reliable:

  • [6.1.0] Added the --incompatible_remote_use_new_exit_code_for_lost_inputs flag, which causes Bazel to exit with code 39 if the remote cache evicted blobs that Bazel needed. (99cff33)
  • [6.1.0] Background download progress is now reported in the UI. (0f524c6)
  • [6.1.0] Bazel now cleans up stale metadata when it detects that remote cache blobs have been evicted. (963640a, 32e4f23, c05ba76)
  • [6.1.0] When using a combined cache, the AC integrity check now applies to disk part as well. (5f2866f)
  • [6.1.0] Fixed --remote_download_minimal to work with bazel test. (e8182ce)
  • [6.2.0] Added the --experimental_remote_cache_eviction_retries flag, which automatically retries the build if it encounters a remote cache eviction error. (24b4589)
  • [6.2.0] All remote metadata is now cleared if any blobs are detected as evicted from the remote cache. (49a9502)
  • [6.2.0] Removed action_id metadata from prefetched inputs. (f62a8b9)
  • [6.2.0] ALREADY_EXISTS when uploading is now treated as a success. (daa3dbe)
  • [6.2.0] Improved the upload early return logic. (50ec6bb)
  • [6.2.0] Fixed failures creating output directories. (4050120)
  • [6.3.0] --experimental_remote_cache_eviction_retries is now disabled if --invocation_id is set. (d9b94cb)
  • [6.2.0] Output symlinks are now gracefully handled when using Build without the Bytes. (ca30372)
  • [6.3.0] The prefetecher action_id metadata is now set for prefected inputs. (3b39ab8)
  • [6.3.0] Fixed local action non-declared symlink issue when using Build without the Bytes. (5c4cf47)
  • [6.3.0] Fixed a potential memory leak in the UI. (ce8836d)
  • [6.4.0] Added the --experimental_remote_require_cached flag, which fails the build if any remotely cachable actions aren't cached. (22f518c)
  • [6.4.0] Added support new-style digest functions. (88412ce)
  • [6.4.0] Added support for multiple digest functions. (f8c8875)
  • Added the --incompatible_disallow_unsound_directory_outputs flag, which disallows materializing an output file as a directory. (77f8603)
  • Added the --remote_download_all flag, which is similar to the --remote_download_{toplevel,minimal} flags. (d097b5d)
  • Added the --experimental_remote_cache_ttl flag, which causes old blobs to be considered potentially evicted from the remote cache. (1ebb04b)
  • Added the --experimental_remote_cache_lease_extension flag, which causes a background thread to periodically send FindMissingBlobs requests to the remote cache during a build. (1a2b792)
  • Added the --experimental_remote_scrubbing_config flag, which allows scrubbing remote cache keys for locally run actions. (24de276)
  • Build without the Bytes now works without setting the --experimental_inmemory_*_files flags. (ba5e617)
  • Changing --remote_download_mode no longer invalidates the analysis cache. (d426b3d)
  • HTTP remote cache failures are now retried. (6115d94)
  • If the remote cache is unavailable at the start of the build, it will now automatically fall back to local execution. (0d36c6b)
  • Tree objects are now emitted in topological order. (c20d7ed)
  • The mtime is now updated on files stored or retrieved from the disk cache. (7a774ff)
  • Fixed --experimental_remote_download_regex to work in incremental builds. (20552d8)
  • Fixed Build without the Bytes when using multiple source roots. (de4746d)
  • Fixed prefetching symlinks. (0a1d505)
  • Fixed runfile symlink handling when using Build without the Bytes. (fb76e6e)

Remote execution (RBE)​

For some projects, using remote execution is the ultimate performance unlock for their Bazel builds. In addition to the remote caching changes covered above, which also apply to remote execution, the following changes improve the remote execution experience:

  • [6.1.0] Added the --experimental_remote_discard_merkle_trees flag, which discards in-memory copies of the input root's Merkle tree and associated input mappings during calls to GetActionResult and Execute. (4069a87)
  • [6.1.0] Made Bazel more responsive and use less memory when --jobs is set to a high value. (4069a87)
  • [6.1.0] Fixed handling of remote cache eviction when uploading inputs. (c1168e1)
  • [6.2.0] Optimized building Merkle trees. (f63ce79, 6d6fa81)
  • [6.2.0] Tree artifacts are now included in the Merkle cache. (0f55d12)
  • [6.3.0] Added support for output_symlinks in ActionResult. (e842fd5, d3fb047)
  • [6.3.0] Remote symlink outputs are now supported when using building without the bytes. (0ff6b88)
  • [6.4.0] The no-remote-exec execution requirement is now part of the action salt. (5a23ab2)

Dynamic execution​

Dynamic execution allows for Bazel to race remote and local execution of actions, potentially allowing you to get the benefit of both modes, without the drawbacks of either. Bazel 7.0 only included a single notable user-facing change to dynamic execution:

  • Added the --experimental_dynamic_ignore_local_signals flag, which allows local failures under dynamic execution to be ignored for exit codes > 127 (signals). (07ee4b7)

Build Event Service (BES)​

Using a build event service can give you unparalleled insight into your Bazel builds at scale. There were a couple nice changes to BES support:

  • [6.1.0] stdout and stderr logs are now uploaded when using --experimental_remote_build_event_upload=minimal. (17b8e44)
  • [6.1.0] When using --experimental_remote_build_event_upload=minimal, bytestream:// is always used for BEP referenced files. (b0c5eb3)
  • Added the --bes_system_keywords flag, which allows specifying non-prefixed notification keywords. (8daa3dc)
  • Added the --build_event_{binary,json,text}_file_upload_mode flags, which specify the upload mode to use for each file type. (ca62ca1)

Logging​

Bazel offers various methods to gain insight into your build. I cover some of the notable changes to those methods below.

Build Event Protocol (BEP)​

The build event protocol is used by build event services, so all of these changes could have also been listed in that section as well. The BEP can also be collected locally with --build_event_json_file, --build_event_binary_file, and --build_event_text_file.

The vast majority of changes added additional information to the BEP, though some are fixes and improvements:

  • [6.3.0] Added the action_cache_statistics field to BuildMetrics.ActionSummary. (7963528)
  • Added the end_time, start_time, and strategy_details fields to ActionExecuted. (2ddacab)
  • Added the exec_kind field to BuildMetrics.ActionSummary.RunnerCount. (0e1d1b6)
  • Added the execution_phase_time_in_ms field to BuildMetrics.ActionSummary.TimingMetrics. (be63eee)
  • Added the package_load_metrics field to BuildMetrics.ActionSummary.PackageMetrics. (0597a07)
  • Added the symlink_target_path field to File. (7fa5796)
  • Added the system_time and user_time fields to BuildMetrics.ActionSummary.ActionData. (5f1a570)
  • Added the worker_ids field to BuildMetrics.WorkerMetrics. (d31dd09)
  • Added the worker_key_hash field to BuildMetrics.WorkerMetrics. (58eeea1)
  • Added the worker_pool_metrics field to BuildMetrics. (284e5a3)
  • Added the CoverageActionsFinishedId event. (c2a6f0c)
  • Added the ExecRequest event. (9a047de)
  • Added the TestProgress event. (d8b8ab0)
  • Added the --experimental_publish_package_metrics_in_bep flag, which populates the BuildMetrics.ActionSummary.PackageMetrics.package_load_metrics field. (0597a07)
  • Added the --experimental_run_bep_event_include_residue flag, which populates the ExecRequest.argv field. (9a047de, dab6383)
  • Deprecated the worker_id field in BuildMetrics.WorkerMetrics. (d31dd09)
  • Fixed Starlark flags set in .bazelrc from appearing in UnstructuredCommandLine. (f272df3)

Timing profile​

The action timing profile, which is enabled by default with --profile, is viewable both locally in Chrome and on build event services. These changes add more detail and clarity to the profile:

  • [6.1.0] Added the bazel_version field to otherData. (7569b0d)
  • [6.2.0] Added the profile_finish_ts field to otherData. (dbc8423)
  • [6.4.0] Added profiling of Bzlmod operations. (e7cfd2e, 8a68310)
  • Added local action cache hits as a stacked chart. (610b56f)
  • Added the --experimental_collect_pressure_stall_indicators flag, which adds Linux PSI data to the profile. (50446bc)
  • Added the --experimental_collect_resource_estimation flag, which adds CPU and memory estimation profiling. (2e2f5d9)
  • Added the ANALYZE_AND_EXECUTE (interleaved loading, analysis and execution) phase. (78140bf)
  • Added profiling of checking outputs. (df3d00a)
  • Added profiling of execution log creation, writing, and sorting. (c2e25ea)
  • Added profiling of long wait times for cancelling the other branch in dynamic execution. (9f2cc56)
  • Added profiling of network handshakes. (bf9b177)
  • Added profiling of symlink tree creation and deletion. (f84329e)
  • Doubles are now used instead of strings for counter series. (6d1dd4e)
  • REMOTE_DOWNLOAD (remote output download) now has a 10ms threshold. (b8e2c5f)
  • Extended the span of checking action cache hits to include all of the work and not only the actual cache lookup. (df3d00a)
  • Removed taskId. (bf2368a)
  • Fixed local execution to use LOCAL_PROCESS_TIME (Local execution process wall time) instead of REMOTE_PROCESS_TIME (Remote execution process wall time). (480b234)

Execution log​

Bazel logs all of the spawns it executes in the execution log, which is enabled with the --execution_log_json_file or --execution_log_binary_file flags. This feature is relatively stable, with just a few noticeable changes:

  • [6.1.0] Added the --execution_log_sort flag, which allows disabling execution log sorting. (1a6ffe6)
  • [6.4.0] Added the is_tool field to File. (0434287)
  • --execution_log_json_file and --execution_log_binary_file are now mutually exclusive. (61fa933)
  • Renamed the remote_cache_hit field in SpawnExec to cache_hit. (60dbc64)
  • Removed the progress_message field from SpawnExec. (0ca0510)
  • Removed the walltime field from SpawnExec. (60e03bf)

Execution graph​

The execution graph, which is enabled with the --experimental_enable_execution_graph_log flag, logs all actions executed during a build. It differs from the execution log in that it contains additional information needed to reconstruct the full dependency graph.

Even though there aren't many changes to the execution graph in Bazel 7.0, I only recently learned about its existence, and wanted to call attention to it:

  • Added the discover_inputs_millis field to Metrics. (0e099d9)
  • Added the --experimental_execution_graph_enable_edges_from_filewrite_actions flag, which adjusts how filewrite action edges are handled. (4973166)
  • Added the --experimental_enable_execution_graph_log and --experimental_execution_graph_log_path flags, which replace the --experimental_execution_graph_log flag. (8ab9c6e)
  • The execution graph is now written to the output base instead of the workspace. (b5808a4)
  • Shared actions are now included in the execution graph. (2036a0f)
  • Test actions no longer output an extra node. (c3260c4)

Other​

  • [6.3.0] Changed --memory_profile_stable_heap_parameters to accept more than one GC specification. (3dc6951)
  • Added the --experimental_command_profile flag, which records a Java Flight Recorder CPU profile into a profile.jfr file in the output base. (5cbb153)

Execution​

Executing build commands is a primary function of Bazel. Some execution related changes can be classified in a particular way, such as remote execution or dynamic execution. For the rest, I've collected them here.

Below I summarize some foundational execution related changes, including "local execution" strategies:

  • [6.1.0] Added the --experimental_writable_outputs flag, which causes the permissions of all output files to 0755 instead of 0555. (88c426e)
  • [6.1.0] Added the --local_extra_resources flag, which allows specifying additional resource types that can limit concurrently running actions. (2b2bea4)
  • [6.1.0] Fixed symlink creation overhead. (c15148a)
  • [6.2.0] ctime is now used in file digest cache keys. (763f1d9)
  • [6.2.0] Optimized file checksumming. (368bf11)
  • [6.3.0] Adjusted --top_level_targets_for_symlinks to work in more cases. (ceb9955)
  • [6.4.0] Added the --allow_analysis_cache_discard flag, which when false causes the build to fail if the analysis cache would be discarded. (1997f09)
  • [6.4.0] Added the blake3 option to --digest_function. (cc49d68)
  • [6.4.0] Added the diff_against_dynamic_baseline option to --experimental_output_directory_naming_scheme. (39b450c)
  • [6.4.0] Added the FORMATTED_DATE entry to the volatile workspace status file. (ee36d32)
  • Added a forced=k option to --test_sharding_strategy. (bd5f3c3)
  • Added the --experimental_gc_thrashing_limits and --gc_thrashing_limits_retained_heap_limiter_mutually_exclusive flags, which causes Bazel to trigger an OOM crash when too much garbage collection thrashing happens. (9f93780)
  • Added the --experimental_throttle_action_cache_check flag, which throttles action cache checks. (3d29b2e)
  • Added the --experimental_skymeld_analysis_overlap_percentage flag, which limits amount of analysis phase and execution phase overlap. (9adbe0f)
  • Added the --experimental_use_semaphore_for_jobs flag, which limits the number of concurrent action execution with a semaphore. (a83a97e)
  • Added the --skip_incompatible_explicit_targets flag, which skips incompatible targets that are explicitly listed on the command line. (136a1ee)
  • Actions can now opt into path mapping with the supports-path-mapping execution requirement. (a239ea8)
  • --flag_alias can now be set on common and always. (86fe599)
  • Elevated the analysis cache discarded message from INFO to WARN. (0a47a1f)
  • Normalized --action_env, --flag_alias, --host_action_env, and --test_env values. (4dc5de8)
  • 0755 instead of 0777 is now used when creating a writable directory. (ff0e61a, 4da0642)
  • Optimized computing digests from the filesystem. (e2a57ac)
  • When using --experimental_merged_skyframe_analysis_execution, symlinks aren't planted for paths in .bazelignore. (e1fbc83)
  • When using --subcommands the mnemonic is now reported. (afa2500)
  • Removed the sandboxfs strategy. (217fafe)
  • Fixed --reuse_sandbox_directories to work with differently-named workspaces. (2dc5ba9)
  • Fixed encoding of non-ascii contents written to parameter files. (dc80fa7)
  • Fixed state tracking for actions that run under multiple strategies. (d46aed6)
  • Fixed docker strategy GID clash. (4082e0f)

Running and testing​

In addition to building targets, Bazel can run applications and tests with the run and test commands. Here were some notable changes to that functionality:

  • [6.1.0] Non-test actions are no longer reported as tests in the UI. (fcb0077)
  • [6.1.0] Non-started tests now count as skipped. (16427c9)
  • [6.2.0] SIGWINCH is now correctly handled when bazel run-ing test rules. (38ece3c)
  • [6.2.0] Fixed missing output from quick tests run with bazel run. (c04f0d4)
  • [6.3.0] Added the --incompatible_check_sharding_support flag, which will fail sharded tests that don't touch the TEST_SHARD_STATUS_FILE file. (f7d795a)
  • [6.3.0] test-setup.sh now raises a signal on exit codes above 128. (90c4bdf)
  • [6.4.0] Runfiles related environment variables are now cleared when using bazel run. (bc83389)
  • [6.4.0] When --test_summary=detailed is used, passing methods are now also included in the test summary. (c75fda9)
  • Added the --run flag, which if false prevents bazel from running the built executable. (6069512)
  • Added the //command_line_option/fragment:test option for the transitive_configs attribute. (6bd7878)
  • Made --experimental_inprocess_symlink_creation work with --nobuild_runfile_links. (7b87ae1)
  • When switching from --enable_runfiles to --noenable_runfiles the previous runfiles symlink tree is now cleaned up. (f84329e)
  • Fixed incrementality issues related to runfiles and a changing --output_base. (c9d7ff9)

Coverage​

Bazel can collect code coverage when running tests. Recent changes made the default settings work for more people:

  • [6.1.0] bazel coverage now works with --remote_download_minimal. (e8ff51f)
  • [6.1.0] @remote_coverage_tools is now only fetched when collecting coverage. (4d188a9)
  • [6.1.0] Fixed LLVM coverage collection for source file paths with a tmp segment. (88b51f5)
  • [6.3.0] Added the flag --experimental_collect_code_coverage_for_generated_files, which collects code coverage for generated files. (9c83049)
  • [6.3.0] Added the metadata_files parameter to the coverage_common.instrumented_files_info function. (ef54ef5)
  • [6.3.0] --experimental_split_coverage_postprocessing now works in combination with --experimental_generate_llvm_lcov. (9d3b375)
  • [6.3.0] Fixed json.gz check to not rely on gcov --version. (7f628d7)
  • The CoverageReport action now uses the no-remote execution requirement instead of local. (188b4ef)
  • The coverage_support_files parameter on the coverage_common.instrumented_files_info function now accepts FilesToRunProvider arguments. (062b83f)
  • Fixed coverage combining to happen after exclusive tests have run. (6eb7dbb)

Persistent Workers​

Persistent workers improve build performance by sending multiple requests to long-running processes. Here are some notable changes to persistent worker support:

  • Added the --experimental_shrink_worker_pool flag, which shrinks the worker pool if memory pressure gets too high. (dce697d)
  • Added the --experimental_worker_allowlist flag, which specifies which mnemonics can use persistent workers. (85dcafe)
  • Added the --experimental_worker_memory_limit_mb flag, which kills workers using more than a given amount of memory. (8d1db5b)
  • Added the --experimental_worker_metrics_poll_interval flag, which allows changing the interval between collecting worker metrics and possibly attempting evictions. (a95847c)
  • Added the --experimental_worker_sandbox_hardening flag, which uses the linux sandbox for worker sandboxing. (6669a4f)
  • Removed support for high priority workers. (8e359e7)

Querying​

Here are some changes that were made to the query family of commands, starting with ones that applied to more than one of the commands:

  • [6.2.0] The aquery and cquery commands now respect the --query_file flag just like the query command. (fb23246)
  • [6.4.0] Added the --consistent_labels flag, which forces consistent label formatting across all output modes that is also compatible with str(Label(...)) in Starlark. (20cdacc)
  • Added the --proto:include_attribute_source_aspects flag, which includes a new field source_aspect_name to the Attribute message that indicates the source aspect that the attribute comes from. (5c7a159)
  • Added a filter in cquery/aquery to skip targets with mismatched configurations. (a2bd3ef)
  • label_flag and label_setting values now consider defaults. (658b3a6)

query​

  • [6.3.0] Added jsonproto option to the --output flag. (a94383f)
  • [6.3.0] Fixed --output=proto --order_output=deps not returning targets in topological order. (2ff87be)
  • [6.4.0] Renamed --output=jsonproto to streamed_jsonproto and made the format valid ndjson. (2cd583a)
  • Duplicates in <rule-inputs> when using query --output=xml --aspect_deps=precise are removed. (5c7a159)

cquery​

  • [6.2.0] Added support for alias targets to the providers function. (156325e)
  • Added the streamed_proto option to the --output flag. (aa88357)
  • Starlark transitions now have full fidelity in cquery. (9575c7f)
  • cquery --output=starlark now respects BuildLanguageOptions. (1447f24)

aquery​

  • [6.1.0] The effective environment is now printed for for all CommandActions. (2ae409b)
  • Added streamed_proto option to the --output flag. (8490321)
  • Added the target paths of UnresolvedSymlink actions. (df82dcd)
  • Added whether or not a FileWrite action's output is executable. (abac1c6)
  • Added RepoMappingManifest to the set of files that --include_file_write_contents affects. (604a9ef)
  • Removed duplicate printing of ExecutionInfo. (dd3b0ec)

Dependency management​

With Bazel 7.0 external dependencies can be managed either with Bzlmod or the WORKSPACE file. Here are some changes that apply to either method:

  • [6.1.0] Improved readability of human-readable download progress. (66b58ee)
  • [6.1.0] Repository fetch progress is now reported during main repo mapping computation. (51e6c38)
  • [6.3.0] Added the archive_type attribute to http_archive. (c7695ce)
  • [6.3.0] Download progress now includes a percentage complete if possible. (6ffff17)
  • [6.3.0] Hash strings can now contain uppercase characters. (cc8ecc5)
  • [6.4.0] Fixed handling of non-ASCII characters in archive entry file names. (10169bb)
  • [6.4.0] Generated patches files now use \n for line endings on all platforms. (07e0d31)
  • Added support for .tbz files in the repository_ctx.download_and_extract function. (6e01b25)
  • Added the --experimental_worker_for_repo_fetching flag, which allows fetching repositories using a worker thread. (1590dbc)
  • Added the --http_connector_attempts and --http_connector_retry_max_timeout flags, which makes connection retry attempts and timeout configurable. (f29db1b)
  • .git directories are now deleted from git_repository external repositories when using strip_prefix. (2977ba6)
  • Extended --unix_digest_hash_attribute_name to also work in the repository cache. (87d6e9a)
  • HTTP 429 (Too Many Requests) errors are now retried. (4ed6a2f)
  • URLs are now used as default canonical IDs in common repo rules. (a6f8923)

Bzlmod​

With Bazel 7.0 Bzlmod is enabled by default. While Bzlmod was made non-experimental in Bazel 6.0, the minor releases contained a lot of additional quality-of-life and feature improvements:

  • [6.1.0] Tildes are now acceped in --override_module. (094a0aa)
  • [6.2.0] Added the --lockfile_mode flag, which controls how the bzlmod lockfile is generated and checked. (3b11a2f)
  • [6.2.0] Added the dev_dependency attribute to register_execution_platforms and register_toolchains. (f39454f)
  • [6.2.0] Added the is_dev_dependency attribute to module_ctx. (1a719ce)
  • [6.2.0] Added the extension_metadata attribute to module_ctx. (6a47481)
  • [6.2.0] Added the max_compatibility_level attribute to bazel_dep, which allows version selection to upgrade a dependency up to the specified compatibility level. (152a001)
  • [6.2.0] Added support for relative paths in --override_module. (f7627e0)
  • [6.2.0] Fixed an issue where WORKSPACE and WORKSPACE-loaded .bzl files couldn't see the Bzlmod root module's mappings when Bzlmod is enabled. (dfdf63a)
  • [6.3.0] Added the root_module_has_non_dev_dependency attribute to module_ctx. (640e850)
  • [6.3.0] Added the show command to bazel mod. (1ae56c2)
  • [6.3.0] REPO.bazel and MODULE.bazel files are now considered workspace boundary markers. (f93b2f3)
  • [6.3.0] Overrides specified by non-root modules no longer cause an error, and are silently ignored instead. (78cb7d5)
  • [6.3.0] The canonical repo name of the platforms module is now forced to be platforms. (343ab03)
  • [6.3.0] Renamed modquery command to mod. (f6c2ef9)
  • [6.3.0] Yanked module versions no longer contribute dependency requirements or emit DEBUG messages for print() statements. (2a2a474)
  • [6.4.0] Added the environ attribute to module_extension. (64554a3)
  • [6.4.0] Added the --experimental_isolated_extension_usages flag, which enables the isolate parameter of use_extension. (19a9710, 3a4b04f)
  • [6.4.0] Builtin modules are now injected at the end of the MODULE.bazel file. (0e58b0d)
  • [6.4.0] Release candidates are now considered equivalent to the actual release for module.bazel_compatibility. (21cd4ef)
  • [6.4.0] Optimized computing root repository mapping. (8a68310)
  • [6.4.0] Optimized memory usage. (74aadb2)
  • [6.4.0] Optimized registry downloading. (8337dd7)
  • Added the --all flag to the fetch command. (0356a3f)
  • Added the --repo flag to the fetch command. (9a1d385)
  • Added support for the use_repo_rule directive in MODULE.bazel files. (ab016be)
  • All labels in Bazel error messages, log output, Build Event Protocol, etc. are now prefixed with @@ instead @ where applicable, to properly denote that they contain canonical repo names. (c456082)
  • Optimized CPU usage. (57b0bd7)

Platforms​

Platforms are where your build tools run (i.e. execution platforms) or where your built products will run (i.e. target platforms). In previous years I catagorized changes along those lines, but this year I'm not making that distinction.

Android​

  • Continued progress on Starlarkifying the Android rules
  • [6.1.0] Made desugar dependencies deterministic. (a306f4f)
  • [6.1.0] Fixed multiplexed workers for busybox tools. (8b1521e)
  • [6.2.0] Added test coverage support to android_local_test. (6bd2cc3)
  • [6.2.0] Fixed worker and multiplex workers for DexBuilder and Desugar actions. (765c0eb)
  • Added the --experimental_persistent_aar_extractor flag, which uses persistent workers for aar extractors. (74bc046)
  • Added the --optimizing_dexer flag, which allows specifying a binary to use to do dexing without sharding. (9337dfe)
  • Added the bazel_android fragment. (bd0f9b0)
  • Added the dexdump tool to android_sdk_repository. (773b50f)
  • Added the dexdump attribute to android_sdk. (1e4b275)
  • Added persistent worker support for GenerateDataBindingBaseClasses. (9092e29)
  • Added persistent worker support for ProcessDatabinding. (9092e29)
  • Added support for R.txt files generated with aapt2 link --package-id. (41f894f)
  • Added support for optimizers rewriting baseline profiles. (5391486)
  • AndroidDataBindingProcessingAction now emits deterministic zip file timestamps. (10af780)
  • Made AndroidInstall actions hermetic with respect to dex shards. (2b104c8)
  • The --no_proguard_location_reference flag is now added unconditionally to the command line of aapt2. (7d911b5)
  • The default Android SDK toolchain is now registered first. (9be1e9b)
  • Baseline profile wildcards are now expanded before optimizer tools see them. (52c3566)
  • Removed support for Databinding v1. (6a19449)

Apple​

  • [6.1.0] xcrun is now used to invoke install_name_tool. (8ec8743)
  • [6.1.0] Dropped support for macOS versions prior to 10.13. (43dadb2)
  • [6.2.0] Patched zlib to fix compatibility with latest Xcode. (1f2b3ed)
  • [6.3.0] Bumped default_macos_sdk_version to 10.11. (86ef4f4)
  • [6.4.0] Added initial visionOS support. (c113e62)
  • [6.4.0] The xcode_autoconf repository rule will now re-run when the DEVELOPER_DIR or XCODE_VERSION environment variable changes. (19979e6)
  • [6.4.0] Removed the -s flag from libtool invocation. (ae7cfa5)
  • Added -dead_strip to opt linker flags. (1da8a82)
  • Added the extra_requested_features and extra_disabled_features parameters to the apple_common.link_multi_arch_binary function. (1f8951c)
  • Linker framework arguments now use the two-argument form (e.g. ["-framework", "UIKit"] instead of ["-Wl,-framework,UIKit"]). (32fb0a2)
  • Moved Apple toolchain setup to apple_support. (699e403)
  • xcode_autoconf now used configure = True instead of local = True. (c747ae7)
  • xcrunwrapper is no longer used for the ObjcBinarySymbolStrip action. (80621fd)
  • Removed apple_common.multi_arch_split. (a76763c)
  • Removed apple_common.apple_crosstool_transition. (534e6f8)
  • Removed darwin as a --cpu value. (d1b4fb7)
  • Removed bitcode support. (37b8e1b)
  • Removed the use of -undefined dynamic_lookup. (4853dfd)

Linux​

  • [6.3.0] --local_termination_grace_seconds is now used when testing sandbox availability. (d0e19ae)
  • Added the --experimental_sandbox_memory_limit flag, which allows setting per-sandbox memory limits. (03996c1)
  • .bazelignore paths on Linux are no longer watched for changes. (4dabe43)
  • Bazel's local CPU resource on Linux is now container aware. Use --local_cpu_resources, --loading_phase_threads or --jobs to override. (ab2953c)

Windows​

  • [6.1.0] The archive_param_file feature is now enabled by default for Windows. (bb0b886)
  • [6.1.0] Fixed --nozip_undeclared_test_outputs on Windows. (cd10d50)
  • [6.2.0] C++ deps pruning is now enabled on Windows when PARSE_SHOWINCLUDES is available. (788801a)
  • [6.3.0] Fixed VS 2022 autodetection. (cd33d14)
  • [6.4.0] Compilation actions using the auto-configured MSVC toolchain are forced to emit error messages in English if the English language pack for Visual Studio is installed. (0f10359)
  • [6.4.0] Fixed Bash runfiles failure when the output base contains uppercase letters. (ea4ab7d)
  • Added the external_include_paths feature to the windows cc toolchain. (850b334)
  • .bazelignore paths on Windows are no longer watched for changes. (4dabe43)
  • The execution platform, instead of the host platform, is now used to decide whether to do Windows-specific things in a few places. (2f0948b)
  • The arm64 version of the embedded JDK is now used for Windows ARM64. (b43418d)
  • Enabled the compiler_param_file feature in the Windows MSVC toolchain. (d47a410)
  • Removed forced link to clang_rt.builtins in the Windows MSVC toolchain. (761b280)
  • Fixed launcher_maker to work with long paths on Windows. (33fed24)

Languages​

While there are lots of programming languages that are supported through standalone Starlark rules, some are still written as "native" rules in Bazel core, or are bundled Starlark rules while Starlarkification is in progress. In the following sections I summarize the notable changes in support of these languages.

Bash​

  • [6.1.0] Fixed runfiles_current_repository with RBE. (497b7e4)
  • [6.1.0] Fix root symlink edge case in runfiles library. (dd24a00)
  • Fixed runfiles calling repository lookup for directly run scripts. (da1a6d7)

C and C++​

  • Continued progress on Starlarkifying C/C++ rules. (starlarkification roadmap)
  • [6.1.0] Added support for .pyd extensions. (073f54b)
  • [6.1.0] Added support for .wasm extensions. (de062a6, 4b6f014)
  • [6.1.0] Added the sanitizer features to unix_cc_toolchain_config. (abae5ca)
  • [6.1.0] The exec transition is now applied to lcov_merger in sh_test and cc_test. (37953c5)
  • [6.1.0] The cc_shared_library.roots attribute was renamed to deps. (68aad18)
  • [6.1.0] libtool is no longer hardcoded when using the unix cc toolchain. (3c47b47)
  • [6.1.0] Removed the -O1 flag from sanitizer feature flags. (e132653)
  • [6.1.0] Removed the static_deps attribute from cc_shared_library. (9815b76)
  • [6.2.0] Exposed cc_proto_aspect as a toplevel symbol. (2aa06cf)
  • [6.3.0] Added the force_no_whole_archive feature, which force disables --whole-archive. (661ebef)
  • [6.3.0] Added the additional_compiler_inputs attribute to cc_library. (ade32e6)
  • [6.3.0] Added the CcSharedLibraryHintInfo provider. (dbb09c9)
  • [6.3.0] File extensions are case sensitive again. (e4990f8)
  • [6.3.0] Unused targets listed in cc_shared_library.dynamic_deps are now linked. (ba5c740)
  • [6.3.0] cc_binary targets with dynamic_deps attributes no longer link indirect dynamic_deps on Unix. (95ae4db)
  • [6.3.0] Added the exclude_bazel_rpaths_in_transitive_libs and link_indirect_dynamic_deps_in_binary features. (95ae4db)
  • [6.3.0] Removed cc_shared_library_permissions. (adfd4df)
  • [6.3.0] Removed the preloaded_deps attribute from cc_shared_library. (3b7e233)
  • [6.3.0] Fixed the cc_shared_library aspect to propagate along all attributes. (590ee17)
  • [6.3.0] Fixed the order of linker inputs in cc_binary and cc_shared_library. (a772452)
  • [6.3.0] Fixed rpath for symlinks in cc_shared_library. (044a14c)
  • [6.3.0] Fixed cc_shared_library to take into account unused CcInfos. (b6b9eec)
  • [6.3.0] Fixed cc_shared_library to take into account indirect top level deps. (f9008f6)
  • [6.3.0] Fixed exports_filter in cc_shared_library. (bc33ac2)
  • [6.4.0] Added the additional_linker_inputs attribute to cc_library. (0589995)
  • [6.4.0] Debug info context is now collected from the cc_library.implementation_deps attribute. (e55fee2)
  • [6.4.0] Data dependencies are now propagated through the cc_library.implementation_deps attribute. (56e9020)
  • [6.4.0] c++14 is now used as the default C++ standard. (978cd23)
  • Added auto-configured Unix toolchain support for BAZEL_CONLYOPTS. (b272cef)
  • Added a feature definition for static_link_cpp_runtimes to the unix cc toolchain config. (6c7147b)
  • Added support for optional toolchains to find_cpp_toolchain. (6b126d6)
  • Added the external_includes attribute to compilation_context. (a6ef0b3)
  • Added the validates_layering_check_in_textual_hdrs feature, which skips the parse_headers action. (8ef60d0)
  • Added the prefer_pic_for_opt_binaries feature, that indicates that PIC compiles are preferred for binaries even in optimized builds. (4084671)
  • Added the --memprof_profile flag, which allows passing an LLVM MemProf to CppCompile actions. (617a3bd)
  • Added the --@bazel_tools//tools/cpp:link_extra_libs flag, which allow. (9f2c62a)
  • Added the link_extra_lib attribute to cc_binarys specifying extra libraries to be linked into every binary. (5eff703)
  • Added the module_files output group, which enables building PCMs from cc_library targets directly. (9b30bf7)
  • Added support for expand_if_available to env_entry. (cc335fd)
  • Added the use_lto_native_object_directory feature, which adds tree artifact support to the thin_lto feature. (db34798, 480c8c8)
  • Added a tool name for objcopy. (2d1f37d)
  • cc_test can now be configured by using a native.toolchain(). (99b672b)
  • --crosstool_top is now unset when --incompatible_enable_cc_toolchain_resolution is set. (0013115)
  • --fdo_optimize no longer accepts a relative path. (afe070e)
  • C++ branch coverage is now enabled when using gcov 8 or later. (57ae1ff)
  • The BAZEL_CURRENT_REPOSITORY preprocessor variable is now only set during compilation if the target depends on the runfiles library via deps or implementation_deps. (1b214d2)
  • The includes parameter in the cc_common.compile() function now accepts depsets as well as lists. (c8d6c11)
  • Made generate_system_module_map.sh more deterministic. (78f98e7)
  • Moved CcSharedLibraryHintInfo to cc_common. (b1c2e8d)
  • libstdc++ (libc++ on macOS) and libm are no longer linked in if none of their symbols are referenced, e.g., in a pure C target. (2482322)
  • When building C++ modules, FDO variables and profile inputs are no longer added. (edeb037)
  • Relocatable object files are no longer wrapped in -Wl,-whole-archive -Wl,-no-whole-archive. (61267b3)
  • Removed the cc_host_toolchain_alias rule. (3543b19)
  • Removed the grep_includes parameter from cc_common functions. (b82e202)

Java​

  • Continued progress on Starlarkifying Java rules. (starlarkification roadmap)
  • [6.1.0] Coverage can now be collected for external targets. (00e9af1)
  • [6.1.0] Fixed coverage collection with the Java 8 runtime. (c266651)
  • [6.1.0] Fixed --experimental_java_classpath=bazel. (ac504cb)
  • [6.2.0] Added the version attribute to java_runtime and JavaRuntimeInfo. (7556e11)
  • [6.2.0] Added -Xep:IgnoredPureGetter:OFF to default javacopts. (3b57894)
  • [6.2.0] Added -Xep:LenientFormatStringValidation:OFF to default javacopts. (33a3b01)
  • [6.2.0] Added -Xep:ReturnMissingNullable:OFF to default javacopts. (e80ca15)
  • [6.2.0] JVM warnings are now redirected to stderr. (abea37b)
  • [6.3.0] local_java_repository now sets the version attribute of java_runtime. (1c1584b)
  • [6.3.0] ijar now handles dynamic constants. (69d2991)
  • [6.4.0] Added a toolchain type for the Java bootstrap runtime. (8715e9a)
  • [6.4.0] Optimized classpath pre-processing in java_stub_template.txt. (4e8f0bd)
  • Added -Xep:EmptyTopLevelDeclaration:OFF to default javacopts. (8d9a06e)
  • Added the bootclasspath parameter to the java_common.compile function. (a75f516)
  • Added the default_cds attribute to java_runtime and JavaRuntimeInfo. (53ff268)
  • Added the exec_compatibility_with and target_compatibility_with attributes to local_java_runtime and default_java_toolchain. (27fe30b)
  • Added the ijar attribute to JavaToolchainInfo. (0dd6a49)
  • Added the proguard_allowlister attribute to JavaToolchainInfo. (8b9e8d5)
  • Added the javac_options_list attribute to compilation_info. (ea154dc)
  • Added the --incompatible_disable_non_executable_java_binary flag, which removes the create_executable attribute from java_binary. (d12c7fa)
  • Added the --incompatible_java_info_merge_runtime_module_flags flag, which causes the JavaInfo constructor to merge add_exports and add_opens of runtime_deps in addition to deps and exports. (e2249f9)
  • Added the --build_target flag to singlejar, which allows changing the build.target property when stamping is enabled. (a1a5f33)
  • darwin_x86_64 and darwin_arm64 now have separate java_tools releases. (3b475b3)
  • java_stub_template.txt is now exported from @java_tools//jdk. (1465771)
  • The --experimental_local_java_optimization_configuration flag now only accepts a single-label. (6e3a421)
  • Proto toolchains are now used in java_lite_proto_library. (8c38be3)
  • Proto toolchains are now used in java_proto_library. (51970d2)
  • Optimized java_common.merge memory usage. (8ffb972)
  • Upgraded default java_toolchain.java_runtime to JDK 17. (75e0f7d)
  • Replaced remote JDK 18 with JDK 20. (19b2e2f, 0e8e611, 7ff98ba)
  • Removed the transitive_deps and transitive_runtime_deps attributes from JavaInfo. (72058be)
  • Removed deprecated targets from @java_tools//jdk. (844b5d2)
  • Fixed proguard output map symlink when proguard_specs is a select(). (c2761af)

Objective-C​

  • [6.3.0] Added the implementation_deps attribute to objc_library. (ae7b9c5)
  • [6.4.0] Added the --incompatible_disable_objc_library_transition flag, which removes objc_libary's custom transition. (0f34e76)
  • Added the target_should_alwayslink attribute to the objc fragment. (c878b59, 3c0f394)
  • Added the --incompatible_disallow_sdk_frameworks_attributes flag, which disallows the sdk_frameworks and weak_sdk_frameworks attributes in objc_library and objc_import. (66121a7)
  • Added the --incompatible_objc_alwayslink_by_default flag, which changes the default of objc.target_should_alwayslink to True. (a8b36c1)
  • Added the --incompatible_objc_provider_remove_linking_info flag, which removes linking information from ObjcProvider. (3e170fb)
  • The apple_common.new_executable_binary_provider and apple_common.new_dynamic_framework_provider functions no longer require the objc argument. (28f9056)
  • The variables_extension parameter on the apple_common.link_multi_arch_binary function can now be None. (87bd420)
  • objc_common no longer sets linking information in ObjcProvider. (0fa7933)
  • Linking no longer uses ObjcProvider information. (426f225)
  • Linking features, in addition to linkopts, are considered when determining the stripping type. (3a31a6c)
  • Tree artifacts in source attributes of objc_library can now have arbitrary extensions. (280ae1a)
  • Removed the runtime_deps attribute from objc_library. (3ea60b7)
  • Removed the objc_archive action (cpp_static_library is used instead). (e1cb203)
  • Removed the objc++-executable action (objc-executable is used instead). (1623f7e, 6d0c210, 004c73c)
  • Fixed the includes attribute of objc_library when --experimental_sibling_repository_layout is set. (bbe453e)

Proto​

  • Continued progress on Starlarkifying Proto rules. (starlarkification roadmap)
  • [6.3.0] Added the output_files attribute to proto_lang_toolchain. (4d14d3f)
  • Added the --incompatible_enable_proto_toolchain_resolution flag, which causes proto language rules to use toolchain resolution. (d435c6d)
  • Removed the proto_compiler attribute from proto_lang_toolchain. (f5fb2f6)
  • Fixed proto generation when using --experimental_sibling_repository_layout. (6c6c196)

Python​

  • Continued progress on Starlarkifying Python rules. (starlarkification roadmap)
  • [6.1.0] Added host transition to the lcov_merger attribute of py_test. (4a6d056)
  • [6.2.0] Fixed runfiles lookup when using a manifest file. (91584dd)
  • Added the --incompatible_python_disable_py2 flag, which causes python_version=PY2, srcs_version=PY2 or srcs_version=PY2ONLY with py_binary, py_test, py_library, py_runtime, or py_runtime_pair to throw an error. (d1bbf4b, 95a57ef)
  • Added the --incompatible_python_disallow_native_rules flag, which causes an error if a native Python rule is used without going through rule_python. (2e558ed)
  • Added the build_python_zip attribute to the py fragment. (38b2789)
  • Added the default_python_version attribute to the py fragment. (c3b2be9)
  • Added the default_to_explicit_init_py attribute to the py fragment. (38b2789)
  • Added the use_toolchains attribute to the py fragment. (c3b2be9)
  • Added the bootstrap_template attribute to py_runtime. (0696ba3)
  • Removed the py_transitions module. (e2c4d3c)

Starlark and Build API​

Starlark is the configuration language used to configure your project. It is also the programming language used to define rules. Bazel also has a Build API which defines standard functions, modules, and rules that can be used from Starlark. Here are some notable changes to both:

  • [6.1.0] Added the --incompatible_use_host_features flag, which causes the --features flag to only apply to the target configuration, while the --host_features flag only applies to the exec configuration. (0ef9c7c)
  • [6.1.0] Added the package_relative_label function on the native module. (b859571)
  • [6.1.0] The map_each callback in template_dict.add_joined can now return None. (db68419)
  • [6.1.0] The map_each callback in template_dict.add_joined can now return a list of strings. (8783459)
  • [6.2.0] Added the module_name and module_version attributes on the native module. (bcf309b)
  • [6.2.0] json.decode now accepts duplicate keys. (8548e20)
  • [6.2.0] Multiple matching select branches are now allowed if they resolve to the same value. (d43737f)
  • [6.4.0] Added the --incompatible_merge_fixed_and_default_shell_env flag, which merges rule supplied and shell provided environment variables. (d1fdc53)
  • [6.4.0] Optimized empty depsets. (fa0ff49)
  • [6.4.0] Optimized single transitive depsets. (216fce5)
  • [6.4.0] Rule and aspect validation output groups are now merged. (cd72583)
  • [6.4.0] When the repr function is called on an exported rule the name of the rule is now included in the output. (002490b)
  • Added the abs() function. (5e37989)
  • Added the allow_closure attribute to template_dict.add_all. (4188edd)
  • Added the compressed_output attribute to genquery. (7f639c6)
  • Added the format_joined callback to template_dict.add_all. (4188edd)
  • Added the initializer parameter to the rule function, which allows specifying a function that computes default values for attributes. (45bac19)
  • Added the --experimental_enable_scl_dialect flag, which allows loading .scl (Starlark Configuration Langauge) files. (a0cd355)
  • Added the --experimental_rule_extension_api flag, which enables the use of rule extension and subrules. (8815980)
  • Added the --incompatible_no_package_distribs flag, which disables the distribs attribute of package. (e8184e0)
  • Added the starlark_doc_extract rule, which is used by newer versions of Stardoc. (fa65782)
  • Changed the default value of attrs in rule() and aspect() to an empty dictionary. (e8f5082)
  • --deleted_packages now accumulates multiple values. (2a5d9c7)
  • attr objects now use value equality rather than reference equality. (31fd464)
  • json.decode now takes an optional default positional parameter. If this parameter is specified and decoding fails, json.decode will return the default value instead of failing Starlark evaluation. (71fb1e4)
  • proto.encode_text() now omits struct fields with None values. (88346f1)
  • Besides for implementation, all arguments to the rule function now need to be named. (cbd63ea)
  • The location of rules that explicitly specify generator_name and/or generator_function attributes is now the top-level call in the BUILD file. (9800ffd)
  • Transitions can now inspect attribute value. (ceddfb1)
  • _whitelist_function_transition is now applied automatically. (60f3319)
  • Optimized calls to functions with kwargs. (2fc7ab9)
  • Optimized depsets in providers. (cb5a033)
  • Optimized provider memory layout. (fc86f15)
  • Optimized singleton tuples (e.g. (single_value, )). (2cc9e13)
  • Optimized statement/expression heavy code. (704027e)
  • Optimized string find/index calls when end isn't specified. (70c821a)
  • Optimized string {l,r,}strip calls. (62ceeaf)
  • Optimized string key dictionary lookups. (6087258)
  • Optimized tuple and list in checks. (d027d48)
  • Optimized type checks. (2e4694d)
  • Optimized OutputGroupInfo. (655849b)
  • Removed the default_provider attribute from the ctx module. (2ce1a1b)
  • Removed the host_configuration attribute from the ctx module. (51e1da9)
  • Removed the host_fragments attribute from the ctx module. (0ca7857)
  • Removed the new_file function from the ctx module. (ffe595c)
  • Removed the exec_tools attribute from genrule. (5ce12ee)
  • Removed the cmd_helper module. (b3749b3)
  • Removed support for _whitelist_function_transition. (4064d78)
  • Fixed ctx.expand_location handling of binary target inputs. (4148241)
  • Fixed genrule to use the execution platform to determine which cmd* to run. (c64fa6d)
  • Fixed encoding of positive infinity in proto.encode_text. (98e3752)

Aspects​

Aspects allow augmenting build dependency graphs with additional information and actions.

  • Console output now includes target status, even if non-validation aspects are requested. (944b154)
  • Only the visibility of an aspect's implicit dependencies are checked now. (bc1df91)
  • Fixed resolving aspect attributes with the same name as an underlying target attribute. (93ad589)

Platforms and toolchains API​

In Bazel 7.0 the C++, Android, and Apple rules completed their migration to support building with Platforms.

Here are some of the platforms and toolchains related changes which weren't tied to any of those migrations:

  • [6.1.0] --platforms is no longer cleared in transitions when no change is made to --cpu. (5b4de12)
  • Added support for platform to Starlark flags platform mappings. (8a7f5e2)
  • Added the --experimental_exec_config flag, which allows setting a custom transition to be used for cfg = "exec". (23de211, f847e3f)
  • Added the --incompatible_auto_exec_groups flag, which automatically creates exec groups for each toolchain used by a rule. (design doc, 6194956)
  • Added the --incompatible_check_visibility_for_toolchains flag, which applies visibility checking to toolchain implementations. (eecd04f)
  • Added the --use_target_platform_for_tests flag, which uses the target platform for running tests. (d181353)
  • --extra_toolchains precedence is now last-wins, instead of first-wins. (a4576c1)
  • Attributes on platform are now non-configurable. (b8faa69)
  • The platform rule is now non-configurable. (87fb462)
  • Made target_compatible_with work better on alias() targets. (1d2e9c8)
  • Root repository mappings now work in the platform_mappings file. (c0fc433)
  • Target incompatibility is now checked before toolchain resolution. (8482c7c)
  • Subsequent settings of --extra_execution_platforms now override previous settings, instead of adding them to a list. (c602cec)
  • Removed the copy_from_rule attribute from exec_group. (f48412f)
  • Removed the host transition. (c18e6d5)

Misc​

There were a handful of changes that I couldn't find a nice home for in the sections above, but I still felt were important or interesting enough to call attention to:

  • [6.2.0] @foo labels can now be used on the command line as the top-level target. (24f6fe8)
  • [6.3.0] Options specified on the pseudo-command common in .rc files are now ignored by commands that do not support them as long as they are valid options for any Bazel command. (44d3953)
  • [6.3.0] Added the always pseudo-command which has the semantics of pre-6.3.0 common in .rc files. (44d3953)
  • [6.3.0] Credential helpers now apply to repository fetching as well. (9731e69)
  • [6.3.0] Wall-time is now used for credential helper invalidation. (5f77aba)
  • Added the --experimental_include_default_values flag, which includes default values for Starlark flags in the canonicalize-flags command. (33e9bf1)
  • --ui_event_filters now accumulates multiple values. (3d1aeb5)
  • JVM options in the JAVA_TOOL_OPTIONS and JDK_JAVA_OPTIONS environment variables no loner propagate to the Bazel server; use --host_jvm_args instead. (22e3ba5)
  • The repo mapping manifest is now generated when possible, not only when Bzlmod is enabled. (cb55897)

Summary​

As you can see, Bazel 7.0 was another massive release (20% larger than last year!). Thankfully, through the rolling releases process, people were able to test, or even actively depend on, these changes well before the first 7.0 release candidate was cut.

Work on Bazel 8.0 is well underway, and I look forward to summarizing its changes next year. Until then, 👋.

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