[bazel] Output explain file for debugging
NO_IFTTT=No changes needed to //build/bazel/scripts/workspace_utils.py:bazel_build_action
Change-Id: I9792f2ee4bd4b4eaa0afb83effabc0ddd7c4bebd
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1441928
Fuchsia-Auto-Submit: Jay Zhuang <jayzhuang@google.com>
Reviewed-by: David Turner <digit@google.com>
Commit-Queue: Jay Zhuang <jayzhuang@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 51b79e3..a8475ac 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2209,6 +2209,11 @@
# This is only used for debugging.
# - Type: string
#
+# bazel_explain_file
+# - Optional: Path to a file containing the explain output of the Bazel build command.
+# This is only used for debugging.
+# - Type: string
+#
# bazel_compdb_file
# - Optional: Path to a file including JSON compilation database for the
# Bazel targets built by this bazel_action().
diff --git a/build/bazel/bazel_action.gni b/build/bazel/bazel_action.gni
index 816e527..94bb9af 100644
--- a/build/bazel/bazel_action.gni
+++ b/build/bazel/bazel_action.gni
@@ -639,6 +639,17 @@
_bazel_command_file = "${target_out_dir}/${target_name}.bazel_command.sh"
_rebased_bazel_command_file = rebase_path(_bazel_command_file, root_build_dir)
+ # A file that will receive the explain output from the bazel_action.py script.
+ #
+ # The output is from dependency checker in Bazel build's execution phase to
+ # explain, for each build step, either why it is being executed, or that it is
+ # up-to-date.
+ #
+ # NOTE: This file will only include explain output from the `build` command,
+ # not other commands like `query`.
+ _bazel_explain_file = "${target_out_dir}/${target_name}.bazel_explain.txt"
+ _rebased_bazel_explain_file = rebase_path(_bazel_explain_file, root_build_dir)
+
_timings_file = "${target_out_dir}/${target_name}.bazel_action_timings.json"
_rebased_timings_file = rebase_path(_timings_file, root_build_dir)
@@ -688,6 +699,7 @@
outputs = [
_path_mapping,
_bazel_command_file,
+ _bazel_explain_file,
_debug_symbols_manifest,
_rust_project_json,
_timings_file,
@@ -736,6 +748,8 @@
_rebased_bazel_command_file,
"--timings-file",
_rebased_timings_file,
+ "--explain-file",
+ _rebased_bazel_explain_file,
"--path-mapping",
_rebased_path_mapping,
"--debug-symbols-manifest",
@@ -954,6 +968,7 @@
rebase_path(_all_licenses_spdx_file, root_build_dir)
debug_symbols_manifest = _rebased_debug_symbols_manifest
bazel_command_file = _rebased_bazel_command_file
+ bazel_explain_file = _rebased_bazel_explain_file
path_mapping = _rebased_path_mapping
timings_file = _rebased_timings_file
build_events_log_json = _rebased_bazel_build_events_log_json
diff --git a/build/bazel/scripts/bazel_action.py b/build/bazel/scripts/bazel_action.py
index 690a5db..e4457c43 100644
--- a/build/bazel/scripts/bazel_action.py
+++ b/build/bazel/scripts/bazel_action.py
@@ -1301,6 +1301,11 @@
help="If specified, write timings of each step in this script to file.",
)
parser.add_argument(
+ "--explain-file",
+ type=Path,
+ help="If specified, write explain output from Bazel to file.",
+ )
+ parser.add_argument(
"--debug-symbols-manifest",
help="If specified, write debug symbols manifest to file.",
)
@@ -1546,7 +1551,12 @@
command_profile_filename = (
f"{args.gn_target_label[2:].replace(':', '/')}.command.profile.gz"
)
- cmd_args += ["--profile", f"{build_dir}/obj/{command_profile_filename}"]
+ cmd_args += [
+ "--profile",
+ f"{build_dir}/obj/{command_profile_filename}",
+ "--explain",
+ build_dir / args.explain_file,
+ ]
if args.command_file:
write_file_if_changed(
diff --git a/build/bazel/scripts/bazel_action_utils.py b/build/bazel/scripts/bazel_action_utils.py
index 716a15f..299796d 100644
--- a/build/bazel/scripts/bazel_action_utils.py
+++ b/build/bazel/scripts/bazel_action_utils.py
@@ -32,6 +32,7 @@
gn_targets_licenses_spdx: str
debug_symbols_manifest: str
bazel_command_file: str = ""
+ bazel_explain_file: str = ""
bazel_compdb_file: str = ""
bazel_rust_project_json: str = ""
path_mapping: str = ""
