pw_bloat: Build and run pw bloat CLI command in Bazel

Defines the pw_bloat Python code as a Bazel library target and adds a
runnable Bazel binary which invokes the equivalent of the `pw bloat`
command.

Usable as

  bazel run //pw_bloat/py:bloat -- /abs/path/to/binary.elf

Tested: The above command works from both outside and within an
activated Pigweed environment, and `pw bloat` continues to function
within a Pigweed environment.

Change-Id: I79fb799e9be184f4f7d0da2865f0cf388cf9b615
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/215456
Lint: Lint 🤖 <[email protected]>
Presubmit-Verified: CQ Bot Account <[email protected]>
Reviewed-by: Armando Montanez <[email protected]>
Commit-Queue: Alexei Frolov <[email protected]>

WORKSPACE

@@ -66,6 +66,15 @@ cipd_repository(
     tag = "version:pw_transfer_test_binaries_528098d588f307881af83f769207b8e6e1b57520-linux-amd64-cipd.cipd",
 )
 
+# Set up bloaty size profiler.
+# Required by: pigweed.
+# Used in modules: //pw_bloat.
+cipd_repository(
+    name = "bloaty",
+    path = "fuchsia/third_party/bloaty/${os}-amd64",
+    tag = "git_revision:c057ba4f43db0506d4ba8c096925b054b02a8bd3",
+)
+
 # Set up Starlark library.
 # Required by: io_bazel_rules_go, com_google_protobuf, rules_python
 # Used in modules: None.

pw_bloat/py/BUILD.bazel

@@ -0,0 +1,45 @@
+# Copyright 2024 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+load("@rules_python//python:defs.bzl", "py_binary", "py_library")
+load("//pw_build:selects.bzl", "TARGET_COMPATIBLE_WITH_HOST_SELECT")
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+py_library(
+    name = "pw_bloat",
+    srcs = [
+        "pw_bloat/bloat.py",
+        "pw_bloat/bloaty_config.py",
+        "pw_bloat/label.py",
+        "pw_bloat/label_output.py",
+    ],
+    data = ["@bloaty//:all"],
+    imports = ["."],
+    deps = [
+        "@pigweed//pw_cli/py:pw_cli",
+        "@python_packages_pyelftools//:pkg",
+        "@rules_python//python/runfiles",
+    ],
+)
+
+py_binary(
+    name = "bloat",
+    srcs = ["pw_bloat/__main__.py"],
+    main = "pw_bloat/__main__.py",
+    target_compatible_with = select(TARGET_COMPATIBLE_WITH_HOST_SELECT),
+    deps = [":pw_bloat"],
+)

pw_bloat/py/pw_bloat/bloat.py

@@ -100,8 +100,18 @@ def run_bloaty(
         subprocess.CalledProcessError: The Bloaty invocation failed.
     """
 
-    default_bloaty = 'bloaty'
-    bloaty_path = os.getenv('BLOATY_PATH', default_bloaty)
+    try:
+        # If running from within a Bazel context, find the Bloaty executable
+        # within the project's runfiles.
+        # pylint: disable=import-outside-toplevel
+        from rules_python.python.runfiles import runfiles  # type: ignore
+
+        r = runfiles.Create()
+        bloaty_path = r.Rlocation("bloaty/bloaty")
+    except ImportError:
+        # Outside of Bazel, use Bloaty from the system path.
+        default_bloaty = 'bloaty'
+        bloaty_path = os.getenv('BLOATY_PATH', default_bloaty)
 
     cmd = [
         bloaty_path,