firmware_builder: add --code-coverage option

Added an option flag --code-coverage that will skip the build for EC
hardware targets and build the tests with code coverage enabled.

BUG=b:156895937
BRANCH=None
TEST=Run firmware_builder.py with --code-coverage option. The 'build'
command will do nothing, and the 'test' command will build the host-
based unit test with code coverage.

Signed-off-by: Paul Fagerburg <pfagerburg@google.com>
Change-Id: Ie3786f574e490a5ba6806e518401842bda609e5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2678937
Tested-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: LaMont Jones <lamontjones@chromium.org>
Commit-Queue: Paul Fagerburg <pfagerburg@chromium.org>

1 files changed, 28 insertions, 3 deletions

diff --git a/firmware_builder.py b/firmware_builder.py
index 243534230a..fc8aa29262 100755
--- a/firmware_builder.py
+++ b/firmware_builder.py
@@ -24,7 +24,19 @@ DEFAULT_BUNDLE_METADATA_FILE = '/tmp/artifact_bundle_metadata'
 
 
 def build(opts):
-    """Builds all EC firmware targets"""
+    """Builds all EC firmware targets
+
+    Note that when we are building unit tests for code coverage, we don't
+    need this step. It builds EC **firmware** targets, but unit tests with
+    code coverage are all host-based. So if the --code-coverage flag is set,
+    we don't need to build the firmware targets and we can return without
+    doing anything but giving an informational message.
+    """
+    if opts.code_coverage:
+        print("When --code-coverage is selected, 'build' is a no-op. "
+            "Run 'test' with --code-coverage instead.")
+        return
+
     # TODO(b/169178847): Add appropriate metric information
     metrics = firmware_pb2.FwBuildMetricList()
     with open(opts.metrics, 'w') as f:
@@ -64,8 +76,14 @@ def test(opts):
     with open(opts.metrics, 'w') as f:
         f.write(json_format.MessageToJson(metrics))
 
-    # Verify all posix-based unit tests build and pass
-    subprocess.run(['make', 'runtests', '-j{}'.format(opts.cpus)],
+    # If building for code coverage, build the 'coverage' target, which
+    # builds the posix-based unit tests for code coverage and assembles
+    # the LCOV information.
+    #
+    # Otherwise, build the 'runtests' target, which verifies all
+    # posix-based unit tests build and pass.
+    target = 'coverage' if opts.code_coverage else 'runtests'
+    subprocess.run(['make', target, '-j{}'.format(opts.cpus)],
                    cwd=os.path.dirname(__file__),
                    check=True)
 
@@ -125,6 +143,13 @@ def parse_args(args):
         'Full pathanme for the directory in which to bundle build artifacts.',
     )
 
+    parser.add_argument(
+        '--code-coverage',
+        required=False,
+        action='store_true',
+        help='Build host-based unit tests for code coverage.',
+    )
+
     # Would make this required=True, but not available until 3.7
     sub_cmds = parser.add_subparsers()