1 files changed, 119 insertions, 0 deletions
diff --git a/scripts/coverage/compare_gcov_json.py b/scripts/coverage/compare_gcov_json.py
new file mode 100755
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+++ b/scripts/coverage/compare_gcov_json.py
@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+#
+# Compare output of two gcovr JSON reports and report differences. To
+# generate the required output first:
+#   - create two build dirs with --enable-gcov
+#   - run set of tests in each
+#   - run make coverage-html in each
+#   - run gcovr --json --exclude-unreachable-branches \
+#           --print-summary -o coverage.json --root ../../ . *.p
+#
+# Author: Alex Bennée <alex.bennee@linaro.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+
+import argparse
+import json
+import sys
+from pathlib import Path
+
+def create_parser():
+    parser = argparse.ArgumentParser(
+        prog='compare_gcov_json',
+        description='analyse the differences in coverage between two runs')
+
+    parser.add_argument('-a', type=Path, default=None,
+                        help=('First file to check'))
+
+    parser.add_argument('-b', type=Path, default=None,
+                        help=('Second file to check'))
+
+    parser.add_argument('--verbose', action='store_true', default=False,
+                        help=('A minimal verbosity level that prints the '
+                              'overall result of the check/wait'))
+    return parser
+
+
+# See https://gcovr.com/en/stable/output/json.html#json-format-reference
+def load_json(json_file_path: Path, verbose = False) -> dict[str, set[int]]:
+
+    with open(json_file_path) as f:
+        data = json.load(f)
+
+    root_dir = json_file_path.absolute().parent
+    covered_lines = dict()
+
+    for filecov in data["files"]:
+        file_path = Path(filecov["file"])
+
+        # account for generated files - map into src tree
+        resolved_path = Path(file_path).absolute()
+        if resolved_path.is_relative_to(root_dir):
+            file_path = resolved_path.relative_to(root_dir)
+            # print(f"remapped {resolved_path} to {file_path}")
+
+        lines = filecov["lines"]
+
+        executed_lines = set(
+            linecov["line_number"]
+            for linecov in filecov["lines"]
+            if linecov["count"] != 0 and not linecov["gcovr/noncode"]
+        )
+
+        # if this file has any coverage add it to the system
+        if len(executed_lines) > 0:
+            if verbose:
+                print(f"file {file_path} {len(executed_lines)}/{len(lines)}")
+            covered_lines[str(file_path)] = executed_lines
+
+    return covered_lines
+
+def find_missing_files(first, second):
+    """
+    Return a list of files not covered in the second set
+    """
+    missing_files = []
+    for f in sorted(first):
+        file_a = first[f]
+        try:
+            file_b = second[f]
+        except KeyError:
+            missing_files.append(f)
+
+    return missing_files
+
+def main():
+    """
+    Script entry point
+    """
+    parser = create_parser()
+    args = parser.parse_args()
+
+    if not args.a or not args.b:
+        print("We need two files to compare")
+        sys.exit(1)
+
+    first_coverage = load_json(args.a, args.verbose)
+    second_coverage = load_json(args.b, args.verbose)
+
+    first_missing = find_missing_files(first_coverage,
+                                       second_coverage)
+
+    second_missing = find_missing_files(second_coverage,
+                                        first_coverage)
+
+    a_name = args.a.parent.name
+    b_name = args.b.parent.name
+
+    print(f"{b_name} missing coverage in {len(first_missing)} files")
+    for f in first_missing:
+        print(f"  {f}")
+
+    print(f"{a_name} missing coverage in {len(second_missing)} files")
+    for f in second_missing:
+        print(f"  {f}")
+
+
+if __name__ == '__main__':
+    main()