detect when code-generated files are accidentally edited by hand (#480)

Author: graebm

.github/workflows/ci.yml

@@ -189,3 +189,13 @@ jobs:
         # note: using "@main" because "@${{env.BUILDER_VERSION}}" doesn't work
         # https://github.com/actions/runner/issues/480
         uses: awslabs/aws-crt-builder/.github/actions/check-submodules@main
+
+  check-codegen-edits:
+    runs-on: ubuntu-20.04 # latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Check for edits to code-generated files
+        run: |
+          ./utils/check_codegen_edits.py

utils/check_codegen_edits.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+import argparse
+import fnmatch
+import os
+import subprocess
+import sys
+
+CODEGEN_PHRASES = [
+    'This file is generated',
+]
+
+IGNORE_PATTERNS = [
+    'utils/*',  # this script has the phrase in it
+]
+
+ERROR_MSG = """
+ERROR: You have changed code-generated files.
+
+If you edited these files by hand, your changes will be erased when the
+code-generator is run again. An SDK team member MUST update the code-gen
+templates with corresponding changes before merging this Pull Request.
+
+You can ignore this error if you are in fact running the code generator.
+"""
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Detect edits to code-generated files")
+    parser.add_argument('--diff-branch', default='main',
+                        help="Branch/commit to diff against")
+    parser.add_argument('--diff-repo', default='origin',
+                        help="Repository to diff against")
+    args = parser.parse_args()
+
+    # chdir to project root
+    os.chdir(os.path.join(os.path.dirname(__file__), '..'))
+
+    # get all files with diffs
+    git_cmd = ['git', 'diff', '--name-only',
+               f"{args.diff_repo}/{args.diff_branch}"]
+    git_result = subprocess.run(git_cmd, check=True, stdout=subprocess.PIPE)
+    diff_files = git_result.stdout.decode().splitlines()
+
+    # figure out which files were code-generated
+    print('Checking files with diffs...')
+    any_codegen = False
+    for filepath in diff_files:
+        is_codegen = False
+        ignore = any([fnmatch.fnmatch(filepath, pat)
+                     for pat in IGNORE_PATTERNS])
+        if not ignore:
+            with open(filepath) as f:
+                text = f.read()
+                for phrase in CODEGEN_PHRASES:
+                    if phrase in text:
+                        is_codegen = True
+                        any_codegen = True
+                        break
+        if is_codegen:
+            print(f"  ⛔️ GENERATED - {filepath}")
+        elif ignore:
+            print(f"  ✅ ignored   - {filepath}")
+        else:
+            print(f"  ✅ normal    - {filepath}")
+
+    if any_codegen:
+        print(ERROR_MSG)
+        sys.exit(-1)
+    else:
+        print("No code-generated files were changed.")
+
+
+if __name__ == '__main__':
+    main()