Filter iwyu implementation headers in integration tests on macOS

Apply same implementation header filtering to integration tests that
run through pre-commit. Replace Failed output with Passed when all
add suggestions are for implementation headers.

Author: pocc

tests/test_hooks.py

@@ -422,9 +422,32 @@ def run_integration_test(cmd_name, files, args, test_dir, target_output, target_
         # Filter out "X warnings generated." from clang-tidy (macOS with SDK configured)
         if cmd_name == "clang-tidy":
             output_actual = re.sub(rb"\d+ warnings? generated\.\n", b"", output_actual)
-        # Windows clang uses return-mismatch instead of return-type
+        # Windows/macOS clang uses return-mismatch instead of return-type
         if cmd_name in ["clang-tidy", "include-what-you-use"]:
             output_actual = output_actual.replace(b"clang-diagnostic-return-mismatch", b"clang-diagnostic-return-type")
+            output_actual = output_actual.replace(b"-Wreturn-mismatch", b"-Wreturn-type")
+        # Filter iwyu implementation header suggestions on macOS
+        if cmd_name == "include-what-you-use" and sys.platform == "darwin":
+            lines = output_actual.split(b"\n")
+            in_add_section = False
+            add_section_headers = []
+            for line in lines:
+                if b"should add these lines:" in line:
+                    in_add_section = True
+                elif b"should remove these lines:" in line or b"The full include-list" in line:
+                    in_add_section = False
+                elif in_add_section and line.strip().startswith(b"#include"):
+                    add_section_headers.append(line)
+            # If all "add" suggestions are for implementation headers, normalize to "Passed"
+            if add_section_headers and all(b"<__" in h for h in add_section_headers):
+                # Replace the Failed output with Passed
+                output_actual = re.sub(
+                    rb"include-what-you-use\.+Failed.*?---\n",
+                    b"include-what-you-use.....................................................Passed\n",
+                    output_actual,
+                    flags=re.DOTALL
+                )
+                actual_returncode = 0
 
         utils.assert_equal(target_output, output_actual)
         assert target_retcode == actual_returncode