Adjust ordering of EXTRA-ARGS to allow tests to override includes (#5870)

Author: jonmeow

testing/file_test/README.md

@@ -217,6 +217,8 @@ Supported comment markers are:
 
     -   `// ARGS`
     -   `// EXTRA-ARGS`
+        -   Included `EXTRA-ARGS` will come before `EXTRA-ARGS` in the main test
+            file.
     -   `// INCLUDE-FILE`
     -   `// --- <filename>`
 

testing/file_test/test_file.cpp

@@ -797,10 +797,14 @@ auto ProcessTestFile(llvm::StringRef test_name, bool running_autoupdate)
   // (recursively).
   llvm::SmallVector<std::string> include_files;
 
+  // Store the main file's `EXTRA-ARGS` so that they can be put after any that
+  // come from `INCLUDE-FILE`.
+  llvm::SmallVector<std::string> main_extra_args;
+
   // Process the main file.
   CARBON_RETURN_IF_ERROR(ProcessFileContent(
       test_name, test_file.input_content, running_autoupdate, &test_file,
-      &found_autoupdate, test_file.test_args, test_file.extra_args,
+      &found_autoupdate, test_file.test_args, main_extra_args,
       test_file.file_splits, include_files));
 
   if (!found_autoupdate) {
@@ -859,6 +863,9 @@ auto ProcessTestFile(llvm::StringRef test_name, bool running_autoupdate)
     }
   }
 
+  // Copy over `EXTRA-ARGS` from the main file (after includes).
+  test_file.extra_args.append(main_extra_args);
+
   return std::move(test_file);
 }
 

testing/file_test/testdata/include_extra_args.carbon

@@ -11,4 +11,4 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //testing/file_test:file_test_base_test -- --dump_output --file_tests=testing/file_test/testdata/include_extra_args.carbon
 
-// CHECK:STDOUT: 6 args: `default_args`, `include_extra_args.carbon`, `include_files/extra_args.carbon`, `foo`, `bar`, `baz`
+// CHECK:STDOUT: 6 args: `default_args`, `include_extra_args.carbon`, `include_files/extra_args.carbon`, `bar`, `baz`, `foo`