[flutter_tools] Set basic error matcher for Linux builds (#71003)

packages/flutter_tools/lib/src/linux/build_linux.dart

@@ -16,6 +16,12 @@ import '../globals.dart' as globals;
 import '../plugins.dart';
 import '../project.dart';
 
+// Matches the following error and warning patterns:
+// - <file path>:<line>:<column>: error: <error...>
+// - <file path>:<line>:<column>: warning: <warning...>
+// - clang: error: <link error...>
+final RegExp errorMatcher = RegExp(r'(?:.*:\d+:\d+|clang):\s?(?:error|warning):\s.*', caseSensitive: false);
+
 /// Builds the Linux project through the Makefile.
 Future<void> buildLinux(
   LinuxProject linuxProject,
@@ -130,6 +136,7 @@ Future<void> _runBuild(Directory buildDir) async {
           'VERBOSE_SCRIPT_LOGGING': 'true'
       },
       trace: true,
+      stdoutErrorMatcher: errorMatcher,
     );
   } on ArgumentError {
     throwToolExit("ninja not found. Run 'flutter doctor' for more information.");

packages/flutter_tools/test/commands.shard/hermetic/build_linux_test.dart

@@ -209,6 +209,55 @@ void main() {
     FeatureFlags: () => TestFeatureFlags(isLinuxEnabled: true),
   });
 
+  testUsingContext('Linux build extracts errors from stdout', () async {
+    final BuildCommand command = BuildCommand();
+    setUpMockProjectFilesForBuild();
+
+    // This contains a mix of routine build output and various types of errors
+    // (Dart error, compile error, link error), edited down for compactness.
+    const String stdout = r'''
+ninja: Entering directory `build/linux/release'
+[1/6] Generating /foo/linux/flutter/ephemeral/libflutter_linux_gtk.so, /foo/linux/flutter/ephemeral/flutter_linux/flutter_linux.h, _phony
+lib/main.dart:4:3: Error: Method not found: 'foo'.
+[2/6] Building CXX object CMakeFiles/foo.dir/main.cc.o
+/foo/linux/main.cc:6:2: error: expected ';' after class
+/foo/linux/main.cc:9:7: warning: unused variable 'unused_variable' [-Wunused-variable]
+/foo/linux/main.cc:10:3: error: unknown type name 'UnknownType'
+/foo/linux/main.cc:12:7: error: 'bar' is a private member of 'Foo'
+[3/6] Building CXX object CMakeFiles/foo_bar.dir/flutter/generated_plugin_registrant.cc.o
+[4/6] Building CXX object CMakeFiles/foo_bar.dir/my_application.cc.o
+[5/6] Linking CXX executable intermediates_do_not_run/foo_bar
+main.cc:(.text+0x13): undefined reference to `Foo::bar()'
+clang: error: linker command failed with exit code 1 (use -v to see invocation)
+ninja: build stopped: subcommand failed.
+''';
+
+    processManager = FakeProcessManager.list(<FakeCommand>[
+      cmakeCommand('release'),
+      ninjaCommand('release',
+        stdout: stdout,
+      ),
+    ]);
+
+    await createTestCommandRunner(command).run(
+      const <String>['build', 'linux', '--no-pub']
+    );
+    // Just the warnings and errors should be surfaced.
+    expect(testLogger.errorText, r'''
+lib/main.dart:4:3: Error: Method not found: 'foo'.
+/foo/linux/main.cc:6:2: error: expected ';' after class
+/foo/linux/main.cc:9:7: warning: unused variable 'unused_variable' [-Wunused-variable]
+/foo/linux/main.cc:10:3: error: unknown type name 'UnknownType'
+/foo/linux/main.cc:12:7: error: 'bar' is a private member of 'Foo'
+clang: error: linker command failed with exit code 1 (use -v to see invocation)
+''');
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fileSystem,
+    ProcessManager: () => processManager,
+    Platform: () => linuxPlatform,
+    FeatureFlags: () => TestFeatureFlags(isLinuxEnabled: true),
+  });
+
   testUsingContext('Linux verbose build sets VERBOSE_SCRIPT_LOGGING', () async {
     final BuildCommand command = BuildCommand();
     setUpMockProjectFilesForBuild();