[ios][tools] do not print out bonjour key not found in non-verbose mode (#174001)

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This tries https://github.com/flutter/flutter/pull/173569 again

That PR was reverted, because I didn't know that `streamOutput` was the
one used during non-verbose mode

The logging logic is a bit convoluted, see:
https://github.com/flutter/flutter/issues/173887


So this PR simply changes the condition from

```
if (!verbose && exitCode == 0)
```

To 

```
if (!verbose && exitCode == 0 && !skipErrorLog)
```

So that if we skipErrorLog (will be true for bonjour features), it
doesn't call `streamOutput`.

*List which issues are fixed by this PR. You must list at least one
issue. An issue is not required if the PR fixes something trivial like a
typo.*

Fixes https://github.com/flutter/flutter/issues/172627

*If you had to change anything in the [flutter/tests] repo, include a
link to the migration guide as per the [breaking change policy].*

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packages/flutter_tools/bin/xcode_backend.dart

@@ -102,7 +102,14 @@ class Context {
 
   Directory directoryFromPath(String path) => Directory(path);
 
-  /// Run given command in a synchronous subprocess.
+  /// Run given command ([bin]) in a synchronous subprocess.
+  ///
+  /// If [allowFail] is true, an exception will not be thrown even if the process returns a
+  /// non-zero exit code. Also, `error:` will not be prefixed to the output to prevent Xcode
+  /// complication failures.
+  ///
+  /// If [skipErrorLog] is true, `stderr` from the process will not be output unless in [verbose]
+  /// mode. If in [verbose], pipes `stderr` to `stdout`.
   ///
   /// Will throw [Exception] if the exit code is not 0.
   ProcessResult runSync(
@@ -110,6 +117,7 @@ class Context {
     List<String> args, {
     bool verbose = false,
     bool allowFail = false,
+    bool skipErrorLog = false,
     String? workingDirectory,
   }) {
     if (verbose) {
@@ -122,22 +130,29 @@ class Context {
     final String resultStderr = result.stderr.toString().trim();
     if (resultStderr.isNotEmpty) {
       final errorOutput = StringBuffer();
-      // If allowFail, do not fail Xcode build. An example is on macOS 26,
-      // plutil reports NSBonjourServices key not found via stderr (rather than
-      // stdout on older macOS), and it should not cause compile failure.
       if (!allowFail && result.exitCode != 0) {
         // "error:" prefix makes this show up as an Xcode compilation error.
         errorOutput.write('error: ');
       }
       errorOutput.write(resultStderr);
-      echoError(errorOutput.toString());
-
+      if (skipErrorLog) {
+        // Even if skipErrorLog, we still want to write to stdout if verbose.
+        if (verbose) {
+          echo(errorOutput.toString());
+        }
+      } else {
+        echoError(errorOutput.toString());
+      }
       // Stream stderr to the Flutter build process.
       // When in verbose mode, `echoError` above will show the logs. So only
       // stream if not in verbose mode to avoid duplicate logs.
       // Also, only stream if exitCode is 0 since errors are handled separately
       // by the tool on failure.
-      if (!verbose && exitCode == 0) {
+      // Also check for `skipErrorLog`, because some errors should not be printed
+      // out. For example, on macOS 26, plutil reports NSBonjourServices key not
+      // found as an error. However, logging it in non-verbose mode would be
+      // confusing, since not having the key is one of the expected states.
+      if (!verbose && exitCode == 0 && !skipErrorLog) {
         streamOutput(errorOutput.toString());
       }
     }
@@ -424,16 +439,17 @@ class Context {
       return;
     }
 
+    final bool verbose = (environment['VERBOSE_SCRIPT_LOGGING'] ?? '').isNotEmpty;
+
     // If there are already NSBonjourServices specified by the app (uncommon),
     // insert the vmService service name to the existing list.
-    ProcessResult result = runSync('plutil', <String>[
-      '-extract',
-      'NSBonjourServices',
-      'xml1',
-      '-o',
-      '-',
-      builtProductsPlist,
-    ], allowFail: true);
+    ProcessResult result = runSync(
+      'plutil',
+      <String>['-extract', 'NSBonjourServices', 'xml1', '-o', '-', builtProductsPlist],
+      verbose: verbose,
+      allowFail: true,
+      skipErrorLog: true,
+    );
     if (result.exitCode == 0) {
       runSync('plutil', <String>[
         '-insert',
@@ -458,14 +474,13 @@ class Context {
     // specified (uncommon). This text will appear below the "Your app would
     // like to find and connect to devices on your local network" permissions
     // popup.
-    result = runSync('plutil', <String>[
-      '-extract',
-      'NSLocalNetworkUsageDescription',
-      'xml1',
-      '-o',
-      '-',
-      builtProductsPlist,
-    ], allowFail: true);
+    result = runSync(
+      'plutil',
+      <String>['-extract', 'NSLocalNetworkUsageDescription', 'xml1', '-o', '-', builtProductsPlist],
+      verbose: verbose,
+      allowFail: true,
+      skipErrorLog: true,
+    );
     if (result.exitCode != 0) {
       runSync('plutil', <String>[
         '-insert',

packages/flutter_tools/test/general.shard/xcode_backend_test.dart

@@ -390,123 +390,153 @@ void main() {
       );
     });
 
-    test('Missing NSBonjourServices key in Info.plist should not fail Xcode compilation', () {
-      final Directory buildDir = fileSystem.directory('/path/to/builds')
-        ..createSync(recursive: true);
-      final File infoPlist = buildDir.childFile('Info.plist')..createSync();
-      final context = TestContext(
-        <String>['test_vm_service_bonjour_service'],
-        <String, String>{
-          'CONFIGURATION': 'Debug',
-          'BUILT_PRODUCTS_DIR': buildDir.path,
-          'INFOPLIST_PATH': 'Info.plist',
-        },
-        commands: <FakeCommand>[
-          FakeCommand(
-            command: <String>[
-              'plutil',
-              '-extract',
-              'NSBonjourServices',
-              'xml1',
-              '-o',
-              '-',
-              infoPlist.path,
+    for (final verbose in <bool>[true, false]) {
+      test(
+        'Missing NSBonjourServices key in Info.plist should not fail Xcode compilation under ${verbose ? 'verbose' : 'non-verbose'} mode',
+        () {
+          final Directory buildDir = fileSystem.directory('/path/to/builds')
+            ..createSync(recursive: true);
+          final File infoPlist = buildDir.childFile('Info.plist')..createSync();
+          const plutilErrorMessage =
+              'Could not extract value, error: No value at that key path or invalid key path: NSBonjourServices';
+          final File pipe = fileSystem.file('/tmp/pipe')..createSync(recursive: true);
+          final context = TestContext(
+            <String>['test_vm_service_bonjour_service'],
+            <String, String>{
+              'CONFIGURATION': 'Debug',
+              'BUILT_PRODUCTS_DIR': buildDir.path,
+              'INFOPLIST_PATH': 'Info.plist',
+              if (verbose) 'VERBOSE_SCRIPT_LOGGING': 'YES',
+            },
+            commands: <FakeCommand>[
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-extract',
+                  'NSBonjourServices',
+                  'xml1',
+                  '-o',
+                  '-',
+                  infoPlist.path,
+                ],
+                exitCode: 1,
+                stderr: plutilErrorMessage,
+              ),
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-insert',
+                  'NSBonjourServices',
+                  '-json',
+                  '["_dartVmService._tcp"]',
+                  infoPlist.path,
+                ],
+              ),
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-extract',
+                  'NSLocalNetworkUsageDescription',
+                  'xml1',
+                  '-o',
+                  '-',
+                  infoPlist.path,
+                ],
+              ),
             ],
-            exitCode: 1,
-            stderr: 'No value at that key path or invalid key path: NSBonjourServices',
-          ),
-          FakeCommand(
-            command: <String>[
-              'plutil',
-              '-insert',
-              'NSBonjourServices',
-              '-json',
-              '["_dartVmService._tcp"]',
-              infoPlist.path,
-            ],
-          ),
-          FakeCommand(
-            command: <String>[
-              'plutil',
-              '-extract',
-              'NSLocalNetworkUsageDescription',
-              'xml1',
-              '-o',
-              '-',
-              infoPlist.path,
-            ],
-          ),
-        ],
-        fileSystem: fileSystem,
-      )..run();
-      expect(context.stderr, isNot(contains('error: ')));
-    });
+            fileSystem: fileSystem,
+            scriptOutputStreamFile: pipe,
+          )..run();
 
-    test(
-      'Missing NSLocalNetworkUsageDescription in Info.plist should not fail Xcode compilation',
-      () {
-        final Directory buildDir = fileSystem.directory('/path/to/builds')
-          ..createSync(recursive: true);
-        final File infoPlist = buildDir.childFile('Info.plist')..createSync();
-        final context = TestContext(
-          <String>['test_vm_service_bonjour_service'],
-          <String, String>{
-            'CONFIGURATION': 'Debug',
-            'BUILT_PRODUCTS_DIR': buildDir.path,
-            'INFOPLIST_PATH': 'Info.plist',
-          },
-          commands: <FakeCommand>[
-            FakeCommand(
-              command: <String>[
-                'plutil',
-                '-extract',
-                'NSBonjourServices',
-                'xml1',
-                '-o',
-                '-',
-                infoPlist.path,
-              ],
-            ),
-            FakeCommand(
-              command: <String>[
-                'plutil',
-                '-insert',
-                'NSBonjourServices.0',
-                '-string',
-                '_dartVmService._tcp',
-                infoPlist.path,
-              ],
-            ),
-            FakeCommand(
-              command: <String>[
-                'plutil',
-                '-extract',
-                'NSLocalNetworkUsageDescription',
-                'xml1',
-                '-o',
-                '-',
-                infoPlist.path,
-              ],
-              exitCode: 1,
-              stderr:
-                  'No value at that key path or invalid key path: NSLocalNetworkUsageDescription',
-            ),
-            FakeCommand(
-              command: <String>[
-                'plutil',
-                '-insert',
-                'NSLocalNetworkUsageDescription',
-                '-string',
-                'Allow Flutter tools on your computer to connect and debug your application. This prompt will not appear on release builds.',
-                infoPlist.path,
-              ],
-            ),
-          ],
-          fileSystem: fileSystem,
-        )..run();
-        expect(context.stderr, isNot(contains('error: ')));
-      },
-    );
+          expect(context.stderr, isNot(startsWith('error: ')));
+          expect(pipe.readAsStringSync(), isNot(contains(plutilErrorMessage)));
+          expect(context.stderr, isNot(contains(plutilErrorMessage)));
+          if (verbose) {
+            expect(context.stdout, contains(plutilErrorMessage));
+          } else {
+            expect(context.stdout, isNot(contains(plutilErrorMessage)));
+          }
+        },
+      );
+
+      test(
+        'Missing NSLocalNetworkUsageDescription in Info.plist should not fail Xcode compilation under ${verbose ? 'verbose' : 'non-verbose'} mode',
+        () {
+          final Directory buildDir = fileSystem.directory('/path/to/builds')
+            ..createSync(recursive: true);
+          final File infoPlist = buildDir.childFile('Info.plist')..createSync();
+          const plutilErrorMessage =
+              'Could not extract value, error: No value at that key path or invalid key path: NSLocalNetworkUsageDescription';
+          final File pipe = fileSystem.file('/tmp/pipe')..createSync(recursive: true);
+          final context = TestContext(
+            <String>['test_vm_service_bonjour_service'],
+            <String, String>{
+              'CONFIGURATION': 'Debug',
+              'BUILT_PRODUCTS_DIR': buildDir.path,
+              'INFOPLIST_PATH': 'Info.plist',
+              if (verbose) 'VERBOSE_SCRIPT_LOGGING': 'YES',
+            },
+            commands: <FakeCommand>[
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-extract',
+                  'NSBonjourServices',
+                  'xml1',
+                  '-o',
+                  '-',
+                  infoPlist.path,
+                ],
+              ),
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-insert',
+                  'NSBonjourServices.0',
+                  '-string',
+                  '_dartVmService._tcp',
+                  infoPlist.path,
+                ],
+              ),
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-extract',
+                  'NSLocalNetworkUsageDescription',
+                  'xml1',
+                  '-o',
+                  '-',
+                  infoPlist.path,
+                ],
+                exitCode: 1,
+                stderr: plutilErrorMessage,
+              ),
+              FakeCommand(
+                command: <String>[
+                  'plutil',
+                  '-insert',
+                  'NSLocalNetworkUsageDescription',
+                  '-string',
+                  'Allow Flutter tools on your computer to connect and debug your application. This prompt will not appear on release builds.',
+                  infoPlist.path,
+                ],
+              ),
+            ],
+            fileSystem: fileSystem,
+            scriptOutputStreamFile: pipe,
+          )..run();
+
+          expect(context.stderr, isNot(startsWith('error: ')));
+          expect(pipe.readAsString(), isNot(contains(plutilErrorMessage)));
+          expect(context.stderr, isNot(contains(plutilErrorMessage)));
+          if (verbose) {
+            expect(context.stdout, contains(plutilErrorMessage));
+          } else {
+            expect(context.stdout, isNot(contains(plutilErrorMessage)));
+          }
+        },
+      );
+    }
   });
 
   for (final platform in platforms) {

packages/flutter_tools/test/integration.shard/xcode_backend_test.dart

@@ -132,27 +132,47 @@ void main() {
     });
 
     for (final buildConfiguration in <String>['Debug', 'Profile']) {
-      test('add keys in $buildConfiguration', () async {
-        infoPlist.writeAsStringSync(emptyPlist);
+      for (final verbose in <bool>[true, false]) {
+        test(
+          'add keys in $buildConfiguration under ${verbose ? 'verbose' : 'non-verbose'} mode',
+          () async {
+            infoPlist.writeAsStringSync(emptyPlist);
+            final File pipe = fileSystem.file('/tmp/pipe')..createSync(recursive: true);
 
-        final ProcessResult result = await Process.run(
-          xcodeBackendPath,
-          <String>['test_vm_service_bonjour_service'],
-          environment: <String, String>{
-            'CONFIGURATION': buildConfiguration,
-            'BUILT_PRODUCTS_DIR': buildDirectory.path,
-            'INFOPLIST_PATH': 'Info.plist',
+            final ProcessResult result = await Process.run(
+              xcodeBackendPath,
+              <String>['test_vm_service_bonjour_service'],
+              environment: <String, String>{
+                'CONFIGURATION': buildConfiguration,
+                'BUILT_PRODUCTS_DIR': buildDirectory.path,
+                'INFOPLIST_PATH': 'Info.plist',
+                if (verbose) 'VERBOSE_SCRIPT_LOGGING': 'YES',
+                'SCRIPT_OUTPUT_STREAM_FILE': pipe.path,
+              },
+            );
+
+            final String actualInfoPlist = infoPlist.readAsStringSync();
+            expect(actualInfoPlist, contains('NSBonjourServices'));
+            expect(actualInfoPlist, contains('dartVmService'));
+            expect(actualInfoPlist, contains('NSLocalNetworkUsageDescription'));
+
+            // Make sure no Xcode compilation error.
+            expect(result.stderr, isNot(startsWith('error:')));
+
+            const plutilErrorMessage =
+                'Could not extract value, error: No value at that key path or invalid key path: NSBonjourServices';
+            expect(pipe.readAsStringSync(), isNot(contains(plutilErrorMessage)));
+            expect(result.stderr, isNot(contains(plutilErrorMessage)));
+            if (verbose) {
+              expect(result.stdout, contains(plutilErrorMessage));
+            } else {
+              expect(result.stdout, isNot(contains(plutilErrorMessage)));
+            }
+
+            expect(result, const ProcessResultMatcher());
           },
         );
-
-        final String actualInfoPlist = infoPlist.readAsStringSync();
-        expect(actualInfoPlist, contains('NSBonjourServices'));
-        expect(actualInfoPlist, contains('dartVmService'));
-        expect(actualInfoPlist, contains('NSLocalNetworkUsageDescription'));
-
-        expect(result.stderr, isNot(startsWith('error:')));
-        expect(result, const ProcessResultMatcher());
-      });
+      }
     }
 
     test(