Fix flutter tool to actually honor --build-number/--build-name flags. (#25520)

packages/flutter_tools/lib/src/android/gradle.dart

@@ -231,7 +231,11 @@ void updateLocalProperties({
 
   void changeIfNecessary(String key, String value) {
     if (settings.values[key] != value) {
-      settings.values[key] = value;
+      if (value == null) {
+        settings.values.remove(key);
+      } else {
+        settings.values[key] = value;
+      }
       changed = true;
     }
   }
@@ -240,15 +244,16 @@ void updateLocalProperties({
 
   if (androidSdk != null)
     changeIfNecessary('sdk.dir', escapePath(androidSdk.directory));
+
   changeIfNecessary('flutter.sdk', escapePath(Cache.flutterRoot));
-  if (buildInfo != null)
+
+  if (buildInfo != null) {
     changeIfNecessary('flutter.buildMode', buildInfo.modeName);
-  final String buildName = buildInfo?.buildName ?? manifest.buildName;
-  if (buildName != null)
+    final String buildName = buildInfo.buildName ?? manifest.buildName;
     changeIfNecessary('flutter.versionName', buildName);
-  final int buildNumber = buildInfo?.buildNumber ?? manifest.buildNumber;
-  if (buildNumber != null)
-    changeIfNecessary('flutter.versionCode', '$buildNumber');
+    final int buildNumber = buildInfo.buildNumber ?? manifest.buildNumber;
+    changeIfNecessary('flutter.versionCode', buildNumber?.toString());
+  }
 
   if (changed)
     settings.writeContents(localProperties);

packages/flutter_tools/test/android/gradle_test.dart

@@ -325,6 +325,48 @@ flutter:
         expectedBuildNumber: '3',
       );
     });
+
+    testUsingAndroidContext('allow build info to unset build name and number', () async {
+      const String manifest = '''
+name: test
+dependencies:
+  flutter:
+    sdk: flutter
+flutter:
+''';
+      await checkBuildVersion(
+        manifest: manifest,
+        buildInfo: const BuildInfo(BuildMode.release, null, buildName: null, buildNumber: null),
+        expectedBuildName: null,
+        expectedBuildNumber: null,
+      );
+      await checkBuildVersion(
+        manifest: manifest,
+        buildInfo: const BuildInfo(BuildMode.release, null, buildName: '1.0.2', buildNumber: 3),
+        expectedBuildName: '1.0.2',
+        expectedBuildNumber: '3',
+      );
+      await checkBuildVersion(
+        manifest: manifest,
+        buildInfo: const BuildInfo(BuildMode.release, null, buildName: '1.0.3', buildNumber: 4),
+        expectedBuildName: '1.0.3',
+        expectedBuildNumber: '4',
+      );
+      // Values don't get unset.
+      await checkBuildVersion(
+        manifest: manifest,
+        buildInfo: null,
+        expectedBuildName: '1.0.3',
+        expectedBuildNumber: '4',
+      );
+      // Values get unset.
+      await checkBuildVersion(
+        manifest: manifest,
+        buildInfo: const BuildInfo(BuildMode.release, null, buildName: null, buildNumber: null),
+        expectedBuildName: null,
+        expectedBuildNumber: null,
+      );
+    });
   });
 }