fix: Report a warning on manifest_version 3 extensions targeting Firefox for Android

docs/index.html

@@ -605,6 +605,11 @@ <h2 id="web-extensions-%2F-manifest.json" tabindex="-1">Web Extensions / manifes
 <td>error</td>
 <td>The version string is not valid because its format is too complex.</td>
 </tr>
+<tr>
+<td><code>MANIFEST_V3_FIREFOX_ANDROID_LIMITATIONS</code></td>
+<td>warning</td>
+<td>The extension is marked as compatible with a Firefox for Android version that doesn't fully support Manifest Version 3</td>
+</tr>
 </tbody>
 </table>
 <h3 id="static-theme-%2F-manifest.json" tabindex="-1">Static Theme / manifest.json <a class="header-anchor" href="#static-theme-%2F-manifest.json">¶</a></h3>

docs/rules.md

@@ -141,6 +141,7 @@ Rules are sorted by severity.
 | `APPLICATIONS_INVALID`                                  | error    | The `applications` property is no longer accepted in Manifest Version 3 and above.                                                                                                 |
 | `VERSION_FORMAT_DEPRECATED`                             | warning  | The version string should be simplified.                                                                                                                                           |
 | `VERSION_FORMAT_INVALID`                                | error    | The version string is not valid because its format is too complex.                                                                                                                 |
+| `MANIFEST_V3_FIREFOX_ANDROID_LIMITATIONS`               | warning  | The extension is marked as compatible with a Firefox for Android version that doesn't fully support Manifest Version 3                                                             |
 
 ### Static Theme / manifest.json
 

src/messages/manifestjson.js

@@ -23,6 +23,19 @@ export const MANIFEST_FIELD_INVALID = {
   file: MANIFEST_JSON,
 };
 
+export const MANIFEST_V3_FIREFOX_ANDROID_LIMITATIONS = {
+  code: 'MANIFEST_V3_FIREFOX_ANDROID_LIMITATIONS',
+  message: i18n._(
+    'Manifest Version 3 is not fully supported on Firefox for Android.'
+  ),
+  // TODO(#5110): replace description with a message including a shorted
+  // link to a documentation page.
+  description: i18n._(
+    'Manifest Version 3 is not fully supported on Firefox for Android.'
+  ),
+  file: MANIFEST_JSON,
+};
+
 export const MANIFEST_FIELD_PRIVILEGEDONLY = 'MANIFEST_FIELD_PRIVILEGEDONLY';
 export function manifestFieldPrivilegedOnly(fieldName) {
   return {

src/parsers/manifestjson.js

@@ -519,6 +519,15 @@ export default class ManifestJSONParser extends JSONParser {
       };
     }
 
+    if (
+      this.parsedJSON.manifest_version >= 3 &&
+      this.parsedJSON.browser_specific_settings?.gecko_android
+    ) {
+      this.collector.addWarning(
+        messages.MANIFEST_V3_FIREFOX_ANDROID_LIMITATIONS
+      );
+    }
+
     if (this.parsedJSON.content_security_policy != null) {
       this.validateCspPolicy(this.parsedJSON.content_security_policy);
     }

tests/unit/parsers/test.manifestjson.js

@@ -365,6 +365,28 @@ describe('ManifestJSONParser', () => {
     expect(manifestJSONParser.isValid).toEqual(true);
   });
 
+  it('should warn when gecko_android is set along with manifest_version 3', () => {
+    const addonLinter = new Linter({ _: ['bar'] });
+    const json = validManifestJSON({
+      browser_specific_settings: {
+        gecko: { id: 'test@ext' },
+        gecko_android: {},
+      },
+      manifest_version: 3,
+    });
+
+    const manifestJSONParser = new ManifestJSONParser(
+      json,
+      addonLinter.collector
+    );
+
+    const { warnings } = addonLinter.collector;
+    expect(warnings).toEqual([
+      expect.objectContaining(messages.MANIFEST_V3_FIREFOX_ANDROID_LIMITATIONS),
+    ]);
+    expect(manifestJSONParser.isValid).toEqual(true);
+  });
+
   describe('browser_style', () => {
     function parseManifest(manifestVersion, manifestKey, browserStyleValue) {
       const manifest = {