core(installability-errors): add url scheme error (#13846)

lighthouse-core/audits/installable-manifest.js

@@ -97,6 +97,11 @@ const UIStrings = {
   'protocol-timeout': `Lighthouse could not determine if there was a service worker. Please try with a newer version of Chrome.`,
   /** Message logged when the web app has been uninstalled o desktop, signalling that the install banner state is being reset. */
   'pipeline-restarted': 'PWA has been uninstalled and installability checks resetting.',
+  /**
+   * @description Error message explaining that the URL of the manifest uses a scheme that is not supported on Android.
+   * @example {data:} scheme
+   */
+  'scheme-not-supported-for-webapk': 'The manifest URL scheme ({scheme}) is not supported on Android.',
 };
 /* eslint-enable max-len */
 
@@ -156,6 +161,17 @@ class InstallableManifest extends Audit {
       // @ts-expect-error errorIds from protocol should match up against the strings dict
       const matchingString = UIStrings[err.errorId];
 
+      if (err.errorId === 'scheme-not-supported-for-webapk') {
+        // If there was no manifest, then there will be at lest one other installability error.
+        // We can ignore this error if that's the case.
+        const manifestUrl = artifacts.WebAppManifest?.url;
+        if (!manifestUrl) continue;
+
+        const scheme = new URL(manifestUrl).protocol;
+        i18nErrors.push(str_(matchingString, {scheme}));
+        continue;
+      }
+
       // Handle an errorId we don't recognize.
       if (matchingString === undefined) {
         i18nErrors.push(str_(UIStrings.noErrorId, {errorId: err.errorId}));

lighthouse-core/test/audits/installable-manifest-test.js

@@ -193,6 +193,39 @@ describe('PWA: webapp install banner audit', () => {
         assert.strictEqual(result.score, 1);
       });
     });
+
+    it('adds scheme to invalid scheme error message', async () => {
+      const artifacts = generateMockArtifacts();
+      artifacts.WebAppManifest.url = 'data:application/json;base64,AAAAAAAAAA';
+      artifacts.InstallabilityErrors.errors.push({
+        errorId: 'scheme-not-supported-for-webapk',
+        errorArguments: [],
+      });
+      const context = generateMockAuditContext();
+
+      const result = await InstallableManifestAudit.audit(artifacts, context);
+      expect(result.score).toEqual(0);
+      expect(result.details.items[0].reason).toBeDisplayString(
+        'The manifest URL scheme (data:) is not supported on Android.'
+      );
+    });
+
+    it('ignores invalid scheme error if there was no manifest url', async () => {
+      const artifacts = generateMockArtifacts();
+      artifacts.WebAppManifest = undefined;
+      artifacts.InstallabilityErrors.errors.push(
+        {errorId: 'no-manifest', errorArguments: []},
+        {errorId: 'scheme-not-supported-for-webapk', errorArguments: []}
+      );
+      const context = generateMockAuditContext();
+
+      const result = await InstallableManifestAudit.audit(artifacts, context);
+      expect(result.score).toEqual(0);
+      expect(result.details.items).toHaveLength(1);
+      expect(result.details.items[0].reason).toBeDisplayString(
+        'Page has no manifest <link> URL'
+      );
+    });
   });
 
   describe('warnings', () => {

third-party/chromium-synchronization/installability-errors-test.js

@@ -69,6 +69,7 @@ Array [
   "platform-not-supported-on-android",
   "prefer-related-applications",
   "prefer-related-applications-only-beta-stable",
+  "scheme-not-supported-for-webapk",
   "start-url-not-valid",
   "url-not-supported-for-webapk",
   "warn-not-offline-capable",