refactor(StartUrl): switch from error to debugString object

lighthouse-core/audits/webapp-install-banner.js

@@ -74,7 +74,11 @@ class WebappInstallBanner extends MultiCheckAudit {
   }
 
   static assessOfflineStartUrl(artifacts, failures) {
-    const hasOfflineStartUrl = artifacts.StartUrl === 200;
+    const hasOfflineStartUrl = artifacts.StartUrl.statusCode === 200;
+    if (artifacts.StartUrl.debugString) {
+      failures.push(artifacts.StartUrl.debugString);
+    }
+
     if (!hasOfflineStartUrl) {
       failures.push('Manifest start_url is not cached by a Service Worker');
     }

lighthouse-core/gather/driver.js

@@ -276,7 +276,7 @@ class Driver {
             }
 
             // If both the data and the url are empty strings, the page had no manifest.
-            return reject('No web app manifest found.');
+            return resolve(null);
           }
 
           resolve(response);

lighthouse-core/gather/gatherers/manifest.js

@@ -25,14 +25,7 @@ class Manifest extends Gatherer {
   afterPass(options) {
     return options.driver.getAppManifest()
       .then(response => {
-        return manifestParser(response.data, response.url, options.url);
-      })
-      .catch(err => {
-        if (err === 'No web app manifest found.') {
-          return null;
-        }
-
-        return Promise.reject(err);
+        return response && manifestParser(response.data, response.url, options.url);
       });
   }
 }

lighthouse-core/gather/gatherers/start-url.js

@@ -49,24 +49,29 @@ class StartUrl extends Gatherer {
   pass(options) {
     return options.driver.getAppManifest()
       .then(response => {
-        return manifestParser(response.data, response.url, options.url);
+        return response && manifestParser(response.data, response.url, options.url);
       })
       .then(manifest => {
-        if (!manifest.value.start_url || !manifest.value.start_url.raw) {
-          return Promise.reject(new Error(`No web app manifest found on page ${options.url}`));
+        if (!manifest || !manifest.value.start_url || !manifest.value.start_url.raw) {
+          throw new Error(`No web app manifest found on page ${options.url}`);
         }
 
         if (manifest.value.start_url.debugString) {
-          return Promise.reject(new Error(manifest.value.start_url.debugString));
+          throw new Error(manifest.value.start_url.debugString);
         }
 
         this.startUrl = manifest.value.start_url.value;
-      }).then(_ => this.executeFetchRequest(options.driver, this.startUrl));
+      })
+      .then(_ => this.executeFetchRequest(options.driver, this.startUrl))
+      .catch(err => {
+        this.debugString = err.message;
+      });
   }
 
   afterPass(options, tracingData) {
-    if (!this.startUrl) {
-      return Promise.reject(new Error('No start_url found inside the manifest'));
+    if (this.debugString || !this.startUrl) {
+      const debugString = this.debugString || 'No start_url found inside the manifest';
+      return Promise.resolve({debugString});
     }
 
     const networkRecords = tracingData.networkRecords;
@@ -76,7 +81,9 @@ class StartUrl extends Gatherer {
     }).pop(); // Take the last record that matches.
 
     return options.driver.goOnline(options)
-      .then(_ => navigationRecord ? navigationRecord.statusCode : -1);
+      .then(_ => {
+        return {statusCode: navigationRecord ? navigationRecord.statusCode : -1};
+      });
   }
 }
 

lighthouse-core/test/audits/webapp-install-banner-test.js

@@ -26,7 +26,7 @@ function generateMockArtifacts() {
         scriptURL: 'https://example.com/sw.js'
       }]
     },
-    StartUrl: 200,
+    StartUrl: {statusCode: 200},
     URL: {finalUrl: 'https://example.com'}
   }));
   const mockArtifacts = Object.assign({}, computedArtifacts, clonedArtifacts);
@@ -128,7 +128,7 @@ describe('PWA: webapp install banner audit', () => {
   it('fails if page had no SW', () => {
     const artifacts = generateMockArtifacts();
     artifacts.ServiceWorker.versions = [];
-    artifacts.StartUrl = -1;
+    artifacts.StartUrl = {statusCode: -1};
 
     return WebappInstallBannerAudit.audit(artifacts).then(result => {
       assert.strictEqual(result.rawValue, false);
@@ -141,7 +141,7 @@ describe('PWA: webapp install banner audit', () => {
 
   it('fails if start_url is not cached', () => {
     const artifacts = generateMockArtifacts();
-    artifacts.StartUrl = -1;
+    artifacts.StartUrl = {statusCode: -1};
 
     return WebappInstallBannerAudit.audit(artifacts).then(result => {
       assert.strictEqual(result.rawValue, false);
@@ -150,4 +150,17 @@ describe('PWA: webapp install banner audit', () => {
       assert.strictEqual(failures.length, 1, failures);
     });
   });
+
+  it('includes debugString from start_url', () => {
+    const artifacts = generateMockArtifacts();
+    artifacts.StartUrl = {debugString: 'Oops it failed!'};
+
+    return WebappInstallBannerAudit.audit(artifacts).then(result => {
+      assert.strictEqual(result.rawValue, false);
+      assert.ok(result.debugString.includes('start_url'), result.debugString);
+      const failures = result.extendedInfo.value.failures;
+      assert.strictEqual(failures.length, 2, failures);
+      assert.equal(failures[0], 'Oops it failed!');
+    });
+  });
 });

lighthouse-core/test/gather/gatherers/manifest-test.js

@@ -55,7 +55,7 @@ describe('Manifest gatherer', () => {
     return manifestGather.afterPass({
       driver: {
         getAppManifest() {
-          return Promise.reject('No web app manifest found.');
+          return Promise.resolve(null);
         }
       }
     }).then(artifact => {

lighthouse-core/test/gather/gatherers/start-url-test.js

@@ -90,8 +90,8 @@ describe('Start-url gatherer', () => {
       startUrlGathererWithQueryString.pass(optionsWithQueryString)
         .then(_ => startUrlGathererWithQueryString.afterPass(optionsWithQueryString, tracingData))
     ]).then(([artifact, artifactWithQueryString]) => {
-      assert.strictEqual(artifact, -1);
-      assert.strictEqual(artifactWithQueryString, -1);
+      assert.deepEqual(artifact, {statusCode: -1});
+      assert.deepEqual(artifactWithQueryString, {statusCode: -1});
     });
   });
 
@@ -113,12 +113,12 @@ describe('Start-url gatherer', () => {
       startUrlGathererWithFragment.pass(optionsWithQueryString)
         .then(_ => startUrlGathererWithFragment.afterPass(optionsWithQueryString, tracingData))
     ]).then(([artifact, artifactWithFragment]) => {
-      assert.strictEqual(artifact, 200);
-      assert.strictEqual(artifactWithFragment, 200);
+      assert.deepEqual(artifact, {statusCode: 200});
+      assert.deepEqual(artifactWithFragment, {statusCode: 200});
     });
   });
 
-  it('returns an error when manifest cannot be found', () => {
+  it('returns a debugString when manifest cannot be found', () => {
     const startUrlGatherer = new StartUrlGatherer();
     const options = {
       url: 'https://ifixit-pwa.appspot.com/',
@@ -127,11 +127,8 @@ describe('Start-url gatherer', () => {
 
     startUrlGatherer.pass(options)
       .then(_ => startUrlGatherer.afterPass(options, tracingData))
-      .then(_ => {
-        assert.ok(false, 'should fail because manifest is empty');
-      })
-      .catch(err => {
-        assert.strictEqual(err.message, `No web app manifest found on page ${options.url}`);
+      .then(artifact => {
+        assert.equal(artifact.debugString, `No web app manifest found on page ${options.url}`);
       });
   });
 
@@ -144,11 +141,8 @@ describe('Start-url gatherer', () => {
 
     startUrlGatherer.pass(options)
       .then(_ => startUrlGatherer.afterPass(options, tracingData))
-      .then(_ => {
-        assert.ok(false, 'should fail because origin is not the same');
-      })
-      .catch(err => {
-        assert.strictEqual(err.message, 'ERROR: start_url must be same-origin as document');
+      .then(artifact => {
+        assert.equal(artifact.debugString, 'ERROR: start_url must be same-origin as document');
       });
   });
 });