clients(lightrider): serialize errors in artifacts

clients/lightrider/lightrider-entry.js

@@ -9,6 +9,7 @@ const lighthouse = require('../../lighthouse-core/index.js');
 
 const LHError = require('../../lighthouse-core/lib/lh-error.js');
 const preprocessor = require('../../lighthouse-core/lib/proto-preprocessor.js');
+const assetSaver = require('../../lighthouse-core/lib/asset-saver.js');
 
 /** @type {Record<'mobile'|'desktop', LH.Config.Json>} */
 const LR_PRESETS = {
@@ -54,15 +55,22 @@ async function runLighthouseInLR(connection, url, flags, lrOpts) {
     const runnerResult = await lighthouse(url, flags, config, connection);
     if (!runnerResult) throw new Error('Lighthouse finished without a runnerResult');
 
+    // pre process the LHR for proto
+    const preprocessedLhr = preprocessor.processForProto(runnerResult.lhr);
+
     // When LR is called with |internal: {keep_raw_response: true, save_lighthouse_assets: true}|,
-    // this code will log artifacts to raw_response.artifacts.
+    // we log artifacts to raw_response.artifacts.
     if (logAssets) {
-      // @ts-ignore - piggyback the artifacts on the LHR.
-      runnerResult.lhr.artifacts = runnerResult.artifacts;
+      // Properly serialize artifact errors.
+      const artifactsJson = JSON.stringify(runnerResult.artifacts, assetSaver.stringifyReplacer);
+
+      return JSON.stringify({
+        ...preprocessedLhr,
+        artifacts: JSON.parse(artifactsJson),
+      });
     }
 
-    // pre process the LHR for proto
-    return JSON.stringify(preprocessor.processForProto(runnerResult.lhr));
+    return JSON.stringify(preprocessedLhr);
   } catch (err) {
     // If an error ruined the entire lighthouse run, attempt to return a meaningful error.
     let runtimeError;

clients/test/lightrider-entry-test.js

@@ -118,5 +118,32 @@ describe('lightrider-entry', () => {
 
       runStub.mockRestore();
     });
+
+    it('exposes artifacts when logAssets is true', async () => {
+      const originalRun = Runner.run;
+      Runner.run = jest.fn().mockReturnValue(Promise.resolve({
+        lhr: {},
+        artifacts: {
+          Artifact: new Error('some error'),
+        },
+      }));
+      afterEach(() => {
+        Runner.run = originalRun;
+      });
+
+      const mockConnection = {};
+      const url = 'https://example.com';
+      const lrFlags = {
+        logAssets: true,
+      };
+      const resultJson = await lhBackground.runLighthouseInLR(mockConnection, url, {}, lrFlags);
+      const result = JSON.parse(resultJson);
+      expect(result.artifacts).toMatchObject({
+        Artifact: {
+          sentinel: '__ErrorSentinel',
+          message: 'some error',
+        },
+      });
+    });
   });
 });

lighthouse-core/lib/asset-saver.js

@@ -288,4 +288,5 @@ module.exports = {
   prepareAssets,
   saveTrace,
   saveLanternNetworkData,
+  stringifyReplacer,
 };