core(tsc): add type checking to runner (#4961)

lighthouse-core/audits/audit.js

@@ -49,6 +49,20 @@ class Audit {
     return {};
   }
 
+  /* eslint-disable no-unused-vars */
+
+  /**
+   *
+   * @param {LH.Artifacts} artifacts
+   * @param {LH.Audit.Context} context
+   * @return {LH.Audit.Product|Promise<LH.Audit.Product>}
+   */
+  static audit(artifacts, context) {
+    throw new Error('audit() method must be overriden');
+  }
+
+  /* eslint-enable no-unused-vars */
+
   /**
    * Computes a clamped score between 0 and 1 based on the measured value. Score is determined by
    * considering a log-normal distribution governed by the two control points, point of diminishing

lighthouse-core/audits/seo/robots-txt.js

@@ -170,7 +170,7 @@ class RobotsTxt extends Audit {
   }
 
   /**
-   * @param {{RobotsTxt: {status: number, content: string}}} artifacts
+   * @param {LH.Artifacts} artifacts
    * @return {LH.Audit.Product}
    */
   static audit(artifacts) {
@@ -198,6 +198,11 @@ class RobotsTxt extends Audit {
       };
     }
 
+    // If status is good, content must be not null.
+    if (content === null) {
+      throw new Error(`Status ${status} was valid, but content was null`);
+    }
+
     const validationErrors = validateRobots(content);
 
     const headings = [

lighthouse-core/config/config.js

@@ -160,7 +160,7 @@ function assertValidAudit(auditDefinition, auditPath) {
   const auditName = auditPath ||
     (auditDefinition && auditDefinition.meta && auditDefinition.meta.name);
 
-  if (typeof auditDefinition.audit !== 'function') {
+  if (typeof auditDefinition.audit !== 'function' || auditDefinition.audit === Audit.audit) {
     throw new Error(`${auditName} has no audit() method.`);
   }
 

lighthouse-core/lib/asset-saver.js

@@ -162,9 +162,13 @@ async function prepareAssets(artifacts, audits) {
   for (const passName of passNames) {
     const trace = artifacts.traces[passName];
     const devtoolsLog = artifacts.devtoolsLogs[passName];
+
+    // Avoid Runner->AssetSaver->Runner circular require by loading Runner here.
+    const Runner = require('../runner.js');
+    const computedArtifacts = Runner.instantiateComputedArtifacts();
     /** @type {Array<Screenshot>} */
     // @ts-ignore TODO(bckenny): need typed computed artifacts
-    const screenshots = await artifacts.requestScreenshots(trace);
+    const screenshots = await computedArtifacts.requestScreenshots(trace);
 
     const traceData = Object.assign({}, trace);
     const screenshotsHTML = screenshotDump(screenshots);