Memory leak fix: release source map info after processed and minor optimizations

CHANGELOG.md

@@ -46,6 +46,7 @@
 - `[jest-core]` Improve performance of SearchSource.findMatchingTests by 15% ([#8184](https://github.com/facebook/jest/pull/8184))
 - `[jest-resolve]` Optimize internal cache lookup performance ([#8183](https://github.com/facebook/jest/pull/8183))
 - `[jest-core]` Dramatically improve watch mode performance ([#8201](https://github.com/facebook/jest/pull/8201))
+- `[jest-reporters]` Fix memory leak of source map info and minor performance improvements ([#8234](https://github.com/facebook/jest/pull/8234))
 
 ## 24.5.0
 

packages/jest-reporters/src/coverage_reporter.ts

@@ -53,29 +53,35 @@ export default class CoverageReporter extends BaseReporter {
     testResult: TestResult,
     _aggregatedResults: AggregatedResult,
   ) {
+    // Coverage and source maps are only appended to the test result for this
+    // handler. Delete when processed to preserve memory.
+
     if (testResult.coverage) {
       this._coverageMap.merge(testResult.coverage);
-      // Remove coverage data to free up some memory.
-      delete testResult.coverage;
+      testResult.coverage = undefined;
+    }
 
-      Object.keys(testResult.sourceMaps).forEach(sourcePath => {
+    const sourceMaps = testResult.sourceMaps;
+    if (sourceMaps) {
+      Object.keys(sourceMaps).forEach(sourcePath => {
         let inputSourceMap: RawSourceMap | undefined;
         try {
           const coverage: FileCoverage = this._coverageMap.fileCoverageFor(
             sourcePath,
           );
-          ({inputSourceMap} = coverage.toJSON() as any);
+          inputSourceMap = (coverage.toJSON() as any).inputSourceMap;
         } finally {
           if (inputSourceMap) {
             this._sourceMapStore.registerMap(sourcePath, inputSourceMap);
           } else {
             this._sourceMapStore.registerURL(
               sourcePath,
-              testResult.sourceMaps[sourcePath],
+              sourceMaps[sourcePath],
             );
           }
         }
       });
+      testResult.sourceMaps = undefined;
     }
   }
 

packages/jest-runner/src/runTest.ts

@@ -253,14 +253,19 @@ async function runTestInternal(
 
     result.perfStats = {end: Date.now(), start};
     result.testFilePath = path;
-    result.coverage = runtime.getAllCoverageInfoCopy();
-    result.sourceMaps = runtime.getSourceMapInfo(
-      new Set(Object.keys(result.coverage || {})),
-    );
     result.console = testConsole.getBuffer();
     result.skipped = testCount === result.numPendingTests;
     result.displayName = config.displayName;
 
+    const coverage = runtime.getAllCoverageInfoCopy();
+    if (coverage) {
+      const coverageKeys = Object.keys(coverage);
+      if (coverageKeys.length) {
+        result.coverage = coverage;
+        result.sourceMaps = runtime.getSourceMapInfo(new Set(coverageKeys));
+      }
+    }
+
     if (globalConfig.logHeapUsage) {
       if (global.gc) {
         global.gc();

packages/jest-test-result/src/formatTestResults.ts

@@ -16,41 +16,41 @@ import {
   TestResult,
 } from './types';
 
-const formatResult = (
+const formatTestResult = (
   testResult: TestResult,
-  codeCoverageFormatter: CodeCoverageFormatter,
-  reporter: CodeCoverageReporter,
+  codeCoverageFormatter?: CodeCoverageFormatter,
+  reporter?: CodeCoverageReporter,
 ): FormattedTestResult => {
-  const now = Date.now();
-  const output: FormattedTestResult = {
-    assertionResults: [],
-    coverage: {},
-    endTime: now,
-    message: '',
-    name: testResult.testFilePath,
-    startTime: now,
-    status: 'failed',
-    summary: '',
-  };
-
+  const assertionResults = testResult.testResults.map(formatTestAssertion);
   if (testResult.testExecError) {
-    output.message = testResult.testExecError.message;
-    output.coverage = {};
+    const now = Date.now();
+    return {
+      assertionResults,
+      coverage: {},
+      endTime: now,
+      message: testResult.failureMessage
+        ? testResult.failureMessage
+        : testResult.testExecError.message,
+      name: testResult.testFilePath,
+      startTime: now,
+      status: 'failed',
+      summary: '',
+    };
   } else {
     const allTestsPassed = testResult.numFailingTests === 0;
-    output.status = allTestsPassed ? 'passed' : 'failed';
-    output.startTime = testResult.perfStats.start;
-    output.endTime = testResult.perfStats.end;
-    output.coverage = codeCoverageFormatter(testResult.coverage, reporter);
-  }
-
-  output.assertionResults = testResult.testResults.map(formatTestAssertion);
-
-  if (testResult.failureMessage) {
-    output.message = testResult.failureMessage;
+    return {
+      assertionResults,
+      coverage: codeCoverageFormatter
+        ? (testResult.coverage, reporter)
+        : testResult.coverage,
+      endTime: testResult.perfStats.end,
+      message: testResult.failureMessage ? testResult.failureMessage : '',
+      name: testResult.testFilePath,
+      startTime: testResult.perfStats.start,
+      status: allTestsPassed ? 'passed' : 'failed',
+      summary: '',
+    };
   }
-
-  return output;
 };
 
 function formatTestAssertion(
@@ -72,13 +72,11 @@ function formatTestAssertion(
 
 export default function formatTestResults(
   results: AggregatedResult,
-  codeCoverageFormatter?: CodeCoverageFormatter | null,
+  codeCoverageFormatter?: CodeCoverageFormatter,
   reporter?: CodeCoverageReporter,
 ): FormattedTestResults {
-  const formatter = codeCoverageFormatter || (coverage => coverage);
-
   const testResults = results.testResults.map(testResult =>
-    formatResult(testResult, formatter, reporter),
+    formatTestResult(testResult, codeCoverageFormatter, reporter),
   );
 
   return {...results, testResults};

packages/jest-test-result/src/types.ts

@@ -126,7 +126,7 @@ export type TestResult = {
     unmatched: number;
     updated: number;
   };
-  sourceMaps: {
+  sourceMaps?: {
     [sourcePath: string]: string;
   };
   testExecError?: SerializableError;