Fix Error Cannot read property converageData of null #7758

packages/jest-reporters/src/__tests__/__snapshots__/generateEmptyCoverage.test.js.snap

@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`generates an empty coverage object for a file without running it 1`] = `
+exports[`generateEmptyCoverage generates an empty coverage object for a file without running it 1`] = `
 Object {
   "b": Object {
     "0": Array [
@@ -13,32 +13,32 @@ Object {
       "line": 5,
       "loc": Object {
         "end": Object {
-          "column": 3,
+          "column": 7,
           "line": 9,
         },
         "start": Object {
-          "column": 2,
+          "column": 6,
           "line": 5,
         },
       },
       "locations": Array [
         Object {
           "end": Object {
-            "column": 3,
+            "column": 7,
             "line": 9,
           },
           "start": Object {
-            "column": 2,
+            "column": 6,
             "line": 5,
           },
         },
         Object {
           "end": Object {
-            "column": 3,
+            "column": 7,
             "line": 9,
           },
           "start": Object {
-            "column": 2,
+            "column": 6,
             "line": 5,
           },
         },
@@ -53,22 +53,22 @@ Object {
     "0": Object {
       "decl": Object {
         "end": Object {
-          "column": 11,
+          "column": 15,
           "line": 4,
         },
         "start": Object {
-          "column": 10,
+          "column": 14,
           "line": 4,
         },
       },
       "line": 4,
       "loc": Object {
         "end": Object {
-          "column": 1,
+          "column": 5,
           "line": 10,
         },
         "start": Object {
-          "column": 20,
+          "column": 24,
           "line": 4,
         },
       },
@@ -87,61 +87,61 @@ Object {
   "statementMap": Object {
     "0": Object {
       "end": Object {
-        "column": 45,
+        "column": 49,
         "line": 2,
       },
       "start": Object {
-        "column": 0,
+        "column": 4,
         "line": 2,
       },
     },
     "1": Object {
       "end": Object {
-        "column": 1,
+        "column": 5,
         "line": 10,
       },
       "start": Object {
-        "column": 10,
+        "column": 14,
         "line": 4,
       },
     },
     "2": Object {
       "end": Object {
-        "column": 3,
+        "column": 7,
         "line": 9,
       },
       "start": Object {
-        "column": 2,
+        "column": 6,
         "line": 5,
       },
     },
     "3": Object {
       "end": Object {
-        "column": 13,
+        "column": 17,
         "line": 6,
       },
       "start": Object {
-        "column": 4,
+        "column": 8,
         "line": 6,
       },
     },
     "4": Object {
       "end": Object {
-        "column": 13,
+        "column": 17,
         "line": 8,
       },
       "start": Object {
-        "column": 4,
+        "column": 8,
         "line": 8,
       },
     },
     "5": Object {
       "end": Object {
-        "column": 2,
+        "column": 6,
         "line": 14,
       },
       "start": Object {
-        "column": 0,
+        "column": 4,
         "line": 12,
       },
     },

packages/jest-reporters/src/__tests__/generateEmptyCoverage.test.js

@@ -5,6 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import {shouldInstrument} from '@jest/transform';
 import istanbulCoverage from 'istanbul-lib-coverage';
 import libSourceMaps from 'istanbul-lib-source-maps';
 import generateEmptyCoverage from '../generateEmptyCoverage';
@@ -15,51 +16,113 @@ import {makeGlobalConfig, makeProjectConfig} from '../../../../TestUtils';
 
 jest.mock('@jest/transform', () => ({
   ...jest.requireActual('@jest/transform'),
-  shouldInstrument: () => true,
+  shouldInstrument: jest.fn(),
 }));
 
-const src = `
-throw new Error('this should not be thrown');
-
-const a = (b, c) => {
-  if (b) {
-    return c;
-  } else {
-    return b;
-  }
-};
-
-module.exports = {
-  a,
-};`;
-
-it('generates an empty coverage object for a file without running it', () => {
+describe('generateEmptyCoverage', () => {
   const coverageMap = istanbulCoverage.createCoverageMap({});
   const sourceMapStore = libSourceMaps.createSourceMapStore();
   const rootDir = '/tmp';
   const filepath = path.join(rootDir, './sum.js');
 
-  const emptyCoverage = generateEmptyCoverage(
-    src,
-    filepath,
-    makeGlobalConfig(),
-    makeProjectConfig({
-      cacheDirectory: os.tmpdir(),
-      rootDir,
-      transform: [['^.+\\.js$', require.resolve('babel-jest')]],
-    }),
-  );
+  it('generates an empty coverage object for a file without running it', () => {
+    const src = `
+    throw new Error('this should not be thrown');
+
+    const a = (b, c) => {
+      if (b) {
+        return c;
+      } else {
+        return b;
+      }
+    };
+
+    module.exports = {
+      a,
+    };`;
+
+    shouldInstrument.mockReturnValueOnce(true);
+
+    const emptyCoverage = generateEmptyCoverage(
+      src,
+      filepath,
+      makeGlobalConfig(),
+      makeProjectConfig({
+        cacheDirectory: os.tmpdir(),
+        rootDir,
+        transform: [['^.+\\.js$', require.resolve('babel-jest')]],
+      }),
+    );
+
+    expect(emptyCoverage).not.toBeNull();
+    expect(typeof emptyCoverage).toBe('object');
+
+    let coverage = emptyCoverage.coverage;
+
+    if (emptyCoverage.sourceMapPath) {
+      coverageMap.addFileCoverage(emptyCoverage.coverage);
+      sourceMapStore.registerURL(filepath, emptyCoverage.sourceMapPath);
+
+      coverage = sourceMapStore.transformCoverage(coverageMap).map;
+    }
+
+    expect(coverage.data).toMatchSnapshot({path: expect.any(String)});
+  });
+
+  it('generates a null coverage result when using /* istanbul ignore file */', () => {
+    const src = `
+    /* istanbul ignore file */
+    const a = (b, c) => {
+      if (b) {
+        return c;
+      } else {
+        return b;
+      }
+    };
+    module.exports = { a };
+    `;
+
+    shouldInstrument.mockReturnValueOnce(true);
+
+    const nullCoverage = generateEmptyCoverage(
+      src,
+      filepath,
+      makeGlobalConfig(),
+      makeProjectConfig({
+        cacheDirectory: os.tmpdir(),
+        rootDir,
+        transform: [['^.+\\.js$', require.resolve('babel-jest')]],
+      }),
+    );
 
-  expect(typeof emptyCoverage).toBe('object');
+    expect(nullCoverage).toBeNull();
+  });
 
-  let coverage = emptyCoverage && emptyCoverage.coverage;
+  it('generates a null coverage result when collectCoverage global config is false', () => {
+    const src = `
+    const a = (b, c) => {
+      if (b) {
+        return c;
+      } else {
+        return b;
+      }
+    };
+    module.exports = { a };
+    `;
 
-  if (emptyCoverage && emptyCoverage.sourceMapPath) {
-    coverageMap.addFileCoverage(emptyCoverage.coverage);
-    sourceMapStore.registerURL(filepath, emptyCoverage.sourceMapPath);
+    shouldInstrument.mockReturnValueOnce(false);
 
-    coverage = sourceMapStore.transformCoverage(coverageMap).map;
-  }
+    const nullCoverage = generateEmptyCoverage(
+      src,
+      filepath,
+      makeGlobalConfig(),
+      makeProjectConfig({
+        cacheDirectory: os.tmpdir(),
+        rootDir,
+        transform: [['^.+\\.js$', require.resolve('babel-jest')]],
+      }),
+    );
 
-  expect(coverage.data).toMatchSnapshot({path: expect.any(String)});
+    expect(nullCoverage).toBeNull();
+  });
 });

packages/jest-reporters/src/generateEmptyCoverage.ts

@@ -33,18 +33,20 @@ export default function(
     collectCoverageFrom: globalConfig.collectCoverageFrom,
     collectCoverageOnlyFrom: globalConfig.collectCoverageOnlyFrom,
   };
+  let coverageWorkerResult: CoverageWorkerResult | null = null;
   if (shouldInstrument(filename, coverageOptions, config)) {
     // Transform file with instrumentation to make sure initial coverage data is well mapped to original code.
     const {code, mapCoverage, sourceMapPath} = new ScriptTransformer(
       config,
     ).transformSource(filename, source, true);
     const extracted = readInitialCoverage(code);
-
-    return {
-      coverage: new FileCoverage(extracted.coverageData),
-      sourceMapPath: mapCoverage ? sourceMapPath : null,
-    };
-  } else {
-    return null;
+    // Check extracted initial coverage is not null, this can happen when using /* istanbul ignore file */
+    if (extracted) {
+      coverageWorkerResult = {
+        coverage: new FileCoverage(extracted.coverageData),
+        sourceMapPath: mapCoverage ? sourceMapPath : null,
+      };
+    }
   }
+  return coverageWorkerResult;
 }