Don't fail the test suite when convert-source-map throws an error

CHANGELOG.md

@@ -39,6 +39,7 @@
 - `[jest-snapshot]` Distinguish empty string from external snapshot not written ([#8880](https://github.com/facebook/jest/pull/8880))
 - `[jest-snapshot]` [**BREAKING**] Distinguish empty string from internal snapshot not written ([#8898](https://github.com/facebook/jest/pull/8898))
 - `[jest-transform]` Properly cache transformed files across tests ([#8890](https://github.com/facebook/jest/pull/8890))
+- `[jest-transform]` Don't fail the test suite when a generated source map is invalid ([#9058](https://github.com/facebook/jest/pull/9058))
 
 ### Chore & Maintenance
 

packages/jest-transform/src/ScriptTransformer.ts

@@ -296,12 +296,21 @@ export default class ScriptTransformer {
     }
 
     if (!transformed.map) {
-      //Could be a potential freeze here.
-      //See: https://github.com/facebook/jest/pull/5177#discussion_r158883570
-      const inlineSourceMap = sourcemapFromSource(transformed.code);
+      try {
+        //Could be a potential freeze here.
+        //See: https://github.com/facebook/jest/pull/5177#discussion_r158883570
+        const inlineSourceMap = sourcemapFromSource(transformed.code);
 
-      if (inlineSourceMap) {
-        transformed.map = inlineSourceMap.toJSON();
+        if (inlineSourceMap) {
+          transformed.map = inlineSourceMap.toJSON();
+        }
+      } catch (e) {
+        const transformPath = this._getTransformPath(filename);
+        console.warn(
+          `jest-transform: The source map produced for the file ${filename} ` +
+            `by ${transformPath} was invalid. Proceeding without source ` +
+            'mapping for that file.',
+        );
       }
     }
 

packages/jest-transform/src/__tests__/__snapshots__/script_transformer.test.js.snap

@@ -254,3 +254,5 @@ exports[`ScriptTransformer uses the supplied preprocessor 2`] = `
 "({\\"Object.<anonymous>\\":function(module,exports,require,__dirname,__filename,global,jest){module.exports = \\"react\\";
 }});"
 `;
+
+exports[`ScriptTransformer warns of unparseable inlined source maps from the preprocessor 1`] = `"jest-transform: The source map produced for the file /fruits/banana.js by preprocessor-with-sourcemaps was invalid. Proceeding without source mapping for that file."`;

packages/jest-transform/src/__tests__/script_transformer.test.js

@@ -406,6 +406,7 @@ describe('ScriptTransformer', () => {
     });
     expect(result.sourceMapPath).toEqual(expect.any(String));
     const mapStr = JSON.stringify(map);
+    expect(writeFileAtomic.sync).toBeCalledTimes(2);
     expect(writeFileAtomic.sync).toBeCalledWith(result.sourceMapPath, mapStr, {
       encoding: 'utf8',
     });
@@ -434,13 +435,50 @@ describe('ScriptTransformer', () => {
       collectCoverage: true,
     });
     expect(result.sourceMapPath).toEqual(expect.any(String));
+    expect(writeFileAtomic.sync).toBeCalledTimes(2);
     expect(writeFileAtomic.sync).toBeCalledWith(
       result.sourceMapPath,
       sourceMap,
       {encoding: 'utf8'},
     );
   });
 
+  it('warns of unparseable inlined source maps from the preprocessor', () => {
+    const warn = console.warn;
+    console.warn = jest.fn();
+
+    config = {
+      ...config,
+      transform: [['^.+\\.js$', 'preprocessor-with-sourcemaps']],
+    };
+    const scriptTransformer = new ScriptTransformer(config);
+
+    const sourceMap = JSON.stringify({
+      mappings: 'AAAA,IAAM,CAAC,GAAW,CAAC,CAAC',
+      version: 3,
+    });
+
+    // Cut off the inlined map prematurely with slice so the JSON ends abruptly
+    const content =
+      'var x = 1;\n' +
+      '//# sourceMappingURL=data:application/json;base64,' +
+      Buffer.from(sourceMap)
+        .toString('base64')
+        .slice(0, 16);
+
+    require('preprocessor-with-sourcemaps').process.mockReturnValue(content);
+
+    const result = scriptTransformer.transform('/fruits/banana.js', {
+      collectCoverage: true,
+    });
+    expect(result.sourceMapPath).toBeNull();
+    expect(writeFileAtomic.sync).toBeCalledTimes(1);
+
+    expect(console.warn).toHaveBeenCalledTimes(1);
+    expect(console.warn.mock.calls[0][0]).toMatchSnapshot();
+    console.warn = warn;
+  });
+
   it('writes source maps if given by the transformer', () => {
     config = {
       ...config,
@@ -462,6 +500,7 @@ describe('ScriptTransformer', () => {
       collectCoverage: true,
     });
     expect(result.sourceMapPath).toEqual(expect.any(String));
+    expect(writeFileAtomic.sync).toBeCalledTimes(2);
     expect(writeFileAtomic.sync).toBeCalledWith(
       result.sourceMapPath,
       JSON.stringify(map),