Prevent a ENOENT crash by checking for file existence in jest-message-util (#5405)

* Prevent a ENOENT crash by checking for existence

Jest tries to load the stack-trace based on the top frame. The problem is, the filename may be provided by the source-map, which is unreliable since it can point to a non-existent file. In such a case, the code would cause a hard crash of "Test suite failed to run" with a stack-trace pointing at "exports.formatStackTrace", which I have corrected here.

* add an integration test for bad-source-map case

* lint CHANGELOG

* use a try-catch rather than fs.existsSync

Author: niieani

CHANGELOG.md

@@ -1,12 +1,14 @@
 ## master
 
-### features
+### Features
 
 * `[jest-mock]` Add util methods to create async functions.
   ([#5318](https://github.com/facebook/jest/pull/5318))
 
 ### Fixes
 
+* `[jest-message-util]` Prevent an `ENOENT` crash when the test file contained a
+  malformed source-map. ([#5405](https://github.com/facebook/jest/pull/5405)).
 * `[jest]` Add `import-local` to `jest` package.
   ([#5353](https://github.com/facebook/jest/pull/5353))
 * `[expect]` Support class instances in `.toHaveProperty()` matcher.

integration-tests/__tests__/bad_source_map.test.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+'use strict';
+
+const runJest = require('../runJest');
+
+test('suite with test cases that contain malformed sourcemaps', () => {
+  const result = runJest('bad-source-map');
+  expect(result.stderr).not.toMatch('ENOENT');
+});

integration-tests/bad-source-map/__tests__/bad-source-map.js

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "testEnvironment": "node"
+  }
+}

integration-tests/bad-source-map/__tests__/bad-source-map.js.map

@@ -70,6 +70,22 @@ const trim = string => (string || '').replace(/^\s+/, '').replace(/\s+$/, '');
 const trimPaths = string =>
   string.match(STACK_PATH_REGEXP) ? trim(string) : string;
 
+const getRenderedCallsite = (fileContent: string, line: number) => {
+  let renderedCallsite = codeFrameColumns(
+    fileContent,
+    {start: {line}},
+    {highlightCode: true},
+  );
+
+  renderedCallsite = renderedCallsite
+    .split('\n')
+    .map(line => MESSAGE_INDENT + line)
+    .join('\n');
+
+  renderedCallsite = `\n${renderedCallsite}\n`;
+  return renderedCallsite;
+};
+
 // ExecError is an error thrown outside of the test suite (not inside an `it` or
 // `before/after each` hooks). If it's thrown, none of the tests in the file
 // are executed.
@@ -228,20 +244,15 @@ export const formatStackTrace = (
     const filename = topFrame.file;
 
     if (path.isAbsolute(filename)) {
-      renderedCallsite = codeFrameColumns(
-        fs.readFileSync(filename, 'utf8'),
-        {
-          start: {line: topFrame.line},
-        },
-        {highlightCode: true},
-      );
-
-      renderedCallsite = renderedCallsite
-        .split('\n')
-        .map(line => MESSAGE_INDENT + line)
-        .join('\n');
-
-      renderedCallsite = `\n${renderedCallsite}\n`;
+      let fileContent;
+      try {
+        // TODO: check & read HasteFS instead of reading the filesystem:
+        // see: https://github.com/facebook/jest/pull/5405#discussion_r164281696
+        fileContent = fs.readFileSync(filename, 'utf8');
+        renderedCallsite = getRenderedCallsite(fileContent, topFrame.line);
+      } catch (e) {
+        // the file does not exist or is inaccessible, we ignore
+      }
     }
   }