fix(jest-runtime): only write map files to disk when mapCoverage: true (#5117)

* fix(jest-runtime): only write map files to disk when `mapCoverage: true`

* docs: update changelog and run prettier

Author: SimenB

CHANGELOG.md

@@ -1,5 +1,12 @@
 ## master
 
+### Fixes
+
+* `[jest-runtime]` fix error for test files providing coverage.
+  ([#5117](https://github.com/facebook/jest/pull/5117))
+
+### Features
+
 * `[jest-config]` Add `forceCoverageMatch` to allow collecting coverage from
   ignored files. ([#5081](https://github.com/facebook/jest/pull/5081))
 

docs/Configuration.md

@@ -242,15 +242,16 @@ Jest will fail if:
 Default: `['']`
 
 Test files are normally ignored from collecting code coverage. With this option,
-you can overwrite this behavior and include otherwise ignored files in code coverage.
+you can overwrite this behavior and include otherwise ignored files in code
+coverage.
 
 For example, if you have tests in source files named with `.t.js` extension as
 following:
 
 ```javascript
 // sum.t.js
 
-export function sum(a,b) {
+export function sum(a, b) {
   return a + b;
 }
 
@@ -262,6 +263,7 @@ if (process.env.NODE_ENV === 'test') {
 ```
 
 You can collect coverage from those files with setting `forceCoverageMatch`.
+
 ```json
 {
   ...
@@ -271,7 +273,6 @@ You can collect coverage from those files with setting `forceCoverageMatch`.
 }
 ```
 
-
 ### `globals` [object]
 
 Default: `{}`

docs/JestPlatform.md

@@ -3,36 +3,42 @@ id: jest-platform
 title: Jest Platform
 ---
 
-You can cherry pick specific features of Jest and use them as standalone packages. Here's a list of the available packages:
+You can cherry pick specific features of Jest and use them as standalone
+packages. Here's a list of the available packages:
 
 ## jest-changed-files
 
-Tool for identifying modified files in a git/hg repository. Exports two functions:
+Tool for identifying modified files in a git/hg repository. Exports two
+functions:
 
--  `getChangedFilesForRoots` returns a promise that resolves to an object with the changed files and repos. 
-- `findRepos` returns a promise that resolves to a set of repositories contained in the specified path.
+* `getChangedFilesForRoots` returns a promise that resolves to an object with
+  the changed files and repos.
+* `findRepos` returns a promise that resolves to a set of repositories contained
+  in the specified path.
 
 ### Example
 
-``` javascript
-const {getChangedFilesForRoots} = require( 'jest-changed-files');
+```javascript
+const {getChangedFilesForRoots} = require('jest-changed-files');
 
 // print the set of modified files since last commit in the current repo
 getChangedFilesForRoots(['./'], {
   lastCommit: true,
 }).then(result => console.log(result.changedFiles));
-
 ```
 
-You can read more about `jest-changed-files` in the [readme file](https://github.com/facebook/jest/blob/master/packages/jest-changed-files/README.md).
+You can read more about `jest-changed-files` in the
+[readme file](https://github.com/facebook/jest/blob/master/packages/jest-changed-files/README.md).
 
 ## jest-diff
 
-Tool for visualizing changes in data. Exports a function that compares two values of any type and returns a "pretty-printed" string illustrating the difference between the two arguments. 
+Tool for visualizing changes in data. Exports a function that compares two
+values of any type and returns a "pretty-printed" string illustrating the
+difference between the two arguments.
 
 ### Example
 
-``` javascript 
+```javascript
 const diff = require('jest-diff');
 
 const a = {a: {b: {c: 5}}};
@@ -46,12 +52,13 @@ console.log(result);
 
 ## jest-docblock
 
-Tool for extracting and parsing the comments at the top of a JavaScript file. Exports various function to manipulate the data inside the comment block.
+Tool for extracting and parsing the comments at the top of a JavaScript file.
+Exports various function to manipulate the data inside the comment block.
 
 ### Example
 
-``` javascript
-const { parseWithComments } = require('jest-docblock');
+```javascript
+const {parseWithComments} = require('jest-docblock');
 
 const code = `
 /**
@@ -66,17 +73,20 @@ const code = `
 const parsed = parseWithComments(code);
 
 // prints an object with two attributes: comments and pragmas.
-console.log(parsed)
+console.log(parsed);
 ```
-You can read more about `jest-docblock` in the [readme file](https://github.com/facebook/jest/blob/master/packages/jest-docblock/README.md).
+
+You can read more about `jest-docblock` in the
+[readme file](https://github.com/facebook/jest/blob/master/packages/jest-docblock/README.md).
 
 ## jest-get-type
 
-Module that identifies the primitive type of any JavaScript value. Exports a function that returns a string with the type of the value passed as argument. 
+Module that identifies the primitive type of any JavaScript value. Exports a
+function that returns a string with the type of the value passed as argument.
 
 ### Example
 
-``` javascript
+```javascript
 const getType = require('jest-get-type');
 
 const array = [1, 2, 3];
@@ -93,74 +103,85 @@ console.log(getType(undefinedValue));
 
 ## jest-validate
 
-Tool for validating configurations submitted by users. Exports a function that takes two arguments: the user's configuration and an object containing an example configuration and other options. The return value is an object with two attributes: 
+Tool for validating configurations submitted by users. Exports a function that
+takes two arguments: the user's configuration and an object containing an
+example configuration and other options. The return value is an object with two
+attributes:
 
-- `hasDeprecationWarnings`, a boolean indicating whether the submitted configuration has deprecation warnings, 
-- `isValid`, a boolean indicating whether the configuration is correct or not. 
+* `hasDeprecationWarnings`, a boolean indicating whether the submitted
+  configuration has deprecation warnings,
+* `isValid`, a boolean indicating whether the configuration is correct or not.
 
-### Example 
+### Example
 
-``` javascript
-const { validate }  = require('jest-validate');
+```javascript
+const {validate} = require('jest-validate');
 
 const configByUser = {
-  transform: '<rootDir>/node_modules/my-custom-transform'
-}
+  transform: '<rootDir>/node_modules/my-custom-transform',
+};
 
 const result = validate(configByUser, {
   comment: '  Documentation: http://custom-docs.com',
-  exampleConfig: { transform: '<rootDir>/node_modules/babel-jest' },
+  exampleConfig: {transform: '<rootDir>/node_modules/babel-jest'},
 });
 
 console.log(result);
 ```
 
-You can read more about `jest-validate` in the [readme file](https://github.com/facebook/jest/blob/master/packages/jest-validate/README.md).
+You can read more about `jest-validate` in the
+[readme file](https://github.com/facebook/jest/blob/master/packages/jest-validate/README.md).
 
 ## jest-worker
 
-Module used for parallelization of tasks. Exports a class `Worker` that takes the path of Node.js module and lets you call the module's exported methods as if they where class methods, returning a promise that resolves when the specified method finishes its execution in a forked process.  
+Module used for parallelization of tasks. Exports a class `Worker` that takes
+the path of Node.js module and lets you call the module's exported methods as if
+they where class methods, returning a promise that resolves when the specified
+method finishes its execution in a forked process.
 
-### Example 
+### Example
 
-``` javascript
+```javascript
 // heavy-task.js
 
 module.exports = {
-  myHeavyTask: (args) => {
+  myHeavyTask: args => {
     // long running CPU intensive task.
-  }
-}
+  },
+};
 ```
 
-``` javascript
+```javascript
 // main.js
 
 async function main() {
   const worker = new Worker(require.resolve('./heavy-task.js'));
 
   // run 2 tasks in parellel with different arguments
   const results = await Promise.all([
-    worker.myHeavyTask({ foo: 'bar' }), 
-    worker.myHeavyTask({bar: 'foo' }),
-  ]); 
+    worker.myHeavyTask({foo: 'bar'}),
+    worker.myHeavyTask({bar: 'foo'}),
+  ]);
 
   console.log(results);
 }
 
 main();
 ```
 
-You can read more about `jest-worker` in the [readme file](https://github.com/facebook/jest/blob/master/packages/jest-worker/README.md).
+You can read more about `jest-worker` in the
+[readme file](https://github.com/facebook/jest/blob/master/packages/jest-worker/README.md).
 
 ## pretty-format
 
-Exports a function that converts any JavaScript value into a human-readable string. Supports all built-in JavaScript types out of the box and allows extension for application-specific types via user-defined plugins.
+Exports a function that converts any JavaScript value into a human-readable
+string. Supports all built-in JavaScript types out of the box and allows
+extension for application-specific types via user-defined plugins.
 
 ### Example
 
-``` javascript
-const prettyFormat = require('pretty-format'); 
+```javascript
+const prettyFormat = require('pretty-format');
 
 const val = {object: {}};
 val.circularReference = val;
@@ -171,4 +192,5 @@ val.array = [-0, Infinity, NaN];
 console.log(prettyFormat(val));
 ```
 
-You can read more about `pretty-format` in the [readme file](https://github.com/facebook/jest/blob/master/packages/pretty-format/README.md).
+You can read more about `pretty-format` in the
+[readme file](https://github.com/facebook/jest/blob/master/packages/pretty-format/README.md).