Standardize filenames in packages/expect (#7306)

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<!-- Please remember to update CHANGELOG.md in the root of the project if you have not done so. -->

## Summary

<!-- Explain the **motivation** for making this change. What existing problem does the pull request solve? -->

References Standardize file naming #4969.

Updates naming in package expect. Uses conventions listed in #4969 (comment):
- Files that primarily export types, objects or classes should use CapitalizedFileNames.js and should mirror what’s inside 1:1.
- Files that export a single function should have the function name with camelCase in it.
- Folder names should use dashes, unless they are special folders.

### Decisions
- Test & snapshot files retained their name, but converted it to camelCase.
- Files which exported an object were named according to the internal object, which was camelCase. However, I believe that the standard referenced above states that objects should have CapitalizedNames. Should the internal objects be renamed too?
    - `matchers.js`
    - `jestMatchersObject.js`
    - `spyMatchers.js`
    - `toThrowmatchers.js`

### Questions
How should `asymmetricMatchers.js` be named? It exports a class `AsymmetricMatcher`, but it also exports a bunch of functions, and was named in camelCase before.


## Test plan

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Output of yarn run test on master and standardize filenames in packages/jest circus branches was the same.

[jest-test-expect-master.txt](https://github.com/facebook/jest/files/2532360/jest-test-expect-master.txt)
[jest-test-expect-standardize-filenames.txt](https://github.com/facebook/jest/files/2532363/jest-test-expect-standardize-filenames.txt)

CHANGELOG.md

@@ -30,6 +30,7 @@
 
 ### Fixes
 
+- `[expect]` Standardize file naming in `expect` ([#7306](https://github.com/facebook/jest/pull/7306))
 - `[jest-each]` Add empty array validation check ([#7249](https://github.com/facebook/jest/pull/7249))
 - `[jest-cli]` Interrupt tests if interactive watch plugin key is pressed ([#7222](https://github.com/facebook/jest/pull/7222))
 - `[jest-cli]` Fix coverage summary reporting ([#7058](https://github.com/facebook/jest/pull/7058))

packages/expect/src/__tests__/asymmetric_matchers.test.js → packages/expect/src/__tests__/asymmetricMatchers.test.js

@@ -20,7 +20,7 @@ const {
   stringNotContaining,
   stringMatching,
   stringNotMatching,
-} = require('../asymmetric_matchers');
+} = require('../asymmetricMatchers');
 
 test('Any.asymmetricMatch()', () => {
   const Thing = function() {};

packages/expect/src/__tests__/extend.test.js

@@ -8,7 +8,7 @@
 
 const matcherUtils = require('jest-matcher-utils');
 const {iterableEquality, subsetEquality} = require('../utils');
-const {equals} = require('../jasmine_utils');
+const {equals} = require('../jasmineUtils');
 const jestExpect = require('../');
 
 jestExpect.extend({

packages/expect/src/__tests__/fake_chalk.test.js → packages/expect/src/__tests__/fakeChalk.test.js

@@ -6,7 +6,7 @@
  */
 'use strict';
 
-const fakeChalk = jest.requireActual('../fake_chalk');
+const fakeChalk = jest.requireActual('../fakeChalk');
 
 describe('Fake Chalk', () => {
   it('returns input when invoked', () => {

packages/expect/src/asymmetric_matchers.js → packages/expect/src/asymmetricMatchers.js

@@ -7,13 +7,7 @@
  * @flow
  */
 
-import {
-  equals,
-  fnNameFor,
-  hasProperty,
-  isA,
-  isUndefined,
-} from './jasmine_utils';
+import {equals, fnNameFor, hasProperty, isA, isUndefined} from './jasmineUtils';
 
 import {emptyObject} from './utils';
 

packages/expect/src/extract_expected_assertions_errors.js → packages/expect/src/extractExpectedAssertionsErrors.js

@@ -14,7 +14,7 @@ import {
   pluralize,
 } from 'jest-matcher-utils';
 
-import {getState, setState} from './jest_matchers_object';
+import {getState, setState} from './jestMatchersObject';
 
 const resetAssertionsLocalState = () => {
   setState({

packages/expect/src/index.js

@@ -23,11 +23,11 @@ import type {
 import * as matcherUtils from 'jest-matcher-utils';
 import {iterableEquality, subsetEquality} from './utils';
 import matchers from './matchers';
-import spyMatchers from './spy_matchers';
+import spyMatchers from './spyMatchers';
 import toThrowMatchers, {
   createMatcher as createThrowMatcher,
-} from './to_throw_matchers';
-import {equals} from './jasmine_utils';
+} from './toThrowMatchers';
+import {equals} from './jasmineUtils';
 import {
   any,
   anything,
@@ -39,15 +39,15 @@ import {
   stringNotContaining,
   stringMatching,
   stringNotMatching,
-} from './asymmetric_matchers';
+} from './asymmetricMatchers';
 import {
   INTERNAL_MATCHER_FLAG,
   getState,
   setState,
   getMatchers,
   setMatchers,
-} from './jest_matchers_object';
-import extractExpectedAssertionsErrors from './extract_expected_assertions_errors';
+} from './jestMatchersObject';
+import extractExpectedAssertionsErrors from './extractExpectedAssertionsErrors';
 
 class JestAssertionError extends Error {
   matcherResult: any;

packages/expect/src/jest_matchers_object.js → packages/expect/src/jestMatchersObject.js

@@ -7,7 +7,7 @@
  * @flow
  */
 
-import {AsymmetricMatcher} from './asymmetric_matchers';
+import {AsymmetricMatcher} from './asymmetricMatchers';
 import type {
   Expect,
   MatchersObject,

packages/expect/src/matchers.js

@@ -32,7 +32,7 @@ import {
   typeEquality,
   isOneline,
 } from './utils';
-import {equals} from './jasmine_utils';
+import {equals} from './jasmineUtils';
 
 type ContainIterable =
   | Array<any>

packages/expect/src/spy_matchers.js → packages/expect/src/spyMatchers.js

@@ -23,7 +23,7 @@ import {
   printWithType,
   RECEIVED_COLOR,
 } from 'jest-matcher-utils';
-import {equals} from './jasmine_utils';
+import {equals} from './jasmineUtils';
 import {iterableEquality, partition, isOneline} from './utils';
 import diff from 'jest-diff';
 

packages/expect/src/to_throw_matchers.js → packages/expect/src/toThrowMatchers.js

@@ -19,7 +19,7 @@ import {
   printExpected,
   printWithType,
 } from 'jest-matcher-utils';
-import {equals} from './jasmine_utils';
+import {equals} from './jasmineUtils';
 import {isError} from './utils';
 
 export const createMatcher = (matcherName: string, fromPromise?: boolean) => (

packages/expect/src/utils.js

@@ -12,7 +12,7 @@ import {
   isA,
   isImmutableUnorderedKeyed,
   isImmutableUnorderedSet,
-} from './jasmine_utils';
+} from './jasmineUtils';
 
 type GetPath = {
   hasEndProp?: boolean,

scripts/browserBuild.js

@@ -45,7 +45,7 @@ function browserBuild(pkgName, entryPath, destination) {
       {
         resolveId(id) {
           return id === 'chalk'
-            ? path.resolve(__dirname, '../packages/expect/build/fake_chalk.js')
+            ? path.resolve(__dirname, '../packages/expect/build/fakeChalk.js')
             : undefined;
         },
       },