feat(saving): only save if the file contents were unchanged

This should speed things up a bit and prevent enditors from flashing the
content when the save occurs (if it's not necessary anyway)

__mocks__/glob.js

@@ -29,6 +29,12 @@ module.exports = jest.fn(function mockGlob(globString, options, callback) {
     callback(null, [])
   } else if (globString.includes('throw-error')) {
     callback(new Error('something weird happened'))
+  } else if (globString.includes('no-change')) {
+    callback(null, [
+      fredProject('no-change/1.js'),
+      fredProject('no-change/2.js'),
+      fredProject('no-change/3.js'),
+    ])
   } else {
     throw new Error(
       `Your test globString: "${globString}"` +

__mocks__/prettier-eslint.js

@@ -6,6 +6,8 @@
 const format = jest.fn(({text, filePath = ''}) => {
   if (text === 'MOCK_SYNTAX_ERROR' || filePath.includes('syntax-error')) {
     throw new Error('Mock error for a syntax error')
+  } else if (filePath.includes('no-change')) {
+    return text
   }
   return `MOCK_OUTPUT for ${filePath || 'stdin'}`
 })

package.json

@@ -24,7 +24,7 @@
     "find-up": "^2.1.0",
     "get-stdin": "^5.0.1",
     "glob": "^7.1.1",
-    "prettier-eslint": "^2.3.3",
+    "prettier-eslint": "^3.0.0",
     "rxjs": "^5.0.3",
     "yargs": "^6.6.0"
   },
@@ -41,7 +41,7 @@
     "cz-conventional-changelog": "^1.2.0",
     "eslint": "^3.10.2",
     "eslint-config-kentcdodds": "^11.1.0",
-    "husky": "^0.12.0",
+    "husky": "^0.13.1",
     "jest-cli": "^18.1.0",
     "opt-cli": "^1.5.1",
     "p-s": "^3.0.3",
@@ -59,7 +59,10 @@
       "kentcdodds/jest"
     ],
     "rules": {
-      "max-len": [2, 80]
+      "max-len": [
+        2,
+        80
+      ]
     }
   },
   "jest": {

src/format-files.js

@@ -62,6 +62,7 @@ async function formatFilesFromGlobs(
   return new Promise(resolve => {
     const successes = []
     const failures = []
+    const unchanged = []
     Rx.Observable
       .from(fileGlobs)
       .mergeMap(getFilesFromGlob, null, concurrentGlobs)
@@ -77,6 +78,8 @@ async function formatFilesFromGlobs(
     function onNext(info) {
       if (info.error) {
         failures.push(info)
+      } else if (info.unchanged) {
+        unchanged.push(info)
       } else {
         successes.push(info)
       }
@@ -105,6 +108,10 @@ async function formatFilesFromGlobs(
           `${failure} formatting ${count} files with prettier-eslint`,
         )
       }
+      if (unchanged.length) {
+        const count = chalk.bold(unchanged.length)
+        console.log(`${count} files were ${chalk.gray('unchanged')}`)
+      }
       resolve({successes, failures})
     }
   })
@@ -129,9 +136,13 @@ function formatFile(filePath, prettierESLintOptions, cliOptions) {
   })
 
   if (cliOptions.write) {
-    format$ = format$.mergeMap(
-      info => rxWriteFile(filePath, info.formatted).map(() => fileInfo),
-    )
+    format$ = format$.mergeMap(info => {
+      if (info.text === info.formatted) {
+        return Rx.Observable.of(Object.assign(fileInfo, {unchanged: true}))
+      } else {
+        return rxWriteFile(filePath, info.formatted).map(() => fileInfo)
+      }
+    })
   } else {
     format$ = format$.map(info => {
       console.log(info.formatted)

src/format-files.test.js

@@ -12,6 +12,7 @@ beforeEach(() => {
   console.error = jest.fn()
   formatMock.mockClear()
   fsMock.writeFile.mockClear()
+  fsMock.readFile.mockClear()
 })
 
 test('sanity test', async () => {
@@ -55,12 +56,9 @@ test('should accept stdin', async () => {
   mockGetStdin.stdin = '  var [ foo, {  bar } ] = window.APP ;'
   await formatFiles({stdin: true})
   expect(formatMock).toHaveBeenCalledTimes(1)
-  expect(formatMock).toHaveBeenCalledWith(
-    expect.objectContaining({
-      // the trim is part of the test
-      text: mockGetStdin.stdin.trim(),
-    }),
-  )
+  // the trim is part of the test
+  const text = mockGetStdin.stdin.trim()
+  expect(formatMock).toHaveBeenCalledWith(expect.objectContaining({text}))
   expect(console.log).toHaveBeenCalledTimes(1)
   expect(console.log).toHaveBeenCalledWith('MOCK_OUTPUT for stdin')
 })
@@ -108,3 +106,12 @@ test('forwards sillyLogs onto prettier-eslint', async () => {
   const options = expect.objectContaining({sillyLogs: true})
   expect(formatMock).toHaveBeenCalledWith(options)
 })
+
+test('wont save file if contents did not change', async () => {
+  const fileGlob = 'no-change/*.js'
+  await formatFiles({_: [fileGlob], write: true})
+  expect(fsMock.readFile).toHaveBeenCalledTimes(3)
+  expect(fsMock.writeFile).toHaveBeenCalledTimes(0)
+  const unchangedOutput = expect.stringMatching(/3.*?files.*?unchanged/)
+  expect(console.log).toHaveBeenCalledWith(unchangedOutput)
+})