feat: load custom pre-compare, compare and store functions 350 (#351)

* feat: adding compare fn module option

* chore: passing tests with custom functions

* feat: add pre-compare function

.gitignore

@@ -1,4 +1,4 @@
 node_modules/
 .DS_Store
 npm-debug.log
-temp-test-*
+temp-*

README.md

@@ -238,7 +238,27 @@ Run with environment variable `DEBUG=snap-shot-it ...` to see log messages.
 Because under the hood it uses [snap-shot-core][snap-shot-core] you might
 want to show messages from both libraries with `DEBUG=snap-shot* ...`
 
+## Data callbacks
 
+You can pass your own NPM modules as `pre-compare`, `compare` and `store` functions using `package.json`. For example, to use both local and 3rd party NPM modules
+
+```json
+{
+  "config": {
+    "snap-shot-it": {
+      "pre-compare": "./pre-compare",
+      "compare": "snap-shot-compare",
+      "store": "./store"
+    }
+  }
+}
+```
+
+Each NPM module in this case should export a definition of a function that matches the expected core function
+
+- `pre-compare` is simply an identity or transformation function
+- `compare` should match [snap-shot-core#compare-function](/~https://github.com/bahmutov/snap-shot-core#compare-function), for example see [snap-shot-compare](/~https://github.com/bahmutov/snap-shot-compare)
+- `store` is another identity or transformation function, see [snap-shot-core#store-function](/~https://github.com/bahmutov/snap-shot-core#store-function)
 
 ## Nested snapshots
 

package.json

@@ -97,6 +97,7 @@
     "dont-crack": "1.2.1",
     "eslint": "5.16.0",
     "eslint-plugin-immutable": "1.0.0",
+    "folktale": "2.3.2",
     "git-issues": "1.3.1",
     "lazy-ass": "1.6.0",
     "license-checker": "25.0.1",

src/subfolders-spec.js → src/e2e-spec.js

@@ -86,6 +86,7 @@ const copyFolder = (sourceFolder, tempFolder) => {
   shell.rm('-rf', tempFolder)
   shell.mkdir(tempFolder)
   shell.cp(join(sourceFolder, 'package.json'), tempFolder)
+  shell.cp(join(sourceFolder, '*.js'), tempFolder)
   shell.cp('-R', join(sourceFolder, 'specs'), tempFolder)
 }
 
@@ -172,3 +173,80 @@ describe('snapshots in same folder', () => {
     })
   })
 })
+
+describe('custom compare function', () => {
+  // folder with specs to run
+  const sourceFolder = join(__dirname, '..', 'test-custom-compare-fn')
+  // temp folder to copy to before running tests
+  const tempFolder = join(__dirname, '..', 'temp-custom-compare-fn')
+
+  beforeEach(() => {
+    copyFolder(sourceFolder, tempFolder)
+  })
+
+  it('transforms value ', function () {
+    this.timeout(5000)
+
+    execa.shellSync('npm test', {
+      cwd: tempFolder,
+      stdio: 'inherit',
+      // only use the limited environment keys
+      // without "CI=1" value
+      env: limitedEnv,
+      extendEnv: false
+    })
+
+    checkSnapshots(tempFolder, {
+      'spec.js': {
+        'random string as 10 As 1': '\naaaaaaaaaa\n'
+      }
+    })
+
+    // run the tests again to check if values are not clashing
+    // but with CI=1 to avoid writing new files accidentally
+    execa.shellSync('npm test', {
+      cwd: tempFolder,
+      stdio: 'inherit',
+      env: { CI: '1' }
+    })
+  })
+})
+
+describe('custom pre-compare function', () => {
+  // folder with specs to run
+  const sourceFolder = join(__dirname, '..', 'test-custom-pre-fn')
+  // temp folder to copy to before running tests
+  const tempFolder = join(__dirname, '..', 'temp-custom-pre-fn')
+
+  beforeEach(() => {
+    copyFolder(sourceFolder, tempFolder)
+  })
+
+  it('transforms value before comparison', function () {
+    this.timeout(5000)
+
+    execa.shellSync('npm test', {
+      cwd: tempFolder,
+      stdio: 'inherit',
+      // only use the limited environment keys
+      // without "CI=1" value
+      env: limitedEnv,
+      extendEnv: false
+    })
+
+    checkSnapshots(tempFolder, {
+      'spec.js': {
+        'stores string as number 1': 5,
+        'stores string as number 2': 3
+      }
+    })
+
+    // run the tests again to check if values are not clashing
+    // but with CI=1 to avoid writing new files accidentally
+    execa.shellSync('npm test', {
+      cwd: tempFolder,
+      stdio: 'inherit',
+      env: { CI: '1' }
+    })
+  })
+})

src/index.js

@@ -2,7 +2,6 @@
 
 const debug = require('debug')('snap-shot-it')
 const { core, restore, prune } = require('snap-shot-core')
-const compare = require('snap-shot-compare')
 const { isDataDriven, dataDriven } = require('@bahmutov/data-driven')
 const { isNamedSnapshotArguments } = require('./named-snapshots')
 const utils = require('./utils')
@@ -140,11 +139,22 @@ function snapshot (value) {
   debug('package config options %o', packageConfigOptions)
   debug('merged options %o', opts)
 
+  const compare = opts.compare
+    ? utils.load(cwd, opts.compare)
+    : require('snap-shot-compare')
+  const store = opts.store ? utils.load(cwd, opts.store) : null
+
+  const preCompare = opts['pre-compare']
+    ? utils.load(cwd, opts['pre-compare'])
+    : R.identity
+  const what = preCompare(value)
+
   const snap = {
-    what: value,
+    what,
     file: currentTest.file,
     ext: EXTENSION,
     compare,
+    store,
     opts
   }
 

src/utils.js

@@ -1,9 +1,13 @@
 const fs = require('fs')
 const path = require('path')
 const R = require('ramda')
+const debug = require('debug')('snap-shot-it')
 
 const defaults = {
-  useRelativePath: false
+  useRelativePath: false,
+  'pre-compare': null,
+  compare: null,
+  store: null
 }
 /**
  * Pick only the keys we know about from whatever the user
@@ -30,4 +34,16 @@ const getPackageConfigOptions = cwd => {
   return pickKnownKeys(options)
 }
 
-module.exports = { getPackageConfigOptions, defaults }
+const load = (cwd, modulePath) => {
+  debug('loading module %s from cwd %s', modulePath, cwd)
+  if (!path.isAbsolute(modulePath)) {
+    const resolved = path.resolve(cwd, modulePath)
+    debug('resolved path: %s', resolved)
+    return require(resolved)
+  } else {
+    debug('trying to load NPM module %s', modulePath)
+    return require(modulePath)
+  }
+}
+
+module.exports = { getPackageConfigOptions, defaults, load }

test-custom-compare-fn/README.md

@@ -0,0 +1,5 @@
+# test-custom-compare-fn
+
+This repo shows how `snap-shot-it` can load a custom compare function via config in `package.json` file.
+
+See /~https://github.com/bahmutov/snap-shot-it/issues/350

test-custom-compare-fn/compaaaaaare.js

@@ -0,0 +1,24 @@
+const Result = require('folktale/result')
+const debug = require('debug')('snap-shot-it')
+
+const compare = ({ expected, value }) => {
+  debug('in compaaaaare.js')
+
+  // convert "expected" to string of same length, but with "a" characters
+  const aaas = value.replace(/./g, 'a')
+  debug('original value: %s', value)
+  debug('aaas: %s', aaas)
+  debug('expected value: %s', expected)
+
+  if (aaas === expected) {
+    return Result.Ok()
+  } else {
+    return Result.Error({
+      message: 'Hmm, not the same "aaaa..."',
+      expected,
+      value: aaas
+    })
+  }
+}
+
+module.exports = compare

test-custom-compare-fn/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "test-custom-compare-fn",
+  "version": "1.0.0",
+  "description": "shows custom compare function",
+  "main": "index.js",
+  "scripts": {
+    "test": "../node_modules/.bin/mocha 'specs/**/*.js'"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "config": {
+    "snap-shot-it": {
+      "compare": "./compaaaaaare",
+      "store": "./store"
+    }
+  }
+}

test-custom-compare-fn/specs/spec.js

@@ -0,0 +1,11 @@
+const snapshot = require('../..')
+
+/* eslint-env mocha */
+it('random string as 10 As', () => {
+  // our custom compare function replaces strings with
+  // same length of "aaaa..." :)
+  const s = Math.random()
+    .toString()
+    .substr(0, 10)
+  snapshot(s)
+})

test-custom-compare-fn/store.js

@@ -0,0 +1,11 @@
+const debug = require('debug')('snap-shot-it')
+
+const store = value => {
+  // converts value before storing it on disk
+  const transformed = value.replace(/./g, 'a')
+  debug('original value: %s', value)
+  debug('transformed: %s', transformed)
+  return transformed
+}
+
+module.exports = store

test-custom-pre-fn/README.md

@@ -0,0 +1,5 @@
+# test-custom-pre-fn
+
+This repo shows how `snap-shot-it` can load a custom pre-compare function via config in `package.json` file and use it to clean up data before comparing.
+
+See /~https://github.com/bahmutov/snap-shot-it/issues/350

test-custom-pre-fn/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "test-custom-pre-fn",
+  "version": "1.0.0",
+  "description": "shows custom pre-compare function",
+  "main": "index.js",
+  "scripts": {
+    "test": "../node_modules/.bin/mocha 'specs/**/*.js'"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "config": {
+    "snap-shot-it": {
+      "pre-compare": "./pre-compare"
+    }
+  }
+}

test-custom-pre-fn/pre-compare.js

@@ -0,0 +1,6 @@
+const preCompare = value => {
+  // assuming the value is a string
+  return value.length
+}
+
+module.exports = preCompare

test-custom-pre-fn/specs/spec.js

@@ -0,0 +1,8 @@
+const snapshot = require('../..')
+
+/* eslint-env mocha */
+it('stores string as number', () => {
+  // should be saved as the length of the string
+  snapshot('aaaaa')
+  snapshot('aaa')
+})