feat(smart-selector): initial commit

packages/smart-selector/.babelrc.js

@@ -0,0 +1,3 @@
+module.exports = require('../../@xen-orchestra/babel-config')(
+  require('./package.json')
+)

packages/smart-selector/.npmignore

@@ -0,0 +1,24 @@
+/benchmark/
+/benchmarks/
+*.bench.js
+*.bench.js.map
+
+/examples/
+example.js
+example.js.map
+*.example.js
+*.example.js.map
+
+/fixture/
+/fixtures/
+*.fixture.js
+*.fixture.js.map
+*.fixtures.js
+*.fixtures.js.map
+
+/test/
+/tests/
+*.spec.js
+*.spec.js.map
+
+__snapshots__/

packages/smart-selector/README.md

@@ -0,0 +1,76 @@
+# ${pkg.name} [![Build Status](https://travis-ci.org/${pkg.shortGitHubPath}.png?branch=master)](https://travis-ci.org/${pkg.shortGitHubPath})
+
+> ${pkg.description}
+
+Differences with [reselect](https://github.com/reactjs/reselect):
+
+- simpler: no custom memoization
+- inputs (and their selectors): are stored in objects, not arrays
+- lazy:
+   - inputs are not computed before accessed
+   - unused inputs do not trigger a call to the transform function
+
+## Install
+
+Installation of the [npm package](https://npmjs.org/package/${pkg.name}):
+
+```
+> npm install --save ${pkg.name}
+```
+
+## Usage
+
+```js
+import createSelector from 'smart-selector'
+
+const getVisibleTodos = createSelector(
+  {
+    filter: state => state.filter,
+    todos: state => state.todos,
+  },
+  inputs => {
+    switch (inputs.filter) {
+      case 'ALL':
+        return inputs.todos
+      case 'COMPLETED':
+        return inputs.todos.filter(todo => todo.completed)
+      case 'ACTIVE':
+        return inputs.todos.filter(todo => !todo.completed)
+    }
+  }
+)
+```
+
+## Development
+
+```
+# Install dependencies
+> yarn
+
+# Run the tests
+> yarn test
+
+# Continuously compile
+> yarn dev
+
+# Continuously run the tests
+> yarn dev-test
+
+# Build for production (automatically called by npm install)
+> yarn build
+```
+
+## Contributions
+
+Contributions are *very* welcomed, either on the documentation or on
+the code.
+
+You may:
+
+- report any [issue](https://github.com/vatesfr/xo-web/issues)
+  you've encountered;
+- fork and create a pull request.
+
+## License
+
+ISC © [Vates SAS](https://vates.fr)

packages/smart-selector/package.json

@@ -0,0 +1,43 @@
+{
+  "private": true,
+  "name": "smart-selector",
+  "version": "0.0.0",
+  "license": "ISC",
+  "description": "",
+  "keywords": [],
+  "homepage": "https://github.com/vatesfr/xen-orchestra/tree/master/packages/smart-selector",
+  "bugs": "https://github.com/vatesfr/xen-orchestra/issues",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/vatesfr/xen-orchestra.git"
+  },
+  "author": {
+    "name": "Julien Fontanet",
+    "email": "julien.fontanet@isonoe.net"
+  },
+  "preferGlobal": false,
+  "main": "dist/",
+  "bin": {},
+  "files": [
+    "dist/"
+  ],
+  "engines": {
+    "node": ">=8"
+  },
+  "devDependencies": {
+    "@babel/cli": "7.1.5",
+    "@babel/core": "7.1.5",
+    "@babel/preset-env": "7.1.5",
+    "babel-plugin-lodash": "^3.3.2",
+    "cross-env": "^5.1.1",
+    "rimraf": "^2.6.2"
+  },
+  "scripts": {
+    "build": "cross-env NODE_ENV=production babel --source-maps --out-dir=dist/ src/",
+    "clean": "rimraf dist/",
+    "dev": "cross-env NODE_ENV=development babel --watch --source-maps --out-dir=dist/ src/",
+    "prebuild": "yarn run clean",
+    "predev": "yarn run clean",
+    "prepublishOnly": "yarn run build"
+  }
+}

packages/smart-selector/src/index.js

@@ -0,0 +1,82 @@
+const { create, keys } = Object
+
+const createSelector = (inputSelectors, transform) => {
+  const previousArgs = [{}] // initialize with non-repeatable args
+  let cache, previousResult, previousThisArg
+  let previousInputs = {}
+
+  const spyDescriptors = {}
+  const inputs = keys(inputSelectors)
+  for (let i = 0, n = inputs.length; i < n; ++i) {
+    const input = inputs[i]
+    spyDescriptors[input] = {
+      enumerable: true,
+      get: () =>
+        input in previousInputs
+          ? previousInputs[input]
+          : (previousInputs[input] =
+              input in cache
+                ? cache[input]
+                : inputSelectors[input].apply(previousThisArg, previousArgs)),
+    }
+  }
+  const spy = create(null, spyDescriptors)
+
+  function selector () {
+    // handle arguments
+    {
+      const { length } = arguments
+      let i = 0
+      if (this === previousThisArg && length === previousArgs.length) {
+        while (i < length && arguments[i] === previousArgs[i]) {
+          ++i
+        }
+        if (i === length) {
+          return previousResult
+        }
+      } else {
+        previousArgs.length = length
+        previousThisArg = this
+      }
+      while (i < length) {
+        previousArgs[i] = arguments[i]
+        ++i
+      }
+    }
+
+    // handle inputs
+    cache = previousInputs
+    previousInputs = {}
+    {
+      const inputs = keys(cache)
+      const { length } = inputs
+      if (length !== 0) {
+        let i = 0
+        while (true) {
+          if (i === length) {
+            // inputs are unchanged
+            return previousResult
+          }
+
+          const input = inputs[i++]
+          const value = inputSelectors[input].apply(this, arguments)
+          if (value !== cache[input]) {
+            // update the value
+            cache[input] = value
+
+            // remove non-computed values
+            while (i < length) {
+              delete cache[inputs[i++]]
+            }
+
+            break
+          }
+        }
+      }
+    }
+
+    return (previousResult = transform(spy))
+  }
+  return selector
+}
+export { createSelector as default }

packages/smart-selector/src/index.spec.js

@@ -0,0 +1,99 @@
+/* eslint-env jest */
+
+import createSelector from './'
+
+const noop = () => {}
+
+describe('createSelector', () => {
+  it('calls input selectors with this and arguments', () => {
+    const thisArg = {}
+    const args = ['arg1', 'arg2']
+    const foo = jest.fn()
+
+    createSelector({ foo }, ({ foo }) => {}).apply(thisArg, args)
+
+    expect(foo.mock.instances).toEqual([thisArg])
+    expect(foo.mock.calls).toEqual([args])
+  })
+
+  it('calls input selectors only when accessed', () => {
+    const foo = jest.fn()
+    createSelector({ foo }, inputs => {
+      expect(foo.mock.calls.length).toBe(0)
+      noop(inputs.foo)
+      expect(foo.mock.calls.length).toBe(1)
+    })()
+  })
+
+  it('does not call the input selectors if this arguments did not change', () => {
+    const foo = jest.fn()
+    const selector = createSelector({ foo }, ({ foo }) => {})
+
+    selector('arg1')
+    expect(foo.mock.calls.length).toBe(1)
+
+    selector('arg1')
+    expect(foo.mock.calls.length).toBe(1)
+
+    selector('arg1', 'arg2')
+    expect(foo.mock.calls.length).toBe(2)
+
+    selector.call({}, 'arg1', 'arg2')
+    expect(foo.mock.calls.length).toBe(3)
+  })
+
+  it('does not call the transform if inputs did not change', () => {
+    const transform = jest.fn(({ foo }) => {})
+    const selector = createSelector(
+      {
+        foo: () => 'foo',
+      },
+      transform
+    )
+
+    selector({})
+    expect(transform.mock.calls.length).toBe(1)
+
+    selector({})
+    expect(transform.mock.calls.length).toBe(1)
+  })
+
+  it('computes only the necessary inputs to determine if transform should be called', () => {
+    let foo = 'foo 1'
+    const bar = 'bar 1'
+    const inputs = {
+      foo: jest.fn(() => foo),
+      bar: jest.fn(() => bar),
+    }
+    const transform = jest.fn(inputs => {
+      if (inputs.foo !== 'foo 1') {
+        return inputs.bar
+      }
+    })
+    const selector = createSelector(inputs, transform)
+
+    selector({})
+    expect(inputs.foo.mock.calls.length).toBe(1)
+    expect(inputs.bar.mock.calls.length).toBe(0)
+
+    selector({})
+    expect(inputs.foo.mock.calls.length).toBe(2)
+    expect(inputs.bar.mock.calls.length).toBe(0)
+
+    foo = 'foo 2'
+
+    selector({})
+    expect(inputs.foo.mock.calls.length).toBe(3)
+    expect(inputs.bar.mock.calls.length).toBe(1)
+
+    foo = 'foo 1'
+
+    selector({})
+    expect(inputs.foo.mock.calls.length).toBe(4)
+    expect(inputs.bar.mock.calls.length).toBe(1)
+
+    selector({})
+    expect(inputs.foo.mock.calls.length).toBe(5)
+    expect(inputs.bar.mock.calls.length).toBe(1)
+  })
+})

yarn.lock

@@ -2,10 +2,10 @@
 # yarn lockfile v1
 
 
-"@babel/cli@^7.0.0", "@babel/cli@^7.1.5":
-  version "7.2.3"
-  resolved "https://registry.yarnpkg.com/@babel/cli/-/cli-7.2.3.tgz#1b262e42a3e959d28ab3d205ba2718e1923cfee6"
-  integrity sha512-bfna97nmJV6nDJhXNPeEfxyMjWnt6+IjUAaDPiYRTBlm8L41n8nvw6UAqUCbvpFfU246gHPxW7sfWwqtF4FcYA==
+"@babel/cli@7.1.5", "@babel/cli@^7.0.0", "@babel/cli@^7.1.5":
+  version "7.1.5"
+  resolved "https://registry.yarnpkg.com/@babel/cli/-/cli-7.1.5.tgz#4ccf0a8cdabeefdd8ce955384530f050935bc4d7"
+  integrity sha512-zbO/DtTnaDappBflIU3zYEgATLToRDmW5uN/EGH1GXaes7ydfjqmAoK++xmJIA+8HfDw7UyPZNdM8fhGhfmMhw==
   dependencies:
     commander "^2.8.1"
     convert-source-map "^1.1.0"
@@ -26,7 +26,27 @@
   dependencies:
     "@babel/highlight" "^7.0.0"
 
-"@babel/core@^7.0.0", "@babel/core@^7.1.0", "@babel/core@^7.1.5":
+"@babel/core@7.1.5", "@babel/core@^7.0.0", "@babel/core@^7.1.5":
+  version "7.1.5"
+  resolved "https://registry.yarnpkg.com/@babel/core/-/core-7.1.5.tgz#abb32d7aa247a91756469e788998db6a72b93090"
+  integrity sha512-vOyH020C56tQvte++i+rX2yokZcRfbv/kKcw+/BCRw/cK6dvsr47aCzm8oC1XHwMSEWbqrZKzZRLzLnq6SFMsg==
+  dependencies:
+    "@babel/code-frame" "^7.0.0"
+    "@babel/generator" "^7.1.5"
+    "@babel/helpers" "^7.1.5"
+    "@babel/parser" "^7.1.5"
+    "@babel/template" "^7.1.2"
+    "@babel/traverse" "^7.1.5"
+    "@babel/types" "^7.1.5"
+    convert-source-map "^1.1.0"
+    debug "^3.1.0"
+    json5 "^0.5.0"
+    lodash "^4.17.10"
+    resolve "^1.3.2"
+    semver "^5.4.1"
+    source-map "^0.5.0"
+
+"@babel/core@^7.1.0":
   version "7.4.0"
   resolved "https://registry.yarnpkg.com/@babel/core/-/core-7.4.0.tgz#248fd6874b7d755010bfe61f557461d4f446d9e9"
   integrity sha512-Dzl7U0/T69DFOTwqz/FJdnOSWS57NpjNfCwMKHABr589Lg8uX1RrlBIJ7L5Dubt/xkLsx0xH5EBFzlBVes1ayA==
@@ -683,53 +703,49 @@
     core-js "^2.6.5"
     regenerator-runtime "^0.13.2"
 
-"@babel/preset-env@^7.0.0", "@babel/preset-env@^7.1.5":
-  version "7.4.2"
-  resolved "https://registry.yarnpkg.com/@babel/preset-env/-/preset-env-7.4.2.tgz#2f5ba1de2daefa9dcca653848f96c7ce2e406676"
-  integrity sha512-OEz6VOZaI9LW08CWVS3d9g/0jZA6YCn1gsKIy/fut7yZCJti5Lm1/Hi+uo/U+ODm7g4I6gULrCP+/+laT8xAsA==
+"@babel/preset-env@7.1.5", "@babel/preset-env@^7.0.0", "@babel/preset-env@^7.1.5":
+  version "7.1.5"
+  resolved "https://registry.yarnpkg.com/@babel/preset-env/-/preset-env-7.1.5.tgz#a28b5482ca8bc2f2d0712234d6c690240b92495d"
+  integrity sha512-pQ+2o0YyCp98XG0ODOHJd9z4GsSoV5jicSedRwCrU8uiqcJahwQiOq0asSZEb/m/lwyu6X5INvH/DSiwnQKncw==
   dependencies:
     "@babel/helper-module-imports" "^7.0.0"
     "@babel/helper-plugin-utils" "^7.0.0"
-    "@babel/plugin-proposal-async-generator-functions" "^7.2.0"
-    "@babel/plugin-proposal-json-strings" "^7.2.0"
-    "@babel/plugin-proposal-object-rest-spread" "^7.4.0"
-    "@babel/plugin-proposal-optional-catch-binding" "^7.2.0"
-    "@babel/plugin-proposal-unicode-property-regex" "^7.4.0"
-    "@babel/plugin-syntax-async-generators" "^7.2.0"
-    "@babel/plugin-syntax-json-strings" "^7.2.0"
-    "@babel/plugin-syntax-object-rest-spread" "^7.2.0"
-    "@babel/plugin-syntax-optional-catch-binding" "^7.2.0"
-    "@babel/plugin-transform-arrow-functions" "^7.2.0"
-    "@babel/plugin-transform-async-to-generator" "^7.4.0"
-    "@babel/plugin-transform-block-scoped-functions" "^7.2.0"
-    "@babel/plugin-transform-block-scoping" "^7.4.0"
-    "@babel/plugin-transform-classes" "^7.4.0"
-    "@babel/plugin-transform-computed-properties" "^7.2.0"
-    "@babel/plugin-transform-destructuring" "^7.4.0"
-    "@babel/plugin-transform-dotall-regex" "^7.2.0"
-    "@babel/plugin-transform-duplicate-keys" "^7.2.0"
-    "@babel/plugin-transform-exponentiation-operator" "^7.2.0"
-    "@babel/plugin-transform-for-of" "^7.4.0"
-    "@babel/plugin-transform-function-name" "^7.2.0"
-    "@babel/plugin-transform-literals" "^7.2.0"
-    "@babel/plugin-transform-modules-amd" "^7.2.0"
-    "@babel/plugin-transform-modules-commonjs" "^7.4.0"
-    "@babel/plugin-transform-modules-systemjs" "^7.4.0"
-    "@babel/plugin-transform-modules-umd" "^7.2.0"
-    "@babel/plugin-transform-named-capturing-groups-regex" "^7.4.2"
-    "@babel/plugin-transform-new-target" "^7.4.0"
-    "@babel/plugin-transform-object-super" "^7.2.0"
-    "@babel/plugin-transform-parameters" "^7.4.0"
-    "@babel/plugin-transform-regenerator" "^7.4.0"
-    "@babel/plugin-transform-shorthand-properties" "^7.2.0"
-    "@babel/plugin-transform-spread" "^7.2.0"
-    "@babel/plugin-transform-sticky-regex" "^7.2.0"
-    "@babel/plugin-transform-template-literals" "^7.2.0"
-    "@babel/plugin-transform-typeof-symbol" "^7.2.0"
-    "@babel/plugin-transform-unicode-regex" "^7.2.0"
-    "@babel/types" "^7.4.0"
-    browserslist "^4.4.2"
-    core-js-compat "^3.0.0"
+    "@babel/plugin-proposal-async-generator-functions" "^7.1.0"
+    "@babel/plugin-proposal-json-strings" "^7.0.0"
+    "@babel/plugin-proposal-object-rest-spread" "^7.0.0"
+    "@babel/plugin-proposal-optional-catch-binding" "^7.0.0"
+    "@babel/plugin-proposal-unicode-property-regex" "^7.0.0"
+    "@babel/plugin-syntax-async-generators" "^7.0.0"
+    "@babel/plugin-syntax-object-rest-spread" "^7.0.0"
+    "@babel/plugin-syntax-optional-catch-binding" "^7.0.0"
+    "@babel/plugin-transform-arrow-functions" "^7.0.0"
+    "@babel/plugin-transform-async-to-generator" "^7.1.0"
+    "@babel/plugin-transform-block-scoped-functions" "^7.0.0"
+    "@babel/plugin-transform-block-scoping" "^7.1.5"
+    "@babel/plugin-transform-classes" "^7.1.0"
+    "@babel/plugin-transform-computed-properties" "^7.0.0"
+    "@babel/plugin-transform-destructuring" "^7.0.0"
+    "@babel/plugin-transform-dotall-regex" "^7.0.0"
+    "@babel/plugin-transform-duplicate-keys" "^7.0.0"
+    "@babel/plugin-transform-exponentiation-operator" "^7.1.0"
+    "@babel/plugin-transform-for-of" "^7.0.0"
+    "@babel/plugin-transform-function-name" "^7.1.0"
+    "@babel/plugin-transform-literals" "^7.0.0"
+    "@babel/plugin-transform-modules-amd" "^7.1.0"
+    "@babel/plugin-transform-modules-commonjs" "^7.1.0"
+    "@babel/plugin-transform-modules-systemjs" "^7.0.0"
+    "@babel/plugin-transform-modules-umd" "^7.1.0"
+    "@babel/plugin-transform-new-target" "^7.0.0"
+    "@babel/plugin-transform-object-super" "^7.1.0"
+    "@babel/plugin-transform-parameters" "^7.1.0"
+    "@babel/plugin-transform-regenerator" "^7.0.0"
+    "@babel/plugin-transform-shorthand-properties" "^7.0.0"
+    "@babel/plugin-transform-spread" "^7.0.0"
+    "@babel/plugin-transform-sticky-regex" "^7.0.0"
+    "@babel/plugin-transform-template-literals" "^7.0.0"
+    "@babel/plugin-transform-typeof-symbol" "^7.0.0"
+    "@babel/plugin-transform-unicode-regex" "^7.0.0"
+    browserslist "^4.1.0"
     invariant "^2.2.2"
     js-levenshtein "^1.1.3"
     semver "^5.3.0"