Add support for Elm assets (#1968)

.gitignore

@@ -12,6 +12,7 @@ lib
 .vscode/
 .idea/
 *.min.js
+test/integration/**/elm-stuff
 test/integration/**/target
 test/integration/**/Cargo.lock
 test/**/node_modules

packages/core/parcel-bundler/package.json

@@ -86,6 +86,7 @@
     "codecov": "^3.0.0",
     "coffeescript": "^2.0.3",
     "cross-env": "^5.1.1",
+    "elm": "^0.19.0",
     "eslint": "^4.13.0",
     "glslify-bundle": "^5.0.0",
     "glslify-deps": "^1.3.0",
@@ -97,6 +98,7 @@
     "mocha": "^5.1.1",
     "ncp": "^2.0.0",
     "nib": "^1.1.2",
+    "node-elm-compiler": "^5.0.1",
     "nyc": "^11.1.0",
     "postcss-modules": "^1.1.0",
     "posthtml-extend": "^0.2.1",

packages/core/parcel-bundler/src/Asset.js

@@ -27,6 +27,7 @@ class Asset {
     this.options = options;
     this.encoding = 'utf8';
     this.type = path.extname(this.name).slice(1);
+    this.hmrPageReload = false;
 
     this.processed = false;
     this.contents = options.rendition ? options.rendition.value : null;

packages/core/parcel-bundler/src/HMRServer.js

@@ -62,8 +62,8 @@ class HMRServer {
       });
     }
 
-    const containsHtmlAsset = assets.some(asset => asset.type === 'html');
-    if (containsHtmlAsset) {
+    const shouldReload = assets.some(asset => asset.hmrPageReload);
+    if (shouldReload) {
       this.broadcast({
         type: 'reload'
       });

packages/core/parcel-bundler/src/Parser.js

@@ -17,6 +17,7 @@ class Parser {
     this.registerExtension('ts', './assets/TypeScriptAsset');
     this.registerExtension('tsx', './assets/TypeScriptAsset');
     this.registerExtension('coffee', './assets/CoffeeScriptAsset');
+    this.registerExtension('elm', './assets/ElmAsset');
     this.registerExtension('vue', './assets/VueAsset');
     this.registerExtension('json', './assets/JSONAsset');
     this.registerExtension('json5', './assets/JSONAsset');

packages/core/parcel-bundler/src/assets/ElmAsset.js

@@ -0,0 +1,130 @@
+const Asset = require('../Asset');
+const commandExists = require('command-exists');
+const localRequire = require('../utils/localRequire');
+const {minify} = require('terser');
+const path = require('path');
+const spawn = require('cross-spawn');
+
+class ElmAsset extends Asset {
+  constructor(name, options) {
+    super(name, options);
+    this.type = 'js';
+    this.hmrPageReload = true;
+  }
+
+  async parse() {
+    let options = {
+      cwd: path.dirname(this.name)
+    };
+
+    // If elm is not installed globally, install it locally.
+    try {
+      await commandExists('elm');
+    } catch (err) {
+      await localRequire('elm', this.name);
+      options.pathToElm = path.join(
+        path.dirname(require.resolve('elm')),
+        'bin',
+        'elm'
+      );
+    }
+
+    this.elm = await localRequire('node-elm-compiler', this.name);
+
+    // Ensure that an elm.json file exists, and initialize one if not.
+    let elmConfig = await this.getConfig(['elm.json'], {load: false});
+    if (!elmConfig) {
+      await this.createElmConfig(options);
+
+      // Ensure we are watching elm.json for changes
+      await this.getConfig(['elm.json'], {load: false});
+    }
+
+    if (this.options.minify) {
+      options.optimize = true;
+    }
+
+    let compiled = await this.elm.compileToString(this.name, options);
+    this.contents = compiled.toString();
+  }
+
+  async collectDependencies() {
+    let dependencies = await this.elm.findAllDependencies(this.name);
+    for (let dependency of dependencies) {
+      this.addDependency(dependency, {includedInParent: true});
+    }
+  }
+
+  async createElmConfig(options) {
+    let cp = spawn(options.pathToElm || 'elm', ['init']);
+    cp.stdin.write('y\n');
+
+    return new Promise((resolve, reject) => {
+      cp.on('error', reject);
+      cp.on('close', function(code) {
+        if (code !== 0) {
+          return reject(new Error('elm init failed.'));
+        }
+
+        return resolve();
+      });
+    });
+  }
+
+  async generate() {
+    let output = this.contents;
+
+    if (this.options.minify) {
+      output = pack(output);
+    }
+
+    return {
+      [this.type]: output
+    };
+
+    // Recommended minification
+    // Based on:
+    // - http://elm-lang.org/0.19.0/optimize
+    function pack(source) {
+      let options = {
+        compress: {
+          keep_fargs: false,
+          passes: 2,
+          pure_funcs: [
+            'F2',
+            'F3',
+            'F4',
+            'F5',
+            'F6',
+            'F7',
+            'F8',
+            'F9',
+            'A2',
+            'A3',
+            'A4',
+            'A5',
+            'A6',
+            'A7',
+            'A8',
+            'A9'
+          ],
+          pure_getters: true,
+          unsafe: true,
+          unsafe_comps: true
+        },
+        mangle: true,
+        rename: false
+      };
+
+      let result = minify(source, options);
+
+      if (result.error) {
+        throw result.error;
+      }
+
+      return result.code;
+    }
+  }
+}
+
+module.exports = ElmAsset;

packages/core/parcel-bundler/src/assets/HTMLAsset.js

@@ -85,6 +85,7 @@ class HTMLAsset extends Asset {
     super(name, options);
     this.type = 'html';
     this.isAstDirty = false;
+    this.hmrPageReload = true;
   }
 
   async parse(code) {

packages/core/parcel-bundler/test/elm.js

@@ -0,0 +1,29 @@
+const assert = require('assert');
+const fs = require('../src/utils/fs');
+const {bundle, assertBundleTree, run} = require('./utils');
+
+describe('elm', function() {
+  it('should produce a basic Elm bundle', async function() {
+    let b = await bundle(__dirname + '/integration/elm/index.js');
+
+    await assertBundleTree(b, {
+      type: 'js',
+      assets: ['Main.elm', 'index.js']
+    });
+
+    let output = await run(b);
+    assert.equal(typeof output().Elm.Main.init, 'function');
+  });
+
+  it('should minify Elm in production mode', async function() {
+    let b = await bundle(__dirname + '/integration/elm/index.js', {
+      production: true
+    });
+
+    let output = await run(b);
+    assert.equal(typeof output().Elm.Main.init, 'function');
+
+    let js = await fs.readFile(__dirname + '/dist/index.js', 'utf8');
+    assert(!js.includes('elm$core'));
+  });
+});

packages/core/parcel-bundler/test/integration/elm/elm.json

@@ -0,0 +1,24 @@
+{
+    "type": "application",
+    "source-directories": [
+        "src"
+    ],
+    "elm-version": "0.19.0",
+    "dependencies": {
+        "direct": {
+            "elm/browser": "1.0.0",
+            "elm/core": "1.0.0",
+            "elm/html": "1.0.0"
+        },
+        "indirect": {
+            "elm/json": "1.0.0",
+            "elm/time": "1.0.0",
+            "elm/url": "1.0.0",
+            "elm/virtual-dom": "1.0.0"
+        }
+    },
+    "test-dependencies": {
+        "direct": {},
+        "indirect": {}
+    }
+}

packages/core/parcel-bundler/test/integration/elm/index.js

@@ -0,0 +1,5 @@
+var local = require('./src/Main.elm');
+
+module.exports = function () {
+    return local;
+};

packages/core/parcel-bundler/test/integration/elm/src/Main.elm

@@ -0,0 +1,47 @@
+module Main exposing (main)
+
+import Browser
+import Html exposing (Html, button, div, text)
+import Html.Events exposing (onClick)
+
+
+type alias Model =
+    { count : Int }
+
+
+initialModel : Model
+initialModel =
+    { count = 0 }
+
+
+type Msg
+    = Increment
+    | Decrement
+
+
+update : Msg -> Model -> Model
+update msg model =
+    case msg of
+        Increment ->
+            { model | count = model.count + 1 }
+
+        Decrement ->
+            { model | count = model.count - 1 }
+
+
+view : Model -> Html Msg
+view model =
+    div []
+        [ button [ onClick Increment ] [ text "+1" ]
+        , div [] [ text <| String.fromInt model.count ]
+        , button [ onClick Decrement ] [ text "-1" ]
+        ]
+
+
+main : Program () Model Msg
+main =
+    Browser.sandbox
+        { init = initialModel
+        , view = view
+        , update = update
+        }