Eliminate dead dependencies from bundle

packages/core/integration-tests/test/integration/process/browser-dep.js

@@ -0,0 +1 @@
+module.exports = () => 'browser';

packages/core/integration-tests/test/integration/process/browser.js

@@ -0,0 +1,5 @@
+const browserDep = require('./browser-dep.js');
+
+const res = browserDep();
+
+module.exports = res;

packages/core/integration-tests/test/integration/process/index-dead.js

@@ -0,0 +1,6 @@
+module.exports = (() => {
+  if (process.browser) {
+    return require('./browser');
+  }
+  return require('./server');
+})()

packages/core/integration-tests/test/integration/process/server-dep.js

@@ -0,0 +1 @@
+module.exports = () => 'server';

packages/core/integration-tests/test/integration/process/server.js

@@ -0,0 +1,5 @@
+const serverDep = require('./server-dep.js');
+
+const res = serverDep();
+
+module.exports = res;

packages/core/integration-tests/test/javascript.js

@@ -895,6 +895,72 @@ describe('javascript', function() {
     assert.equal(output(), false);
   });
 
+  it('should eliminate dead dependencies on --target=browser when minified', async function() {
+    let b = await bundle(
+      path.join(__dirname, '/integration/process/index-dead.js'),
+      {
+        minify: true,
+        target: 'browser'
+      }
+    );
+
+    await assertBundleTree(b, {
+      name: 'index-dead.js',
+      assets: ['index-dead.js', 'browser.js', 'browser-dep.js']
+    });
+
+    let output = await run(b);
+    assert.equal(output, 'browser');
+  });
+
+  it('should not eliminate dead dependencies on --target=node', async function() {
+    let b = await bundle(
+      path.join(__dirname, '/integration/process/index-dead.js'),
+      {
+        minify: true,
+        target: 'node'
+      }
+    );
+
+    await assertBundleTree(b, {
+      name: 'index-dead.js',
+      assets: [
+        'index-dead.js',
+        'browser.js',
+        'browser-dep.js',
+        'server.js',
+        'server-dep.js'
+      ]
+    });
+
+    let output = await run(b);
+    assert.equal(output, 'server');
+  });
+
+  it('should not eliminate dead dependencies on --target=electron', async function() {
+    let b = await bundle(
+      path.join(__dirname, '/integration/process/index-dead.js'),
+      {
+        minify: true,
+        target: 'node'
+      }
+    );
+
+    await assertBundleTree(b, {
+      name: 'index-dead.js',
+      assets: [
+        'index-dead.js',
+        'browser.js',
+        'browser-dep.js',
+        'server.js',
+        'server-dep.js'
+      ]
+    });
+
+    let output = await run(b);
+    assert.equal(output, 'server');
+  });
+
   it('should support adding implicit dependencies', async function() {
     let b = await bundle(path.join(__dirname, '/integration/json/index.js'), {
       delegate: {

packages/core/parcel-bundler/package.json

@@ -34,6 +34,7 @@
     "@parcel/watcher": "^1.11.0",
     "@parcel/workers": "^1.11.0",
     "ansi-to-html": "^0.6.4",
+    "babel-plugin-minify-dead-code-elimination": "^0.5.0",
     "babylon-walk": "^1.0.2",
     "browserslist": "^4.1.0",
     "chalk": "^2.1.0",

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

@@ -153,17 +153,41 @@ class JSAsset extends Asset {
     await babel(this);
 
     // Inline environment variables
-    if (this.options.target === 'browser' && ENV_RE.test(this.contents)) {
+    const hasProcessEnv = ENV_RE.test(this.contents);
+    if (this.options.target === 'browser' && hasProcessEnv) {
       await this.parseIfNeeded();
       this.traverseFast(envVisitor);
     }
 
     // Inline process.browser
-    if (this.options.target === 'browser' && BROWSER_RE.test(this.contents)) {
+    const hasProcessBrowser = BROWSER_RE.test(this.contents);
+    if (this.options.target === 'browser' && hasProcessBrowser) {
       await this.parseIfNeeded();
       this.traverse(processVisitor);
       this.isAstDirty = true;
     }
+
+    if (
+      this.options.minify &&
+      this.options.target === 'browser' &&
+      (hasProcessBrowser || hasProcessEnv)
+    ) {
+      await babel7(this, {
+        internal: true,
+        config: {
+          plugins: [
+            [
+              require('babel-plugin-minify-dead-code-elimination'),
+              {
+                keepFnName: true,
+                keepFnArgs: true,
+                keepClassName: true
+              }
+            ]
+          ]
+        }
+      });
+    }
   }
 
   async transform() {

yarn.lock

@@ -1850,6 +1850,11 @@ babel-helper-define-map@^6.24.1:
     babel-types "^6.26.0"
     lodash "^4.17.4"
 
+babel-helper-evaluate-path@^0.5.0:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/babel-helper-evaluate-path/-/babel-helper-evaluate-path-0.5.0.tgz#a62fa9c4e64ff7ea5cea9353174ef023a900a67c"
+  integrity sha512-mUh0UhS607bGh5wUMAQfOpt2JX2ThXMtppHRdRU1kL7ZLRWIXxoV2UIV1r2cAeeNeU1M5SB5/RSUgUxrK8yOkA==
+
 babel-helper-explode-assignable-expression@^6.24.1:
   version "6.24.1"
   resolved "https://registry.yarnpkg.com/babel-helper-explode-assignable-expression/-/babel-helper-explode-assignable-expression-6.24.1.tgz#f25b82cf7dc10433c55f70592d5746400ac22caa"
@@ -1886,6 +1891,11 @@ babel-helper-hoist-variables@^6.24.1:
     babel-runtime "^6.22.0"
     babel-types "^6.24.1"
 
+babel-helper-mark-eval-scopes@^0.4.3:
+  version "0.4.3"
+  resolved "https://registry.yarnpkg.com/babel-helper-mark-eval-scopes/-/babel-helper-mark-eval-scopes-0.4.3.tgz#d244a3bef9844872603ffb46e22ce8acdf551562"
+  integrity sha1-0kSjvvmESHJgP/tG4izorN9VFWI=
+
 babel-helper-optimise-call-expression@^6.24.1:
   version "6.24.1"
   resolved "https://registry.yarnpkg.com/babel-helper-optimise-call-expression/-/babel-helper-optimise-call-expression-6.24.1.tgz#f7a13427ba9f73f8f4fa993c54a97882d1244257"
@@ -1914,6 +1924,11 @@ babel-helper-remap-async-to-generator@^6.24.1:
     babel-traverse "^6.24.1"
     babel-types "^6.24.1"
 
+babel-helper-remove-or-void@^0.4.3:
+  version "0.4.3"
+  resolved "https://registry.yarnpkg.com/babel-helper-remove-or-void/-/babel-helper-remove-or-void-0.4.3.tgz#a4f03b40077a0ffe88e45d07010dee241ff5ae60"
+  integrity sha1-pPA7QAd6D/6I5F0HAQ3uJB/1rmA=
+
 babel-helper-replace-supers@^6.24.1:
   version "6.24.1"
   resolved "https://registry.yarnpkg.com/babel-helper-replace-supers/-/babel-helper-replace-supers-6.24.1.tgz#bf6dbfe43938d17369a213ca8a8bf74b6a90ab1a"
@@ -1948,6 +1963,16 @@ babel-plugin-check-es2015-constants@^6.22.0:
   dependencies:
     babel-runtime "^6.22.0"
 
+babel-plugin-minify-dead-code-elimination@^0.5.0:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-minify-dead-code-elimination/-/babel-plugin-minify-dead-code-elimination-0.5.0.tgz#d23ef5445238ad06e8addf5c1cf6aec835bcda87"
+  integrity sha512-XQteBGXlgEoAKc/BhO6oafUdT4LBa7ARi55mxoyhLHNuA+RlzRmeMAfc31pb/UqU01wBzRc36YqHQzopnkd/6Q==
+  dependencies:
+    babel-helper-evaluate-path "^0.5.0"
+    babel-helper-mark-eval-scopes "^0.4.3"
+    babel-helper-remove-or-void "^0.4.3"
+    lodash.some "^4.6.0"
+
 babel-plugin-syntax-async-functions@^6.8.0:
   version "6.13.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-syntax-async-functions/-/babel-plugin-syntax-async-functions-6.13.0.tgz#cad9cad1191b5ad634bf30ae0872391e0647be95"
@@ -6525,6 +6550,11 @@ lodash.noop@~2.3.0:
   resolved "https://registry.yarnpkg.com/lodash.noop/-/lodash.noop-2.3.0.tgz#3059d628d51bbf937cd2a0b6fc3a7f212a669c2c"
   integrity sha1-MFnWKNUbv5N80qC2/Dp/ISpmnCw=
 
+lodash.some@^4.6.0:
+  version "4.6.0"
+  resolved "https://registry.yarnpkg.com/lodash.some/-/lodash.some-4.6.0.tgz#1bb9f314ef6b8baded13b549169b2a945eb68e4d"
+  integrity sha1-G7nzFO9ri63tE7VJFpsqlF62jk0=
+
 lodash.sortby@^4.7.0:
   version "4.7.0"
   resolved "https://registry.yarnpkg.com/lodash.sortby/-/lodash.sortby-4.7.0.tgz#edd14c824e2cc9c1e0b0a1b42bb5210516a42438"