Support array in package.json's sideEffects property

src/Asset.js

@@ -125,7 +125,7 @@ class Asset {
 
   async getPackage() {
     if (!this._package) {
-      this._package = await this.getConfig(['package.json']);
+      this._package = await this.resolver.findPackage(path.dirname(this.name));
     }
 
     return this._package;

src/packagers/JSConcatPackager.js

@@ -141,8 +141,8 @@ class JSConcatPackager extends Packager {
     this.addedAssets.add(asset);
     let {js} = asset.generated;
 
-    // If the asset's package has the sideEffects: false flag set, and there are no used
-    // exports marked, exclude the asset from the bundle.
+    // If the asset has no side effects according to the its package's sideEffects flag,
+    // and there are no used exports marked, exclude the asset from the bundle.
     if (
       asset.cacheData.sideEffects === false &&
       (!asset.usedExports || asset.usedExports.size === 0)

src/scope-hoisting/hoist.js

@@ -1,4 +1,6 @@
+const path = require('path');
 const matchesPattern = require('../visitors/matches-pattern');
+const mm = require('micromatch');
 const t = require('babel-types');
 const template = require('babel-template');
 const rename = require('./renamer');
@@ -28,14 +30,32 @@ const TYPEOF = {
   require: 'function'
 };
 
+function hasSideEffects(asset, {sideEffects} = asset._package) {
+  switch (typeof sideEffects) {
+    case 'undefined':
+      return true;
+    case 'boolean':
+      return sideEffects;
+    case 'string':
+      return mm.isMatch(
+        path.relative(asset._package.pkgdir, asset.name),
+        sideEffects,
+        {matchBase: true}
+      );
+    case 'object':
+      return sideEffects.some(sideEffects =>
+        hasSideEffects(asset, {sideEffects})
+      );
+  }
+}
+
 module.exports = {
   Program: {
     enter(path, asset) {
       asset.cacheData.imports = asset.cacheData.imports || Object.create(null);
       asset.cacheData.exports = asset.cacheData.exports || Object.create(null);
       asset.cacheData.wildcards = asset.cacheData.wildcards || [];
-      asset.cacheData.sideEffects =
-        asset._package && asset._package.sideEffects;
+      asset.cacheData.sideEffects = asset._package && hasSideEffects(asset);
 
       let shouldWrap = false;
       path.traverse({

test/graphql.js

@@ -31,7 +31,6 @@ describe('graphql', function() {
           firstName
           lastName
         }
-
       `.definitions
     );
   });

test/integration/scope-hoisting/es6/side-effects-array/a.js

@@ -0,0 +1,3 @@
+import {foo} from 'bar';
+
+output = foo(2);

test/scope-hoisting.js

@@ -281,6 +281,22 @@ describe('scope hoisting', function() {
       assert.deepEqual(output, 'bar');
     });
 
+    it('supports the package.json sideEffects flag with an array', async function() {
+      let b = await bundle(
+        __dirname + '/integration/scope-hoisting/es6/side-effects-array/a.js'
+      );
+
+      let calls = [];
+      let output = await run(b, {
+        sideEffect: caller => {
+          calls.push(caller);
+        }
+      });
+
+      assert(calls.toString() == 'foo', "side effect called for 'foo'");
+      assert.deepEqual(output, 4);
+    });
+
     it('missing exports should be replaced with an empty object', async function() {
       let b = await bundle(
         __dirname + '/integration/scope-hoisting/es6/empty-module/a.js'