skip dead branches (#93)

src/ast-utils.js

@@ -31,3 +31,42 @@ export function flatten ( node ) {
 
 	return { name, keypath: parts.join( '.' ) };
 }
+
+export function isTruthy ( node ) {
+	if ( node.type === 'Literal' ) return !!node.value;
+	if ( node.type === 'ParenthesizedExpression' ) return isTruthy( node.expression );
+	if ( node.operator in operators ) return operators[ node.operator ]( node );
+}
+
+export function isFalsy ( node ) {
+	return not( isTruthy( node ) );
+}
+
+function not ( value ) {
+	return value === undefined ? value : !value;
+}
+
+function equals ( a, b, strict ) {
+	if ( a.type !== b.type ) return undefined;
+	if ( a.type === 'Literal' ) return strict ? a.value === b.value : a.value == b.value;
+}
+
+const operators = {
+	'==': x => {
+		return equals( x.left, x.right, false );
+	},
+
+	'!=': x => not( operators['==']( x ) ),
+
+	'===': x => {
+		return equals( x.left, x.right, true );
+	},
+
+	'!==': x => not( operators['===']( x ) ),
+
+	'!': x => isFalsy( x.argument ),
+
+	'&&': x => isTruthy( x.left ) && isTruthy( x.right ),
+
+	'||': x => isTruthy( x.left ) || isTruthy( x.right )
+};

src/transform.js

@@ -2,7 +2,7 @@ import acorn from 'acorn';
 import { walk } from 'estree-walker';
 import MagicString from 'magic-string';
 import { attachScopes, makeLegalIdentifier } from 'rollup-pluginutils';
-import { flatten, isReference } from './ast-utils.js';
+import { flatten, isReference, isTruthy, isFalsy } from './ast-utils.js';
 import { PREFIX, HELPERS_ID } from './helpers.js';
 import { getName } from './utils.js';
 
@@ -61,6 +61,12 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
 
 	walk( ast, {
 		enter ( node, parent ) {
+			// skip dead branches
+			if ( parent && ( parent.type === 'IfStatement' || parent.type === 'ConditionalExpression' ) ) {
+				if ( node === parent.consequent && isFalsy( parent.test ) ) return this.skip();
+				if ( node === parent.alternate && isTruthy( parent.test ) ) return this.skip();
+			}
+
 			if ( node.scope ) scope = node.scope;
 			if ( /^Function/.test( node.type ) ) scopeDepth += 1;
 

test/function/skips-dead-branches/_config.js

@@ -0,0 +1,9 @@
+const assert = require( 'assert' );
+
+module.exports = {
+	global: global => {
+		assert.equal( global.a, undefined );
+		assert.equal( global.b, 2 );
+		assert.equal( global.c, undefined );
+	}
+};

test/function/skips-dead-branches/a.js

@@ -0,0 +1 @@
+global.a = 1;

test/function/skips-dead-branches/b.js

@@ -0,0 +1,2 @@
+global.b = 2;
+module.exports = 'b';

test/function/skips-dead-branches/c.js

@@ -0,0 +1,2 @@
+global.c = 3;
+module.exports = 'c';

test/function/skips-dead-branches/main.js

@@ -0,0 +1,7 @@
+if ( 'development' === 'production' ) {
+	require( './a.js' );
+}
+
+module.exports = true ?
+	require( './b.js' ) :
+	require( './c.js' );

test/test.js

@@ -19,18 +19,23 @@ function executeBundle ( bundle ) {
 	let fn;
 
 	try {
-		fn = new Function( 'module', 'exports', 'require', 'assert', code );
+		fn = new Function( 'module', 'exports', 'require', 'global', 'assert', code );
 	} catch ( err ) {
 		// syntax error
 		console.log( code );
 		throw err;
 	}
 
 	const module = { exports: {} };
+	const global = {};
 
-	fn( module, module.exports, () => {}, assert );
+	fn( module, module.exports, () => {}, global, assert );
 
-	return module.exports;
+	return {
+		code,
+		exports: module.exports,
+		global
+	};
 }
 
 describe( 'rollup-plugin-commonjs', () => {
@@ -49,11 +54,12 @@ describe( 'rollup-plugin-commonjs', () => {
 					entry: `function/${dir}/main.js`,
 					plugins: [ commonjs() ]
 				}).then( bundle => {
-					const exports = executeBundle( bundle );
+					const { code, exports, global } = executeBundle( bundle );
 
-					if ( config.exports ) {
-						config.exports( exports );
-					}
+					if ( config.show ) console.error( code );
+
+					if ( config.exports ) config.exports( exports );
+					if ( config.global ) config.global( global );
 				});
 			});
 		});
@@ -193,7 +199,7 @@ describe( 'rollup-plugin-commonjs', () => {
 				entry: 'samples/extension/main.coffee',
 				plugins: [ commonjs({ extensions: ['.coffee' ]}) ]
 			}).then( bundle => {
-				assert.equal( executeBundle( bundle ), 42 );
+				assert.equal( executeBundle( bundle ).exports, 42 );
 			});
 		});
 
@@ -208,11 +214,11 @@ describe( 'rollup-plugin-commonjs', () => {
 					format: 'cjs'
 				});
 
-				const bundleExports = executeBundle( bundle );
+				const { exports, global } = executeBundle( bundle );
 
-				assert.equal( bundleExports.immediate1, global.setImmediate, generated.code );
-				assert.equal( bundleExports.immediate2, global.setImmediate, generated.code );
-				assert.equal( bundleExports.immediate3, null, generated.code );
+				assert.equal( exports.immediate1, global.setImmediate, generated.code );
+				assert.equal( exports.immediate2, global.setImmediate, generated.code );
+				assert.equal( exports.immediate3, null, generated.code );
 			});
 		});
 
@@ -222,7 +228,7 @@ describe( 'rollup-plugin-commonjs', () => {
 					entry: 'samples/umd/correct-scoping.js',
 					plugins: [ commonjs() ]
 				}).then( bundle => {
-					assert.equal( executeBundle( bundle ), 'object' );
+					assert.equal( executeBundle( bundle ).exports, 'object' );
 				});
 			});
 
@@ -231,7 +237,7 @@ describe( 'rollup-plugin-commonjs', () => {
 					entry: 'samples/umd/protobuf.js',
 					plugins: [ commonjs() ]
 				}).then( bundle => {
-					assert.equal( executeBundle( bundle ), true );
+					assert.equal( executeBundle( bundle ).exports, true );
 				});
 			});
 
@@ -253,8 +259,8 @@ describe( 'rollup-plugin-commonjs', () => {
 			return rollup({
 				entry: 'samples/deconflict-helpers/main.js',
 				plugins: [ commonjs() ]
-			}).then( executeBundle ).then( module => {
-				assert.notEqual( module.exports, 'nope' );
+			}).then( executeBundle ).then( ({ exports }) => {
+				assert.notEqual( exports, 'nope' );
 			});
 		});