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optimise output where possible
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@Rich-Harris
Rich-Harris committed Sep 2, 2016
1 parent 04cd209 commit 8a3e99e
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Showing 6 changed files with 130 additions and 44 deletions.
146 changes: 115 additions & 31 deletions src/transform.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,13 @@ const firstpassGlobal = /\b(?:require|module|exports|global)\b/;
const firstpassNoGlobal = /\b(?:require|module|exports)\b/;
const importExportDeclaration = /^(?:Import|Export(?:Named|Default))Declaration/;

function deconflict ( identifier, code ) {
function deconflict ( scope, identifier ) {
let i = 1;
let deconflicted = identifier;

while ( ~code.indexOf( deconflicted ) ) deconflicted = `${identifier}_${i++}`;
while ( scope.contains( deconflicted ) ) deconflicted = `${identifier}_${i++}`;
scope.declarations[ deconflicted ] = true;

return deconflicted;
}

Expand All @@ -40,9 +42,6 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
const firstpass = ignoreGlobal ? firstpassNoGlobal : firstpassGlobal;
if ( !firstpass.test( code ) ) return null;

const namedExports = {};
if ( customNamedExports ) customNamedExports.forEach( name => namedExports[ name ] = true );

const ast = tryParse( code, id );

// if there are top-level import/export declarations, this is ES not CommonJS
Expand All @@ -62,25 +61,36 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
let scope = attachScopes( ast, 'scope' );
const uses = { module: false, exports: false, global: false };

let scopeDepth = 0;
let lexicalDepth = 0;
let programDepth = 0;

const HELPERS_NAME = deconflict( scope, 'commonjsHelpers' );

const namedExports = {};
if ( customNamedExports ) customNamedExports.forEach( name => namedExports[ name ] = true );

const HELPERS_NAME = deconflict( 'commonjsHelpers', code );
// TODO handle transpiled modules
let shouldWrap = /__esModule/.test( code );

walk( ast, {
enter ( node, parent ) {
if ( sourceMap ) {
magicString.addSourcemapLocation( node.start );
magicString.addSourcemapLocation( node.end );
}

// 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;
if ( node._skip ) return this.skip();

if ( sourceMap ) {
magicString.addSourcemapLocation( node.start );
magicString.addSourcemapLocation( node.end );
}
programDepth += 1;

if ( node.scope ) scope = node.scope;
if ( /^Function/.test( node.type ) ) lexicalDepth += 1;

// Is this an assignment to exports or module.exports?
if ( node.type === 'AssignmentExpression' ) {
Expand All @@ -94,6 +104,14 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
const match = exportsPattern.exec( flattened.keypath );
if ( !match || flattened.keypath === 'exports' ) return;

uses[ flattened.name ] = true;

// we're dealing with `module.exports = ...` or `[module.]exports.foo = ...` –
// if this isn't top-level, we'll need to wrap the module
if ( programDepth > 3 ) shouldWrap = true;

node.left._skip = true;

if ( flattened.keypath === 'module.exports' && node.right.type === 'ObjectExpression' ) {
return node.right.properties.forEach( prop => {
if ( prop.computed || prop.key.type !== 'Identifier' ) return;
Expand All @@ -103,7 +121,6 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
}

if ( match[1] ) namedExports[ match[1] ] = true;

return;
}

Expand All @@ -120,12 +137,20 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
if ( node.type === 'Identifier' ) {
if ( ( node.name in uses ) && isReference( node, parent ) && !scope.contains( node.name ) ) {
uses[ node.name ] = true;
if ( node.name === 'global' && !ignoreGlobal ) magicString.overwrite( node.start, node.end, `${HELPERS_NAME}.commonjsGlobal` );
if ( node.name === 'global' && !ignoreGlobal ) {
magicString.overwrite( node.start, node.end, `${HELPERS_NAME}.commonjsGlobal`, true );
}

// if module or exports are used outside the context of an assignment
// expression, we need to wrap the module
if ( node.name === 'module' || node.name === 'exports' ) {
shouldWrap = true;
}
}
return;
}

if ( node.type === 'ThisExpression' && scopeDepth === 0 && !ignoreGlobal ) {
if ( node.type === 'ThisExpression' && lexicalDepth === 0 ) {
uses.global = true;
if ( !ignoreGlobal ) magicString.overwrite( node.start, node.end, `${HELPERS_NAME}.commonjsGlobal`, true );
return;
Expand Down Expand Up @@ -160,8 +185,9 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
},

leave ( node ) {
programDepth -= 1;
if ( node.scope ) scope = scope.parent;
if ( /^Function/.test( node.type ) ) scopeDepth -= 1;
if ( /^Function/.test( node.type ) ) lexicalDepth -= 1;
}
});

Expand All @@ -172,7 +198,8 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
return null; // not a CommonJS module
}

const importBlock = [ `import * as ${HELPERS_NAME} from '${HELPERS_ID}';` ].concat(
const includeHelpers = shouldWrap || uses.global;
const importBlock = ( includeHelpers ? [ `import * as ${HELPERS_NAME} from '${HELPERS_ID}';` ] : [] ).concat(
sources.map( source => {
// import the actual module before the proxy, so that we know
// what kind of proxy to build
Expand All @@ -182,27 +209,84 @@ export default function transform ( code, id, isEntry, ignoreGlobal, customNamed
const { name, importsDefault } = required[ source ];
return `import ${importsDefault ? `${name} from ` : ``}'${PREFIX}${source}';`;
})
).join( '\n' );
).join( '\n' ) + '\n\n';

const namedExportDeclarations = [];
let wrapperStart = '';
let wrapperEnd = '';

const moduleName = deconflict( scope, getName( id ) );
if ( !isEntry ) {
const exportModuleExports = `export { ${moduleName} as __moduleExports };`;
namedExportDeclarations.push( exportModuleExports );
}

const args = `module${uses.exports ? ', exports' : ''}`;
if ( shouldWrap ) {
const args = `module${uses.exports ? ', exports' : ''}`;

const name = getName( id );
const name = getName( id );

const wrapperStart = `\n\nvar ${name} = ${HELPERS_NAME}.createCommonjsModule(function (${args}) {\n`;
const wrapperEnd = `\n});\n\n`;
wrapperStart = `var ${moduleName} = ${HELPERS_NAME}.createCommonjsModule(function (${args}) {\n`;
wrapperEnd = `\n});`;

const exportBlock = ( isEntry ? [] : [ `export { ${name} as __moduleExports };` ] ).concat(
/__esModule/.test( code ) ? `export default ${HELPERS_NAME}.unwrapExports(${name});\n` : `export default ${name};\n`,
Object.keys( namedExports )
.filter( key => !blacklistedExports[ key ] )
.map( x => {
if (x === name) {
return `var ${x}$$1 = ${name}.${x};\nexport { ${x}$$1 as ${x} };`;
.forEach( x => {
let declaration;

if ( x === name ) {
const deconflicted = deconflict( scope, name );
declaration = `var ${deconflicted} = ${moduleName}.${x};\nexport { ${deconflicted} as ${x} };`;
} else {
return `export var ${x} = ${name}.${x};`;
declaration = `export var ${x} = ${moduleName}.${x};`;
}
})
).join( '\n' );

namedExportDeclarations.push( declaration );
});
} else {
let hasDefaultExport = false;
const names = [];

ast.body.forEach( node => {
if ( node.type === 'ExpressionStatement' && node.expression.type === 'AssignmentExpression' ) {
const { left, right } = node.expression;
const flattened = flatten( left );

const match = exportsPattern.exec( flattened.keypath );
if ( !match ) return;

if ( flattened.keypath === 'module.exports' ) {
hasDefaultExport = true;
magicString.overwrite( node.start, right.start, `var ${moduleName} = ` );
} else {
const name = match[1];
const deconflicted = deconflict( scope, name );

names.push({ name, deconflicted });

magicString.overwrite( node.start, right.start, `var ${deconflicted} = ` );

const declaration = name === deconflicted ?
`export { ${name} };` :
`export { ${deconflicted} as ${name} };`;

namedExportDeclarations.push( declaration );
}
}
});

if ( !hasDefaultExport ) {
wrapperEnd = `\n\nvar ${moduleName} = {\n${
names.map( ({ name, deconflicted }) => `\t${name}: ${deconflicted}` ).join( ',\n' )
}\n};`;
}
}

const defaultExport = /__esModule/.test( code ) ?
`export default ${HELPERS_NAME}.unwrapExports(${moduleName});` :
`export default ${moduleName};`;

const exportBlock = '\n\n' + [ defaultExport ].concat( namedExportDeclarations ).join( '\n' );

magicString.trim()
.prepend( importBlock + wrapperStart )
Expand Down
6 changes: 3 additions & 3 deletions test/form/optimised-default-export-function/output.js
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
var __moduleExports = function foo () {};
var input = function foo () {};

export default __moduleExports;
export { __moduleExports };
export default input;
export { input as __moduleExports };
6 changes: 3 additions & 3 deletions test/form/optimised-default-export/output.js
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
var __moduleExports = 42;
var input = 42;

export default __moduleExports;
export { __moduleExports };
export default input;
export { input as __moduleExports };
6 changes: 3 additions & 3 deletions test/form/optimised-named-export-conflicts/output.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,12 @@ var bar = 2;
var foo_1 = 'a';
var bar_1 = 'b';

var __moduleExports = {
var input = {
foo: foo_1,
bar: bar_1
};

export default __moduleExports;
export { __moduleExports };
export default input;
export { input as __moduleExports };
export { foo_1 as foo };
export { bar_1 as bar };
6 changes: 3 additions & 3 deletions test/form/optimised-named-export/output.js
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Original file line number Diff line number Diff line change
@@ -1,12 +1,12 @@
var foo = 'a';
var bar = 'b';

var __moduleExports = {
var input = {
foo: foo,
bar: bar
};

export default __moduleExports;
export { __moduleExports };
export default input;
export { input as __moduleExports };
export { foo };
export { bar };
4 changes: 3 additions & 1 deletion test/test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,9 @@ describe( 'rollup-plugin-commonjs', () => {
plugins: [ commonjs() ]
}).then( bundle => {
const { code } = bundle.generate({ format: 'cjs' });
if ( config.show ) console.error( code );
if ( config.show || config.solo ) {
console.error( code );
}

const { exports, global } = execute( code );

Expand Down

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