dataToNamedExports helper

Author: guybedford

README.md

@@ -103,6 +103,25 @@ makeLegalIdentifier( 'foo-bar' ); // 'foo_bar'
 makeLegalIdentifier( 'typeof' ); // '_typeof'
 ```
 
+### dataToNamedExports
+
+Helper for treeshakable data imports
+
+```js
+import { dataToNamedExports } from 'rollup-pluginutils';
+
+const esModuleSource = dataToNamedExports({
+  custom: 'data',
+  to: ['treeshake']
+});
+/*
+Outputs the string ES module source:
+  export const custom = 'data';
+  export const to = ['treeshake'];
+  export default { custom, to };
+*/
+```
+
 
 ## License
 

package.json

@@ -24,7 +24,8 @@
   },
   "dependencies": {
     "estree-walker": "^0.3.0",
-    "micromatch": "^2.3.11"
+    "micromatch": "^2.3.11",
+    "tosource": "^1.0.0"
   },
   "repository": "rollup/rollup-pluginutils",
   "keywords": [

rollup.config.js

@@ -4,7 +4,7 @@ import buble from 'rollup-plugin-buble';
 export default {
 	entry: 'src/index.js',
 	plugins: [ buble() ],
-	external: [ 'path', 'estree-walker', 'micromatch' ],
+	external: [ 'path', 'estree-walker', 'micromatch', 'tosource' ],
 
 	targets: [
 		{

src/dataToNamedExports.js

@@ -0,0 +1,30 @@
+import makeLegalIdentifier from './makeLegalIdentifier';
+import tosource from 'tosource';
+
+// convert data object into separate named exports (and default)
+export default function dataToNamedExports ( obj ) {
+  let output = '';
+  let defaultExports = '\n';
+  const usedLegalKeys = Object.create( null );
+  let index = 0;
+  const keys = Object.keys( obj );
+  for ( let i = 0; i < keys.length; i++ ) {
+    const key = keys[i];
+    const legalKey = makeLegalIdentifier( key );
+    output += `export const ${ legalKey } = ${tosource( obj[key] )};\n`;
+    while ( usedLegalKeys[legalKey + (index || '')] )
+      index++;
+    index = 0;
+    usedLegalKeys[legalKey + ( index || '' )] = true;
+    if ( defaultExports.length > 1 )
+      defaultExports += ',\n';
+    if ( key === legalKey )
+      defaultExports += `  ${ key }`;
+    else
+      defaultExports += `  ${ `'${ key }'` }: ${ legalKey }`;
+  }
+  if ( defaultExports.length > 3 )
+    defaultExports += '\n';
+  output += `export default {${ defaultExports }};`;
+  return output;
+};

src/index.js

@@ -2,3 +2,4 @@ export { default as addExtension } from './addExtension';
 export { default as attachScopes } from './attachScopes';
 export { default as createFilter } from './createFilter';
 export { default as makeLegalIdentifier } from './makeLegalIdentifier';
+export { default as dataToNamedExports } from './dataToNamedExports';

test/test.js

@@ -442,4 +442,21 @@ describe( 'rollup-pluginutils', function () {
 			assert.equal( makeLegalIdentifier( 'arguments' ), '_arguments' );
 		});
 	});
+
+	describe( 'dataToNamedExports', function () {
+		var dataToNamedExports = utils.dataToNamedExports;
+
+		it( 'outputs treeshakable data', function () {
+			assert.equal( dataToNamedExports({ some: 'data', another: 'data' }), `export const some = "data";\nexport const another = "data";\nexport default {\n  some,\n  another\n};` );
+		});
+
+		it( 'handles illegal identifiers', function () {
+			assert.equal( dataToNamedExports({ '1': 'data', 'default': 'data' }), `export const _1 = "data";\nexport const _default = "data";\nexport default {\n  '1': _1,\n  'default': _default\n};` );
+		});
+
+		it( 'supports non-JSON data', function () {
+			const date = new Date();
+			assert.equal( dataToNamedExports({ inf: Infinity, date }), `export const inf = Infinity;\nexport const date = new Date(${date.getTime()});\nexport default {\n  inf,\n  date\n};` );
+		});
+	});
 });