Add extractAssignedNames (#59)

README.md

@@ -37,16 +37,12 @@ See [rollup-plugin-inject](https://github.com/rollup/rollup-plugin-inject) or [r
 
 ```js
 import { attachScopes } from 'rollup-pluginutils';
-import { parse } from 'acorn';
 import { walk } from 'estree-walker';
 
 export default function myPlugin ( options = {} ) {
   return {
     transform ( code ) {
-      const ast = parse( code, {
-        ecmaVersion: 6,
-        sourceType: 'module'
-      });
+      const ast = this.parse( code );
 
       let scope = attachScopes( ast, 'scope' );
 
@@ -128,6 +124,33 @@ Outputs the string ES module source:
 */
 ```
 
+### extractAssignedNames
+
+Extract the names of all assignment targets from patterns.
+
+```js
+import { extractAssignedNames } from 'rollup-pluginutils';
+import { walk } from 'estree-walker';
+
+export default function myPlugin ( options = {} ) {
+  return {
+    transform ( code ) {
+      const ast = this.parse( code );
+
+      walk( ast, {
+        enter ( node ) {
+          if ( node.type === 'VariableDeclarator' ) {
+          	const declaredNames = extractAssignedNames(node.id);
+          	// do something with the declared names
+          	// e.g. for `const {x, y: z} = ... => declaredNames = ['x', 'z']
+          }
+        }
+      });
+    }
+  };
+}
+```
+
 
 ## License
 

src/attachScopes.ts

@@ -1,56 +1,12 @@
 import { Node, walk } from 'estree-walker';
+import extractAssignedNames from './extractAssignedNames';
 import { AttachedScope, AttachScopes } from './pluginutils';
 
 const blockDeclarations = {
 	const: true,
 	let: true
 };
 
-interface Extractors {
-	[key: string]: (names: Array<string>, param: Node) => void;
-}
-
-const extractors: Extractors = {
-	Literal(names: Array<string>, param: Node) {
-		names.push(param.value as string);
-	},
-
-	Identifier(names: Array<string>, param: Node) {
-		names.push(param.name);
-	},
-
-	ObjectPattern(names: Array<string>, param: Node) {
-		param.properties.forEach((prop: Node) => {
-			if (prop.type === 'RestElement') {
-				extractors.RestElement(names, prop);
-			} else {
-				extractors[(prop.value || prop.key).type](names, prop.value || prop.key);
-			}
-		});
-	},
-
-	ArrayPattern(names: Array<string>, param: Node) {
-		param.elements.forEach((element: Node) => {
-			if (element) extractors[element.type](names, element);
-		});
-	},
-
-	RestElement(names: Array<string>, param: Node) {
-		extractors[param.argument.type](names, param.argument);
-	},
-
-	AssignmentPattern(names: Array<string>, param: Node) {
-		return extractors[param.left.type](names, param.left);
-	}
-};
-
-function extractNames(param: Node): Array<string> {
-	const names: Array<string> = [];
-
-	extractors[param.type](names, param);
-	return names;
-}
-
 interface ScopeOptions {
 	parent?: AttachedScope;
 	block?: boolean;
@@ -70,7 +26,7 @@ class Scope implements AttachedScope {
 
 		if (options.params) {
 			options.params.forEach(param => {
-				extractNames(param).forEach(name => {
+				extractAssignedNames(param).forEach(name => {
 					this.declarations[name] = true;
 				});
 			});
@@ -83,7 +39,7 @@ class Scope implements AttachedScope {
 			// is a block scope, so we need to go up
 			this.parent!.addDeclaration(node, isBlockDeclaration, isVar);
 		} else if (node.id) {
-			extractNames(node.id).forEach(name => {
+			extractAssignedNames(node.id).forEach(name => {
 				this.declarations[name] = true;
 			});
 		}

src/extractAssignedNames.ts

@@ -0,0 +1,46 @@
+import { Node } from 'estree-walker';
+
+interface Extractors {
+	[key: string]: (names: Array<string>, param: Node) => void;
+}
+
+const extractors: Extractors = {
+	ArrayPattern(names: Array<string>, param: Node) {
+		for (const element of param.elements) {
+			if (element) extractors[element.type](names, element);
+		}
+	},
+
+	AssignmentPattern(names: Array<string>, param: Node) {
+		extractors[param.left.type](names, param.left);
+	},
+
+	Identifier(names: Array<string>, param: Node) {
+		names.push(param.name);
+	},
+
+	MemberExpression() {},
+
+	ObjectPattern(names: Array<string>, param: Node) {
+		for (const prop of param.properties) {
+			if (prop.type === 'RestElement') {
+				extractors.RestElement(names, prop);
+			} else {
+				extractors[prop.value.type](names, prop.value);
+			}
+		}
+	},
+
+	RestElement(names: Array<string>, param: Node) {
+		extractors[param.argument.type](names, param.argument);
+	}
+};
+
+const extractAssignedNames = function extractAssignedNames(param: Node): Array<string> {
+	const names: Array<string> = [];
+
+	extractors[param.type](names, param);
+	return names;
+};
+
+export { extractAssignedNames as default };

src/index.ts

@@ -3,3 +3,4 @@ export { default as attachScopes } from './attachScopes';
 export { default as createFilter } from './createFilter';
 export { default as makeLegalIdentifier } from './makeLegalIdentifier';
 export { default as dataToEsm } from './dataToEsm';
+export { default as extractAssignedNames } from './extractAssignedNames';

src/pluginutils.d.ts

@@ -33,3 +33,6 @@ export const makeLegalIdentifier: MakeLegalIdentifier;
 
 export type DataToEsm = (data: any, options?: DataToEsmOptions) => string;
 export const dataToEsm: DataToEsm;
+
+export type ExtractAssignedNames = (param: Node) => Array<string>;
+export const extractAssignedNames: ExtractAssignedNames;