Make it idempotent (#20)

Author: ehmicky

index.js

@@ -12,27 +12,34 @@ export const npmRunPath = ({
 } = {}) => {
 	const cwdPath = path.resolve(toPath(cwd));
 	const result = [];
+	const pathParts = pathOption.split(path.delimiter);
 
 	if (preferLocal) {
-		applyPreferLocal(result, cwdPath);
+		applyPreferLocal(result, pathParts, cwdPath);
 	}
 
 	if (addExecPath) {
-		applyExecPath(result, execPath, cwdPath);
+		applyExecPath(result, pathParts, execPath, cwdPath);
 	}
 
 	return [...result, pathOption].join(path.delimiter);
 };
 
-const applyPreferLocal = (result, cwdPath) => {
+const applyPreferLocal = (result, pathParts, cwdPath) => {
 	for (const directory of traversePathUp(cwdPath)) {
-		result.push(path.join(directory, 'node_modules/.bin'));
+		const pathPart = path.join(directory, 'node_modules/.bin');
+		if (!pathParts.includes(pathPart)) {
+			result.push(pathPart);
+		}
 	}
 };
 
 // Ensure the running `node` binary is used
-const applyExecPath = (result, execPath, cwdPath) => {
-	result.push(path.resolve(cwdPath, toPath(execPath), '..'));
+const applyExecPath = (result, pathParts, execPath, cwdPath) => {
+	const pathPart = path.resolve(cwdPath, toPath(execPath), '..');
+	if (!pathParts.includes(pathPart)) {
+		result.push(pathPart);
+	}
 };
 
 export const npmRunPathEnv = ({env = process.env, ...options} = {}) => {

test.js

@@ -4,11 +4,11 @@ import {fileURLToPath, pathToFileURL} from 'node:url';
 import test from 'ava';
 import {npmRunPath, npmRunPathEnv} from './index.js';
 
-const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const localBinaryDirectory = fileURLToPath(new URL('node_modules/.bin', import.meta.url));
 
 const testLocalDirectory = (t, addExecPath, preferLocal, expectedResult) => {
 	t.is(
-		npmRunPath({path: '', addExecPath, preferLocal}).split(path.delimiter)[0] === path.join(__dirname, 'node_modules/.bin'),
+		npmRunPath({path: '', addExecPath, preferLocal}).split(path.delimiter)[0] === localBinaryDirectory,
 		expectedResult,
 	);
 };
@@ -20,7 +20,7 @@ test('"preferLocal: false", "addExecPath: false" does not add node_modules/.bin
 
 const testLocalDirectoryEnv = (t, addExecPath, preferLocal, expectedResult) => {
 	t.is(
-		npmRunPathEnv({env: {PATH: 'foo'}, addExecPath, preferLocal}).PATH.split(path.delimiter)[0] === path.join(__dirname, 'node_modules/.bin'),
+		npmRunPathEnv({env: {PATH: 'foo'}, addExecPath, preferLocal}).PATH.split(path.delimiter)[0] === localBinaryDirectory,
 		expectedResult,
 	);
 };
@@ -30,6 +30,15 @@ test('"addExecPath: false" still adds node_modules/.bin - npmRunPathEnv()', test
 test('"preferLocal: false" does not add node_modules/.bin - npmRunPathEnv()', testLocalDirectoryEnv, undefined, false, false);
 test('"preferLocal: false", "addExecPath: false" does not add node_modules/.bin - npmRunPathEnv()', testLocalDirectoryEnv, false, false, false);
 
+test('node_modules/.bin is not added twice', t => {
+	const firstPathEnv = npmRunPath({path: ''});
+	const pathEnv = npmRunPath({path: firstPathEnv});
+	const execPaths = pathEnv
+		.split(path.delimiter)
+		.filter(pathPart => pathPart === localBinaryDirectory);
+	t.is(execPaths.length, 1);
+});
+
 test('the `cwd` option changes the current directory', t => {
 	t.is(
 		npmRunPath({path: '', cwd: './dir'}).split(path.delimiter)[0],
@@ -49,6 +58,15 @@ test('push `execPath` later in the PATH', t => {
 	t.is(pathEnv.at(-2), path.dirname(process.execPath));
 });
 
+test('`execPath` is not added twice', t => {
+	const firstPathEnv = npmRunPath({path: ''});
+	const pathEnv = npmRunPath({path: firstPathEnv});
+	const execPaths = pathEnv
+		.split(path.delimiter)
+		.filter(pathPart => pathPart === path.dirname(process.execPath));
+	t.is(execPaths.length, 1);
+});
+
 const testExecPath = (t, preferLocal, addExecPath, expectedResult) => {
 	const pathEnv = npmRunPath({
 		path: '',