Fix repeated execPath directory

index.js

@@ -19,10 +19,18 @@ const npmRunPath = options => {
 		cwdPath = path.resolve(cwdPath, '..');
 	}
 
-	// Ensure the running `node` binary is used
-	result.push(path.dirname(process.execPath));
+	const execDir = getExecDir(options);
 
-	return result.concat(options.path).join(path.delimiter);
+	return result.concat(execDir, options.path).join(path.delimiter);
+};
+
+// Ensure the running `node` binary is used.
+// Noop if the directory is already in `PATH`
+const getExecDir = function (options) {
+	const execDir = path.normalize(path.dirname(process.execPath));
+	return options.path.split(path.delimiter).some(inputPath => path.normalize(inputPath) === execDir) ?
+		[] :
+		[execDir];
 };
 
 module.exports = npmRunPath;

test.js

@@ -13,3 +13,17 @@ test('main', t => {
 		path.join(__dirname, 'node_modules/.bin')
 	);
 });
+
+test('does not repeat execPath directory', t => {
+	const execDir = path.dirname(process.execPath);
+	const result = npmRunPath({path: execDir});
+	const execDirs = result.split(path.delimiter).filter(resultPath => resultPath === execDir);
+	t.is(execDirs.length, 1);
+});
+
+test('does not repeat execPath directory even when using a different form', t => {
+	const execDir = `${path.dirname(process.execPath)}/.`;
+	const result = npmRunPath({path: execDir});
+	const execDirs = result.split(path.delimiter).filter(resultPath => path.normalize(resultPath) === path.normalize(execDir));
+	t.is(execDirs.length, 1);
+});