address PR review feedback

- resolve the default npx CLI path inside launch error handling\n- report missing npm once without spawning\n- preserve explicit path injection and shell-free exact-pin behavior\n\nCo-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: priyanshu92

plugins/power-pages/scripts/launch-playwright-mcp.js

@@ -57,12 +57,24 @@ function resolveNpxCli({
 
 function launch({
   browser = detectBrowser(),
-  npxCliPath = resolveNpxCli(),
+  npxCliPath,
+  resolveNpxCliFn = resolveNpxCli,
   spawnFn = spawn,
   exitFn = (code) => process.exit(code),
   writeError = (message) => process.stderr.write(message),
 } = {}) {
-  const child = spawnFn(process.execPath, [npxCliPath, ...buildMcpArgs(browser)], {
+  let resolvedNpxCliPath = npxCliPath;
+  if (resolvedNpxCliPath === undefined) {
+    try {
+      resolvedNpxCliPath = resolveNpxCliFn();
+    } catch (error) {
+      writeError(`Failed to start Playwright MCP: ${error.message}\n`);
+      exitFn(1);
+      return null;
+    }
+  }
+
+  const child = spawnFn(process.execPath, [resolvedNpxCliPath, ...buildMcpArgs(browser)], {
     stdio: 'inherit',
     shell: false,
   });

plugins/power-pages/scripts/tests/launch-playwright-mcp.test.js

@@ -78,13 +78,16 @@ test('fullscreen config maximizes the browser and uses the real viewport size',
   assert.equal(config.browser.contextOptions.viewport, null);
 });
 
-test('launch uses Node and raw argv without a shell', () => {
+test('launch preserves an explicit npx CLI path and uses raw argv without a shell', () => {
   let spawnCall;
   const child = new EventEmitter();
 
   launch({
     browser: 'msedge',
     npxCliPath: 'C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npx-cli.js',
+    resolveNpxCliFn() {
+      assert.fail('explicit npxCliPath must bypass default resolution');
+    },
     spawnFn(command, args, options) {
       spawnCall = { command, args, options };
       return child;
@@ -113,6 +116,37 @@ test('launch uses Node and raw argv without a shell', () => {
   assert.equal(spawnCall.exitCode, 7);
 });
 
+test('launch reports missing npm once and does not spawn', () => {
+  const exits = [];
+  let spawnCalls = 0;
+  let stderr = '';
+
+  const child = launch({
+    browser: 'chrome',
+    resolveNpxCliFn() {
+      throw new Error('Could not locate npm/bin/npx-cli.js');
+    },
+    spawnFn() {
+      spawnCalls += 1;
+      return new EventEmitter();
+    },
+    exitFn(code) {
+      exits.push(code);
+    },
+    writeError(message) {
+      stderr += message;
+    },
+  });
+
+  assert.equal(child, null);
+  assert.equal(spawnCalls, 0);
+  assert.deepEqual(exits, [1]);
+  assert.equal(
+    stderr,
+    'Failed to start Playwright MCP: Could not locate npm/bin/npx-cli.js\n',
+  );
+});
+
 test('launch reports spawn errors and exits with failure', () => {
   const child = new EventEmitter();
   const exits = [];