fix(windows): use tasklist fallback when wmic unavailable for shell detection

On newer Windows builds wmic is removed, causing getWindowsAncestors to
silently fail and default to COMSPEC (cmd.exe) even when running from
pwsh. Add tasklist as a fallback strategy, and use PSModulePath env var
heuristic when only intermediary processes (node.exe) are found in the
tree.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dorlugasigal

src/cli/index.js

@@ -75,48 +75,66 @@ function getWindowsAncestors(startPid, maxDepth = 4) {
   const safePid = parseInt(startPid, 10);
   if (!Number.isFinite(safePid) || safePid <= 0) return names;
 
+  // Strategy 1: wmic (available on older Windows builds)
   try {
     const result = execFileSync(
       'wmic',
       ['process', 'get', 'Name,ParentProcessId,ProcessId', '/format:csv'],
       { stdio: ['pipe', 'pipe', 'ignore'], encoding: 'utf8', timeout: 5000, windowsHide: true },
     );
 
-    // Parse CSV output — first non-empty line is the header
     const lines = result.split(/\r?\n/).filter((l) => l.trim());
-    if (lines.length === 0) return names;
-
-    const header = lines[0].split(',').map((h) => h.trim());
-    const nameIdx = header.indexOf('Name');
-    const pidIdx = header.indexOf('ProcessId');
-    const ppidIdx = header.indexOf('ParentProcessId');
-    if (nameIdx === -1 || pidIdx === -1 || ppidIdx === -1) return names;
-
-    const processes = new Map();
-    for (let i = 1; i < lines.length; i++) {
-      const cols = lines[i].split(',');
-      if (cols.length <= Math.max(nameIdx, pidIdx, ppidIdx)) continue;
-      const pid = parseInt(cols[pidIdx], 10);
-      if (Number.isFinite(pid)) {
-        processes.set(pid, {
-          name: cols[nameIdx].trim().toLowerCase(),
-          ppid: parseInt(cols[ppidIdx], 10),
-        });
+    if (lines.length > 0) {
+      const header = lines[0].split(',').map((h) => h.trim());
+      const nameIdx = header.indexOf('Name');
+      const pidIdx = header.indexOf('ProcessId');
+      const ppidIdx = header.indexOf('ParentProcessId');
+      if (nameIdx !== -1 && pidIdx !== -1 && ppidIdx !== -1) {
+        const processes = new Map();
+        for (let i = 1; i < lines.length; i++) {
+          const cols = lines[i].split(',');
+          if (cols.length <= Math.max(nameIdx, pidIdx, ppidIdx)) continue;
+          const pid = parseInt(cols[pidIdx], 10);
+          if (Number.isFinite(pid)) {
+            processes.set(pid, {
+              name: cols[nameIdx].trim().toLowerCase(),
+              ppid: parseInt(cols[ppidIdx], 10),
+            });
+          }
+        }
+
+        let currentPid = safePid;
+        for (let i = 0; i < maxDepth; i++) {
+          const proc = processes.get(currentPid);
+          if (!proc) break;
+          log.debug(`Process tree: ${proc.name}`);
+          names.push(proc.name);
+          if (!Number.isFinite(proc.ppid) || proc.ppid === 0 || proc.ppid === currentPid) break;
+          currentPid = proc.ppid;
+        }
+        if (names.length > 0) return names;
       }
     }
+  } catch (err) {
+    log.debug(`wmic not available: ${err.message}`);
+  }
 
-    // Walk up the tree in memory — no more subprocess calls
-    let currentPid = safePid;
-    for (let i = 0; i < maxDepth; i++) {
-      const proc = processes.get(currentPid);
-      if (!proc) break;
-      log.debug(`Process tree: ${proc.name}`);
-      names.push(proc.name);
-      if (!Number.isFinite(proc.ppid) || proc.ppid === 0 || proc.ppid === currentPid) break;
-      currentPid = proc.ppid;
+  // Strategy 2: tasklist for direct parent name (always available on Windows)
+  try {
+    const result = execFileSync('tasklist', ['/FI', `PID eq ${safePid}`, '/FO', 'CSV', '/NH'], {
+      stdio: ['pipe', 'pipe', 'ignore'],
+      encoding: 'utf8',
+      timeout: 5000,
+      windowsHide: true,
+    });
+    const match = result.match(/"([^"]+)"/);
+    if (match) {
+      const name = match[1].toLowerCase();
+      log.debug(`Process tree (tasklist): ${name}`);
+      names.push(name);
     }
   } catch (err) {
-    log.debug(`Could not query process tree: ${err.message}`);
+    log.debug(`tasklist failed: ${err.message}`);
   }
 
   return names;
@@ -188,6 +206,19 @@ function getDefaultShell() {
       log.debug(`Using detected shell: cmd.exe`);
       return 'cmd.exe';
     }
+
+    // Heuristic: PSModulePath env var is set by PowerShell and inherited by children.
+    // When the tree walk only found intermediaries (node.exe), this detects the real shell.
+    const psModulePath = (process.env.PSModulePath || '').toLowerCase();
+    if (psModulePath.includes('\\powershell\\')) {
+      log.debug('Detected pwsh.exe via PSModulePath');
+      return 'pwsh.exe';
+    }
+    if (psModulePath.includes('\\windowspowershell\\')) {
+      log.debug('Detected powershell.exe via PSModulePath');
+      return 'powershell.exe';
+    }
+
     const fallback = process.env.COMSPEC || 'cmd.exe';
     log.debug(`Falling back to: ${fallback}`);
     return fallback;

test/cli/cli.test.js

@@ -530,8 +530,10 @@ describe('CLI', () => {
       const origPlatform = os.platform;
       const origExecFileSync = child_process.execFileSync;
       const origComspec = process.env.COMSPEC;
+      const origPSModulePath = process.env.PSModulePath;
       os.platform = () => 'win32';
       process.env.COMSPEC = 'C:\\Windows\\System32\\cmd.exe';
+      delete process.env.PSModulePath;
       child_process.execFileSync = (cmd) => {
         if (cmd === 'wmic') {
           return ['Node,Name,ParentProcessId,ProcessId', `PC,explorer.exe,0,${process.ppid}`].join(
@@ -551,6 +553,8 @@ describe('CLI', () => {
         child_process.execFileSync = origExecFileSync;
         if (origComspec !== undefined) process.env.COMSPEC = origComspec;
         else delete process.env.COMSPEC;
+        if (origPSModulePath !== undefined) process.env.PSModulePath = origPSModulePath;
+        else delete process.env.PSModulePath;
       }
     });
   });