fix(exec): run the .cmd shim of a bin with a dot in its name on Windows

workspaces/libnpmexec/lib/run-script.js

@@ -1,9 +1,26 @@
+const { extname, resolve } = require('node:path')
 const ciInfo = require('ci-info')
 const runScript = require('@npmcli/run-script')
 const pkgJson = require('@npmcli/package-json')
 const { log, output } = require('proc-log')
 const noTTY = require('./no-tty.js')
 const isWindowsShell = require('./is-windows.js')
+const { fileExists, localFileExists } = require('./file-exists.js')
+
+// cmd.exe looks up a command that already has an extension by its exact name
+// before it tries PATHEXT. For a bin with a dot in its name that finds the
+// extensionless sh shim, and Windows opens it with whatever program is
+// registered for that "extension" instead of running it. Point cmd.exe at the
+// .cmd shim next to it instead.
+const hasCmdShim = async (bin, binPaths, runPath) => {
+  const shim = `${bin}.cmd`
+  for (const binPath of binPaths) {
+    if (await fileExists(resolve(binPath, shim))) {
+      return true
+    }
+  }
+  return !!(await localFileExists(resolve(runPath), shim, '/'))
+}
 
 const run = async ({
   args,
@@ -23,6 +40,9 @@ const run = async ({
       // literally; double quotes still expand $(), backticks, $var and "
       args[0] = `'${args[0].replace(/'/g, `'\\''`)}'`
     }
+  } else if (args.length > 0 && extname(args[0]) &&
+    await hasCmdShim(args[0], binPaths, runPath)) {
+    args[0] = `${args[0]}.cmd`
   }
 
   // turn list of args into command string

workspaces/libnpmexec/test/run-script.js

@@ -1,3 +1,4 @@
+const { resolve } = require('node:path')
 const t = require('tap')
 
 const mockRunScript = async (t, mocks, { level = 0 } = {}) => {
@@ -130,6 +131,35 @@ t.test('isWindows', async t => {
   await runScript()
 })
 
+t.test('isWindows runs the .cmd shim of a bin with a dot in its name', async t => {
+  const dir = t.testdir({
+    global: { 'dot.bin.cmd': '' },
+    project: {
+      node_modules: { '.bin': { 'local.bin.cmd': '' } },
+      nested: {},
+    },
+  })
+  let pkg
+  const { runScript } = await mockRunScript(t, {
+    'ci-info': { isCI: true },
+    '@npmcli/run-script': async (opts) => {
+      pkg = opts.pkg
+    },
+    '../lib/is-windows.js': true,
+  })
+  const binPaths = [resolve(dir, 'global')]
+  const runPath = resolve(dir, 'project', 'nested')
+
+  await runScript({ args: ['dot.bin', 'arg'], binPaths, runPath })
+  t.equal(pkg.scripts.npx, 'dot.bin.cmd', 'shim found in binPaths')
+
+  await runScript({ args: ['local.bin'], binPaths, runPath })
+  t.equal(pkg.scripts.npx, 'local.bin.cmd', 'shim found in a node_modules/.bin above runPath')
+
+  await runScript({ args: ['no.shim'], binPaths, runPath })
+  t.equal(pkg.scripts.npx, 'no.shim', 'left alone without a .cmd shim')
+})
+
 t.test('escapes executable name to neutralize shell metacharacters', async t => {
   let pkg
   const { runScript } = await mockRunScript(t, {