fix: parse options.env more similarly to process.env (#98)

This fix attempts to parse `options.env` in a similar way to how it is
parsed in `child_process.spawn`, namely by doing a simple sorted
case-insensitive lookup for `path` and `pathext`.

The intent is to support folks who pass in to opts `{ env:
...process.env}`, as this removes the built in case insensitivity that
is present on the original `process.env` object.

lib/index.js

@@ -100,8 +100,8 @@ const spawnWithShell = (cmd, args, opts, extra) => {
     let pathToInitial
     try {
       pathToInitial = which.sync(initialCmd, {
-        path: (options.env && options.env.PATH) || process.env.PATH,
-        pathext: (options.env && options.env.PATHEXT) || process.env.PATHEXT,
+        path: (options.env && findInObject(options.env, 'PATH')) || process.env.PATH,
+        pathext: (options.env && findInObject(options.env, 'PATHEXT')) || process.env.PATHEXT,
       }).toLowerCase()
     } catch (err) {
       pathToInitial = initialCmd.toLowerCase()
@@ -192,4 +192,14 @@ const stdioResult = (stdout, stderr, { stdioString = true, stdio }) => {
   return result
 }
 
+// case insensitive lookup in an object
+const findInObject = (obj, key) => {
+  key = key.toLowerCase()
+  for (const objKey of Object.keys(obj).sort()) {
+    if (objKey.toLowerCase() === key) {
+      return obj[objKey]
+    }
+  }
+}
+
 module.exports = promiseSpawn

test/shell.js

@@ -206,5 +206,42 @@ t.test('cmd', (t) => {
     t.ok(proc.called)
   })
 
+  t.test('which respects variant casing for provided env PATH/PATHEXT', async (t) => {
+    const PATH = 'C:\\Windows\\System32'
+    const PATHEXT = 'EXE'
+
+    const promiseSpawnMock = t.mock('../lib/index.js', {
+      which: {
+        sync: (key, opts) => {
+          t.equal(key, 'dir')
+          t.equal(opts.path, PATH)
+          t.equal(opts.pathext, PATHEXT)
+          return 'dir.exe'
+        },
+      },
+    })
+
+    const proc = spawk.spawn('cmd.exe', ['/d', '/s', '/c', 'dir ^"with^ spaces^"'], {
+      shell: false,
+      windowsVerbatimArguments: true,
+    })
+
+    const result = await promiseSpawnMock('dir', ['with spaces'], {
+      env: {
+        pAtH: PATH,
+        pathEXT: PATHEXT,
+      },
+      shell: 'cmd.exe',
+    })
+    t.hasStrict(result, {
+      code: 0,
+      signal: undefined,
+      stdout: '',
+      stderr: '',
+    })
+
+    t.ok(proc.called)
+  })
+
   t.end()
 })