1 files changed, 55 insertions, 2 deletions

diff --git a/src/util/node-utils.js b/src/util/node-utils.js
index 252e920..345d10a 100644
--- a/src/util/node-utils.js
+++ b/src/util/node-utils.js
@@ -1,6 +1,8 @@
 // Utility functions which are only relevant to particular Node.js constructs.
 
-import {fileURLToPath} from 'url';
+import {readdir, stat} from 'node:fs/promises';
+import * as path from 'node:path';
+import {fileURLToPath} from 'node:url';
 
 import _commandExists from 'command-exists';
 
@@ -45,5 +47,56 @@ export function promisifyProcess(proc, showLogging = true) {
 // is great 'cuz (module === require.main) doesn't work without CommonJS
 // modules.
 export function isMain(importMetaURL) {
-  return process.argv[1] === fileURLToPath(importMetaURL);
+  const metaPath = fileURLToPath(importMetaURL);
+  const relative = path.relative(process.argv[1], metaPath);
+  const isIndexJS = path.basename(metaPath) === 'index.js';
+  return [
+    '',
+    isIndexJS && 'index.js'
+  ].includes(relative);
+}
+
+// Like readdir... but it's recursive! This returns a flat list of file paths.
+// By default, the paths include the provided top/root path, but this can be
+// changed with prefixPath to prefix some other path, or to just return paths
+// relative to the root. Change pathStyle to specify posix or win32, or leave
+// it as the default device-correct style. Provide a filterDir function to
+// control which directory names are traversed at all, and filterFile to
+// select which filenames are included in the final list.
+export async function traverse(rootPath, {
+  pathStyle = 'device',
+  filterFile = () => true,
+  filterDir = () => true,
+  prefixPath = rootPath,
+} = {}) {
+  const pathJoinDevice = path.join;
+  const pathJoinStyle = {
+    'device': path.join,
+    'posix': path.posix.join,
+    'win32': path.win32.join,
+  }[pathStyle];
+
+  if (!pathJoinStyle) {
+    throw new Error(`Expected pathStyle to be device, posix, or win32`);
+  }
+
+  const recursive = (names, ...subdirectories) =>
+    Promise.all(names.map(async name => {
+      const devicePath = pathJoinDevice(rootPath, ...subdirectories, name);
+      const stats = await stat(devicePath);
+
+      if (stats.isDirectory() && !filterDir(name)) return [];
+      else if (stats.isFile() && !filterFile(name)) return [];
+      else if (!stats.isDirectory() && !stats.isFile()) return [];
+
+      if (stats.isDirectory()) {
+        return recursive(await readdir(devicePath), ...subdirectories, name);
+      } else {
+        return pathJoinStyle(prefixPath, ...subdirectories, name);
+      }
+    }));
+
+  const names = await readdir(rootPath);
+  const results = await recursive(names);
+  return results.flat(Infinity);
 }