Add caching

index.d.ts

@@ -1,14 +1,25 @@
-declare function _exports(code: string, options: FromMemOptions): Promise<unknown>;
-export = _exports;
+export = fromMem;
+/**
+ * Import or require the given code from memory.  Knows about the different
+ * Peggy output formats.  Returns the exports of the module.
+ *
+ * @param {string} code Code to import
+ * @param {FromMemOptions} options Options.  Most important is filename.
+ * @returns {Promise<unknown>} The evaluated code.
+ */
+declare function fromMem(code: string, options: FromMemOptions): Promise<unknown>;
+declare namespace fromMem {
+    export { guessModuleType, FromMemOptions, ModuleType };
+}
 /**
  * Options for how to process code.
  */
-export type FromMemOptions = {
+type FromMemOptions = {
     /**
-     * What format does the code have?  Throws an error if the format is not
-     * "commonjs", "es", "umd", or "bare".
+     * What format does the code have?  "guess" means to read the closest
+     * package.json file looking for the "type" key.
      */
-    format?: "amd" | "bare" | "commonjs" | "es" | "globals" | "umd" | undefined;
+    format?: "amd" | "bare" | "commonjs" | "es" | "globals" | "guess" | "umd" | undefined;
     /**
      * What is the fully-qualified synthetic
      * filename for the code?  Most important is the directory, which is used to
@@ -31,3 +42,16 @@ export type FromMemOptions = {
      */
     globalExport?: string | undefined;
 };
+/**
+ * Figure out the module type for the given file.  If no package.json is
+ * found, default to "commonjs".
+ *
+ * @param {string} filename Fully-qualified filename to start from.
+ * @returns {Promise<ModuleType>}
+ * @throws On invalid package.json
+ */
+declare function guessModuleType(filename: string): Promise<ModuleType>;
+declare namespace guessModuleType {
+    function clearCache(): void;
+}
+type ModuleType = "commonjs" | "es";

index.js

@@ -151,12 +151,21 @@ async function importString(code, dirname, options) {
   return mod.namespace;
 }
 
+/**
+ * @typedef {"commonjs"|"es"} ModuleType
+ */
+
+/**
+ * @type Record<string, ModuleType>
+ */
+let cache = {};
+
 /**
  * Figure out the module type for the given file.  If no package.json is
  * found, default to "commonjs".
  *
  * @param {string} filename Fully-qualified filename to start from.
- * @returns {Promise<"commonjs"|"es">}
+ * @returns {Promise<ModuleType>}
  * @throws On invalid package.json
  */
 async function guessModuleType(filename) {
@@ -167,13 +176,23 @@ async function guessModuleType(filename) {
     default:
       // Fall-through
   }
+
+  /** @type {ModuleType} */
+  let res = "commonjs";
   let dir = fp.dir;
   let prev = undefined;
+  const pending = [];
   while (dir !== prev) {
+    const cached = cache[dir];
+    if (cached) {
+      return cached;
+    }
+    pending.push(dir);
     try {
       const pkg = await fs.readFile(path.join(dir, "package.json"), "utf8");
       const pkgj = JSON.parse(pkg);
-      return (pkgj.type === "module") ? "es" : "commonjs";
+      res = (pkgj.type === "module") ? "es" : "commonjs";
+      break;
     } catch (err) {
       // If the file just didn't exist, keep going.
       if (/** @type {NodeJS.ErrnoException} */ (err).code !== "ENOENT") {
@@ -183,9 +202,16 @@ async function guessModuleType(filename) {
     prev = dir;
     dir = path.dirname(dir);
   }
-  return "commonjs";
+  for (const p of pending) {
+    cache[p] = res;
+  }
+  return res;
 }
 
+guessModuleType.clearCache = function clearCache() {
+  cache = {};
+};
+
 /**
  * Import or require the given code from memory.  Knows about the different
  * Peggy output formats.  Returns the exports of the module.
@@ -194,7 +220,7 @@ async function guessModuleType(filename) {
  * @param {FromMemOptions} options Options.  Most important is filename.
  * @returns {Promise<unknown>} The evaluated code.
  */
-module.exports = async function fromMem(code, options) {
+async function fromMem(code, options) {
   options = {
     format: "commonjs",
     context: {},
@@ -239,4 +265,8 @@ module.exports = async function fromMem(code, options) {
     default:
       throw new Error(`Unsupported output format: "${options.format}"`);
   }
-};
+}
+
+fromMem.guessModuleType = guessModuleType;
+
+module.exports = fromMem;

package.json

@@ -17,11 +17,11 @@
   "author": "Joe Hildebrand <[email protected]>",
   "license": "MIT",
   "devDependencies": {
-    "@peggyjs/eslint-config": "3.2.2",
-    "@types/node": "20.11.19",
-    "@types/semver": "7.5.7",
+    "@peggyjs/eslint-config": "3.2.3",
+    "@types/node": "20.11.20",
+    "@types/semver": "7.5.8",
     "c8": "9.1.0",
-    "eslint": "8.56.0",
+    "eslint": "8.57.0",
     "typescript": "5.3.3"
   },
   "packageManager": "[email protected]",