feat(compartment-mapper): Add Node.js power adapter

packages/compartment-mapper/NEWS.md

@@ -1,5 +1,12 @@
 User-visible changes to the compartment mapper:
 
+# Next release
+
+- Adds an `"@endo/compartment-mapper/node-powers.js"` entry point utility
+  module that exports `makeNodeReadPowers` and `makeNodeWritePowers` that adapt
+  the Node.js `fs` module to the promise and URL oriented interfaces expected
+  by compartment mapper functions.
+
 # 0.3.0 (2021-06-01)
 
 - Reenables CommonJS support with a fast lexer and without a dependency on

packages/compartment-mapper/node-powers.js

@@ -0,0 +1 @@
+export { makeNodeReadPowers, makeNodeWritePowers } from './src/node-powers.js';

packages/compartment-mapper/package.json

@@ -27,6 +27,7 @@
     "./archive.js": "./archive.js",
     "./import-archive.js": "./import-archive.js",
     "./bundle.js": "./bundle.js",
+    "./node-powers.js": "./node-powers.js",
     "./package.json": "./package.json"
   },
   "scripts": {

packages/compartment-mapper/src/node-powers.js

@@ -0,0 +1,49 @@
+// @ts-check
+
+/**
+ * @param {typeof import('fs')} fs
+ * @returns {ReadPowers}
+ */
+export const makeNodeReadPowers = fs => {
+  /**
+   * @param {string} location
+   */
+  const read = async location =>
+    fs.promises.readFile(new URL(location).pathname);
+
+  /**
+   * @param {string} location
+   */
+  const canonical = async location => {
+    try {
+      if (location.endsWith('/')) {
+        const realPath = await fs.promises.realpath(
+          new URL(location).pathname.replace(/\/$/, ''),
+        );
+        return new URL(`${realPath}/`, location).toString();
+      } else {
+        const realPath = await fs.promises.realpath(new URL(location).pathname);
+        return new URL(realPath, location).toString();
+      }
+    } catch {
+      return location;
+    }
+  };
+
+  return { read, canonical };
+};
+
+/**
+ * @param {typeof import('fs')} fs
+ * @returns {WritePowers}
+ */
+export const makeNodeWritePowers = fs => {
+  /**
+   * @param {string} location
+   * @param {Uint8Array} data
+   */
+  const write = async (location, data) =>
+    fs.promises.writeFile(new URL(location).pathname, data);
+
+  return { write };
+};

packages/compartment-mapper/src/types.js

@@ -94,6 +94,12 @@
  * @returns {Promise<Uint8Array>} bytes
  */
 
+/**
+ * @callback CanonicalFn
+ * @param {string} location
+ * @returns {Promise<string>} canonical location
+ */
+
 /**
  * @typedef {Object} Application
  * @property {ExecuteFn} import
@@ -110,6 +116,17 @@
  * @returns {Promise<Uint8Array>}
  */
 
+/**
+ * @typedef {Object} ReadPowers
+ * @property {ReadFn} read
+ * @property {CanonicalFn} canonical
+ */
+
+/**
+ * @typedef {Object} WritePowers
+ * @property {WriteFn} write
+ */
+
 // /////////////////////////////////////////////////////////////////////////////
 
 // Shared machinery for assembling applications: