Expose Module.FS (#1692)

Makefile

@@ -87,10 +87,7 @@ node_modules/.installed : src/js/package.json
 	touch node_modules/.installed
 
 build/pyodide.js: src/js/*.js src/js/pyproxy.gen.js node_modules/.installed
-	npx typescript src/js/pyodide.js \
-		--lib ES2018 --allowJs \
-		--declaration --emitDeclarationOnly \
-		--outDir build
+	npx typescript --project src/js
 	npx rollup -c src/js/rollup.config.js
 
 src/js/pyproxy.gen.js : src/core/pyproxy.* src/core/*.h

docs/project/changelog.md

@@ -47,6 +47,9 @@ substitutions:
 
 - {{ Enhancement }} Pyodide can experimentally be used in Node.js {pr}`1689`
 
+- {{ Enhancement }} Pyodide now exposes the emscripten `FS` module as `fileSystem`,
+  allowing for direct manipulation of the in-memory filesystem {pr}`1692`
+
 ## Standard library
 
 - The following standard library modules are now available as standalone packages

src/js/api.js

@@ -7,6 +7,7 @@ export { loadPackage, loadedPackages, isPyProxy };
  * @typedef {import('./pyproxy.gen').Py2JsResult} Py2JsResult
  * @typedef {import('./pyproxy.gen').PyProxy} PyProxy
  * @typedef {import('./pyproxy.gen').TypedArray} TypedArray
+ * @typedef {import('emscripten')} Emscripten
  */
 
 /**
@@ -329,8 +330,23 @@ setInterruptBuffer = Module.setInterruptBuffer;
 export { setInterruptBuffer };
 
 export function makePublicAPI() {
+  /**
+   * An alias to the `Emscripten File System API
+   * <https://emscripten.org/docs/api_reference/Filesystem-API.html>`_.
+   *
+   * This provides a wide range of POSIX-`like` file/device operations, including
+   * `mount
+   * <https://emscripten.org/docs/api_reference/Filesystem-API.html#FS.mount>`_
+   * which can be used to extend the in-memory filesystem with features like `persistence
+   * <https://emscripten.org/docs/api_reference/Filesystem-API.html#persistent-data>`_.
+   *
+   * @type {FS} The Emscripten File System API.
+   */
+  const fileSystem = Module.FS;
+
   let namespace = {
     globals,
+    fileSystem,
     pyodide_py,
     version,
     loadPackage,
@@ -348,6 +364,7 @@ export function makePublicAPI() {
     PythonError,
     PyBuffer,
   };
+
   namespace._module = Module; // @private
   Module.public_api = namespace;
   return namespace;

src/js/module.js

@@ -1,3 +1,8 @@
+/**
+ * The Emscripten Module.
+ *
+ * @private @type {import('emscripten').Module}
+ */
 export let Module = {};
 Module.noImageDecoding = true;
 Module.noAudioDecoding = true;

src/js/package-lock.json

@@ -129,6 +129,12 @@
         "defer-to-connect": "^1.0.1"
       }
     },
+    "@types/emscripten": {
+      "version": "1.39.5",
+      "resolved": "https://registry.npmjs.org/@types/emscripten/-/emscripten-1.39.5.tgz",
+      "integrity": "sha512-DIOOg+POSrYl+OlNRHQuIEqCd8DCtynG57H862UCce16nXJX7J8eWxNGgOcf8Eyge8zXeSs27mz1UcFu8L/L7g==",
+      "dev": true
+    },
     "@types/eslint": {
       "version": "7.2.14",
       "resolved": "https://registry.npmjs.org/@types/eslint/-/eslint-7.2.14.tgz",

src/js/package.json

@@ -8,12 +8,21 @@
     "rollup-plugin-terser": "^7.0.2",
     "tsd": "^0.15.1",
     "typescript": "^4.2.4",
-    "mocha": "^9.0.2"
+    "mocha": "^9.0.2",
+    "@types/emscripten": "^1.39.5"
   },
   "type": "module",
   "scripts": {
     "test": "mocha --timeout 15000"
   },
+  "tsd": {
+    "compilerOptions": {
+      "lib": [
+        "ES2018",
+        "DOM"
+      ]
+    }
+  },
   "dependencies": {
     "node-fetch": "^2.6.1"
   }

src/js/test/filesystem.test.js

@@ -0,0 +1,15 @@
+import assert from "assert";
+import { loadPyodide } from "../pyodide.js";
+
+describe("fileSystem", () => {
+  let pyodide;
+  it("loadPyodide", async () => {
+    pyodide = await loadPyodide({ indexURL: "../../build/" });
+  });
+  const exists = () => {
+    return pyodide.runPython("import os; os.path.exists('/tmp/js-test')");
+  };
+  it("no dir", async () => assert.equal(exists(), false));
+  it("mkdir", async () => pyodide.fileSystem.mkdir("/tmp/js-test"));
+  it("made dir", async () => assert.equal(exists(), true));
+});

src/js/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "http://json.schemastore.org/tsconfig",
+  "compilerOptions": {
+    "allowJs": true,
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "lib": ["ES2018", "DOM"],
+    "outDir": "../../build",
+    "rootDir": "."
+  },
+  "include": ["./*.js"],
+  "exclude": ["rollup.config.js"]
+}