Refactor pyexec (#1318)

This is some refactoring I did on the way towards resolving pyscript#1313.
I added a new _run_pyscript Python function which executes the code
inside a context manager that sets the display target. We can then
return a JS object wrapper directly from Python.

I moved the "installation" of the pyscript module to loadInterpreter,
and pyimport pyscript_py there and give it a type. This avoids a bunch
of creating and deleting of proxies for pyscript_py and allows us to
give it a type once and for all.

I also did some minor logic cleanup in a few places.

pyscriptjs/directoryManifest.mjs

@@ -0,0 +1,44 @@
+// This logic split out because it is shared by:
+// 1. esbuild.mjs
+// 2. Jest setup.ts
+
+import { join } from 'path';
+import { opendir, readFile } from 'fs/promises';
+
+/**
+ * List out everything in a directory, but skip __pycache__ directory. Used to
+ * list out the directory paths and the [file path, file contents] pairs in the
+ * Python package. All paths are relative to the directory we are listing. The
+ * directories are sorted topologically so that a parent directory always
+ * appears before its children.
+ *
+ * This is consumed in main.ts which calls mkdir for each directory and then
+ * writeFile to create each file.
+ *
+ * @param {string} dir The path to the directory we want to list out
+ * @returns {dirs: string[], files: [string, string][]}
+ */
+export async function directoryManifest(dir) {
+    const result = { dirs: [], files: [] };
+    await _directoryManifestHelper(dir, '.', result);
+    return result;
+}
+
+/**
+ * Recursive helper function for directoryManifest
+ */
+async function _directoryManifestHelper(root, dir, result) {
+    const dirObj = await opendir(join(root, dir));
+    for await (const d of dirObj) {
+        const entry = join(dir, d.name);
+        if (d.isDirectory()) {
+            if (d.name === '__pycache__') {
+                continue;
+            }
+            result.dirs.push(entry);
+            await _directoryManifestHelper(root, entry, result);
+        } else if (d.isFile()) {
+            result.files.push([entry, await readFile(join(root, entry), { encoding: 'utf-8' })]);
+        }
+    }
+}

pyscriptjs/environment.yml

@@ -3,7 +3,7 @@ channels:
     - conda-forge
     - microsoft
 dependencies:
-    - python=3.9
+    - python=3.11
     - pip
     - pytest=7
     - nodejs=16
@@ -18,3 +18,7 @@ dependencies:
           - playwright
           - pytest-playwright
           - pytest-xdist
+          # We need Pyodide and micropip so we can import them in our Python
+          # unit tests
+          - pyodide_py==0.22
+          - micropip==0.2.2

pyscriptjs/esbuild.mjs

@@ -1,8 +1,11 @@
-const { build } = require('esbuild');
-const { spawn } = require('child_process');
-const { join } = require('path');
-const { watchFile } = require('fs');
-const { cp, lstat, readdir, opendir, readFile } = require('fs/promises');
+import { build } from 'esbuild';
+import { spawn } from 'child_process';
+import { dirname, join } from 'path';
+import { watchFile } from 'fs';
+import { cp, lstat, readdir } from 'fs/promises';
+import { directoryManifest } from './directoryManifest.mjs';
+
+const __dirname = dirname(new URL(import.meta.url).pathname);
 
 const production = !process.env.NODE_WATCH || process.env.NODE_ENV === 'production';
 
@@ -15,44 +18,6 @@ if (!production) {
     copy_targets.push({ src: 'build/*', dest: 'examples/build' });
 }
 
-/**
- * List out everything in a directory, but skip __pycache__ directory. Used to
- * list out the directory paths and the [file path, file contents] pairs in the
- * Python package. All paths are relative to the directory we are listing. The
- * directories are sorted topologically so that a parent directory always
- * appears before its children.
- *
- * This is consumed in main.ts which calls mkdir for each directory and then
- * writeFile to create each file.
- *
- * @param {string} dir The path to the directory we want to list out
- * @returns {dirs: string[], files: [string, string][]}
- */
-async function directoryManifest(dir) {
-    const result = { dirs: [], files: [] };
-    await _directoryManifestHelper(dir, '.', result);
-    return result;
-}
-
-/**
- * Recursive helper function for directoryManifest
- */
-async function _directoryManifestHelper(root, dir, result) {
-    const dirObj = await opendir(join(root, dir));
-    for await (const d of dirObj) {
-        const entry = join(dir, d.name);
-        if (d.isDirectory()) {
-            if (d.name === '__pycache__') {
-                continue;
-            }
-            result.dirs.push(entry);
-            await _directoryManifestHelper(root, entry, result);
-        } else if (d.isFile()) {
-            result.files.push([entry, await readFile(join(root, entry), { encoding: 'utf-8' })]);
-        }
-    }
-}
-
 /**
  * An esbuild plugin that injects the Pyscript Python package.
  *

pyscriptjs/jest.config.js

@@ -1,6 +1,7 @@
 //jest.config.js
 module.exports = {
     preset: 'ts-jest',
+    setupFilesAfterEnv: ['./tests/unit/setup.ts'],
     testEnvironment: './jest-environment-jsdom.js',
     extensionsToTreatAsEsm: ['.ts'],
     transform: {

pyscriptjs/package.json

@@ -2,13 +2,13 @@
     "name": "pyscript",
     "version": "0.0.1",
     "scripts": {
-        "build": "npm run tsc && node esbuild.js",
-        "dev": "NODE_WATCH=1 node esbuild.js",
+        "build": "npm run tsc && node esbuild.mjs",
+        "dev": "NODE_WATCH=1 node esbuild.mjs",
         "tsc": "tsc --noEmit",
-        "format:check": "prettier --check './src/**/*.{js,html,ts}'",
-        "format": "prettier --write './src/**/*.{js,html,ts}'",
-        "lint": "eslint './src/**/*.{js,html,ts}'",
-        "lint:fix": "eslint --fix './src/**/*.{js,html,ts}'",
+        "format:check": "prettier --check './src/**/*.{mjs,js,html,ts}'",
+        "format": "prettier --write './src/**/*.{mjs,js,html,ts}'",
+        "lint": "eslint './src/**/*.{mjs,js,html,ts}'",
+        "lint:fix": "eslint --fix './src/**/*.{mjs,js,html,ts}'",
         "xprelint": "npm run format",
         "test": "cross-env NODE_OPTIONS=--experimental-vm-modules jest --coverage",
         "test:watch": "cross-env NODE_OPTIONS=--experimental-vm-modules jest --watch"

pyscriptjs/src/interpreter_client.ts

@@ -45,13 +45,23 @@ export class InterpreterClient extends Object {
     }
 
     /**
-     * delegates the code to be run to the underlying interface of
-     * the remote interpreter.
-     * Python exceptions are turned into JS exceptions.
-     * */
+     * Run user Python code. See also the _run_pyscript docstring.
+     *
+     * The result is wrapped in an object to avoid accidentally awaiting a
+     * Python Task or Future returned as the result of the computation.
+     *
+     * @param code the code to run
+     * @param id The id for the default display target (or undefined if no
+     * default display target).
+     * @returns Either:
+     * 1. An Object of the form {result: the_result} if the result is
+     *    serializable (or transferable), or
+     * 2. a Synclink Proxy wrapping an object of this if the result is not
+     *    serializable.
+     */
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    async run(code: string): Promise<{ result: any }> {
-        return await this._remote.run(code);
+    async run(code: string, id?: string): Promise<{ result: any }> {
+        return this._remote.pyscript_py._run_pyscript(code, id);
     }
 
     /**

pyscriptjs/src/main.ts

@@ -21,14 +21,6 @@ import { RemoteInterpreter } from './remote_interpreter';
 import { robustFetch } from './fetch';
 import * as Synclink from 'synclink';
 
-// pyscript_package is injected from src/python by bundlePyscriptPythonPlugin in
-// esbuild.js
-
-// @ts-ignore
-import python_package from 'pyscript_python_package.esbuild_injected.json';
-
-declare const python_package: { dirs: string[]; files: [string, string] };
-
 const logger = getLogger('pyscript/main');
 
 /**
@@ -271,17 +263,6 @@ export class PyScriptApp {
         // XXX: maybe the following calls could be parallelized, instead of
         // await()ing immediately. For now I'm using await to be 100%
         // compatible with the old behavior.
-        logger.info('importing pyscript');
-
-        // Write pyscript package into file system
-        for (const dir of python_package.dirs) {
-            await interpreter._remote.FS.mkdir('/home/pyodide/' + dir);
-        }
-        for (const [path, value] of python_package.files) {
-            await interpreter._remote.FS.writeFile('/home/pyodide/' + path, value);
-        }
-        //Refresh the module cache so Python consistently finds pyscript module
-        await interpreter._remote.invalidate_module_path_cache();
 
         // inject `define_custom_element` and showWarning it into the PyScript
         // module scope
@@ -290,11 +271,7 @@ export class PyScriptApp {
         // await interpreter._remote.setHandler('showWarning', Synclink.proxy(showWarning));
         interpreter._unwrapped_remote.setHandler('define_custom_element', define_custom_element);
         interpreter._unwrapped_remote.setHandler('showWarning', showWarning);
-        const pyscript_module = (await interpreter.pyimport('pyscript')) as Synclink.Remote<
-            PyProxy & { _set_version_info(string): void }
-        >;
-        await pyscript_module._set_version_info(version);
-        await pyscript_module.destroy();
+        await interpreter._remote.pyscript_py._set_version_info(version);
 
         // import some carefully selected names into the global namespace
         await interpreter.run(`

pyscriptjs/src/pyexec.ts

@@ -2,8 +2,7 @@ import { getLogger } from './logger';
 import { ensureUniqueId } from './utils';
 import { UserError, ErrorCode } from './exceptions';
 import { InterpreterClient } from './interpreter_client';
-import type { PyProxyCallable, PyProxy } from 'pyodide';
-import type { Remote } from 'synclink';
+import type { PyProxyCallable } from 'pyodide';
 
 const logger = getLogger('pyexec');
 
@@ -13,18 +12,9 @@ export async function pyExec(
     outElem: HTMLElement,
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
 ): Promise<{ result: any }> {
-    const pyscript_py = (await interpreter.pyimport('pyscript')) as Remote<
-        PyProxy & {
-            set_current_display_target(id: string): void;
-            uses_top_level_await(code: string): boolean;
-        }
-    >;
     ensureUniqueId(outElem);
-    await pyscript_py.set_current_display_target(outElem.id);
-    try {
-        try {
-            if (await pyscript_py.uses_top_level_await(pysrc)) {
-                throw new UserError(
+    if (await interpreter._remote.pyscript_py.uses_top_level_await(pysrc)) {
+        const err = new UserError(
             ErrorCode.TOP_LEVEL_AWAIT,
             'The use of top-level "await", "async for", and ' +
                 '"async with" has been removed.' +
@@ -32,8 +22,12 @@ export async function pyExec(
                 'your code and schedule it using asyncio.ensure_future() or similar.' +
                 '\nSee https://docs.pyscript.net/latest/guides/asyncio.html for more information.',
         );
+        displayPyException(err, outElem);
+        return { result: undefined };
     }
-            return await interpreter.run(pysrc);
+
+    try {
+        return await interpreter.run(pysrc, outElem.id);
     } catch (e) {
         const err = e as Error;
         // XXX: currently we display exceptions in the same position as
@@ -43,10 +37,6 @@ export async function pyExec(
         displayPyException(err, outElem);
         return { result: undefined };
     }
-    } finally {
-        await pyscript_py.set_current_display_target(undefined);
-        await pyscript_py.destroy();
-    }
 }
 
 /**

pyscriptjs/src/python/pyscript/__init__.py

@@ -6,14 +6,17 @@ import io
 import re
 import time
 from collections import namedtuple
+from contextlib import contextmanager
 from textwrap import dedent
 
 import js
 
 try:
-    from pyodide.ffi import create_proxy
+    from pyodide.code import eval_code
+    from pyodide.ffi import JsProxy, create_proxy
 except ImportError:
-    from pyodide import create_proxy
+    from pyodide import JsProxy, create_proxy, eval_code
+
 
 loop = asyncio.get_event_loop()
 
@@ -188,8 +191,13 @@ def write(element_id, value, append=False, exec_id=0):
     )
 
 
-def set_current_display_target(target_id):
+@contextmanager
+def _display_target(target_id):
     get_current_display_target._id = target_id
+    try:
+        yield
+    finally:
+        get_current_display_target._id = None
 
 
 def get_current_display_target():
@@ -200,17 +208,14 @@ get_current_display_target._id = None
 
 
 def display(*values, target=None, append=True):
-    default_target = get_current_display_target()
-    if default_target is None and target is None:
+    if target is None:
+        target = get_current_display_target()
+    if target is None:
         raise Exception(
             "Implicit target not allowed here. Please use display(..., target=...)"
         )
-    if target is not None:
     for v in values:
         Element(target).write(v, append=append)
-    else:
-        for v in values:
-            Element(default_target).write(v, append=append)
 
 
 class Element:
@@ -702,3 +707,32 @@ def _install_deprecated_globals_2022_12_1(ns):
         "Please use <code>pyscript</code> instead."
     )
     ns["PyScript"] = DeprecatedGlobal("PyScript", PyScript, message)
+
+
+def _run_pyscript(code: str, id: str = None) -> JsProxy:
+    """Execute user code inside context managers.
+
+    Uses the __main__ global namespace.
+
+    The output is wrapped inside a JavaScript object since an object is not
+    thenable. This is so we do not accidentally `await` the result of the python
+    execution, even if it's awaitable (Future, Task, etc.)
+
+    Parameters
+    ----------
+    code :
+       The code to run
+
+    id :
+       The id for the default display target (or None if no default display target).
+
+    Returns
+    -------
+        A Js Object of the form {result: the_result}
+    """
+    import __main__
+
+    with _display_target(id):
+        result = eval_code(code, globals=__main__.__dict__)
+
+    return js.Object.new(result=result)

pyscriptjs/src/python_package.ts

@@ -0,0 +1,9 @@
+// This file exists because I can only convince jest to mock real file system
+// files, not fake modules. This confuses me because jest.mock has a virtual
+// option for mocking things that don't live in the file system but it doesn't
+// seem to work.
+
+// @ts-ignore
+import python_package from 'pyscript_python_package.esbuild_injected.json';
+declare const python_package: { dirs: string[]; files: [string, string][] };
+export { python_package };

pyscriptjs/src/remote_interpreter.ts

@@ -7,6 +7,8 @@ import type { loadPyodide as loadPyodideDeclaration, PyodideInterface, PyProxy,
 import type { ProxyMarked } from 'synclink';
 import * as Synclink from 'synclink';
 
+import { python_package } from './python_package';
+
 declare const loadPyodide: typeof loadPyodideDeclaration;
 const logger = getLogger('pyscript/pyodide');
 
@@ -30,6 +32,13 @@ type PATHInterface = {
     dirname(path: string): string;
 } & ProxyMarked;
 
+type PyScriptPyModule = ProxyMarked & {
+    _set_version_info(ver: string): void;
+    uses_top_level_await(code: string): boolean;
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    _run_pyscript(code: string, display_target_id?: string): { result: any };
+};
+
 /*
 RemoteInterpreter class is responsible to process requests from the
 `InterpreterClient` class -- these can be requests for installation of
@@ -51,6 +60,7 @@ export class RemoteInterpreter extends Object {
     FS: FSInterface;
     PATH: PATHInterface;
     PATH_FS: PATHFSInterface;
+    pyscript_py: PyScriptPyModule;
 
     globals: PyProxyDict & ProxyMarked;
     // TODO: Remove this once `runtimes` is removed!
@@ -106,40 +116,28 @@ export class RemoteInterpreter extends Object {
         // TODO: Remove this once `runtimes` is removed!
         this.interpreter = this.interface;
 
+        // Write pyscript package into file system
+        for (const dir of python_package.dirs) {
+            this.FS.mkdir('/home/pyodide/' + dir);
+        }
+        for (const [path, value] of python_package.files) {
+            this.FS.writeFile('/home/pyodide/' + path, value);
+        }
+        //Refresh the module cache so Python consistently finds pyscript module
+        this.invalidate_module_path_cache();
+
         this.globals = Synclink.proxy(this.interface.globals as PyProxyDict);
+        logger.info('importing pyscript');
+        this.pyscript_py = Synclink.proxy(this.interface.pyimport('pyscript')) as PyProxy & typeof this.pyscript_py;
 
         if (config.packages) {
             logger.info('Found packages in configuration to install. Loading micropip...');
             await this.loadPackage('micropip');
         }
         logger.info('pyodide loaded and initialized');
-        await this.run('print("Python initialization complete")');
+        this.pyscript_py._run_pyscript('print("Python initialization complete")');
     }
 
-    /* eslint-disable */
-    async run(code: string): Promise<{ result: any }> {
-        /**
-         * eslint wants `await` keyword to be used i.e.
-         * { result: await this.interface.runPython(code) }
-         * However, `await` is not a no-op (no-operation) i.e.
-         * `await 42` is NOT the same as `42` i.e. if the awaited
-         * thing is not a promise, it is wrapped inside a promise and
-         * that promise is awaited. Thus, it changes the execution order.
-         * See https://stackoverflow.com/questions/55262996/does-awaiting-a-non-promise-have-any-detectable-effect
-         * Thus, `eslint` is disabled for this block / snippet.
-         */
-
-        /**
-         * The output of `runPython` is wrapped inside an object
-         * since an object is not thennable and avoids return of
-         * a coroutine directly. This is so we do not `await` the results
-         * of the underlying python execution, even if it's an
-         * awaitable object (Future, Task, etc.)
-         */
-        return { result: this.interface.runPython(code) };
-    }
-    /* eslint-enable */
-
     /**
      * delegates the registration of JS modules to
      * the underlying interface.

pyscriptjs/tests/py-unit/conftest.py

@@ -6,10 +6,6 @@ import pytest
 
 pyscriptjs = Path(__file__).parents[2]
 
-import pytest  # noqa
-
-pyscriptjs = Path(__file__).parents[2]
-
 # add pyscript folder to path
 python_source = pyscriptjs / "src" / "python"
 sys.path.append(str(python_source))
@@ -18,6 +14,7 @@ sys.path.append(str(python_source))
 python_plugins_source = pyscriptjs / "src" / "plugins" / "python"
 sys.path.append(str(python_plugins_source))
 
+
 # patch pyscript module where needed
 import pyscript  # noqa: E402
 import pyscript_plugins_tester as ppt  # noqa: E402

pyscriptjs/tests/py-unit/micropip.py

@@ -1,4 +0,0 @@
-"""Mock module that emulates some of the pyodide js module features for the sake of tests"""
-from unittest.mock import Mock
-
-install = Mock()

pyscriptjs/tests/py-unit/pyodide/ffi.py

@@ -1,4 +0,0 @@
-"""Mock module that emulates some of the pyodide js module features for the sake of tests"""
-from unittest.mock import Mock
-
-create_proxy = Mock(side_effect=lambda x: x)

pyscriptjs/tests/py-unit/pyodide/pyodide.py

@@ -1,4 +0,0 @@
-"""Mock module that emulates some of the pyodide js module features for the sake of tests"""
-from unittest.mock import Mock
-
-create_proxy = Mock(side_effect=lambda x: x)

pyscriptjs/tests/unit/pyodide.test.ts

@@ -1,18 +1,26 @@
 import type { AppConfig } from '../../src/pyconfig';
 import { InterpreterClient } from '../../src/interpreter_client';
-import { RemoteInterpreter } from '../../src/remote_interpreter';
 import { CaptureStdio } from '../../src/stdio';
 import * as Synclink from 'synclink';
 import { describe, beforeAll, afterAll, it, expect } from '@jest/globals';
+// We can't import RemoteInterpreter at top level because we need to mock the
+// Python package in setup.ts
+// But we can import the types at top level.
+// TODO: is there a better way to handle this?
+import type { RemoteInterpreter } from '../../src/remote_interpreter';
 
 describe('RemoteInterpreter', () => {
     let interpreter: InterpreterClient;
     let stdio: CaptureStdio = new CaptureStdio();
+    let RemoteInterpreter;
     const { port1, port2 } = new MessageChannel();
     beforeAll(async () => {
         const SRC = '../pyscriptjs/node_modules/pyodide/pyodide.js';
         const config: AppConfig = { interpreters: [{ src: SRC }] };
+        // Dynamic import of RemoteInterpreter sees our mocked Python package.
+        ({ RemoteInterpreter } = await import('../../src/remote_interpreter'));
         const remote_interpreter = new RemoteInterpreter(SRC);
+
         port1.start();
         port2.start();
         Synclink.expose(remote_interpreter, port2);

pyscriptjs/tests/unit/setup.ts

@@ -0,0 +1,6 @@
+import { jest } from '@jest/globals';
+import { directoryManifest } from '../../directoryManifest.mjs';
+
+jest.unstable_mockModule('../../src/python_package', async () => ({
+    python_package: await directoryManifest('./src/python/'),
+}));