Add an argument to loadPyodide to pass environment variables (#3870)

This also updates the command line runner to pass in all ambient environment
variables except that `HOME` is set to the working directory.

`homedir` is now deprecated. I added handling for `homedir` and `env.HOME`: 
if both are passed, raise an error, otherwise they mean the same thing.

docs/project/changelog.md

@@ -45,6 +45,11 @@ myst:
   new array with the result values from the iterable appended.
   {pr}`3904`
 
+- {{ Enhancement }} It is now possible to pass environment variables to
+  `loadPyodide` via the `env` argument. `homedir` is deprecated in favor of
+  `{env: {HOME: whatever_directory}}`.
+  {pr}`3870`
+
 ### Packages
 
 - OpenBLAS has been added and scipy now uses OpenBLAS rather than CLAPACK

docs/project/deprecation-timeline.md

@@ -16,6 +16,9 @@ deprecation warnings. More details about each item can often be found in the
 
 - The methods `PyProxy.supportsHas`, `PyProxy.isCallable`, etc will be removed.
 
+- Support for the `homedir` argument will be removed in favor of
+  `env: {HOME: "/the/home/directory"}`.
+
 ## 0.24.0
 
 - The `messageCallback` and `errorCallback` argument to `loadPackage` and

src/js/module.ts

@@ -86,7 +86,7 @@ export function createModule(): any {
  * @param path The path to the home directory.
  * @private
  */
-function setHomeDirectory(Module: Module, path: string) {
+function createHomeDirectory(Module: Module, path: string) {
   Module.preRun.push(function () {
     const fallbackPath = "/";
     try {
@@ -97,11 +97,16 @@ function setHomeDirectory(Module: Module, path: string) {
       console.error(`Using '${fallbackPath}' for a home directory instead`);
       path = fallbackPath;
     }
-    Module.ENV.HOME = path;
     Module.FS.chdir(path);
   });
 }
 
+function setEnvironment(Module: Module, env: { [key: string]: string }) {
+  Module.preRun.push(function () {
+    Object.assign(Module.ENV, env);
+  });
+}
+
 /**
  * Mount local directories to the virtual file system. Only for Node.js.
  * @param module The Emscripten Module.
@@ -171,7 +176,8 @@ export function initializeFileSystem(Module: Module, config: ConfigType) {
   }
 
   installStdlib(Module, stdLibURL);
-  setHomeDirectory(Module, config.homedir);
+  createHomeDirectory(Module, config.env.HOME);
+  setEnvironment(Module, config.env);
   mountLocalDirectories(Module, config._node_mounts);
   Module.preRun.push(() => initializeNativeFS(Module));
 }

src/js/pyodide.ts

@@ -74,7 +74,7 @@ function finalizeBootstrap(API: any, config: ConfigType) {
   let import_module = API.importlib.import_module;
 
   API.sys = import_module("sys");
-  API.sys.path.insert(0, config.homedir);
+  API.sys.path.insert(0, config.env.HOME);
   API.os = import_module("os");
 
   // Set up globals
@@ -174,6 +174,7 @@ export type ConfigType = {
   jsglobals?: object;
   args: string[];
   _node_mounts: string[];
+  env: { [key: string]: string };
 };
 
 /**
@@ -204,7 +205,7 @@ export async function loadPyodide(
 
     /**
      * The home directory which Pyodide will use inside virtual file system.
-     * Default: ``"/home/pyodide"``
+     * This is deprecated, use ``{env: {HOME : some_dir}}`` instead.
      */
     homedir?: string;
     /**
@@ -246,6 +247,17 @@ export async function loadPyodide(
      * more details. Default: ``[]``
      */
     args?: string[];
+    /**
+     * Environment variables to pass to Python. This can be accessed inside of
+     * Python at runtime via `os.environ`. Certain environment variables change
+     * the way that Python loads:
+     * https://docs.python.org/3.10/using/cmdline.html#environment-variables
+     * Default: {}
+     * If `env.HOME` is undefined, it will be set to a default value of
+     * `"/home/pyodide"`
+     */
+    env?: { [key: string]: string };
+
     /**
      * @ignore
      */
@@ -264,12 +276,25 @@ export async function loadPyodide(
     fullStdLib: false,
     jsglobals: globalThis,
     stdin: globalThis.prompt ? globalThis.prompt : undefined,
-    homedir: "/home/pyodide",
     lockFileURL: indexURL! + "repodata.json",
     args: [],
     _node_mounts: [],
+    env: {},
   };
   const config = Object.assign(default_config, options) as ConfigType;
+  if (options.homedir) {
+    console.warn(
+      "The homedir argument to loadPyodide is deprecated. " +
+        "Use 'env: { HOME: value }' instead of 'homedir: value'.",
+    );
+    if (options.env && options.env.HOME) {
+      throw new Error("Set both env.HOME and homedir arguments");
+    }
+    config.env.HOME = config.homedir;
+  }
+  if (!config.env.HOME) {
+    config.env.HOME = "/home/pyodide";
+  }
 
   const Module = createModule();
   Module.print = config.stdout;

src/templates/python

@@ -80,9 +80,9 @@ async function main() {
     try {
         py = await loadPyodide({
             args,
+            env: Object.assign({}, process.env, {HOME: process.cwd() }),
             fullStdLib: false,
             _node_mounts: dirsToMount(),
-            homedir: process.cwd(),
             // Strip out messages written to stderr while loading
             // After Pyodide is loaded we will replace stdstreams with setupStreams.
             stderr(e) {

src/tests/test_cmdline_runner.py

@@ -136,7 +136,7 @@ def test_invalid_cmdline_option(selenium):
     assert result.returncode != 0
     assert result.stdout == ""
     assert (
-        re.sub("/[/a-z]*/dist/python", "<...>/python", result.stderr)
+        re.sub("/.*/dist/python", "<...>/python", result.stderr)
         == """\
 Argument expected for the -c option
 usage: <...>/python [option] ... [-c cmd | -m mod | file | -] [arg] ...

src/tests/test_pyodide.py

@@ -1307,19 +1307,35 @@ def test_custom_stdin_stdout2(selenium):
 
 def test_home_directory(selenium_standalone_noload):
     selenium = selenium_standalone_noload
-    home = "/home/custom_home"
     selenium.run_js(
         """
-        let pyodide = await loadPyodide({
-            homedir : "%s",
+        const homedir = "/home/custom_home";
+        const pyodide = await loadPyodide({
+            homedir,
         });
         return pyodide.runPython(`
             import os
-            os.getcwd() == "%s"
+            os.getcwd() == "${homedir}"
+        `)
+        """
+    )
+    assert "The homedir argument to loadPyodide is deprecated" in selenium.logs
+
+
+def test_env(selenium_standalone_noload):
+    selenium = selenium_standalone_noload
+    hashval = selenium.run_js(
+        """
+        let pyodide = await loadPyodide({
+            env : {PYTHONHASHSEED : 1},
+        });
+        return pyodide.runPython(`
+            hash((1,2,3))
         `)
         """
-        % (home, home)
     )
+    # This may need to be updated when the Python version changes.
+    assert hashval == -2022708474
 
 
 def test_version_variable(selenium):