https://github.com/python/cpython/commit/4f1f648c3bd36a875501778786bb8d718ab33869
commit: 4f1f648c3bd36a875501778786bb8d718ab33869
branch: 3.14
author: Miss Islington (bot) <31488909+miss-isling...@users.noreply.github.com>
committer: ambv <luk...@langa.pl>
date: 2025-07-22T13:25:35+02:00
summary:
[3.14] gh-136251: Improvements to WASM demo REPL (GH-136252) (GH-136977)
(cherry picked from commit d1d526afe7ce62c787b150652a2ba136cb949d74)
Co-authored-by: adam j hartz <a...@smatz.net>
Co-authored-by: Hood Chatham <roberthoodchat...@gmail.com>
files:
A Misc/NEWS.d/next/Tools-Demos/2025-07-05-15-10-42.gh-issue-136251.GRM6o8.rst
A Tools/wasm/emscripten/web_example/index.html
D Tools/wasm/emscripten/web_example/python.html
M Makefile.pre.in
M Python/emscripten_syscalls.c
M Tools/wasm/README.md
M configure
M configure.ac
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 66b34b779f27cb..fae5e384d3245f 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -1096,7 +1096,7 @@ $(DLLLIBRARY) libpython$(LDVERSION).dll.a: $(LIBRARY_OBJS)
# wasm32-emscripten browser web example
WEBEX_DIR=$(srcdir)/Tools/wasm/emscripten/web_example/
-web_example/python.html: $(WEBEX_DIR)/python.html
+web_example/index.html: $(WEBEX_DIR)/index.html
@mkdir -p web_example
@cp $< $@
@@ -1124,7 +1124,7 @@ web_example/python.mjs web_example/python.wasm:
$(BUILDPYTHON)
cp python.wasm web_example/python.wasm
.PHONY: web_example
-web_example: web_example/python.mjs web_example/python.worker.mjs
web_example/python.html web_example/server.py $(WEB_STDLIB)
+web_example: web_example/python.mjs web_example/python.worker.mjs
web_example/index.html web_example/server.py $(WEB_STDLIB)
############################################################################
# Header files
diff --git
a/Misc/NEWS.d/next/Tools-Demos/2025-07-05-15-10-42.gh-issue-136251.GRM6o8.rst
b/Misc/NEWS.d/next/Tools-Demos/2025-07-05-15-10-42.gh-issue-136251.GRM6o8.rst
new file mode 100644
index 00000000000000..6a35afe15e3875
--- /dev/null
+++
b/Misc/NEWS.d/next/Tools-Demos/2025-07-05-15-10-42.gh-issue-136251.GRM6o8.rst
@@ -0,0 +1 @@
+Fixes and usability improvements for ``Tools/wasm/emscripten/web_example``
diff --git a/Python/emscripten_syscalls.c b/Python/emscripten_syscalls.c
index 886262acbc6810..d3eedad30e3639 100644
--- a/Python/emscripten_syscalls.c
+++ b/Python/emscripten_syscalls.c
@@ -100,7 +100,7 @@ EM_JS_MACROS(void, _emscripten_promising_main_js, (void), {
return;
}
const origResolveGlobalSymbol = resolveGlobalSymbol;
- if (!Module.onExit && process?.exit) {
+ if (!Module.onExit && globalThis?.process?.exit) {
Module.onExit = (code) => process.exit(code);
}
// * wrap the main symbol with WebAssembly.promising,
diff --git a/Tools/wasm/README.md b/Tools/wasm/README.md
index 232321c515721e..9288598a0abc29 100644
--- a/Tools/wasm/README.md
+++ b/Tools/wasm/README.md
@@ -22,7 +22,7 @@ https://github.com/psf/webassembly for more information.
### Build
To cross compile to the ``wasm32-emscripten`` platform you need
-[the Emscripten compiler toolchain](https://emscripten.org/),
+[the Emscripten compiler toolchain](https://emscripten.org/),
a Python interpreter, and an installation of Node version 18 or newer.
Emscripten version 4.0.2 is recommended; newer versions may also work, but all
official testing is performed with that version. All commands below are
relative
@@ -86,11 +86,11 @@ CLI you will need to write your own alternative to
`node_entry.mjs`.
### The Web Example
-When building for Emscripten, the web example will be built automatically. It
is
-in the ``web_example`` directory. To run the web example, ``cd`` into the
+When building for Emscripten, the web example will be built automatically. It
+is in the ``web_example`` directory. To run the web example, ``cd`` into the
``web_example`` directory, then run ``python server.py``. This will start a web
-server; you can then visit ``http://localhost:8000/python.html`` in a browser
to
-see a simple REPL example.
+server; you can then visit ``http://localhost:8000/`` in a browser to see a
+simple REPL example.
The web example relies on a bug fix in Emscripten version 3.1.73 so if you
build
with earlier versions of Emscripten it may not work. The web example uses
diff --git a/Tools/wasm/emscripten/web_example/python.html
b/Tools/wasm/emscripten/web_example/index.html
similarity index 52%
rename from Tools/wasm/emscripten/web_example/python.html
rename to Tools/wasm/emscripten/web_example/index.html
index 078f86eb764419..9c89c9c0ed3bf5 100644
--- a/Tools/wasm/emscripten/web_example/python.html
+++ b/Tools/wasm/emscripten/web_example/index.html
@@ -1,31 +1,39 @@
<!doctype html>
<html lang="en">
<head>
- <meta charset="UTF-8" />
- <meta http-equiv="X-UA-Compatible" content="IE=edge" />
- <meta name="viewport" content="width=device-width, initial-scale=1.0"
/>
- <meta name="author" content="Katie Bell" />
- <meta name="description" content="Simple REPL for Python WASM" />
+ <meta charset="UTF-8">
+ <meta http-equiv="X-UA-Compatible" content="IE=edge">
+ <meta name="viewport" content="width=device-width, initial-scale=1.0">
+ <meta name="author" content="Katie Bell, Adam Hartz">
+ <meta name="description" content="Simple REPL for Python WASM">
<title>wasm-python terminal</title>
<link
rel="stylesheet"
href="https://unpkg.com/xterm@4.18.0/css/xterm.css";
crossorigin
integrity="sha384-4eEEn/eZgVHkElpKAzzPx/Kow/dTSgFk1BNe+uHdjHa+NkZJDh5Vqkq31+y7Eycd"
- />
+ >
<style>
body {
font-family: arial;
max-width: 800px;
margin: 0 auto;
}
- #code {
+ #editor {
+ padding: 5px;
+ border: 1px solid black;
width: 100%;
- height: 180px;
+ height: 300px;
}
#info {
padding-top: 20px;
}
+ .error {
+ border: 1px solid red;
+ background-color: #ffd9d9;
+ padding: 5px;
+ margin-top: 20px;
+ }
.button-container {
display: flex;
justify-content: end;
@@ -41,8 +49,14 @@
src="https://unpkg.com/xterm@4.18.0/lib/xterm.js";
crossorigin
integrity="sha384-yYdNmem1ioP5Onm7RpXutin5A8TimLheLNQ6tnMi01/ZpxXdAwIm2t4fJMx1Djs+"
- />
+ ></script>
+ <script
+ src="https://cdnjs.cloudflare.com/ajax/libs/ace/1.43.1/ace.js";
+ crossorigin
+
integrity="sha512-kmA5vhcxOkZI0ReiKJMGNb8/KKbgbExIlnt6aXuPtl86AgHBEi6OHHOz2wsTazBDGZKxe7fmiE+pIuZJQks4+A=="
+ ></script>
<script type="module">
+ const _magic_ctrlc_string = "__WASM_REPL_CTRLC_" + (Date.now()) +
"__";
class WorkerManager {
constructor(
workerURL,
@@ -132,11 +146,14 @@
class WasmTerminal {
constructor() {
- this.inputBuffer = new BufferQueue();
- this.input = "";
- this.resolveInput = null;
- this.activeInput = false;
- this.inputStartCursor = null;
+ try {
+ this.history =
JSON.parse(sessionStorage.getItem('__python_wasm_repl.history'));
+ this.historyBuffer = this.history.slice();
+ } catch(e) {
+ this.history = [];
+ this.historyBuffer = [];
+ }
+ this.reset();
this.xterm = new Terminal({
scrollback: 10000,
@@ -155,6 +172,18 @@
this.xterm.onData(this.handleTermData);
}
+ reset() {
+ this.inputBuffer = new BufferQueue();
+ this.input = "";
+ this.resolveInput = null;
+ this.activeInput = false;
+ this.inputStartCursor = null;
+
+ this.cursorPosition = 0;
+ this.historyIndex = -1;
+ this.beforeHistoryNav = "";
+ }
+
open(container) {
this.xterm.open(container);
}
@@ -186,9 +215,34 @@
if (!(ord === 0x1b || ord == 0x7f || ord < 32)) {
this.inputBuffer.addData(data);
}
- // TODO: Handle ANSI escape sequences
+ // TODO: Handle more escape sequences?
} else if (ord === 0x1b) {
// Handle special characters
+ switch (data.slice(1)) {
+ case "[A": // up
+ this.historyBack();
+ break;
+ case "[B": // down
+ this.historyForward();
+ break;
+ case "[C": // right
+ this.cursorRight();
+ break;
+ case "[D": // left
+ this.cursorLeft();
+ break;
+ case "[H": // home key
+ this.cursorHome(true);
+ break;
+ case "[F": // end key
+ this.cursorEnd(true);
+ break;
+ case "[3~": // delete key
+ this.deleteAtCursor();
+ break;
+ default:
+ break;
+ }
} else if (ord < 32 || ord === 0x7f) {
switch (data) {
case "\x0c": // CTRL+L
@@ -201,8 +255,18 @@
this.input + this.writeLine("\n"),
);
this.input = "";
+ this.cursorPosition = 0;
this.activeInput = false;
break;
+ case "\x03": // CTRL+C
+ this.input = "";
+ this.cursorPosition = 0;
+ this.historyIndex = -1;
+ this.resolveInput(_magic_ctrlc_string + "\n");
+ break;
+ case "\x09": // TAB
+ this.handleTab();
+ break;
case "\x7F": // BACKSPACE
case "\x08": // CTRL+H
this.handleCursorErase(true);
@@ -211,14 +275,20 @@
// Send empty input
if (this.input === "") {
this.resolveInput("");
+ this.cursorPosition = 0;
this.activeInput = false;
}
}
} else {
this.handleCursorInsert(data);
+ this.updateHistory();
}
};
+ clearLine() {
+ this.xterm.write("\x1b[K");
+ }
+
writeLine(line) {
this.xterm.write(line.slice(0, -1));
this.xterm.write("\r\n");
@@ -226,8 +296,36 @@
}
handleCursorInsert(data) {
- this.input += data;
+ const trailing = this.input.slice(this.cursorPosition);
+ this.input =
+ this.input.slice(0, this.cursorPosition) +
+ data +
+ trailing;
+ this.cursorPosition += data.length;
this.xterm.write(data);
+ if (trailing.length !== 0) {
+ this.xterm.write(trailing);
+ this.xterm.write("\x1b[" + trailing.length + "D");
+ }
+ this.updateHistory();
+ }
+
+ handleTab() {
+ // handle tabs: from the current position, add spaces until
+ // this.cursorPosition is a multiple of 4.
+ const prefix = this.input.slice(0, this.cursorPosition);
+ const suffix = this.input.slice(this.cursorPosition);
+ const count = 4 - (this.cursorPosition % 4);
+ const toAdd = " ".repeat(count);
+ this.input = prefix + toAdd + suffix;
+ this.cursorHome(false);
+ this.clearLine();
+ this.xterm.write(this.input);
+ if (suffix) {
+ this.xterm.write("\x1b[" + suffix.length + "D");
+ }
+ this.cursorPosition += count;
+ this.updateHistory();
}
handleCursorErase() {
@@ -238,9 +336,113 @@
) {
return;
}
- this.input = this.input.slice(0, -1);
- this.xterm.write("\x1B[D");
- this.xterm.write("\x1B[P");
+ const trailing = this.input.slice(this.cursorPosition);
+ this.input =
+ this.input.slice(0, this.cursorPosition - 1) +
trailing;
+ this.cursorLeft();
+ this.clearLine();
+ if (trailing.length !== 0) {
+ this.xterm.write(trailing);
+ this.xterm.write("\x1b[" + trailing.length + "D");
+ }
+ this.updateHistory();
+ }
+
+ deleteAtCursor() {
+ if (this.cursorPosition < this.input.length) {
+ const trailing = this.input.slice(
+ this.cursorPosition + 1,
+ );
+ this.input =
+ this.input.slice(0, this.cursorPosition) +
trailing;
+ this.clearLine();
+ if (trailing.length !== 0) {
+ this.xterm.write(trailing);
+ this.xterm.write("\x1b[" + trailing.length + "D");
+ }
+ this.updateHistory();
+ }
+ }
+
+ cursorRight() {
+ if (this.cursorPosition < this.input.length) {
+ this.cursorPosition += 1;
+ this.xterm.write("\x1b[C");
+ }
+ }
+
+ cursorLeft() {
+ if (this.cursorPosition > 0) {
+ this.cursorPosition -= 1;
+ this.xterm.write("\x1b[D");
+ }
+ }
+
+ cursorHome(updatePosition) {
+ if (this.cursorPosition > 0) {
+ this.xterm.write("\x1b[" + this.cursorPosition + "D");
+ if (updatePosition) {
+ this.cursorPosition = 0;
+ }
+ }
+ }
+
+ cursorEnd() {
+ if (this.cursorPosition < this.input.length) {
+ this.xterm.write(
+ "\x1b[" +
+ (this.input.length - this.cursorPosition) +
+ "C",
+ );
+ this.cursorPosition = this.input.length;
+ }
+ }
+
+ updateHistory() {
+ if (this.historyIndex !== -1) {
+ this.historyBuffer[this.historyIndex] = this.input;
+ } else {
+ this.beforeHistoryNav = this.input;
+ }
+ }
+
+ historyBack() {
+ if (this.history.length === 0) {
+ return;
+ } else if (this.historyIndex === -1) {
+ // we're not currently navigating the history; store
+ // the current command and then look at the end of our
+ // history buffer
+ this.beforeHistoryNav = this.input;
+ this.historyIndex = this.history.length - 1;
+ } else if (this.historyIndex > 0) {
+ this.historyIndex -= 1;
+ }
+ this.input = this.historyBuffer[this.historyIndex];
+ this.cursorHome(false);
+ this.clearLine();
+ this.xterm.write(this.input);
+ this.cursorPosition = this.input.length;
+ }
+
+ historyForward() {
+ if (this.history.length === 0 || this.historyIndex === -1)
{
+ // we're not currently navigating the history; NOP.
+ return;
+ } else if (this.historyIndex < this.history.length - 1) {
+ this.historyIndex += 1;
+ this.input = this.historyBuffer[this.historyIndex];
+ } else if (this.historyIndex == this.history.length - 1) {
+ // we're coming back from the last history value; reset
+ // the input to whatever it was when we started going
+ // through the history
+ this.input = this.beforeHistoryNav;
+ this.historyIndex = -1;
+ }
+ this.cursorHome(false);
+ this.clearLine();
+ this.xterm.write(this.input);
+ this.cursorPosition = this.input.length;
}
prompt = async () => {
@@ -263,12 +465,29 @@
// Hack to ensure cursor input start doesn't end up
after user input
setTimeout(() => {
this.handleCursorInsert(
- this.inputBuffer.nextLine(),
+ this.inputBuffer.nextLine()
);
}, 1);
}
return new Promise((resolve, reject) => {
this.resolveInput = (value) => {
+ if (
+ value.replace(/\s/g, "").length != 0 &&
+ value != _magic_ctrlc_string + "\n"
+ ) {
+ if (this.historyIndex !== -1) {
+ this.historyBuffer[this.historyIndex] =
+ this.history[this.historyIndex];
+ }
+ this.history.push(value.slice(0, -1));
+ this.historyBuffer.push(value.slice(0, -1));
+ this.historyIndex = -1;
+ this.cursorPosition = 0;
+ try {
+
sessionStorage.setItem('__python_wasm_repl.history',
JSON.stringify(this.history));
+ } catch(e) {
+ }
+ }
resolve(value);
};
});
@@ -327,8 +546,6 @@
const stopButton = document.getElementById("stop");
const clearButton = document.getElementById("clear");
- const codeBox = document.getElementById("codebox");
-
window.onload = () => {
const terminal = new WasmTerminal();
terminal.open(document.getElementById("terminal"));
@@ -362,8 +579,9 @@
runButton.addEventListener("click", (e) => {
terminal.clear();
+ terminal.reset(); // reset the history
programRunning(true);
- const code = codeBox.value;
+ const code = editor.getValue();
pythonWorkerManager.run({
args: ["main.py"],
files: { "main.py": code },
@@ -372,10 +590,28 @@
replButton.addEventListener("click", (e) => {
terminal.clear();
+ terminal.reset(); // reset the history
+ const REPL = `
+class WASMREPLKeyboardInterrupt(KeyboardInterrupt):
+ pass
+
+import sys
+import code
+import builtins
+
+def _interrupt_aware_input(prompt=''):
+ line = builtins.input(prompt)
+ if line.strip() == "${_magic_ctrlc_string}":
+ raise KeyboardInterrupt()
+ return line
+
+cprt = 'Type "help", "copyright", "credits" or "license" for more information.'
+banner = f'Python {sys.version} on {sys.platform}\\n{cprt}'
+
+code.interact(banner=banner, readfunc=_interrupt_aware_input, exitmsg='')
+`;
programRunning(true);
- // Need to use "-i -" to force interactive mode.
- // Looks like isatty always returns false in emscripten
- pythonWorkerManager.run({ args: ["-i", "-"], files: {} });
+ pythonWorkerManager.run({ args: ["-c", REPL], files: {} });
});
stopButton.addEventListener("click", (e) => {
@@ -395,6 +631,7 @@
const finishedCallback = () => {
programRunning(false);
+ pythonWorkerManager.reset();
};
const pythonWorkerManager = new WorkerManager(
@@ -404,30 +641,63 @@
finishedCallback,
);
};
+ var editor;
+ document.addEventListener("DOMContentLoaded", () => {
+ editor = ace.edit("editor");
+ editor.session.setMode("ace/mode/python");
+ });
</script>
</head>
<body>
- <h1>Simple REPL for Python WASM</h1>
- <textarea id="codebox" cols="108" rows="16">
-print('Welcome to WASM!')
-</textarea
- >
- <div class="button-container">
- <button id="run" disabled>Run</button>
- <button id="repl" disabled>Start REPL</button>
- <button id="stop" disabled>Stop</button>
- <button id="clear" disabled>Clear</button>
+ <div id="repldemo">
+ <h1>Simple REPL for Python WASM</h1>
+ <div id="editor">print('Welcome to WASM!')</div>
+ <div class="button-container">
+ <button id="run" disabled>Run code</button>
+ <button id="repl" disabled>Start REPL</button>
+ <button id="stop" disabled>Stop</button>
+ <button id="clear" disabled>Clear</button>
+ </div>
+ <div id="terminal"></div>
+ <div id="info">
+ The simple REPL provides a limited Python experience in the
+ browser.
+ <a
+
href="https://github.com/python/cpython/blob/main/Tools/wasm/README.md";
+ >
+ Tools/wasm/README.md
+ </a>
+ contains a list of known limitations and issues. Networking,
+ subprocesses, and threading are not available.
+ </div>
</div>
- <div id="terminal"></div>
- <div id="info">
- The simple REPL provides a limited Python experience in the
browser.
- <a
-
href="https://github.com/python/cpython/blob/main/Tools/wasm/README.md";
- >
- Tools/wasm/README.md
- </a>
- contains a list of known limitations and issues. Networking,
- subprocesses, and threading are not available.
+ <div id="buffererror" class="error" style="display: none">
+ <p>
+ <code>SharedArrayBuffer</code>, which is required for this
demo,
+ is not available in your browser environment. One common cause
+ of this failure is loading <code>index.html</code> directly in
+ your browser instead of using <code>server.py</code> as
+ described in
+ <a
+
href="https://github.com/python/cpython/blob/main/Tools/wasm/README.md#the-web-example";
+ >
+ Tools/wasm/README.md
+ </a>.
+ </p>
+ <p>
+ For more details about security requirements for
+ <code>SharedArrayBuffer</code>, see
+ <a
+
href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer#security_requirements";
+ >this MDN page</a
+ >.
+ </p>
+ <script>
+ if (typeof SharedArrayBuffer === 'undefined') {
+ document.getElementById('repldemo').style.display = 'none';
+ document.getElementById('buffererror').style.display =
'block';
+ }
+ </script>
</div>
</body>
</html>
diff --git a/configure b/configure
index 2242865313e57c..946cd471f64d32 100755
--- a/configure
+++ b/configure
@@ -9603,7 +9603,7 @@ fi
as_fn_append LDFLAGS_NODIST " -sWASM_BIGINT"
as_fn_append LINKFORSHARED " -sFORCE_FILESYSTEM -lidbfs.js -lnodefs.js
-lproxyfs.js -lworkerfs.js"
- as_fn_append LINKFORSHARED " -sEXPORTED_RUNTIME_METHODS=FS,callMain,ENV"
+ as_fn_append LINKFORSHARED "
-sEXPORTED_RUNTIME_METHODS=FS,callMain,ENV,HEAPU32"
as_fn_append LINKFORSHARED "
-sEXPORTED_FUNCTIONS=_main,_Py_Version,__PyRuntime,__PyEM_EMSCRIPTEN_COUNT_ARGS_OFFSET,_PyGILState_GetThisThreadState,__Py_DumpTraceback"
as_fn_append LINKFORSHARED " -sSTACK_SIZE=5MB"
as_fn_append LINKFORSHARED " -sTEXTDECODER=2"
diff --git a/configure.ac b/configure.ac
index a05b3b18efec36..6b15beb050c1af 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2335,7 +2335,7 @@ AS_CASE([$ac_sys_system],
dnl Include file system support
AS_VAR_APPEND([LINKFORSHARED], [" -sFORCE_FILESYSTEM -lidbfs.js
-lnodefs.js -lproxyfs.js -lworkerfs.js"])
- AS_VAR_APPEND([LINKFORSHARED], ["
-sEXPORTED_RUNTIME_METHODS=FS,callMain,ENV"])
+ AS_VAR_APPEND([LINKFORSHARED], ["
-sEXPORTED_RUNTIME_METHODS=FS,callMain,ENV,HEAPU32"])
AS_VAR_APPEND([LINKFORSHARED], ["
-sEXPORTED_FUNCTIONS=_main,_Py_Version,__PyRuntime,__PyEM_EMSCRIPTEN_COUNT_ARGS_OFFSET,_PyGILState_GetThisThreadState,__Py_DumpTraceback"])
AS_VAR_APPEND([LINKFORSHARED], [" -sSTACK_SIZE=5MB"])
dnl Avoid bugs in JS fallback string decoding path
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