gh-127111: Emscripten Make web example work again

Makefile.pre.in

@@ -269,10 +269,6 @@ SRCDIRS= 	@SRCDIRS@
 # Other subdirectories
 SUBDIRSTOO=	Include Lib Misc
 
-# assets for Emscripten browser builds
-WASM_ASSETS_DIR=.$(prefix)
-WASM_STDLIB=$(WASM_ASSETS_DIR)/lib/python$(VERSION)/os.py
-
 # Files and directories to be distributed
 CONFIGFILES=	configure configure.ac acconfig.h pyconfig.h.in Makefile.pre.in
 DISTFILES=	README.rst ChangeLog $(CONFIGFILES)
@@ -737,6 +733,9 @@ build_all:	check-clean-src check-app-store-compliance $(BUILDPYTHON) platform sh
 build_wasm: check-clean-src $(BUILDPYTHON) platform sharedmods \
 		python-config checksharedmods
 
+.PHONY: build_emscripten
+build_emscripten: build_wasm web_example
+
 # Check that the source is clean when building out of source.
 .PHONY: check-clean-src
 check-clean-src:
@@ -1016,23 +1015,38 @@ $(DLLLIBRARY) libpython$(LDVERSION).dll.a: $(LIBRARY_OBJS)
 	else true; \
 	fi
 
-# wasm32-emscripten browser build
-# wasm assets directory is relative to current build dir, e.g. "./usr/local".
-# --preload-file turns a relative asset path into an absolute path.
+# wasm32-emscripten browser web example
+
+WEBEX_DIR=$(srcdir)/Tools/wasm/emscripten/web_example/
+web_example/python.html: $(WEBEX_DIR)/python.html
+	@mkdir -p web_example
+	@cp $< $@
+
+web_example/python.worker.mjs: $(WEBEX_DIR)/python.worker.mjs
+	@mkdir -p web_example
+	@cp $< $@
 
-.PHONY: wasm_stdlib
-wasm_stdlib: $(WASM_STDLIB)
-$(WASM_STDLIB): $(srcdir)/Lib/*.py $(srcdir)/Lib/*/*.py \
-	    $(srcdir)/Tools/wasm/wasm_assets.py \
+web_example/server.py: $(WEBEX_DIR)/server.py
+	@mkdir -p web_example
+	@cp $< $@
+
+WEB_STDLIB=web_example/python$(VERSION)$(ABI_THREAD).zip
+$(WEB_STDLIB): $(srcdir)/Lib/*.py $(srcdir)/Lib/*/*.py \
+	    $(WEBEX_DIR)/wasm_assets.py \
 	    Makefile pybuilddir.txt Modules/Setup.local
-	$(PYTHON_FOR_BUILD) $(srcdir)/Tools/wasm/wasm_assets.py \
-	    --buildroot . --prefix $(prefix)
+	$(PYTHON_FOR_BUILD) $(WEBEX_DIR)/wasm_assets.py \
+	    --buildroot . --prefix $(prefix) -o $@
 
-python.html: $(srcdir)/Tools/wasm/python.html python.worker.js
-	@cp $(srcdir)/Tools/wasm/python.html $@
+web_example/python.mjs web_example/python.wasm: $(BUILDPYTHON)
+	@if test $(HOST_GNU_TYPE) != 'wasm32-unknown-emscripten' ; then \
+		echo "Can only build web_example when target is Emscripten" ;\
+		exit 1 ;\
+	fi
+	cp python.mjs web_example/python.mjs
+	cp python.wasm web_example/python.wasm
 
-python.worker.js: $(srcdir)/Tools/wasm/python.worker.js
-	@cp $(srcdir)/Tools/wasm/python.worker.js $@
+.PHONY: web_example
+web_example: web_example/python.mjs web_example/python.worker.mjs web_example/python.html web_example/server.py $(WEB_STDLIB)
 
 ############################################################################
 # Header files
@@ -3053,8 +3067,7 @@ clean-retain-profile: pycremoval
 	find build -name '*.py[co]' -exec rm -f {} ';' || true
 	-rm -f pybuilddir.txt
 	-rm -f _bootstrap_python
-	-rm -f python.html python*.js python.data python*.symbols python*.map
-	-rm -f $(WASM_STDLIB)
+	-rm -rf web_example python.mjs python.wasm python*.symbols python*.map
 	-rm -f Programs/_testembed Programs/_freeze_module
 	-rm -rf Python/deepfreeze
 	-rm -f Python/frozen_modules/*.h

Tools/wasm/python.html → Tools/wasm/emscripten/web_example/python.html

@@ -47,7 +47,7 @@
 
     async initialiseWorker() {
         if (!this.worker) {
-            this.worker = new Worker(this.workerURL)
+            this.worker = new Worker(this.workerURL, {type: "module"})
             this.worker.addEventListener('message', this.handleMessageFromWorker)
         }
     }
@@ -347,7 +347,7 @@
         programRunning(false)
     }
 
-    const pythonWorkerManager = new WorkerManager('./python.worker.js', stdio, readyCallback, finishedCallback)
+    const pythonWorkerManager = new WorkerManager('./python.worker.mjs', stdio, readyCallback, finishedCallback)
 }
     </script>
 </head>

Tools/wasm/python.worker.js → Tools/wasm/emscripten/web_example/python.worker.mjs

@@ -1,3 +1,5 @@
+import createEmscriptenModule from "./python.mjs";
+
 class StdinBuffer {
     constructor() {
         this.sab = new SharedArrayBuffer(128 * Int32Array.BYTES_PER_ELEMENT)
@@ -59,29 +61,42 @@ const stderr = (charCode) => {
 
 const stdinBuffer = new StdinBuffer()
 
-var Module = {
+const emscriptenSettings = {
     noInitialRun: true,
     stdin: stdinBuffer.stdin,
     stdout: stdout,
     stderr: stderr,
     onRuntimeInitialized: () => {
         postMessage({type: 'ready', stdinBuffer: stdinBuffer.sab})
+    },
+    async preRun(Module) {
+        // TODO: remove fixed version number
+        // Prevent complaints about not finding exec-prefix by making a lib-dynload directory
+        Module.FS.mkdirTree("/lib/python3.14/lib-dynload/");
+        Module.addRunDependency("install-stdlib");
+        const resp = await fetch("python3.14.zip");
+        const stdlibBuffer = await resp.arrayBuffer();
+        Module.FS.writeFile(`/lib/python314.zip`, new Uint8Array(stdlibBuffer), { canOwn: true });
+        Module.removeRunDependency("install-stdlib");
     }
 }
 
-onmessage = (event) => {
+const modulePromise = createEmscriptenModule(emscriptenSettings);
+
+
+onmessage = async (event) => {
     if (event.data.type === 'run') {
+        const Module = await modulePromise;
         if (event.data.files) {
             for (const [filename, contents] of Object.entries(event.data.files)) {
                 Module.FS.writeFile(filename, contents)
             }
         }
-        const ret = callMain(event.data.args)
+        const ret = Module.callMain(event.data.args);
         postMessage({
             type: 'finished',
             returnCode: ret
         })
     }
 }
 
-importScripts('python.js')

Tools/wasm/wasm_webserver.py → Tools/wasm/emscripten/web_example/server.py

@@ -14,13 +14,6 @@
 
 
 class MyHTTPRequestHandler(server.SimpleHTTPRequestHandler):
-    extensions_map = server.SimpleHTTPRequestHandler.extensions_map.copy()
-    extensions_map.update(
-        {
-            ".wasm": "application/wasm",
-        }
-    )
-
     def end_headers(self) -> None:
         self.send_my_headers()
         super().end_headers()
@@ -42,5 +35,6 @@ def main() -> None:
         bind=args.bind,
     )
 
+
 if __name__ == "__main__":
     main()

Tools/wasm/wasm_assets.py → Tools/wasm/emscripten/web_example/wasm_assets.py

@@ -19,7 +19,7 @@
 from typing import Dict
 
 # source directory
-SRCDIR = pathlib.Path(__file__).parent.parent.parent.absolute()
+SRCDIR = pathlib.Path(__file__).parents[4].absolute()
 SRCDIR_LIB = SRCDIR / "Lib"
 
 
@@ -28,9 +28,7 @@
 WASM_STDLIB_ZIP = (
     WASM_LIB / f"python{sys.version_info.major}{sys.version_info.minor}.zip"
 )
-WASM_STDLIB = (
-    WASM_LIB / f"python{sys.version_info.major}.{sys.version_info.minor}"
-)
+WASM_STDLIB = WASM_LIB / f"python{sys.version_info.major}.{sys.version_info.minor}"
 WASM_DYNLOAD = WASM_STDLIB / "lib-dynload"
 
 
@@ -114,9 +112,7 @@ def get_sysconfigdata(args: argparse.Namespace) -> pathlib.Path:
     assert isinstance(args.builddir, pathlib.Path)
     data_name: str = sysconfig._get_sysconfigdata_name()  # type: ignore[attr-defined]
     if not data_name.startswith(SYSCONFIG_NAMES):
-        raise ValueError(
-            f"Invalid sysconfig data name '{data_name}'.", SYSCONFIG_NAMES
-        )
+        raise ValueError(f"Invalid sysconfig data name '{data_name}'.", SYSCONFIG_NAMES)
     filename = data_name + ".py"
     return args.builddir / filename
 
@@ -131,7 +127,7 @@ def filterfunc(filename: str) -> bool:
         return pathname not in args.omit_files_absolute
 
     with zipfile.PyZipFile(
-        args.wasm_stdlib_zip,
+        args.output,
         mode="w",
         compression=args.compression,
         optimize=optimize,
@@ -195,6 +191,12 @@ def path(val: str) -> pathlib.Path:
     default=pathlib.Path("/usr/local"),
     type=path,
 )
+parser.add_argument(
+    "-o",
+    "--output",
+    help="output file",
+    type=path,
+)
 
 
 def main() -> None:
@@ -204,7 +206,6 @@ def main() -> None:
     args.srcdir = SRCDIR
     args.srcdir_lib = SRCDIR_LIB
     args.wasm_root = args.buildroot / relative_prefix
-    args.wasm_stdlib_zip = args.wasm_root / WASM_STDLIB_ZIP
     args.wasm_stdlib = args.wasm_root / WASM_STDLIB
     args.wasm_dynload = args.wasm_root / WASM_DYNLOAD
 
@@ -234,12 +235,10 @@ def main() -> None:
     args.wasm_dynload.mkdir(parents=True, exist_ok=True)
     marker = args.wasm_dynload / ".empty"
     marker.touch()
-    # os.py is a marker for finding the correct lib directory.
-    shutil.copy(args.srcdir_lib / "os.py", args.wasm_stdlib)
     # The rest of stdlib that's useful in a WASM context.
     create_stdlib_zip(args)
-    size = round(args.wasm_stdlib_zip.stat().st_size / 1024**2, 2)
-    parser.exit(0, f"Created {args.wasm_stdlib_zip} ({size} MiB)\n")
+    size = round(args.output.stat().st_size / 1024**2, 2)
+    parser.exit(0, f"Created {args.output} ({size} MiB)\n")
 
 
 if __name__ == "__main__":

configure.ac

@@ -1854,9 +1854,13 @@ if test "$Py_OPT" = 'true' ; then
       LDFLAGS_NODIST="$LDFLAGS_NODIST -fno-semantic-interposition"
       ], [], [-Werror])
   ])
-elif test "$ac_sys_system" = "Emscripten" -o "$ac_sys_system" = "WASI"; then
-  dnl Emscripten does not support shared extensions yet. Build
-  dnl "python.[js,wasm]", "pybuilddir.txt", and "platform" files.
+elif test "$ac_sys_system" = "Emscripten"; then
+  dnl Build "python.[js,wasm]", "pybuilddir.txt", and "platform" files.
+  DEF_MAKE_ALL_RULE="build_emscripten"
+  REQUIRE_PGO="no"
+  DEF_MAKE_RULE="all"
+elif test "$ac_sys_system" = "WASI"; then
+  dnl Build "python.wasm", "pybuilddir.txt", and "platform" files.
   DEF_MAKE_ALL_RULE="build_wasm"
   REQUIRE_PGO="no"
   DEF_MAKE_RULE="all"
@@ -2321,14 +2325,14 @@ AS_CASE([$ac_sys_system],
     AS_VAR_IF([Py_DEBUG], [yes], [wasm_debug=yes], [wasm_debug=no])
 
     dnl Start with 20 MB and allow to grow
-    AS_VAR_APPEND([LDFLAGS_NODIST], [" -sALLOW_MEMORY_GROWTH -sTOTAL_MEMORY=20971520"])
+    AS_VAR_APPEND([LDFLAGS_NODIST], [" -sALLOW_MEMORY_GROWTH -sINITIAL_MEMORY=20971520"])
 
     dnl map int64_t and uint64_t to JS bigint
     AS_VAR_APPEND([LDFLAGS_NODIST], [" -sWASM_BIGINT"])
 
     dnl Include file system support
     AS_VAR_APPEND([LDFLAGS_NODIST], [" -sFORCE_FILESYSTEM -lidbfs.js -lnodefs.js -lproxyfs.js -lworkerfs.js"])
-    AS_VAR_APPEND([LDFLAGS_NODIST], [" -sEXPORTED_RUNTIME_METHODS=FS"])
+    AS_VAR_APPEND([LDFLAGS_NODIST], [" -sEXPORTED_RUNTIME_METHODS=FS,callMain"])
 
     AS_VAR_IF([enable_wasm_dynamic_linking], [yes], [
       AS_VAR_APPEND([LINKFORSHARED], [" -sMAIN_MODULE"])
@@ -2339,7 +2343,6 @@ AS_CASE([$ac_sys_system],
       AS_VAR_APPEND([LDFLAGS_NODIST], [" -sUSE_PTHREADS"])
       AS_VAR_APPEND([LINKFORSHARED], [" -sPROXY_TO_PTHREAD"])
     ])
-    AS_VAR_APPEND([LDFLAGS_NODIST], [" -sALLOW_MEMORY_GROWTH"])
     dnl not completely sure whether or not we want -sEXIT_RUNTIME, keeping it for now.
     AS_VAR_APPEND([LDFLAGS_NODIST], [" -sEXIT_RUNTIME"])
     WASM_LINKFORSHARED_DEBUG="-gseparate-dwarf --emit-symbol-map"