Move stack switching logic into a new stack switching folder. (#3987)

This is a minor rearrangment.

I renamed "continuations" stuff to "stack_switching" and made a new folder
for stack switching logic. I also added logic in esbuild.config.mjs to calculate
which functions exported from stack_switching.mjs and automatically copy them to
Module and into the Emscripten namespace. This makes unit testing a little neater
since there is no modification of the Module object.

Makefile

@@ -25,7 +25,7 @@ all: check \
 	dist/module_webworker_dev.js
 	echo -e "\nSUCCESS!"
 
-src/core/pyodide_pre.o: src/js/_pyodide.out.js src/core/pre.js src/core/create_invokes.out.js
+src/core/pyodide_pre.o: src/js/_pyodide.out.js src/core/pre.js src/core/stack_switching/stack_switching.out.js
 # Our goal here is to inject src/js/_pyodide.out.js into an archive file so that
 # when linked, Emscripten will include it. We use the same pathway that EM_JS
 # uses, but EM_JS is itself unsuitable. Why? Because the C preprocessor /
@@ -57,7 +57,7 @@ src/core/pyodide_pre.o: src/js/_pyodide.out.js src/core/pre.js src/core/create_i
 	echo '()<::>{' >> tmp.dat             # zero argument argspec and start body
 	cat src/js/_pyodide.out.js >> tmp.dat # All of _pyodide.out.js is body
 	echo '}' >> tmp.dat                   # Close function body
-	cat src/core/create_invokes.out.js >> tmp.dat
+	cat src/core/stack_switching/stack_switching.out.js >> tmp.dat
 	cat src/core/pre.js >> tmp.dat           # And pre.js
 	echo "pyodide_js_init();" >> tmp.dat     # Then execute the function.
 
@@ -129,8 +129,8 @@ node_modules/.installed : src/js/package.json src/js/package-lock.json
 dist/pyodide.js src/js/_pyodide.out.js: src/js/*.ts src/js/pyproxy.gen.ts src/js/error_handling.gen.ts node_modules/.installed
 	cd src/js && npm run tsc && node esbuild.config.mjs && cd -
 
-src/core/create_invokes.out.js : src/core/create_invokes.mjs src/core/runtime_wasm.mjs
-	cd src/core && npx esbuild --bundle create_invokes.mjs --outfile=create_invokes.out.js
+src/core/stack_switching/stack_switching.out.js : src/core/stack_switching/*.mjs
+	node src/core/stack_switching/esbuild.config.mjs
 
 dist/package.json : src/js/package.json
 	cp $< $@
@@ -226,9 +226,10 @@ benchmark: all
 
 clean:
 	rm -fr dist/*
-	rm -fr src/*/*.o
-	rm -fr src/*/*.gen.*
 	rm -fr node_modules
+	find src -name '*.o' -delete
+	find src -name '*.gen.*' -delete
+	find src -name '*.out.*' -delete
 	make -C packages clean
 	echo "The Emsdk, CPython are not cleaned. cd into those directories to do so."
 

src/core/create_invokes.mjs → src/core/stack_switching/create_invokes.mjs

@@ -21,10 +21,6 @@ import {
   typeCodes,
 } from "./runtime_wasm.mjs";
 
-if (typeof Module === "undefined") {
-  globalThis.Module = {};
-}
-
 /**
  * These produce the following pseudocode:
  * ```
@@ -136,15 +132,13 @@ export function createInvokeModule(sig) {
   return mod.generate();
 }
 
-let jsWrapperTag;
+export let jsWrapperTag;
 try {
   jsWrapperTag = new WebAssembly.Tag({ parameters: ["externref"] });
-  Module.jsWrapperTag = jsWrapperTag;
 } catch (e) {}
 
-if (jsWrapperTag) {
-  Module.wrapException = (e) => new WebAssembly.Exception(jsWrapperTag, [e]);
-}
+export const wrapException = (e) =>
+  new WebAssembly.Exception(jsWrapperTag, [e]);
 
 function createInvoke(sig) {
   if (!jsWrapperTag) {
@@ -162,19 +156,16 @@ function createInvoke(sig) {
   });
   return instance.exports["o"];
 }
-Module.createInvoke = createInvoke;
 
 // We patched Emscripten to call this function on the wasmImports just prior to
 // wasm instantiation if it is defined. It replaces all invoke functions with
 // our Wasm invokes if wasm EH is available.
-Module.adjustWasmImports = function (wasmImports) {
-  if (jsWrapperTag) {
-    const i = "invoke_";
-    for (let name of Object.keys(wasmImports)) {
-      if (!name.startsWith(i)) {
-        continue;
-      }
-      wasmImports[name] = createInvoke(name.slice(i.length));
+export function adjustWasmImports(wasmImports) {
+  const i = "invoke_";
+  for (let name of Object.keys(wasmImports)) {
+    if (!name.startsWith(i)) {
+      continue;
     }
+    wasmImports[name] = createInvoke(name.slice(i.length));
   }
-};
+}

src/core/stack_switching/esbuild.config.mjs

@@ -0,0 +1,44 @@
+/**
+ * Bundle the stack switching folder as iife and then export names exported from
+ * stack_switching.mjs onto Module and into the Emscripten namespace.
+ */
+
+import { build } from "esbuild";
+import { dirname, join } from "node:path";
+
+const __dirname = dirname(new URL(import.meta.url).pathname);
+
+const outfile = join(__dirname, "stack_switching.out.js");
+const globalName = "StackSwitching";
+
+const config = {
+  entryPoints: [join(__dirname, "stack_switching.mjs")],
+  outfile,
+  format: "iife",
+  bundle: true,
+  globalName,
+  metafile: true,
+};
+
+// First build as "esm" to get the list of exports. The metafile doesn't list
+// exports except when we set `format: "esm"`. Setting bundle: false saves a
+// tiny amount of time on this pass.
+const { metafile } = await build(
+  Object.assign({}, config, { format: "esm", bundle: false }),
+);
+
+// The file name is the metafile.outputs key. It is relative to the current
+// working directory, so it's annoying to work it out. There will only be one
+// key in any case, so we just extract it with Object.values().
+const exports = Object.values(metafile.outputs)[0].exports;
+
+// Add a footer that destructures the exports into the Emscripten namespace.
+// Also Object.assign them onto Module.
+const footer = `
+  const {${exports}} = ${globalName};
+  Object.assign(Module, ${globalName});
+`.replaceAll(/\s/g, "");
+config.footer = { js: footer };
+
+// Build again, this time as an iife bundle with our extra footer.
+await build(config);

src/core/stack_switching/stack_switching.mjs

@@ -0,0 +1,17 @@
+/**
+ * Files exported from here are copied into the Emscripten namespace.
+ * See esbuild.config.mjs.
+ */
+
+import {
+  jsWrapperTag,
+  wrapException,
+  adjustWasmImports,
+} from "./create_invokes.mjs";
+
+export { jsWrapperTag };
+
+if (jsWrapperTag) {
+  Module.adjustWasmImports = adjustWasmImports;
+  Module.wrapException = wrapException;
+}

src/js/test/unit/continuations.test.mjs → src/js/test/unit/stack_switching.test.mjs

@@ -1,7 +1,6 @@
 import { expect } from "chai";
 
-import { readFileSync, writeFileSync } from "node:fs";
-import * as vm from "node:vm";
+import { readFileSync } from "node:fs";
 import loadWabt from "wabt";
 import { URL } from "url"; // in Browser, the URL in native accessible on window
 import {
@@ -12,8 +11,8 @@ import {
   TypeSection,
   WASM_PRELUDE,
   insertSectionPrefix,
-} from "../../../core/runtime_wasm.mjs";
-import { createInvokeModule } from "../../../core/create_invokes.mjs";
+} from "../../../core/stack_switching/runtime_wasm.mjs";
+import { createInvokeModule } from "../../../core/stack_switching/create_invokes.mjs";
 
 const __dirname = new URL(".", import.meta.url).pathname;
 
@@ -29,7 +28,7 @@ function fromWat(wat) {
 function fromWatFile(file) {
   return parseWat(
     file,
-    readFileSync(__dirname + "invokes/" + file, { encoding: "utf8" }),
+    readFileSync(__dirname + "wat/" + file, { encoding: "utf8" }),
     {
       mutable_globals: true,
       exceptions: true,