web: Allow building an MVP vanilla WASM module

Author: danielhjacobs

.github/workflows/release_nightly.yml

@@ -336,6 +336,7 @@ jobs:
         with:
           toolchain: 1.81.0
           targets: wasm32-unknown-unknown
+          components: rust-src
 
       - name: Setup Node.js
         uses: actions/setup-node@v4

.github/workflows/test_extension_dockerfile.yml

@@ -21,6 +21,7 @@ jobs:
         with:
           toolchain: stable
           targets: wasm32-unknown-unknown
+          components: rust-src
 
       - name: Setup Node.js
         uses: actions/setup-node@v4

.github/workflows/test_web.yml

@@ -52,6 +52,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
         with:
           targets: wasm32-unknown-unknown
+          components: rust-src
 
       - name: Cache Cargo output
         uses: Swatinem/rust-cache@v2
@@ -117,6 +118,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
         with:
           targets: wasm32-unknown-unknown
+          components: rust-src
 
       - name: Cache Cargo output
         uses: Swatinem/rust-cache@v2

web/README.md

@@ -45,6 +45,7 @@ to update to the latest stable version of rust. You may run `rustup update` to d
 rust using the above instructions).
 
 For the compiler to be able to output WebAssembly, an additional target has to be added to it: `rustup target add wasm32-unknown-unknown`
+Because we use `RUSTC_BOOTSTRAP` in order to use certain Nightly flags with stable Rust you will also need to run `rustup component add rust-src`.
 
 #### Java
 
@@ -106,6 +107,7 @@ In this project, you may run the following commands to build all packages:
     -   There is `npm run build:dual-wasm` as well, to build a second WebAssembly module that makes use of some WebAssembly extensions,
         potentially resulting in better performance in browsers that support them, at the expense of longer build time.
     -   `npm run build:repro` enables reproducible builds. Note that this also requires a `version_seal.json`, which is not provided in the normal Git repository - only specially-marked reproducible source archives. Running this without a version seal will generate one based on the current state of your environment.
+    -   You will also need to run `rustup component add rust-src` with either of the previous two commands since we rebuild std for the vanilla WASM module.
 
 From here, you may follow the instructions to [use Ruffle on your website](packages/selfhosted/README.md),
 run a demo locally with `npm run demo`, or [install the extension in your browser](https://github.com/ruffle-rs/ruffle/wiki/Using-Ruffle#browser-extension).

web/docker/Dockerfile

@@ -11,7 +11,7 @@ RUN wget --progress=:giga https://github.com/WebAssembly/binaryen/releases/downl
     mv wasm-opt /usr/local/bin
 
 # Installing Rust using rustup:
-RUN wget 'https://sh.rustup.rs' --quiet -O- | sh -s -- -y --profile minimal --target wasm32-unknown-unknown
+RUN wget 'https://sh.rustup.rs' --quiet -O- | sh -s -- -y --profile minimal --target wasm32-unknown-unknown --component rust-src
 ENV PATH="/root/.cargo/bin:$PATH"
 # wasm-bindgen-cli version must match wasm-bindgen crate version.
 # Be sure to update in test_web.yml, release_nightly.yml, Cargo.toml, and web/README.md as well.

web/packages/core/tools/build_wasm.ts

@@ -42,12 +42,19 @@ function cargoBuild({
     profile,
     features,
     rustFlags,
+    extensions,
 }: {
     profile?: string;
     features?: string[];
     rustFlags?: string[];
+    extensions?: boolean;
 }) {
     let args = ["build", "--locked", "--target", "wasm32-unknown-unknown"];
+    if (!extensions) {
+        args.push("-Z");
+        args.push("build-std=std,panic_abort");
+    }
+
     if (profile) {
         args.push("--profile", profile);
     }
@@ -73,6 +80,7 @@ function cargoBuild({
     execFileSync("cargo", args, {
         env: Object.assign(Object.assign({}, process.env), {
             RUSTFLAGS: totalRustFlags,
+            RUSTC_BOOTSTRAP: extensions ? "0" : "1",
         }),
         stdio: "inherit",
     });
@@ -95,13 +103,16 @@ function buildWasm(
         );
         wasmBindgenFlags.push("--reference-types");
         wasmOptFlags.push("--enable-reference-types");
+    } else {
+        rustFlags.push("-C", "target-cpu=mvp");
     }
     let originalWasmPath;
     if (wasmSource === "cargo" || wasmSource === "cargo_and_store") {
         console.log(`Building ${flavor} with cargo...`);
         cargoBuild({
             profile,
             rustFlags,
+            extensions,
         });
         originalWasmPath = `../../../target/wasm32-unknown-unknown/${profile}/ruffle_web.wasm`;
         if (wasmSource === "cargo_and_store") {