Add Emscripten tests (#196)

See #194 

This installs (and caches) the emsdk toolchain at the last version compatible w/ stable rust. It also tests on both asmjs and wasm32, uses node by default, and works around an asm.js bug.

.cargo/config

@@ -3,3 +3,7 @@
 runner = 'wasm-bindgen-test-runner'
 [target.wasm32-wasi]
 runner = 'wasmtime'
+
+# Just run on node by default (that's where emscripten is tested)
+[target.'cfg(target_os = "emscripten")']
+runner = 'node'

.github/workflows/tests.yml

@@ -125,7 +125,6 @@ jobs:
           override: true
       - run: cargo test --features=std
 
-  # TODO: Add emscripten when it's working with Cross
   cross-tests:
     name: Cross Test
     runs-on: ubuntu-latest
@@ -224,6 +223,40 @@ jobs:
           mv /tmp/wasmtime ~/.cargo/bin
       - run: cargo test --target wasm32-wasi
 
+  emscripten-tests:
+    name: Emscripten tests
+    runs-on: ubuntu-latest
+    env:
+      EMSDK_VERSION: 1.39.20 # Last emsdk compatible with Rust's LLVM 11
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+      - run: rustup target add wasm32-unknown-emscripten
+      - run: rustup target add asmjs-unknown-emscripten
+      - name: Cache emsdk
+        id: cache-emsdk
+        uses: actions/cache@v2
+        with:
+          path: ~/emsdk
+          key: ${{ runner.os }}-${{ env.EMSDK_VERSION }}-emsdk
+      - name: Install emsdk
+        if: steps.cache-emsdk.outputs.cache-hit != 'true'
+        run: |
+          git clone https://github.com/emscripten-core/emsdk.git ~/emsdk
+          cd ~/emsdk
+          ./emsdk install $EMSDK_VERSION
+          ./emsdk activate $EMSDK_VERSION
+      - run: echo "$HOME/emsdk/upstream/emscripten" >> $GITHUB_PATH
+      - name: wasm test
+        run: cargo test --target=wasm32-unknown-emscripten --features=std
+      - name: asm.js test
+        run: | # Debug info breaks on asm.js
+          RUSTFLAGS="$RUSTFLAGS -C debuginfo=0"
+          cargo test --target=asmjs-unknown-emscripten --features=std
+
   build:
     name: Build only
     runs-on: ubuntu-latest