Add support for wasm-bindgen.

.bazelci/presubmit.yml

@@ -40,6 +40,10 @@ tasks:
     - "-@examples//hello_lib:hello_lib_doc_test"
     - "-//tools/runfiles:runfiles_doc_test"
     - "-@examples//ffi/rust_calling_c/simple/..."
+    # See https://github.com/bazelbuild/bazel/issues/9987
+    - "-@examples//ffi/rust_calling_c:matrix_dylib_test"
+    # rust-lld isn't available on RBE
+    - "-@examples//hello_world_wasm:hello_world_wasm_test"
   examples:
     name: Examples
     platform: ubuntu1804

AUTHORS

@@ -7,6 +7,7 @@
 # The email address is not required for organizations.
 
 Google Inc.
+Spotify AB
 Damien Martin-Guillerez <[email protected]>
 David Chen <[email protected]>
 Florian Weikert <[email protected]>

CONTRIBUTORS

@@ -19,3 +19,4 @@ Kristina Chodorow <[email protected]>
 Philipp Wollermann <[email protected]>
 Ulf Adams <[email protected]>
 Justine Alexandra Roberts Tunney <[email protected]>
+John Edmonds <[email protected]>

README.md

@@ -22,6 +22,15 @@ This repository provides rules for building [Rust][rust] projects with [Bazel](h
   </ul>
 </div>
 
+#### WebAssembly
+
+To build a `rust_binary` for wasm32-unknown-unknown add the `--platforms=//rust/platform:wasm` flag.
+
+    bazel build @examples//hello_world_wasm --platforms=//rust/platform:wasm
+
+`rust_wasm_bindgen` will automatically transition to the wasm platform and can be used when
+building wasm code for the host target.
+
 ### Protobuf
 <div class="toc">
   <ul>

WORKSPACE

@@ -41,6 +41,9 @@ rust_proto_repositories()
 load("@io_bazel_rules_rust//bindgen:repositories.bzl", "rust_bindgen_repositories")
 rust_bindgen_repositories()
 
+load("@io_bazel_rules_rust//wasm_bindgen:repositories.bzl", "rust_wasm_bindgen_repositories")
+rust_wasm_bindgen_repositories()
+
 # Stardoc and its dependencies
 http_archive(
     name = "io_bazel_skydoc",
@@ -54,9 +57,16 @@ skydoc_repositories()
 load("@io_bazel_rules_sass//:package.bzl", "rules_sass_dependencies")
 rules_sass_dependencies()
 
-load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories")
+load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories", "npm_install")
 node_repositories()
 
+# Dependencies for the @examples//hello_world_wasm example.
+npm_install(
+    name = "npm",
+    package_json = "//:package.json",
+    package_lock_json = "//:package-lock.json",
+)
+
 load("@io_bazel_rules_sass//:defs.bzl", "sass_repositories")
 sass_repositories()
 # --- end stardoc

examples/WORKSPACE

@@ -37,10 +37,31 @@ http_archive(
     ],
 )
 
+http_archive(
+    name = "build_bazel_rules_nodejs",
+    url = "https://github.com/bazelbuild/rules_nodejs/archive/0.16.2.zip",
+    strip_prefix = "rules_nodejs-0.16.2",
+    sha256 = "9b72bb0aea72d7cbcfc82a01b1e25bf3d85f791e790ddec16c65e2d906382ee0"
+)
+
+load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories", "npm_install")
+node_repositories()
+
+# Dependencies for the @examples//hello_world_wasm example.
+npm_install(
+    name = "npm",
+    package_json = "@io_bazel_rules_rust//:package.json",
+    package_lock_json = "@io_bazel_rules_rust//:package-lock.json",
+)
+
 load("@io_bazel_rules_rust//bindgen:repositories.bzl", "rust_bindgen_repositories")
 
 rust_bindgen_repositories()
 
+load("@io_bazel_rules_rust//wasm_bindgen:repositories.bzl", "rust_wasm_bindgen_repositories")
+
+rust_wasm_bindgen_repositories()
+
 load("@io_bazel_rules_rust//:workspace.bzl", "bazel_version")
 
 bazel_version(name = "bazel_version")

examples/hello_world_wasm/BUILD

@@ -0,0 +1,39 @@
+package(default_visibility = ["//visibility:public"])
+
+load(
+    "@io_bazel_rules_rust//rust:rust.bzl",
+    "rust_binary",
+)
+
+load(
+    "@io_bazel_rules_rust//wasm_bindgen:wasm_bindgen.bzl",
+    "rust_wasm_bindgen",
+)
+
+load(
+    "@build_bazel_rules_nodejs//:defs.bzl",
+    "jasmine_node_test",
+)
+
+rust_binary(
+    name = "hello_world_wasm",
+    srcs = ["main.rs"],
+    edition = "2018",
+    deps = ["@io_bazel_rules_rust//wasm_bindgen/raze:wasm_bindgen"],
+)
+
+rust_wasm_bindgen(
+    name = "hello_world_wasm_bindgen",
+    wasm_file = ":hello_world_wasm"
+)
+
+jasmine_node_test(
+    name = "hello_world_wasm_test",
+    srcs = [
+        "hello_world_wasm_test.js",
+    ],
+    data = [
+        ":hello_world_wasm_bindgen_bg.wasm",
+        "@npm//jasmine",
+    ],
+)

examples/hello_world_wasm/hello_world_wasm_test.js

@@ -0,0 +1,10 @@
+const fs = require('fs');
+const path = require('path');
+
+describe('Calling WebAssembly code', () => {
+  it('Should run WebAssembly code', async () => {
+    const buf = fs.readFileSync(path.join(__dirname, 'hello_world_wasm_bindgen_bg.wasm'));
+    const res = await WebAssembly.instantiate(buf);
+    expect(res.instance.exports.hello_world(2)).toEqual(4);
+  })
+});

examples/hello_world_wasm/main.rs

@@ -0,0 +1,10 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+pub fn hello_world(i: i32) -> i32 {
+    i * 2
+}
+
+fn main() {
+    println!("Hello {}", hello_world(2));
+}

package.json

@@ -0,0 +1,7 @@
+{
+  "private": true,
+  "devDependencies": {
+    "jasmine": "3.4.0"
+  },
+  "scripts": {}
+}

rust/platform/BUILD

@@ -3,3 +3,11 @@ package(default_visibility = ["//visibility:public"])
 load(":platform.bzl", "declare_config_settings")
 
 declare_config_settings()
+
+package_group(
+    name = "function_transition_whitelist",
+    packages = [
+        "//...",
+    ],
+)
+

rust/platform/platform.bzl

@@ -79,3 +79,15 @@ def declare_config_settings():
             name = triple,
             constraint_values = triple_to_constraint_set(triple),
         )
+
+    native.constraint_value(
+        name = "wasm32",
+        constraint_setting = "@platforms//cpu"
+    )
+
+    native.platform(
+        name = "wasm",
+        constraint_values = [
+            "@io_bazel_rules_rust//rust/platform:wasm32",
+        ]
+    )

rust/platform/triple_mappings.bzl

@@ -43,6 +43,7 @@ _SYSTEM_TO_BINARY_EXT = {
     "darwin": "",
     "windows": ".exe",
     "emscripten": ".js",
+    "unknown": "",
 }
 
 _SYSTEM_TO_STATICLIB_EXT = {
@@ -52,6 +53,7 @@ _SYSTEM_TO_STATICLIB_EXT = {
     # TODO(acmcarther): To be verified
     "windows": ".lib",
     "emscripten": ".js",
+    "unknown": "",
 }
 
 _SYSTEM_TO_DYLIB_EXT = {
@@ -61,6 +63,7 @@ _SYSTEM_TO_DYLIB_EXT = {
     # TODO(acmcarther): To be verified
     "windows": ".dll",
     "emscripten": ".js",
+    "unknown": ".wasm",
 }
 
 def cpu_arch_to_constraints(cpu_arch):
@@ -120,6 +123,9 @@ def triple_to_constraint_set(triple):
     if len(component_parts) == 4:
         abi = component_parts[3]
 
+    if cpu_arch == "wasm32":
+        return ["@io_bazel_rules_rust//rust/platform:wasm32"]
+
     constraint_set = []
     constraint_set += cpu_arch_to_constraints(cpu_arch)
     constraint_set += vendor_to_constraints(vendor)

rust/private/dummy_cc_toolchain/BUILD

@@ -0,0 +1,13 @@
+load(":dummy_cc_toolchain.bzl", "dummy_cc_toolchain")
+dummy_cc_toolchain(name = "dummy_cc_wasm32")
+
+# When compiling Rust code for wasm32, we avoid linking to cpp code so we introduce a dummy cc
+# toolchain since we know we'll never look it up.
+# TODO([email protected]): Need to support linking C code to rust code when compiling for wasm32.
+toolchain(
+    name = "dummy_cc_wasm32_toolchain",
+    toolchain = ":dummy_cc_wasm32",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+    target_compatible_with = ["//rust/platform:wasm32"]
+)
+

rust/private/dummy_cc_toolchain/dummy_cc_toolchain.bzl

@@ -0,0 +1,8 @@
+def _dummy_cc_toolchain_impl(ctx):
+    return [platform_common.ToolchainInfo()]
+
+dummy_cc_toolchain = rule(
+    implementation = _dummy_cc_toolchain_impl,
+    attrs = {},
+)
+