fix: rustc_compile_action emits CcInfo for wasm32 targets (#1979)

This change allows `cc_binary()`, `cc_library()`, etc. targets to depend
on `rust_libary()`, `rust_static_library()`, etc. targets when targeting
`wasm32`.

.bazelci/presubmit.yml

@@ -621,6 +621,21 @@ tasks:
   #   working_directory: examples/zig_cross_compiling
   #   build_targets:
   #     - "//..."
+  nix_cross_compiling:
+    name: Nix cross compiling test
+    platform: ubuntu2204
+    working_directory: examples/nix_cross_compiling
+    setup:
+      - curl -L https://nixos.org/nix/install | bash
+      - sudo cp ~/.nix-profile/bin/nix* /usr/local/bin/
+      - sudo mkdir /etc/nix
+      - echo "experimental-features = nix-command flakes" | sudo tee --append /etc/nix/nix.conf
+    build_targets:
+      # Root `build_test` target is called directly to catch missing platforms
+      # that would otherwise be quietly skipped due to `target_compatible_with`.
+      - "//:nix_cross_compiling"
+    test_targets:
+      - "//..."
 
 buildifier:
   version: latest

.envrc

@@ -0,0 +1,10 @@
+# `nix-direnv` to provide developer tools to terminals and VSCode when working
+# in the repo.
+#
+# See:
+#  - https://github.com/nix-community/nix-direnv
+#  - https://marketplace.visualstudio.com/items?itemName=mkhl.direnv
+
+# Use `path:` syntax to avoid copying the entire repo to the Nix Store.
+nix_direnv_watch_file ./nix/flake.nix
+use flake path:./nix

crate_universe/flake.nix

@@ -0,0 +1,26 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+      {
+        packages.cargo-bazel = pkgs.rustPlatform.buildRustPackage {
+          pname = "cargo-bazel";
+          version = (builtins.fromTOML (builtins.readFile ./Cargo.toml)).package.version;
+
+          src = ./.;
+          cargoLock.lockFile = ./Cargo.lock;
+
+          # Tests cannot be run via Cargo due to the dependency on the
+          # Bazel `runfiles` crate.
+          doCheck = false;
+        };
+      });
+}

examples/.bazelignore

@@ -4,4 +4,5 @@ crate_universe
 crate_universe_unnamed
 ios
 ios_build
+nix_cross_compiling
 zig_cross_compiling

examples/nix_cross_compiling/.bazelrc

@@ -0,0 +1,15 @@
+# Sensible Defaults
+build --sandbox_default_allow_network=false
+build --incompatible_strict_action_env
+build --action_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
+build --incompatible_enable_cc_toolchain_resolution=true
+
+# Require Platform Transitions
+## This works by setting the targte platform to an invalid platform
+## and each `x_binary()` and `x_library()` rule unfortunately needs
+## to tag itself with `platform_missing` to get excluded from glob
+## builds like `build //...` but still have a way to include them
+## by removing the filter line for things like Rust Analyzer.
+build --host_platform=//bazel/platforms:host
+build --platforms=//bazel/platforms:missing
+build --build_tag_filters=-platform_missing

examples/nix_cross_compiling/.gitignore

@@ -0,0 +1 @@
+/bazel-*

examples/nix_cross_compiling/BUILD.bazel

@@ -0,0 +1,150 @@
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("//bazel:transitions.bzl", "platform_transition_binary")
+
+# Disabled targets need the user to supply a sysroot in `flake.nix` first.
+
+build_test(
+    name = "nix_cross_compiling",
+    targets = [
+        # ":cc_binary_aarch64-apple-darwin",
+        # ":cc_binary_aarch64-apple-ios",
+        ":cc_binary_aarch64-linux-android",
+        ":cc_binary_aarch64-unknown-linux-gnu",
+        ":cc_binary_wasm32-unknown-unknown",
+        ":cc_binary_wasm32-wasi",
+        # ":cc_binary_x86_64-apple-darwin",
+        # ":cc_binary_x86_64-pc-windows-msvc",
+        ":cc_binary_x86_64-unknown-linux-gnu",
+        ":cc_binary_x86_64-unknown-nixos-gnu",
+        # ":rust_binary_aarch64-apple-darwin",
+        # ":rust_binary_aarch64-apple-ios",
+        ":rust_binary_aarch64-linux-android",
+        ":rust_binary_aarch64-unknown-linux-gnu",
+        ":rust_binary_wasm32-unknown-unknown",
+        ":rust_binary_wasm32-wasi",
+        # ":rust_binary_x86_64-apple-darwin",
+        # ":rust_binary_x86_64-pc-windows-msvc",
+        ":rust_binary_x86_64-unknown-linux-gnu",
+        ":rust_binary_x86_64-unknown-nixos-gnu",
+    ],
+)
+
+# platform_transition_binary(
+#     name = "cc_binary_aarch64-apple-darwin",
+#     binary = "//cc_binary",
+#     target_platform = "//bazel/platforms:aarch64-apple-darwin",
+# )
+
+# platform_transition_binary(
+#     name = "cc_binary_aarch64-apple-ios",
+#     binary = "//cc_binary",
+#     target_platform = "//bazel/platforms:aarch64-apple-ios",
+# )
+
+platform_transition_binary(
+    name = "cc_binary_aarch64-linux-android",
+    binary = "//cc_binary",
+    target_platform = "//bazel/platforms:aarch64-linux-android",
+)
+
+platform_transition_binary(
+    name = "cc_binary_aarch64-unknown-linux-gnu",
+    binary = "//cc_binary",
+    target_platform = "//bazel/platforms:aarch64-unknown-linux-gnu",
+)
+
+platform_transition_binary(
+    name = "cc_binary_wasm32-unknown-unknown",
+    binary = "//cc_binary",
+    target_platform = "//bazel/platforms:wasm32-unknown-unknown",
+)
+
+platform_transition_binary(
+    name = "cc_binary_wasm32-wasi",
+    binary = "//cc_binary",
+    target_platform = "//bazel/platforms:wasm32-wasi",
+)
+
+# platform_transition_binary(
+#     name = "cc_binary_x86_64-apple-darwin",
+#     binary = "//cc_binary",
+#     target_platform = "//bazel/platforms:x86_64-apple-darwin",
+# )
+
+# platform_transition_binary(
+#     name = "cc_binary_x86_64-pc-windows-msvc",
+#     binary = "//cc_binary",
+#     target_platform = "//bazel/platforms:x86_64-pc-windows-msvc",
+# )
+
+platform_transition_binary(
+    name = "cc_binary_x86_64-unknown-linux-gnu",
+    binary = "//cc_binary",
+    target_platform = "//bazel/platforms:x86_64-unknown-linux-gnu",
+)
+
+platform_transition_binary(
+    name = "cc_binary_x86_64-unknown-nixos-gnu",
+    binary = "//cc_binary",
+    target_platform = "//bazel/platforms:x86_64-unknown-nixos-gnu",
+)
+
+# platform_transition_binary(
+#     name = "rust_binary_aarch64-apple-darwin",
+#     binary = "//rust_binary",
+#     target_platform = "//bazel/platforms:aarch64-apple-darwin",
+# )
+
+# platform_transition_binary(
+#     name = "rust_binary_aarch64-apple-ios",
+#     binary = "//rust_binary",
+#     target_platform = "//bazel/platforms:aarch64-apple-ios",
+# )
+
+platform_transition_binary(
+    name = "rust_binary_aarch64-linux-android",
+    binary = "//rust_binary",
+    target_platform = "//bazel/platforms:aarch64-linux-android",
+)
+
+platform_transition_binary(
+    name = "rust_binary_aarch64-unknown-linux-gnu",
+    binary = "//rust_binary",
+    target_platform = "//bazel/platforms:aarch64-unknown-linux-gnu",
+)
+
+platform_transition_binary(
+    name = "rust_binary_wasm32-unknown-unknown",
+    binary = "//rust_binary",
+    target_platform = "//bazel/platforms:wasm32-unknown-unknown",
+)
+
+platform_transition_binary(
+    name = "rust_binary_wasm32-wasi",
+    binary = "//rust_binary",
+    target_platform = "//bazel/platforms:wasm32-wasi",
+)
+
+# platform_transition_binary(
+#     name = "rust_binary_x86_64-apple-darwin",
+#     binary = "//rust_binary",
+#     target_platform = "//bazel/platforms:x86_64-apple-darwin",
+# )
+
+# platform_transition_binary(
+#     name = "rust_binary_x86_64-pc-windows-msvc",
+#     binary = "//rust_binary",
+#     target_platform = "//bazel/platforms:x86_64-pc-windows-msvc",
+# )
+
+platform_transition_binary(
+    name = "rust_binary_x86_64-unknown-linux-gnu",
+    binary = "//rust_binary",
+    target_platform = "//bazel/platforms:x86_64-unknown-linux-gnu",
+)
+
+platform_transition_binary(
+    name = "rust_binary_x86_64-unknown-nixos-gnu",
+    binary = "//rust_binary",
+    target_platform = "//bazel/platforms:x86_64-unknown-nixos-gnu",
+)

examples/nix_cross_compiling/README.md

@@ -0,0 +1,3 @@
+# Nix + Bazel Cross Compiling
+
+Blog Post: <https://blog.consumingchaos.com/posts/nix-bazel-cross-compiling/>

examples/nix_cross_compiling/WORKSPACE.bazel

@@ -0,0 +1,87 @@
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+# Nix
+http_archive(
+    name = "io_tweag_rules_nixpkgs",
+    sha256 = "54946958c311f48c17c9b2e70683b621fec135258b75173f3900f901d52d8115",
+    strip_prefix = "rules_nixpkgs-2b4702c8a0d1d7ea474ea0913344e8add2759f9c",
+    urls = ["https://github.com/tweag/rules_nixpkgs/archive/2b4702c8a0d1d7ea474ea0913344e8add2759f9c.tar.gz"],
+)
+
+load("@io_tweag_rules_nixpkgs//nixpkgs:repositories.bzl", "rules_nixpkgs_dependencies")
+
+rules_nixpkgs_dependencies()
+
+load("//bazel:nix_repositories.bzl", "nix_repositories")
+
+nix_repositories()
+
+# Rust
+local_repository(
+    name = "rules_rust",
+    path = "../..",
+)
+
+load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies")
+
+rules_rust_dependencies()
+
+load("@rules_rust//crate_universe:defs.bzl", "crates_repository", "render_config", "splicing_config")
+load("//bazel/cargo:crates_repository.bzl", CARGO_ANNOTATIONS = "ANNOTATIONS", CARGO_PACKAGES = "PACKAGES")
+
+crates_repository(
+    name = "crate_index",
+    annotations = CARGO_ANNOTATIONS,
+    cargo_lockfile = "//bazel/cargo:Cargo.lock",
+    generate_build_scripts = False,
+    generator = "@cargo-bazel//:bin/cargo-bazel",
+    lockfile = "//bazel/cargo:cargo-bazel-lock.json",
+    packages = CARGO_PACKAGES,
+    render_config = render_config(
+        platforms_template = "@//bazel/cargo/platforms:{triple}",
+    ),
+    rust_toolchain_cargo_template = "@nix_rust//:bin/{tool}",
+    rust_toolchain_rustc_template = "@nix_rust//:bin/{tool}",
+    splicing_config = splicing_config(
+        resolver_version = "2",
+    ),
+    supported_platform_triples = [
+        "aarch64-apple-darwin",
+        "aarch64-apple-ios",
+        "aarch64-linux-android",
+        "aarch64-unknown-linux-gnu",
+        "wasm32-unknown-unknown",
+        "wasm32-wasi",
+        "x86_64-apple-darwin",
+        "x86_64-pc-windows-msvc",
+        "x86_64-unknown-linux-gnu",
+    ],
+)
+
+load("@crate_index//:defs.bzl", "crate_repositories")
+
+crate_repositories()
+
+# Toolchains
+register_toolchains(
+    "//bazel/toolchains/cc/aarch64-apple-darwin:toolchain",
+    "//bazel/toolchains/cc/aarch64-apple-ios:toolchain",
+    "//bazel/toolchains/cc/aarch64-linux-android:toolchain",
+    "//bazel/toolchains/cc/aarch64-unknown-linux-gnu:toolchain",
+    "//bazel/toolchains/cc/wasm32-unknown-unknown:toolchain",
+    "//bazel/toolchains/cc/wasm32-wasi:toolchain",
+    "//bazel/toolchains/cc/x86_64-apple-darwin:toolchain",
+    "//bazel/toolchains/cc/x86_64-pc-windows-msvc:toolchain",
+    "//bazel/toolchains/cc/x86_64-unknown-linux-gnu:toolchain",
+    "//bazel/toolchains/cc/x86_64-unknown-nixos-gnu:toolchain",
+    "//bazel/toolchains/rust/aarch64-apple-darwin:toolchain",
+    "//bazel/toolchains/rust/aarch64-apple-ios:toolchain",
+    "//bazel/toolchains/rust/aarch64-linux-android:toolchain",
+    "//bazel/toolchains/rust/aarch64-unknown-linux-gnu:toolchain",
+    "//bazel/toolchains/rust/wasm32-unknown-unknown:toolchain",
+    "//bazel/toolchains/rust/wasm32-wasi:toolchain",
+    "//bazel/toolchains/rust/x86_64-apple-darwin:toolchain",
+    "//bazel/toolchains/rust/x86_64-pc-windows-msvc:toolchain",
+    "//bazel/toolchains/rust/x86_64-unknown-linux-gnu:toolchain",
+    "//bazel/toolchains/rust/x86_64-unknown-nixos-gnu:toolchain",
+)