Add rust_expand and rust_expand_aspect for generating macro expanded source files.

.bazelci/presubmit.yml

@@ -411,6 +411,16 @@ tasks:
       - "//..."
     test_targets:
       - "//..."
+  expand_examples_ubuntu2004:
+    name: Expand Examples
+    platform: ubuntu2004
+    working_directory: examples/expand
+    build_targets:
+      - "//..."
+    test_targets:
+      - "//..."
+    build_flags:
+      - "--config=expanded"
   cc_common_link_ubuntu2004:
     name: Build via cc_common.link
     platform: ubuntu2004

examples/.bazelignore

@@ -2,5 +2,6 @@ android
 cargo_manifest_dir/external_crate
 crate_universe
 crate_universe_unnamed
+expand
 ios
 ios_build

examples/expand/.bazelrc

@@ -0,0 +1,10 @@
+# `.bazelrc` is a Bazel configuration file.
+# https://bazel.build/docs/best-practices#bazelrc-file
+
+# Enable rustc expand targets
+build:expanded --aspects=@rules_rust//rust:defs.bzl%rust_expand_aspect
+build:expanded --output_groups=+expanded
+
+# This import should always be last to allow users to override
+# settings for local development.
+try-import %workspace%/user.bazelrc

examples/expand/BUILD.bazel

@@ -0,0 +1,62 @@
+load("@bazel_skylib//rules:diff_test.bzl", "diff_test")
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_expand", "rust_library", "rust_test")
+
+package(default_visibility = ["//test:__subpackages__"])
+
+# Declaration of targets.
+
+rust_binary(
+    name = "ok_binary",
+    srcs = ["src/main.rs"],
+    edition = "2021",
+)
+
+rust_library(
+    name = "ok_library",
+    srcs = ["src/lib.rs"],
+    edition = "2021",
+)
+
+rust_test(
+    name = "ok_test",
+    srcs = ["src/lib.rs"],
+    edition = "2021",
+)
+
+# Expand targets.
+
+rust_expand(
+    name = "ok_binary_expand",
+    deps = [":ok_binary"],
+)
+
+rust_expand(
+    name = "ok_library_expand",
+    deps = [":ok_library"],
+)
+
+rust_expand(
+    name = "ok_test_expand",
+    testonly = True,
+    deps = [":ok_test"],
+)
+
+# Assert on expanded targets.
+
+diff_test(
+    name = "ok_binary_expand_test",
+    file1 = ":ok_binary.expand.expected.rs",
+    file2 = ":ok_binary_expand",
+)
+
+diff_test(
+    name = "ok_library_expand_test",
+    file1 = ":ok_library.expand.expected.rs",
+    file2 = ":ok_library_expand",
+)
+
+diff_test(
+    name = "ok_test_expand_test",
+    file1 = ":ok_test.expand.expected.rs",
+    file2 = ":ok_test_expand",
+)

examples/expand/README.md

@@ -0,0 +1,76 @@
+### Expand Example
+
+Rustc can be used to expand all macros so that you can inspect the generated source files easier.
+
+This feature is enabled via `-Zunpretty=expanded`. The `-Z` flag is only available in the nightly
+version of `rustc`.
+
+
+### Expanding
+
+Build and test your targets normally.
+
+```
+bazel build //:ok_binary   
+INFO: Analyzed target //:ok_binary (0 packages loaded, 0 targets configured).
+INFO: Found 1 target...
+Target //:ok_binary up-to-date:
+  bazel-bin/ok_binary
+INFO: Elapsed time: 0.081s, Critical Path: 0.00s
+INFO: 1 process: 1 internal.
+INFO: Build completed successfully, 1 total action
+```
+
+Use the aspect to generate the expanded files in as a one-off build.
+
+```
+bazel build --config=expanded //:ok_binary
+INFO: Analyzed target //:ok_binary (1 packages loaded, 2 targets configured).
+INFO: Found 1 target...
+Aspect @rules_rust//rust/private:expand.bzl%rust_expand_aspect of //:ok_binary up-to-date:
+  bazel-bin/ok_binary.expand.rs
+INFO: Elapsed time: 0.149s, Critical Path: 0.00s
+INFO: 1 process: 1 internal.
+INFO: Build completed successfully, 1 total action
+```
+
+Targeting tests is valid as well.
+
+```
+bazel build --config=expanded //:ok_test  
+INFO: Analyzed target //:ok_test (0 packages loaded, 2 targets configured).
+INFO: Found 1 target...
+Aspect @rules_rust//rust/private:expand.bzl%rust_expand_aspect of //:ok_test up-to-date:
+  bazel-bin/test-397521499/ok_test.expand.rs
+INFO: Elapsed time: 0.113s, Critical Path: 0.00s
+INFO: 1 process: 1 internal.
+INFO: Build completed successfully, 1 total action
+```
+
+Finally, manually wire up a `rust_expand` target explicitly if you want a target to build.
+
+```
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_expand")
+
+rust_binary(
+    name = "ok_binary",
+    srcs = ["src/main.rs"],
+    edition = "2021",
+)
+
+rust_expand(
+    name = "ok_binary_expand",
+    deps = [":ok_binary"],
+)
+```
+
+```
+bazel build //:ok_binary_expand
+INFO: Analyzed target //:ok_binary_expand (0 packages loaded, 1 target configured).
+INFO: Found 1 target...
+Target //:ok_binary_expand up-to-date:
+  bazel-bin/ok_binary.expand.rs
+INFO: Elapsed time: 0.090s, Critical Path: 0.00s
+INFO: 1 process: 1 internal.
+INFO: Build completed successfully, 1 total action
+```

examples/expand/WORKSPACE.bazel

@@ -0,0 +1,16 @@
+workspace(name = "examples")
+
+local_repository(
+    name = "rules_rust",
+    path = "../../",
+)
+
+load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_register_toolchains")
+
+rules_rust_dependencies()
+
+rust_register_toolchains(
+    edition = "2021",
+    iso_date = "2022-11-01",
+    version = "nightly",
+)

examples/expand/ok_binary.expand.expected.rs

@@ -0,0 +1,11 @@
+#![feature(prelude_import)]
+#[prelude_import]
+use std::prelude::rust_2021::*;
+#[macro_use]
+extern crate std;
+fn main() {
+    {
+        ::std::io::_print(::core::fmt::Arguments::new_v1(&["Hello world\n"],
+                &[]));
+    };
+}

examples/expand/ok_library.expand.expected.rs

@@ -0,0 +1,10 @@
+#![feature(prelude_import)]
+#[prelude_import]
+use std::prelude::rust_2021::*;
+#[macro_use]
+extern crate std;
+pub fn greeting() -> String { "Hello World".to_owned() }
+
+// too_many_args/clippy.toml will require no more than 2 args.
+pub fn with_args(_: u32, _: u32, _: u32) {}
+

examples/expand/ok_test.expand.expected.rs

@@ -0,0 +1,47 @@
+#![feature(prelude_import)]
+#[prelude_import]
+use std::prelude::rust_2021::*;
+#[macro_use]
+extern crate std;
+pub fn greeting() -> String { "Hello World".to_owned() }
+
+// too_many_args/clippy.toml will require no more than 2 args.
+pub fn with_args(_: u32, _: u32, _: u32) {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    extern crate test;
+    #[cfg(test)]
+    #[rustc_test_marker = "tests::it_works"]
+    pub const it_works: test::TestDescAndFn =
+        test::TestDescAndFn {
+            desc: test::TestDesc {
+                name: test::StaticTestName("tests::it_works"),
+                ignore: false,
+                ignore_message: ::core::option::Option::None,
+                compile_fail: false,
+                no_run: false,
+                should_panic: test::ShouldPanic::No,
+                test_type: test::TestType::UnitTest,
+            },
+            testfn: test::StaticTestFn(||
+                    test::assert_test_result(it_works())),
+        };
+    fn it_works() {
+        match (&greeting(), &"Hello World".to_owned()) {
+            (left_val, right_val) => {
+                if !(*left_val == *right_val) {
+                        let kind = ::core::panicking::AssertKind::Eq;
+                        ::core::panicking::assert_failed(kind, &*left_val,
+                            &*right_val, ::core::option::Option::None);
+                    }
+            }
+        };
+    }
+}
+#[rustc_main]
+pub fn main() -> () {
+    extern crate test;
+    test::test_main_static(&[&it_works])
+}

examples/expand/src/lib.rs

@@ -0,0 +1,15 @@
+pub fn greeting() -> String {
+    "Hello World".to_owned()
+}
+
+// too_many_args/clippy.toml will require no more than 2 args.
+pub fn with_args(_: u32, _: u32, _: u32) {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn it_works() {
+        assert_eq!(greeting(), "Hello World".to_owned());
+    }
+}

examples/expand/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello world");
+}

rust/defs.bzl

@@ -26,6 +26,7 @@ load(
     _rust_clippy_aspect = "rust_clippy_aspect",
 )
 load("//rust/private:common.bzl", _rust_common = "rust_common")
+load("//rust/private:expand.bzl", _rust_expand = "rust_expand", _rust_expand_aspect = "rust_expand_aspect")
 load(
     "//rust/private:rust.bzl",
     _rust_binary = "rust_binary",
@@ -103,6 +104,12 @@ rust_clippy = _rust_clippy
 capture_clippy_output = _capture_clippy_output
 # See @rules_rust//rust/private:clippy.bzl for a complete description.
 
+rust_expand_aspect = _rust_expand_aspect
+# See @rules_rust//rust/private:expand.bzl for a complete description.
+
+rust_expand = _rust_expand
+# See @rules_rust//rust/private:expand.bzl for a complete description.
+
 error_format = _error_format
 # See @rules_rust//rust/private:rustc.bzl for a complete description.