feat: Add rust_lint_group and cargo_lints rule to define lint groups (bazelbuild#2993)

Chatted about this previously in
[Slack](https://bazelbuild.slack.com/archives/CSV56UT0F/p1718030356910019).
The goal with this PR is to make it easier to define and share lint
configurations for your build.

The PR adds two new rules, `rust_lint_group` and `cargo_lints`. It also
adds a "lints" attr to `rust_library` and `rust_binary` rules that
expects a new `LintsInfo` provider.

* `rust_lint_group` allows you to define Rust, Clippy, and Rustdoc lints
in a `BUILD` file.
* `cargo_lints` automatically generates a set of lints by reading a
crate's `Cargo.toml`, and optionally the workspace's Cargo.toml for
workspace inheritance.

Then the rustc, clippy, and rustdoc actions are all updated to check for
the `LintsInfo` provider and appends the correct arguments so the lints
take effect.

Honestly this is my first large change to a set of Bazel rules, so I
definitely could have done something wrong here!

The change is split into two commits, the first introduces
`rust_lint_group` which IMO is relatively straight forward. Some
attributes are defined on a rule which are then formatted into command
line flags and passed around with a provider.

The second commit adds `cargo_lints` and is much larger, a few things
worth considering:

* I was back and forth a bit on using a `repository_rule` or a regular
`rule`. While the `repository_rule` maps well to a Cargo Workspace and
you'd only need to define it once, not everyone uses workspaces and so I
figured a regular `rule` was more general.
* Parsing a `Cargo.toml` is done via a new Rust binary called
`cargo_toml_info`. I tried to keep the external dependencies on this
binary to a minimum, it only has one at the moment which is
[`cargo_toml`](https://docs.rs/cargo_toml/latest/cargo_toml/) and I
based this change largely off of
bazelbuild#2772. I tried to make the
tool general though so other Cargo metadata rules could use it in the
future.

There aren't any! I wasn't sure where the best place to start was, any
guidance here is appreciated!

Author: ParkMyCar

.bazelci/presubmit.yml

@@ -25,6 +25,21 @@ single_rust_channel_targets: &single_rust_channel_targets
   # These tests are expected to fail as they require both a nightly and stable toolchain.
   - "-//test/unit/channel_transitions/..."
   - "-//test/unpretty/..."
+single_rust_channel_min_version_targets: &single_rust_channel_min_version_targets
+  # START - Copied from 'single_rust_channel_targets'.
+  # TODO: Figure out how to do proper list inheritence.
+  - "--"
+  - "//..."
+  # TODO: Remove this and replace `cargo_bootstrap_repository` with a
+  # http_archive for a release: https://github.com/cross-rs/cross/issues/1356
+  - "-//crate_universe/tools/cross_installer/..."
+  # These tests are expected to fail as they require both a nightly and stable toolchain.
+  - "-//test/unit/channel_transitions/..."
+  - "-//test/unpretty/..."
+  # END - Copied from 'single_rust_channel_targets'.
+  #
+  # These tests exercise behavior only available versions of Rust >1.80
+  - "-//test/unit/lint_flags/..."
 default_linux_targets: &default_linux_targets
   - "--"
   - "//..."
@@ -297,16 +312,16 @@ tasks:
     name: "Min Rust Version"
     platform: ubuntu2004
     shell_commands: *min_rust_version_shell_commands
-    build_targets: *single_rust_channel_targets
-    test_targets: *single_rust_channel_targets
+    build_targets: *single_rust_channel_min_version_targets
+    test_targets: *single_rust_channel_min_version_targets
   ubuntu2004_min_rust_version_with_aspects:
     name: "Min Rust Version With Aspects"
     platform: ubuntu2004
     shell_commands: *min_rust_version_shell_commands
     build_flags: *aspects_flags
-    build_targets: *single_rust_channel_targets
+    build_targets: *single_rust_channel_min_version_targets
     test_flags: *aspects_flags
-    test_targets: *single_rust_channel_targets
+    test_targets: *single_rust_channel_min_version_targets
   ubuntu2004_stable_toolchain:
     name: "Only Stable Toolchain"
     platform: ubuntu2004

MODULE.bazel

@@ -158,6 +158,12 @@ use_repo(
     "rules_rust_wasm_bindgen_cli",
 )
 
+cargo_internal_deps = use_extension("//cargo/private:internal_extensions.bzl", "i")
+use_repo(
+    cargo_internal_deps,
+    "rrcti__cargo_toml-0.20.5",
+)
+
 rust = use_extension("//rust:extensions.bzl", "rust")
 rust.toolchain(edition = "2021")
 use_repo(rust, "rust_toolchains")

WORKSPACE.bazel

@@ -45,6 +45,10 @@ load("@rules_rust//bindgen:transitive_repositories.bzl", "rust_bindgen_transitiv
 
 rust_bindgen_transitive_dependencies()
 
+load("@rules_rust//cargo:deps.bzl", "cargo_dependencies")
+
+cargo_dependencies()
+
 load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
 
 rust_analyzer_dependencies()

cargo/defs.bzl

@@ -13,9 +13,15 @@ load(
     "//cargo/private:cargo_dep_env.bzl",
     _cargo_dep_env = "cargo_dep_env",
 )
+load(
+    "//cargo/private:cargo_lints.bzl",
+    _extract_cargo_lints = "extract_cargo_lints",
+)
 
 cargo_bootstrap_repository = _cargo_bootstrap_repository
 cargo_env = _cargo_env
 
 cargo_build_script = _cargo_build_script
 cargo_dep_env = _cargo_dep_env
+
+extract_cargo_lints = _extract_cargo_lints

cargo/deps.bzl

@@ -0,0 +1,9 @@
+"""
+The dependencies for running the cargo_toml_info binary.
+"""
+
+load("//cargo/private/cargo_toml_info/3rdparty/crates:defs.bzl", "crate_repositories")
+
+def cargo_dependencies():
+    """Define dependencies of the `cargo` Bazel tools"""
+    return crate_repositories()

cargo/private/cargo_lints.bzl

@@ -0,0 +1,72 @@
+"""
+Rule used to retrieve the lints specified in the [lints section] of a `Cargo.toml`.
+
+[lints section](https://doc.rust-lang.org/cargo/reference/manifest.html#the-lints-section)
+"""
+
+# buildifier: disable=bzl-visibility
+load("//rust/private:providers.bzl", "LintsInfo")
+
+def _extract_cargo_lints(ctx):
+    # Cargo.toml's to read from.
+    inputs = [ctx.file.manifest]
+    args = ctx.actions.args()
+
+    args.add("--manifest_toml={0}".format(ctx.file.manifest.path))
+    if ctx.attr.workspace:
+        inputs.append(ctx.file.workspace)
+        args.add("--workspace_toml={0}".format(ctx.file.workspace.path))
+    args.add("lints")
+
+    # Files to output our formatted arguments into.
+    rustc_lints_out = ctx.actions.declare_file(ctx.label.name + ".rustc" + ".lints")
+    clippy_lints_out = ctx.actions.declare_file(ctx.label.name + ".clippy" + ".lints")
+    rustdoc_lints_out = ctx.actions.declare_file(ctx.label.name + ".rustdoc" + ".lints")
+
+    args.add(rustc_lints_out)
+    args.add(clippy_lints_out)
+    args.add(rustdoc_lints_out)
+
+    outputs = [rustc_lints_out, clippy_lints_out, rustdoc_lints_out]
+
+    ctx.actions.run(
+        outputs = outputs,
+        executable = ctx.file._cargo_toml_info,
+        inputs = inputs,
+        arguments = [args],
+        mnemonic = "CargoLints",
+        progress_message = "Reading Cargo metadata to get Lints for {}".format(ctx.attr.name),
+    )
+
+    return [
+        DefaultInfo(files = depset(outputs), runfiles = ctx.runfiles(outputs)),
+        LintsInfo(
+            rustc_lint_flags = [],
+            rustc_lint_files = [rustc_lints_out],
+            clippy_lint_flags = [],
+            clippy_lint_files = [clippy_lints_out],
+            rustdoc_lint_flags = [],
+            rustdoc_lint_files = [rustdoc_lints_out],
+        ),
+    ]
+
+extract_cargo_lints = rule(
+    implementation = _extract_cargo_lints,
+    attrs = {
+        "manifest": attr.label(
+            allow_single_file = True,
+            mandatory = True,
+            doc = "Cargo.toml to read lints from.",
+        ),
+        "workspace": attr.label(
+            allow_single_file = True,
+            doc = "Workspace Cargo.toml that the manifest Cargo.toml inherits from.",
+        ),
+        "_cargo_toml_info": attr.label(
+            allow_single_file = True,
+            executable = True,
+            default = Label("//cargo/private/cargo_toml_info:cargo_toml_info"),
+            cfg = "exec",
+        ),
+    },
+)

cargo/private/cargo_toml_info/3rdparty/BUILD.bazel

@@ -0,0 +1,12 @@
+load("//crate_universe:defs.bzl", "crate", "crates_vendor")
+
+crates_vendor(
+    name = "crates_vendor",
+    cargo_lockfile = "Cargo.Bazel.lock",
+    mode = "remote",
+    packages = {
+        "cargo_toml": crate.spec(version = "0.20.5"),
+    },
+    repository_name = "rrcti",
+    tags = ["manual"],
+)

cargo/private/cargo_toml_info/3rdparty/Cargo.Bazel.lock

@@ -0,0 +1,38 @@
+###############################################################################
+# @generated
+# DO NOT MODIFY: This file is auto-generated by a crate_universe tool. To
+# regenerate this file, run the following:
+#
+#     bazel run @@//cargo/private/cargo_toml_info/3rdparty:crates_vendor
+###############################################################################
+
+package(default_visibility = ["//visibility:public"])
+
+exports_files(
+    [
+        "cargo-bazel.json",
+        "crates.bzl",
+        "defs.bzl",
+    ] + glob(
+        include = ["*.bazel"],
+        allow_empty = True,
+    ),
+)
+
+filegroup(
+    name = "srcs",
+    srcs = glob(
+        include = [
+            "*.bazel",
+            "*.bzl",
+        ],
+        allow_empty = True,
+    ),
+)
+
+# Workspace Member Dependencies
+alias(
+    name = "cargo_toml",
+    actual = "@rrcti__cargo_toml-0.20.5//:cargo_toml",
+    tags = ["manual"],
+)