add examples of extracting lints from Cargo

* adds standalone example using WORKSPACE
* extends existing example using bzlmod

Author: ParkMyCar

cargo/private/cargo_lints.bzl

@@ -67,7 +67,7 @@ extract_cargo_lints = rule(
         "_cargo_toml_info": attr.label(
             allow_single_file = True,
             executable = True,
-            default = "@rules_rust//cargo/private/cargo_toml_info",
+            default = Label("//cargo/private/cargo_toml_info:cargo_toml_info"),
             cfg = "exec",
         ),
     },

examples/WORKSPACE.bazel

@@ -28,6 +28,10 @@ load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
 
 rust_analyzer_dependencies()
 
+load("@rules_rust//cargo:deps.bzl", "cargo_dependencies")
+
+cargo_dependencies()
+
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 # We need to load rules_java before anything proto-related happens because otherwise it will pull in its own rules_java which isn't compatible with rules_jvm_external.

examples/bazel_env/rust/hello_world/BUILD.bazel

@@ -1,4 +1,5 @@
 load("@crates//:defs.bzl", "all_crate_deps")
+load("@rules_rust//cargo:defs.bzl", "extract_cargo_lints")
 load("@rules_rust//rust:defs.bzl", "rust_binary")
 
 package(default_visibility = ["//visibility:public"])
@@ -8,8 +9,14 @@ exports_files([
     "src/main.rs",
 ])
 
+extract_cargo_lints(
+    name = "cargo_lints",
+    manifest = "Cargo.toml",
+)
+
 rust_binary(
     name = "hello_world",
     srcs = ["src/main.rs"],
+    lint_config = ":cargo_lints",
     deps = all_crate_deps(normal = True),
 )

examples/bazel_env/rust/hello_world/Cargo.toml

@@ -6,3 +6,6 @@ publish = false
 
 [lib]
 path = "fake.rs"
+
+[lints.rust]
+dead_code = "allow"

examples/bazel_env/rust/hello_world/src/main.rs

@@ -15,3 +15,9 @@
 fn main() {
     println!("Hello, world!");
 }
+
+// Note: Would normally cause Rustc to lint `dead_code` but we allow this lint in the Cargo.toml of
+// this crate.
+fn unused(x: usize) -> String {
+    format!("I am unused {x}")
+}

examples/cargo_lints/BUILD.bazel

@@ -0,0 +1,26 @@
+load("@rules_rust//cargo:defs.bzl", "extract_cargo_lints")
+load("@rules_rust//rust:defs.bzl", "rust_clippy", "rust_doc", "rust_library")
+
+package(default_visibility = ["//visibility:public"])
+
+extract_cargo_lints(
+    name = "hello_world_lints",
+    manifest = "Cargo.toml",
+)
+
+rust_library(
+    name = "hello_world",
+    srcs = ["src/lib.rs"],
+    edition = "2021",
+    lint_config = ":hello_world_lints",
+)
+
+rust_clippy(
+    name = "hello_world_clippy",
+    deps = [":hello_world"],
+)
+
+rust_doc(
+    name = "hello_world_doc",
+    crate = ":hello_world",
+)

examples/cargo_lints/Cargo.lock

@@ -0,0 +1,17 @@
+[package]
+name = "hello_world"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+
+
+[lints.rust]
+dead_code = "allow"
+
+[lints.clippy]
+absurd_extreme_comparisons = "allow"
+needless_if = "allow"
+
+[lints.rustdoc]
+invalid_html_tags = "allow"

examples/cargo_lints/Cargo.toml

@@ -0,0 +1,18 @@
+//! This module contains code that would normally lint for Rust, Clippy, or Rustdoc, but we
+//! explicitly 'allow' said lints in the Cargo.toml of this crate.
+
+/// Would trigger Rustdoc's `invalid_html_tags` lint.
+///
+/// <h1>
+/// </script>
+pub fn add(a: usize, b: usize) -> usize {
+    // Would trigger Clippy's `absurd_extreme_comparisons` and `needless_if` lints.
+    if 100 > i32::MAX {}
+
+    a + b
+}
+
+// Would trigger Rust's `dead_code` lint.
+fn sub(a: usize, b: usize) -> usize {
+    a - b
+}