Optionally capture clippy lints as a build output (#937)

* Allow clippy lints to optionally be captured as a build output, so they
can be consumed by downstream tools integrated with the build system.

* Fix buildifier lint.

* Fix buildifier lints.

* Fix missing import of ClippyInfo

* Fix path for //:capture_clippy_output

* Return ClippyInfo even if there is no crate info

* Add test for failure semantics when capturing clippy output.

* Fully qualify :providers.bzl

* Rename ClippyConfigInfo to CaptureClippyOutputInfo

* Update doc fields to state that captured output uses the configured error_format

* Sort loads.

* Sort loads.

* Merge capture_output logic into a single if block.

* Regenerate documentation

* Build documentation for capture_clippy_output.

* Update docs.

* Update human-readable docs to specify that captured clippy output uses the configured error_format.

* Make redundant doc fields consistent. Move CaptureClippyOutputInfo to provider.bzl. Improve readability of clippy_failure_test.sh

Author: jfgoog

BUILD.bazel

@@ -1,5 +1,5 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
-load("//rust:rust.bzl", "error_format", "extra_rustc_flags")
+load("//rust:rust.bzl", "capture_clippy_output", "error_format", "extra_rustc_flags")
 
 exports_files(["LICENSE"])
 
@@ -46,3 +46,9 @@ alias(
     actual = "//tools/rustfmt",
     visibility = ["//visibility:public"],
 )
+
+capture_clippy_output(
+    name = "capture_clippy_output",
+    build_setting_default = False,
+    visibility = ["//visibility:public"],
+)

docs/BUILD.bazel

@@ -61,6 +61,7 @@ PAGES = dict([
             "rust_test_suite",
             "error_format",
             "extra_rustc_flags",
+            "capture_clippy_output",
         ],
     ),
     page(

docs/defs.md

@@ -10,6 +10,25 @@
 * [rust_test_suite](#rust_test_suite)
 * [error_format](#error_format)
 * [extra_rustc_flags](#extra_rustc_flags)
+* [capture_clippy_output](#capture_clippy_output)
+
+<a id="#capture_clippy_output"></a>
+
+## capture_clippy_output
+
+<pre>
+capture_clippy_output(<a href="#capture_clippy_output-name">name</a>)
+</pre>
+
+Control whether to print clippy output or store it to a file, using the configured error_format.
+
+**ATTRIBUTES**
+
+
+| Name  | Description | Type | Mandatory | Default |
+| :------------- | :------------- | :------------- | :------------- | :------------- |
+| <a id="capture_clippy_output-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/docs/build-ref.html#name">Name</a> | required |  |
+
 
 <a id="#error_format"></a>
 

docs/flatten.md

@@ -3,6 +3,7 @@
 * [CrateInfo](#CrateInfo)
 * [DepInfo](#DepInfo)
 * [StdLibInfo](#StdLibInfo)
+* [capture_clippy_output](#capture_clippy_output)
 * [cargo_bootstrap_repository](#cargo_bootstrap_repository)
 * [cargo_build_script](#cargo_build_script)
 * [cargo_env](#cargo_env)
@@ -47,6 +48,24 @@
 * [rustfmt_test](#rustfmt_test)
 
 
+<a id="#capture_clippy_output"></a>
+
+## capture_clippy_output
+
+<pre>
+capture_clippy_output(<a href="#capture_clippy_output-name">name</a>)
+</pre>
+
+Control whether to print clippy output or store it to a file, using the configured error_format.
+
+**ATTRIBUTES**
+
+
+| Name  | Description | Type | Mandatory | Default |
+| :------------- | :------------- | :------------- | :------------- | :------------- |
+| <a id="capture_clippy_output-name"></a>name |  A unique name for this target.   | <a href="https://bazel.build/docs/build-ref.html#name">Name</a> | required |  |
+
+
 <a id="#cargo_bootstrap_repository"></a>
 
 ## cargo_bootstrap_repository

docs/symbols.bzl

@@ -42,6 +42,7 @@ load(
 )
 load(
     "@rules_rust//rust:defs.bzl",
+    _capture_clippy_output = "capture_clippy_output",
     _error_format = "error_format",
     _extra_rustc_flags = "extra_rustc_flags",
     _rust_analyzer = "rust_analyzer",
@@ -147,6 +148,7 @@ error_format = _error_format
 extra_rustc_flags = _extra_rustc_flags
 incompatible_flag = _incompatible_flag
 fail_when_enabled = _fail_when_enabled
+capture_clippy_output = _capture_clippy_output
 
 CrateInfo = _CrateInfo
 DepInfo = _DepInfo

rust/defs.bzl

@@ -20,6 +20,7 @@ load(
 )
 load(
     "//rust/private:clippy.bzl",
+    _capture_clippy_output = "capture_clippy_output",
     _rust_clippy = "rust_clippy",
     _rust_clippy_aspect = "rust_clippy_aspect",
 )
@@ -91,6 +92,9 @@ rust_clippy_aspect = _rust_clippy_aspect
 rust_clippy = _rust_clippy
 # See @rules_rust//rust/private:clippy.bzl for a complete description.
 
+capture_clippy_output = _capture_clippy_output
+# See @rules_rust//rust/private:clippy.bzl for a complete description.
+
 error_format = _error_format
 # See @rules_rust//rust/private:rustc.bzl for a complete description.
 

rust/private/clippy.bzl

@@ -15,6 +15,7 @@
 """A module defining clippy rules"""
 
 load("//rust/private:common.bzl", "rust_common")
+load("//rust/private:providers.bzl", "CaptureClippyOutputInfo", "ClippyInfo")
 load(
     "//rust/private:rustc.bzl",
     "collect_deps",
@@ -51,7 +52,7 @@ def _get_clippy_ready_crate_info(target, aspect_ctx):
 def _clippy_aspect_impl(target, ctx):
     crate_info = _get_clippy_ready_crate_info(target, ctx)
     if not crate_info:
-        return []
+        return [ClippyInfo(output = depset([]))]
 
     toolchain = find_toolchain(ctx)
     cc_toolchain, feature_configuration = find_cc_toolchain(ctx)
@@ -75,10 +76,6 @@ def _clippy_aspect_impl(target, ctx):
         build_info,
     )
 
-    # A marker file indicating clippy has executed successfully.
-    # This file is necessary because "ctx.actions.run" mandates an output.
-    clippy_marker = ctx.actions.declare_file(ctx.label.name + ".clippy.ok")
-
     args, env = construct_arguments(
         ctx = ctx,
         attr = ctx.rule.attr,
@@ -97,24 +94,35 @@ def _clippy_aspect_impl(target, ctx):
         emit = ["dep-info", "metadata"],
     )
 
-    # Turn any warnings from clippy or rustc into an error, as otherwise
-    # Bazel will consider the execution result of the aspect to be "success",
-    # and Clippy won't be re-triggered unless the source file is modified.
-    if "__bindgen" in ctx.rule.attr.tags:
-        # bindgen-generated content is likely to trigger warnings, so
-        # only fail on clippy warnings
-        args.rustc_flags.add("-Dclippy::style")
-        args.rustc_flags.add("-Dclippy::correctness")
-        args.rustc_flags.add("-Dclippy::complexity")
-        args.rustc_flags.add("-Dclippy::perf")
-    else:
-        # fail on any warning
-        args.rustc_flags.add("-Dwarnings")
-
     if crate_info.is_test:
         args.rustc_flags.add("--test")
 
-    args.process_wrapper_flags.add("--touch-file", clippy_marker.path)
+    if ctx.attr._capture_output[CaptureClippyOutputInfo].capture_output:
+        clippy_out = ctx.actions.declare_file(ctx.label.name + ".clippy.out")
+        args.process_wrapper_flags.add("--stdout-file", clippy_out.path)
+
+        # If we are capturing the output, we want the build system to be able to keep going
+        # and consume the output. Some clippy lints are denials, so we treat them as warnings.
+        args.rustc_flags.add("-Wclippy::all")
+    else:
+        # A marker file indicating clippy has executed successfully.
+        # This file is necessary because "ctx.actions.run" mandates an output.
+        clippy_out = ctx.actions.declare_file(ctx.label.name + ".clippy.ok")
+        args.process_wrapper_flags.add("--touch-file", clippy_out.path)
+
+        # Turn any warnings from clippy or rustc into an error, as otherwise
+        # Bazel will consider the execution result of the aspect to be "success",
+        # and Clippy won't be re-triggered unless the source file is modified.
+        if "__bindgen" in ctx.rule.attr.tags:
+            # bindgen-generated content is likely to trigger warnings, so
+            # only fail on clippy warnings
+            args.rustc_flags.add("-Dclippy::style")
+            args.rustc_flags.add("-Dclippy::correctness")
+            args.rustc_flags.add("-Dclippy::complexity")
+            args.rustc_flags.add("-Dclippy::perf")
+        else:
+            # fail on any warning
+            args.rustc_flags.add("-Dwarnings")
 
     # Upstream clippy requires one of these two filenames or it silently uses
     # the default config. Enforce the naming so users are not confused.
@@ -127,15 +135,16 @@ def _clippy_aspect_impl(target, ctx):
     ctx.actions.run(
         executable = ctx.executable._process_wrapper,
         inputs = compile_inputs,
-        outputs = [clippy_marker],
+        outputs = [clippy_out],
         env = env,
         tools = [toolchain.clippy_driver],
         arguments = args.all,
         mnemonic = "Clippy",
     )
 
     return [
-        OutputGroupInfo(clippy_checks = depset([clippy_marker])),
+        OutputGroupInfo(clippy_checks = depset([clippy_out])),
+        ClippyInfo(output = depset([clippy_out])),
     ]
 
 # Example: Run the clippy checker on all targets in the codebase.
@@ -146,6 +155,10 @@ rust_clippy_aspect = aspect(
     fragments = ["cpp"],
     host_fragments = ["cpp"],
     attrs = {
+        "_capture_output": attr.label(
+            doc = "Value of the `capture_clippy_output` build setting",
+            default = Label("//:capture_clippy_output"),
+        ),
         "_cc_toolchain": attr.label(
             doc = (
                 "Required attribute to access the cc_toolchain. See [Accessing the C++ toolchain]" +
@@ -170,6 +183,7 @@ rust_clippy_aspect = aspect(
             cfg = "exec",
         ),
     },
+    provides = [ClippyInfo],
     toolchains = [
         str(Label("//rust:toolchain")),
         "@bazel_tools//tools/cpp:toolchain_type",
@@ -260,3 +274,20 @@ rust_clippy(
 ```
 """,
 )
+
+def _capture_clippy_output_impl(ctx):
+    """Implementation of the `capture_clippy_output` rule
+
+    Args:
+        ctx (ctx): The rule's context object
+
+    Returns:
+        list: A list containing the CaptureClippyOutputInfo provider
+    """
+    return [CaptureClippyOutputInfo(capture_output = ctx.build_setting_value)]
+
+capture_clippy_output = rule(
+    doc = "Control whether to print clippy output or store it to a file, using the configured error_format.",
+    implementation = _capture_clippy_output_impl,
+    build_setting = config.bool(flag = True),
+)

rust/private/providers.bzl

@@ -68,3 +68,15 @@ StdLibInfo = provider(
         "std_rlibs": "List[File]: All `.rlib` files",
     },
 )
+
+CaptureClippyOutputInfo = provider(
+    doc = "Value of the `capture_clippy_output` build setting",
+    fields = {"capture_output": "Value of the `capture_clippy_output` build setting"},
+)
+
+ClippyInfo = provider(
+    doc = "Provides information on a clippy run.",
+    fields = {
+        "output": "File with the clippy output.",
+    },
+)

rust/rust.bzl

@@ -16,6 +16,7 @@
 
 load(
     "//rust:defs.bzl",
+    _capture_clippy_output = "capture_clippy_output",
     _error_format = "error_format",
     _extra_rustc_flags = "extra_rustc_flags",
     _rust_analyzer = "rust_analyzer",
@@ -81,6 +82,9 @@ rust_clippy_aspect = _rust_clippy_aspect
 rust_clippy = _rust_clippy
 # See @rules_rust//rust:private/clippy.bzl for a complete description.
 
+capture_clippy_output = _capture_clippy_output
+# See @rules_rust//rust:private/clippy.bzl for a complete description.
+
 rust_analyzer_aspect = _rust_analyzer_aspect
 # See @rules_rust//rust:private/rust_analyzer.bzl for a complete description.
 

rust/rust_common.bzl

@@ -14,6 +14,7 @@
 
 """Module with Rust definitions required to write custom Rust rules."""
 
-load("//rust/private:providers.bzl", _CrateInfo = "CrateInfo")
+load("//rust/private:providers.bzl", _ClippyInfo = "ClippyInfo", _CrateInfo = "CrateInfo")
 
 CrateInfo = _CrateInfo
+ClippyInfo = _ClippyInfo