Document lint configuration values in Clippy's book

.github/workflows/clippy_bors.yml

@@ -157,6 +157,11 @@ jobs:
     - name: Test metadata collection
       run: cargo collect-metadata
 
+    - name: Test lint_configuration.md is up-to-date
+      run: |
+        echo "run \`cargo collect-metadata\` if this fails"
+        git update-index --refresh
+
   integration_build:
     needs: changelog
     runs-on: ubuntu-latest

README.md

@@ -194,11 +194,21 @@ value` mapping e.g.
 ```toml
 avoid-breaking-exported-api = false
 disallowed-names = ["toto", "tata", "titi"]
-cognitive-complexity-threshold = 30
 ```
 
-See the [list of configurable lints](https://rust-lang.github.io/rust-clippy/master/index.html#Configuration),
-the lint descriptions contain the names and meanings of these configuration variables.
+The [table of configurations](https://doc.rust-lang.org/nightly/clippy/lint_configuration.html)
+contains all config values, their default, and a list of lints they affect.
+Each [configurable lint](https://rust-lang.github.io/rust-clippy/master/index.html#Configuration)
+, also contains information about these values.
+
+For configurations that are a list type with default values such as
+[disallowed-names](https://rust-lang.github.io/rust-clippy/master/index.html#disallowed_names),
+you can use the unique value `".."` to extend the default values instead of replacing them.
+
+```toml
+# default of disallowed-names is ["foo", "baz", "quux"]
+disallowed-names = ["bar", ".."] # -> ["bar", "foo", "baz", "quux"]
+```
 
 > **Note**
 >

book/src/SUMMARY.md

@@ -5,6 +5,7 @@
 - [Installation](installation.md)
 - [Usage](usage.md)
 - [Configuration](configuration.md)
+    - [Lint Configuration](lint_configuration.md)
 - [Clippy's Lints](lints.md)
 - [Continuous Integration](continuous_integration/README.md)
     - [GitHub Actions](continuous_integration/github_actions.md)

book/src/configuration.md

@@ -8,11 +8,21 @@ basic `variable = value` mapping eg.
 ```toml
 avoid-breaking-exported-api = false
 disallowed-names = ["toto", "tata", "titi"]
-cognitive-complexity-threshold = 30
 ```
 
-See the [list of configurable lints](https://rust-lang.github.io/rust-clippy/master/index.html#Configuration),
-the lint descriptions contain the names and meanings of these configuration variables.
+The [table of configurations](./lint_configuration.md)
+contains all config values, their default, and a list of lints they affect.
+Each [configurable lint](https://rust-lang.github.io/rust-clippy/master/index.html#Configuration)
+, also contains information about these values.
+
+For configurations that are a list type with default values such as
+[disallowed-names](https://rust-lang.github.io/rust-clippy/master/index.html#disallowed_names),
+you can use the unique value `".."` to extend the default values instead of replacing them.
+
+```toml
+# default of disallowed-names is ["foo", "baz", "quux"]
+disallowed-names = ["bar", ".."] # -> ["bar", "foo", "baz", "quux"]
+```
 
 To deactivate the "for further information visit *lint-link*" message you can define the `CLIPPY_DISABLE_DOCS_LINKS`
 environment variable.

book/src/development/adding_lints.md

@@ -699,6 +699,10 @@ for some users. Adding a configuration is done in the following steps:
        `clippy.toml` file with the configuration value and a rust file that
        should be linted by Clippy. The test can otherwise be written as usual.
 
+5. Update [Lint Configuration](../lint_configuration.md)
+
+   Run `cargo collect-metadata` to generate documentation changes for the book.
+
 [`clippy_lints::utils::conf`]: https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/utils/conf.rs
 [`clippy_lints` lib file]: https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/lib.rs
 [`tests/ui`]: https://github.com/rust-lang/rust-clippy/blob/master/tests/ui

clippy_lints/src/utils/conf.rs

@@ -219,7 +219,8 @@ define_Conf! {
     ///
     /// #### Noteworthy
     ///
-    /// A type, say `SomeType`, listed in this configuration has the same behavior of `["SomeType" , "*"], ["*", "SomeType"]` in `arithmetic_side_effects_allowed_binary`.
+    /// A type, say `SomeType`, listed in this configuration has the same behavior of
+    /// `["SomeType" , "*"], ["*", "SomeType"]` in `arithmetic_side_effects_allowed_binary`.
     (arithmetic_side_effects_allowed: rustc_data_structures::fx::FxHashSet<String> = <_>::default()),
     /// Lint: ARITHMETIC_SIDE_EFFECTS.
     ///

clippy_lints/src/utils/internal_lints/metadata_collector.rs

@@ -14,6 +14,7 @@ use clippy_utils::diagnostics::span_lint;
 use clippy_utils::ty::{match_type, walk_ptrs_ty_depth};
 use clippy_utils::{last_path_segment, match_def_path, match_function_call, match_path, paths};
 use if_chain::if_chain;
+use itertools::Itertools;
 use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::{
@@ -34,8 +35,10 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::process::Command;
 
-/// This is the output file of the lint collector.
-const OUTPUT_FILE: &str = "../util/gh-pages/lints.json";
+/// This is the json output file of the lint collector.
+const JSON_OUTPUT_FILE: &str = "../util/gh-pages/lints.json";
+/// This is the markdown output file of the lint collector.
+const MARKDOWN_OUTPUT_FILE: &str = "../book/src/lint_configuration.md";
 /// These lints are excluded from the export.
 const BLACK_LISTED_LINTS: &[&str] = &["lint_author", "dump_hir", "internal_metadata_collector"];
 /// These groups will be ignored by the lint group matcher. This is useful for collections like
@@ -176,6 +179,23 @@ This lint has the following configuration variables:
                 )
             })
     }
+
+    fn configs_to_markdown(&self, map_fn: fn(&ClippyConfiguration) -> String) -> String {
+        self.config
+            .iter()
+            .filter(|config| config.deprecation_reason.is_none())
+            .filter(|config| !config.lints.is_empty())
+            .map(map_fn)
+            .join("\n")
+    }
+
+    fn get_markdown_docs(&self) -> String {
+        format!(
+            "## Lint Configuration Options\n| <div style=\"width:290px\">Option</div> | Default Value |\n|--|--|\n{}\n\n{}\n",
+            self.configs_to_markdown(ClippyConfiguration::to_markdown_table_entry),
+            self.configs_to_markdown(ClippyConfiguration::to_markdown_paragraph),
+        )
+    }
 }
 
 impl Drop for MetadataCollector {
@@ -199,12 +219,37 @@ impl Drop for MetadataCollector {
 
         collect_renames(&mut lints);
 
-        // Outputting
-        if Path::new(OUTPUT_FILE).exists() {
-            fs::remove_file(OUTPUT_FILE).unwrap();
+        // Outputting json
+        if Path::new(JSON_OUTPUT_FILE).exists() {
+            fs::remove_file(JSON_OUTPUT_FILE).unwrap();
         }
-        let mut file = OpenOptions::new().write(true).create(true).open(OUTPUT_FILE).unwrap();
+        let mut file = OpenOptions::new()
+            .write(true)
+            .create(true)
+            .open(JSON_OUTPUT_FILE)
+            .unwrap();
         writeln!(file, "{}", serde_json::to_string_pretty(&lints).unwrap()).unwrap();
+
+        // Outputting markdown
+        if Path::new(MARKDOWN_OUTPUT_FILE).exists() {
+            fs::remove_file(MARKDOWN_OUTPUT_FILE).unwrap();
+        }
+        let mut file = OpenOptions::new()
+            .write(true)
+            .create(true)
+            .open(MARKDOWN_OUTPUT_FILE)
+            .unwrap();
+        writeln!(
+            file,
+            "<!--
+This file is generated by `cargo collect-metadata`.
+Please use that command to update the file and do not edit it by hand.
+-->
+
+{}",
+            self.get_markdown_docs(),
+        )
+        .unwrap();
     }
 }
 
@@ -505,6 +550,28 @@ impl ClippyConfiguration {
             deprecation_reason,
         }
     }
+
+    fn to_markdown_paragraph(&self) -> String {
+        format!(
+            "### {}\n{}\n\n**Default Value:** `{}` (`{}`)\n\n{}\n\n",
+            self.name,
+            self.doc
+                .lines()
+                .map(|line| line.strip_prefix("    ").unwrap_or(line))
+                .join("\n"),
+            self.default,
+            self.config_type,
+            self.lints
+                .iter()
+                .map(|name| name.to_string().split_whitespace().next().unwrap().to_string())
+                .map(|name| format!("* [{name}](https://rust-lang.github.io/rust-clippy/master/index.html#{name})"))
+                .join("\n"),
+        )
+    }
+
+    fn to_markdown_table_entry(&self) -> String {
+        format!("| [{}](#{}) | `{}` |", self.name, self.name, self.default)
+    }
 }
 
 fn collect_configs() -> Vec<ClippyConfiguration> {