Support option group documentation (#7593)

Author: MichaReiser

crates/ruff_dev/src/generate_options.rs

@@ -16,6 +16,12 @@ pub(crate) fn generate() -> String {
 fn generate_set(output: &mut String, set: &Set) {
     writeln!(output, "### {title}\n", title = set.title()).unwrap();
 
+    if let Some(documentation) = set.metadata().documentation() {
+        output.push_str(documentation);
+        output.push('\n');
+        output.push('\n');
+    }
+
     let mut visitor = CollectOptionsVisitor::default();
     set.metadata().record(&mut visitor);
 

crates/ruff_macros/src/config.rs

@@ -10,7 +10,12 @@ use syn::{
 };
 
 pub(crate) fn derive_impl(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
-    let DeriveInput { ident, data, .. } = input;
+    let DeriveInput {
+        ident,
+        data,
+        attrs: struct_attributes,
+        ..
+    } = input;
 
     match data {
         Data::Struct(DataStruct {
@@ -50,12 +55,39 @@ pub(crate) fn derive_impl(input: DeriveInput) -> syn::Result<proc_macro2::TokenS
                 };
             }
 
-            Ok(quote! {
+            let docs: Vec<&Attribute> = struct_attributes
+                .iter()
+                .filter(|attr| attr.path().is_ident("doc"))
+                .collect();
+
+            // Convert the list of `doc` attributes into a single string.
+            let doc = dedent(
+                &docs
+                    .into_iter()
+                    .map(parse_doc)
+                    .collect::<syn::Result<Vec<_>>>()?
+                    .join("\n"),
+            )
+            .trim_matches('\n')
+            .to_string();
+
+            let documentation = if doc.is_empty() {
+                None
+            } else {
+                Some(quote!(
+                    fn documentation() -> Option<&'static str> {
+                        Some(&#doc)
+                    }
+                ))
+            };
 
+            Ok(quote! {
                 impl crate::options_base::OptionsMetadata for #ident {
                     fn record(visit: &mut dyn crate::options_base::Visit) {
                         #(#output);*
                     }
+
+                    #documentation
                 }
             })
         }

crates/ruff_workspace/src/options.rs

@@ -2412,8 +2412,15 @@ impl OptionsMetadata for FormatOrOutputFormat {
     fn record(visit: &mut dyn Visit) {
         FormatOptions::record(visit);
     }
+
+    fn documentation() -> Option<&'static str> {
+        FormatOptions::documentation()
+    }
 }
 
+/// Experimental: Configures how `ruff format` formats your code.
+///
+/// Please provide feedback in [this discussion](https://github.com/astral-sh/ruff/discussions/7310).
 #[derive(
     Debug, PartialEq, Eq, Default, Serialize, Deserialize, ConfigurationOptions, CombineOptions,
 )]

crates/ruff_workspace/src/options_base.rs

@@ -16,6 +16,10 @@ pub trait OptionsMetadata {
     /// Visits the options metadata of this object by calling `visit` for each option.
     fn record(visit: &mut dyn Visit);
 
+    fn documentation() -> Option<&'static str> {
+        None
+    }
+
     /// Returns the extracted metadata.
     fn metadata() -> OptionSet
     where
@@ -51,14 +55,18 @@ impl Display for OptionEntry {
 #[derive(Copy, Clone, Eq, PartialEq)]
 pub struct OptionSet {
     record: fn(&mut dyn Visit),
+    doc: fn() -> Option<&'static str>,
 }
 
 impl OptionSet {
     pub fn of<T>() -> Self
     where
         T: OptionsMetadata + 'static,
     {
-        Self { record: T::record }
+        Self {
+            record: T::record,
+            doc: T::documentation,
+        }
     }
 
     /// Visits the options in this set by calling `visit` for each option.
@@ -67,6 +75,11 @@ impl OptionSet {
         record(visit);
     }
 
+    pub fn documentation(&self) -> Option<&'static str> {
+        let documentation = self.doc;
+        documentation()
+    }
+
     /// Returns `true` if this set has an option that resolves to `name`.
     ///
     /// The name can be separated by `.` to find a nested option.