glib-macros: Properties: copy property docs to getter

We take the docs directly preceding a `#[property]` and copy them into the
generated getter method.

Author: carlosmn

glib-macros/src/lib.rs

@@ -1344,6 +1344,10 @@ pub fn cstr_bytes(item: TokenStream) -> TokenStream {
 /// * `connect_$property_notify()`
 /// * `notify_$property()`
 ///
+/// # Documentation
+///
+/// Doc comments preceding a `#[property]` attribute will be copied to the generated getter method.
+///
 /// ## Extension trait
 /// You can choose to move the method definitions to a trait by using `#[properties(wrapper_type = super::MyType, ext_trait = MyTypePropertiesExt)]`.
 /// The trait name is optional, and defaults to `MyTypePropertiesExt`, where `MyType` is extracted from the wrapper type.
@@ -1407,7 +1411,9 @@ pub fn cstr_bytes(item: TokenStream) -> TokenStream {
 ///     pub struct Foo {
 ///         #[property(get, set = Self::set_fizz)]
 ///         fizz: RefCell<String>,
+///         /// The author's name
 ///         #[property(name = "author-name", get, set, type = String, member = name)]
+///         /// The author's childhood nickname
 ///         #[property(name = "author-nick", get, set, type = String, member = nick)]
 ///         author: RefCell<Author>,
 ///         #[property(get, set, explicit_notify, lax_validation)]

glib-macros/src/properties.rs

@@ -12,7 +12,7 @@ use syn::parse::Parse;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::Token;
-use syn::{parse_quote_spanned, LitStr};
+use syn::{parse_quote_spanned, Attribute, LitStr};
 
 pub struct PropsMacroInput {
     wrapper_ty: syn::Path,
@@ -255,6 +255,7 @@ struct PropDesc {
     field_ident: syn::Ident,
     ty: syn::Type,
     name: syn::LitStr,
+    comments: Vec<Attribute>,
     override_class: Option<syn::Type>,
     override_interface: Option<syn::Type>,
     nullable: bool,
@@ -271,6 +272,7 @@ impl PropDesc {
         attrs_span: proc_macro2::Span,
         field_ident: syn::Ident,
         field_ty: syn::Type,
+        comments: Vec<Attribute>,
         attrs: ReceivedAttrs,
     ) -> syn::Result<Self> {
         let ReceivedAttrs {
@@ -321,6 +323,7 @@ impl PropDesc {
             field_ident,
             ty,
             name,
+            comments,
             override_class,
             override_interface,
             nullable,
@@ -524,26 +527,33 @@ fn expand_set_property_fn(props: &[PropDesc]) -> TokenStream2 {
 }
 
 fn parse_fields(fields: syn::Fields) -> syn::Result<Vec<PropDesc>> {
-    fields
-        .into_iter()
-        .flat_map(|field| {
-            let syn::Field {
-                ident, attrs, ty, ..
-            } = field;
-            attrs
-                .into_iter()
-                .filter(|a| a.path().is_ident("property"))
-                .map(move |prop_attrs| {
-                    let span = prop_attrs.span();
-                    PropDesc::new(
-                        span,
-                        ident.as_ref().unwrap().clone(),
-                        ty.clone(),
-                        prop_attrs.parse_args()?,
-                    )
-                })
-        })
-        .collect::<syn::Result<_>>()
+    let mut properties = vec![];
+
+    for field in fields.into_iter() {
+        let syn::Field {
+            ident, attrs, ty, ..
+        } = field;
+        // Store the comments until the next `#[property]` we see and then attach them to it.
+        let mut comments: Vec<Attribute> = vec![];
+        for prop_attr in attrs.iter() {
+            if prop_attr.path().is_ident("doc") {
+                comments.push(prop_attr.clone());
+            } else if prop_attr.path().is_ident("property") {
+                let span = prop_attr.span();
+                let existing_comments = comments;
+                comments = vec![];
+                properties.push(PropDesc::new(
+                    span,
+                    ident.as_ref().unwrap().clone(),
+                    ty.clone(),
+                    existing_comments,
+                    prop_attr.parse_args()?,
+                )?);
+            }
+        }
+    }
+
+    Ok(properties)
 }
 
 /// Converts a glib property name to a correct rust ident
@@ -567,7 +577,7 @@ fn expand_impl_getset_properties(props: &[PropDesc]) -> Vec<syn::ImplItemFn> {
         let ident = name_to_ident(name);
         let ty = &p.ty;
 
-        let getter = p.get.is_some().then(|| {
+        let mut getter: Option<syn::ImplItemFn> = p.get.is_some().then(|| {
             let span = p.attrs_span;
             parse_quote_spanned!(span=>
                 #[must_use]
@@ -578,6 +588,12 @@ fn expand_impl_getset_properties(props: &[PropDesc]) -> Vec<syn::ImplItemFn> {
             )
         });
 
+        if let Some(ref mut getter) = getter {
+            for lit in &p.comments {
+                getter.attrs.push(lit.clone());
+            }
+        }
+
         let setter = (p.set.is_some() && !p.is_construct_only).then(|| {
             let ident = format_ident!("set_{}", ident);
             let target_ty = quote!(<<#ty as #crate_ident::property::Property>::Value as #crate_ident::prelude::HasParamSpec>::SetValue);