Merge #4660

4660: Enable hover and autocomplete docs on macro generated items r=aloucks a=aloucks

Enable hover and autocomplete docs on macro generated items. This de-sugars doc comments into `doc` attributes in some cases, but not all. Comments and `doc` attributes are then merged together. 

This PR is essentially a partial implementation of what's being suggested #3182, but it's not all the way there yet. ~I still need to add unit tests~, but I wanted to first get feedback on whether or not this was an acceptable path forward.

Fixes #4564
Fixes #3984
Fixes #3180
Related #3182

![macro_item_docs](https://user-images.githubusercontent.com/221559/83336760-15012200-a284-11ea-8d0d-b6a615850044.gif)



Co-authored-by: Aaron Loucks <[email protected]>

2 files changed, 55 insertions, 3 deletions

diff --git a/crates/ra_hir_def/src/attr.rs b/crates/ra_hir_def/src/attr.rs
index 8b6c0bede..2eeba0572 100644
--- a/crates/ra_hir_def/src/attr.rs
+++ b/crates/ra_hir_def/src/attr.rs
@@ -87,12 +87,18 @@ impl Attrs {
     }
 
     pub(crate) fn new(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Attrs {
+        let docs = ast::CommentIter::from_syntax_node(owner.syntax()).doc_comment_text().map(
+            |docs_text| Attr {
+                input: Some(AttrInput::Literal(SmolStr::new(docs_text))),
+                path: ModPath::from(hir_expand::name!(doc)),
+            },
+        );
         let mut attrs = owner.attrs().peekable();
         let entries = if attrs.peek().is_none() {
             // Avoid heap allocation
             None
         } else {
-            Some(attrs.flat_map(|ast| Attr::from_src(ast, hygiene)).collect())
+            Some(attrs.flat_map(|ast| Attr::from_src(ast, hygiene)).chain(docs).collect())
         };
         Attrs { entries }
     }
diff --git a/crates/ra_hir_def/src/docs.rs b/crates/ra_hir_def/src/docs.rs
index b221ae1ce..2630b3d89 100644
--- a/crates/ra_hir_def/src/docs.rs
+++ b/crates/ra_hir_def/src/docs.rs
@@ -29,6 +29,13 @@ impl Documentation {
         Documentation(s.into())
     }
 
+    pub fn from_ast<N>(node: &N) -> Option<Documentation>
+    where
+        N: ast::DocCommentsOwner + ast::AttrsOwner,
+    {
+        docs_from_ast(node)
+    }
+
     pub fn as_str(&self) -> &str {
         &*self.0
     }
@@ -70,6 +77,45 @@ impl Documentation {
     }
 }
 
-pub(crate) fn docs_from_ast(node: &impl ast::DocCommentsOwner) -> Option<Documentation> {
-    node.doc_comment_text().map(|it| Documentation::new(&it))
+pub(crate) fn docs_from_ast<N>(node: &N) -> Option<Documentation>
+where
+    N: ast::DocCommentsOwner + ast::AttrsOwner,
+{
+    let doc_comment_text = node.doc_comment_text();
+    let doc_attr_text = expand_doc_attrs(node);
+    let docs = merge_doc_comments_and_attrs(doc_comment_text, doc_attr_text);
+    docs.map(|it| Documentation::new(&it))
+}
+
+fn merge_doc_comments_and_attrs(
+    doc_comment_text: Option<String>,
+    doc_attr_text: Option<String>,
+) -> Option<String> {
+    match (doc_comment_text, doc_attr_text) {
+        (Some(mut comment_text), Some(attr_text)) => {
+            comment_text.push_str("\n\n");
+            comment_text.push_str(&attr_text);
+            Some(comment_text)
+        }
+        (Some(comment_text), None) => Some(comment_text),
+        (None, Some(attr_text)) => Some(attr_text),
+        (None, None) => None,
+    }
+}
+
+fn expand_doc_attrs(owner: &dyn ast::AttrsOwner) -> Option<String> {
+    let mut docs = String::new();
+    for attr in owner.attrs() {
+        if let Some(("doc", value)) =
+            attr.as_simple_key_value().as_ref().map(|(k, v)| (k.as_str(), v.as_str()))
+        {
+            docs.push_str(value);
+            docs.push_str("\n\n");
+        }
+    }
+    if docs.is_empty() {
+        None
+    } else {
+        Some(docs.trim_end_matches("\n\n").to_owned())
+    }
 }