Teach CompletionItem about documentation

crates/ra_ide_api/src/completion/completion_item.rs

@@ -15,6 +15,7 @@ pub struct CompletionItem {
     label: String,
     kind: Option<CompletionItemKind>,
     detail: Option<String>,
+    documentation: Option<String>,
     lookup: Option<String>,
     insert_text: Option<String>,
     insert_text_format: InsertTextFormat,
@@ -77,6 +78,7 @@ impl CompletionItem {
             insert_text: None,
             insert_text_format: InsertTextFormat::PlainText,
             detail: None,
+            documentation: None,
             lookup: None,
             kind: None,
             text_edit: None,
@@ -90,6 +92,10 @@ impl CompletionItem {
     pub fn detail(&self) -> Option<&str> {
         self.detail.as_ref().map(|it| it.as_str())
     }
+    /// A doc-comment
+    pub fn documentation(&self) -> Option<&str> {
+        self.documentation.as_ref().map(|it| it.as_str())
+    }
     /// What string is used for filtering.
     pub fn lookup(&self) -> &str {
         self.lookup
@@ -127,6 +133,7 @@ pub(crate) struct Builder {
     insert_text: Option<String>,
     insert_text_format: InsertTextFormat,
     detail: Option<String>,
+    documentation: Option<String>,
     lookup: Option<String>,
     kind: Option<CompletionItemKind>,
     text_edit: Option<TextEdit>,
@@ -142,6 +149,7 @@ impl Builder {
             source_range: self.source_range,
             label: self.label,
             detail: self.detail,
+            documentation: self.documentation,
             insert_text_format: self.insert_text_format,
             lookup: self.lookup,
             kind: self.kind,
@@ -184,6 +192,14 @@ impl Builder {
         self.detail = detail.map(Into::into);
         self
     }
+    #[allow(unused)]
+    pub(crate) fn documentation(self, docs: impl Into<String>) -> Builder {
+        self.set_documentation(Some(docs))
+    }
+    pub(crate) fn set_documentation(mut self, docs: Option<impl Into<String>>) -> Builder {
+        self.documentation = docs.map(Into::into);
+        self
+    }
     pub(super) fn from_resolution(
         mut self,
         ctx: &CompletionContext,

crates/ra_lsp_server/src/conv.rs

@@ -1,6 +1,6 @@
 use lsp_types::{
-    self, CreateFile, DocumentChangeOperation, DocumentChanges, Location, LocationLink,
+    self, CreateFile, Documentation, DocumentChangeOperation, DocumentChanges, Location, LocationLink,
-    Position, Range, RenameFile, ResourceOp, SymbolKind, TextDocumentEdit, TextDocumentIdentifier,
+    MarkupContent, MarkupKind, Position, Range, RenameFile, ResourceOp, SymbolKind, TextDocumentEdit, TextDocumentIdentifier,
     TextDocumentItem, TextDocumentPositionParams, Url, VersionedTextDocumentIdentifier,
     WorkspaceEdit,
 };
@@ -87,6 +87,13 @@ impl ConvWith for CompletionItem {
             None
         };
 
+        let documentation = self.documentation().map(|value| {
+            Documentation::MarkupContent(MarkupContent {
+                kind: MarkupKind::Markdown,
+                value: value.to_string(),
+            })
+        });
+
         let mut res = lsp_types::CompletionItem {
             label: self.label().to_string(),
             detail: self.detail().map(|it| it.to_string()),
@@ -94,6 +101,7 @@ impl ConvWith for CompletionItem {
             kind: self.kind().map(|it| it.conv()),
             text_edit: Some(text_edit),
             additional_text_edits,
+            documentation: documentation,
             ..Default::default()
         };
         res.insert_text_format = Some(match self.insert_text_format() {