Pass Documentation up to LSP and add "rust" to our codeblocks there

crates/ra_lsp_server/src/conv.rs

@@ -87,13 +87,6 @@ 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()),
@@ -101,7 +94,7 @@ impl ConvWith for CompletionItem {
             kind: self.kind().map(|it| it.conv()),
             text_edit: Some(text_edit),
             additional_text_edits,
-            documentation: documentation,
+            documentation: self.documentation().map(|it| it.conv()),
             ..Default::default()
         };
         res.insert_text_format = Some(match self.insert_text_format() {
@@ -160,6 +153,16 @@ impl ConvWith for Range {
     }
 }
 
+impl Conv for ra_ide_api::Documentation {
+    type Output = lsp_types::Documentation;
+    fn conv(self) -> Documentation {
+        Documentation::MarkupContent(MarkupContent {
+            kind: MarkupKind::Markdown,
+            value: crate::markdown::sanitize_markdown(self).into(),
+        })
+    }
+}
+
 impl ConvWith for TextEdit {
     type Ctx = LineIndex;
     type Output = Vec<lsp_types::TextEdit>;

crates/ra_lsp_server/src/lib.rs

@@ -2,6 +2,7 @@ mod caps;
 mod cargo_target_spec;
 mod conv;
 mod main_loop;
+mod markdown;
 mod project_model;
 pub mod req;
 mod server_world;

crates/ra_lsp_server/src/main_loop/handlers.rs

@@ -1,7 +1,7 @@
 use gen_lsp_server::ErrorCode;
 use lsp_types::{
     CodeActionResponse, CodeLens, Command, Diagnostic, DiagnosticSeverity,
-    DocumentFormattingParams, DocumentHighlight, DocumentSymbol, Documentation, FoldingRange,
+    DocumentFormattingParams, DocumentHighlight, DocumentSymbol, FoldingRange,
     FoldingRangeKind, FoldingRangeParams, Hover, HoverContents, Location, MarkupContent,
     MarkupKind, ParameterInformation, ParameterLabel, Position, PrepareRenameResponse, Range,
     RenameParams, SignatureInformation, SymbolInformation, TextDocumentIdentifier, TextEdit,
@@ -401,12 +401,9 @@ pub fn handle_signature_help(
                 documentation: None,
             })
             .collect();
-        let documentation = call_info.doc.map(|value| {
-            Documentation::MarkupContent(MarkupContent {
-                kind: MarkupKind::Markdown,
-                value,
-            })
-        });
+
+        let documentation = call_info.doc.map(|it| it.conv());
+
         let sig_info = SignatureInformation {
             label: call_info.label,
             documentation,

crates/ra_lsp_server/src/markdown.rs

@@ -0,0 +1,38 @@
+use ra_ide_api::Documentation;
+
+pub(crate) fn sanitize_markdown(docs: Documentation) -> Documentation {
+    let docs: String = docs.into();
+
+    // Massage markdown
+    let mut processed_lines = Vec::new();
+    let mut in_code_block = false;
+    for line in docs.lines() {
+        if line.starts_with("```") {
+            in_code_block = !in_code_block;
+        }
+
+        let line = if in_code_block && line.starts_with("```") && !line.contains("rust") {
+            "```rust".into()
+        } else {
+            line.to_string()
+        };
+
+        processed_lines.push(line);
+    }
+
+    Documentation::new(&processed_lines.join("\n"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_codeblock_adds_rust() {
+        let comment = "```\nfn some_rust() {}\n```";
+        assert_eq!(
+            sanitize_markdown(Documentation::new(comment)).contents(),
+            "```rust\nfn some_rust() {}\n```"
+        );
+    }
+}