Move display related things from hover to display

crates/ra_ide_api/src/display.rs

@@ -5,6 +5,7 @@ mod function_signature;
 mod navigation_target;
 mod structure;
 
+use crate::db::RootDatabase;
 use ra_syntax::{ast::{self, AstNode, TypeParamsOwner}, SyntaxKind::{ATTR, COMMENT}};
 
 pub use navigation_target::NavigationTarget;
@@ -53,3 +54,29 @@ pub(crate) fn where_predicates<N: TypeParamsOwner>(node: &N) -> Vec<String> {
     }
     res
 }
+
+pub(crate) fn rust_code_markup<CODE: AsRef<str>>(val: CODE) -> String {
+    rust_code_markup_with_doc::<_, &str>(val, None)
+}
+
+pub(crate) fn rust_code_markup_with_doc<CODE, DOC>(val: CODE, doc: Option<DOC>) -> String
+where
+    CODE: AsRef<str>,
+    DOC: AsRef<str>,
+{
+    if let Some(doc) = doc {
+        format!("```rust\n{}\n```\n\n{}", val.as_ref(), doc.as_ref())
+    } else {
+        format!("```rust\n{}\n```", val.as_ref())
+    }
+}
+
+// FIXME: this should not really use navigation target. Rather, approximately
+// resolved symbol should return a `DefId`.
+pub(crate) fn doc_text_for(db: &RootDatabase, nav: NavigationTarget) -> Option<String> {
+    match (nav.description(db), nav.docs(db)) {
+        (Some(desc), docs) => Some(rust_code_markup_with_doc(desc, docs)),
+        (None, Some(docs)) => Some(docs),
+        _ => None,
+    }
+}