IDE: Show documentation for symbol on hover

Author: Duhemm

language-server/src/dotty/tools/languageserver/DottyLanguageServer.scala

@@ -338,13 +338,17 @@ class DottyLanguageServer extends LanguageServer
     implicit val ctx = driver.currentCtx
 
     val pos = sourcePosition(driver, uri, params.getPosition)
-    val tp = Interactive.enclosingType(driver.openedTrees(uri), pos)
+    val trees = driver.openedTrees(uri)
+    val tp = Interactive.enclosingType(trees, pos)
     val tpw = tp.widenTermRefExpr
 
     if (tpw == NoType) new Hover
     else {
+      import dotty.tools.dotc.core.Comments._
+      val symbol = Interactive.enclosingSourceSymbol(trees, pos)
+      val doc = ctx.docCtx.flatMap(_.docstring(symbol)).map(_.raw + " / ").getOrElse("")
       val str = tpw.show.toString
-      new Hover(List(JEither.forLeft(str)).asJava, null)
+      new Hover(List(JEither.forLeft(doc + str)).asJava, null)
     }
   }
 

language-server/test/dotty/tools/languageserver/HoverTest.scala

@@ -9,6 +9,13 @@ class HoverTest {
   @Test def hoverOnWhiteSpace0: Unit =
     code"$m1 $m2".withSource.hover(m1 to m2, "")
 
+  @Test def hoverOnClassShowsDoc: Unit = {
+    code"""$m1 /** foo */ ${m2}class Foo $m3 $m4""".withSource
+      .hover(m1 to m2, "")
+      .hover(m2 to m3, "/** foo */ / Foo")
+      .hover(m3 to m4, "")
+  }
+
   @Test def hoverOnClass0: Unit = {
     code"""$m1 ${m2}class Foo $m3 $m4""".withSource
       .hover(m1 to m2, "")