SI-6626 make @throws tags create links to exceptions

In scaladoc, this turns exceptions in @throws tags into links
(when it can find the target exception), instead of just showing
the name.

Author: gourlaysama

src/scaladoc/scala/tools/nsc/doc/base/CommentFactoryBase.scala

@@ -345,12 +345,28 @@ trait CommentFactoryBase { this: MemberLookupBase =>
           Map.empty[String, Body] ++ pairs
         }
 
+        def linkedExceptions: Map[String, Body] = {
+          val m = allSymsOneTag(SimpleTagKey("throws"))
+
+          m.map { case (name,body) =>
+            val link = memberLookup(pos, name, site)
+            val newBody = body match {
+              case Body(List(Paragraph(Chain(content)))) =>
+                val descr = Text(" ") +: content
+                val entityLink = EntityLink(Monospace(Text(name)), link)
+                Body(List(Paragraph(Chain(entityLink +: descr))))
+              case _ => body
+            }
+            (name, newBody)
+          }
+        }
+
         val com = createComment (
           body0           = Some(parseUncycloAtSymbol(docBody.toString, pos, site)),
           authors0        = allTags(SimpleTagKey("author")),
           see0            = allTags(SimpleTagKey("see")),
           result0         = oneTag(SimpleTagKey("return")),
-          throws0         = allSymsOneTag(SimpleTagKey("throws")),
+          throws0         = linkedExceptions,
           valueParams0    = allSymsOneTag(SimpleTagKey("param")),
           typeParams0     = allSymsOneTag(SimpleTagKey("tparam")),
           version0        = oneTag(SimpleTagKey("version")),

src/scaladoc/scala/tools/nsc/doc/html/page/Template.scala

@@ -605,7 +605,7 @@ class Template(universe: doc.Universe, generator: DiagramGenerator, tpl: DocTemp
             <dd>{
               val exceptionsXml: List[NodeSeq] =
                 for((name, body) <- comment.throws.toList.sortBy(_._1) ) yield
-                  <span class="cmt">{Text(name) ++ bodyToHtml(body)}</span>
+                  <span class="cmt">{bodyToHtml(body)}</span>
               exceptionsXml.reduceLeft(_ ++ Text("") ++ _)
             }</dd>
           }

src/scaladoc/scala/tools/partest/ScaladocModelTest.scala

@@ -182,14 +182,16 @@ abstract class ScaladocModelTest extends DirectTest {
       }
     }
 
-    def countLinks(c: Comment, p: EntityLink => Boolean) = {
-      def countLinks(body: Any): Int = body match {
+    def countLinks(c: Comment, p: EntityLink => Boolean): Int = countLinksInBody(c.body, p)
+
+    def countLinksInBody(body: Body, p: EntityLink => Boolean): Int = {
+      def countLinks(b: Any): Int = b match {
         case el: EntityLink if p(el) => 1
         case s: Seq[_]  => s.toList.map(countLinks(_)).sum
         case p: Product => p.productIterator.toList.map(countLinks(_)).sum
         case _          => 0
       }
-      countLinks(c.body)
+      countLinks(body)
     }
 
     def testDiagram(doc: DocTemplateEntity, diag: Option[Diagram], nodes: Int, edges: Int) = {

test/scaladoc/run/t6626.check

@@ -0,0 +1,7 @@
+newSource:10: warning: Could not find any member to link for "SomeUnknownException".
+  /**
+  ^
+newSource:10: warning: Could not find any member to link for "IOException".
+  /**
+  ^
+Done.

test/scaladoc/run/t6626.scala

@@ -0,0 +1,42 @@
+import scala.tools.nsc.doc.base._
+import scala.tools.nsc.doc.base.comment._
+import scala.tools.nsc.doc.model._
+import scala.tools.partest.ScaladocModelTest
+
+object Test extends ScaladocModelTest {
+
+  override def code = """
+
+package org.foo
+
+class MyException extends Exception
+
+class MyOtherException extends Exception
+
+object Foo {
+  /**
+    * Test exception linking
+    *
+    * @throws org.foo.MyException linked with a fully-qualified name
+    * @throws MyOtherException linked with a relative name
+    * @throws SomeUnknownException not linked at all (but with some text)
+    * @throws IOException
+    */
+  def test(): Unit = ???
+}
+    """
+
+  def scaladocSettings = ""
+
+  def testModel(rootPackage: Package) = {
+    // get the quick access implicit defs in scope (_package(s), _class(es), _trait(s), object(s) _method(s), _value(s))
+    import access._
+
+    val a = rootPackage._package("org")._package("foo")._object("Foo")._method("test")
+    val throws = a.comment.get.throws
+    val allbodies = Body(throws.values.flatMap(_.blocks).toSeq)
+
+    val links = countLinksInBody(allbodies, _.link.isInstanceOf[LinkToTpl[_]])
+    assert(links == 2, links + " ==  2 (links to MyException and MyOtherException)")
+  }
+}