Handle empty doc comments ("///") on unittests

src/dparse/ast.d

@@ -3686,3 +3686,65 @@ unittest // issue #398: Support extern(C++, <string expressions...>)
     checkText(ns[1], `"bar"`);
     checkText(ns[2], `"baz"`);
 }
+
+unittest // Differentiate between no and empty DDOC comments, e.g. for DDOC unittests
+{
+    import dparse.lexer, dparse.parser, dparse.rollback_allocator;
+
+    auto src = q{
+        ///
+        unittest {}
+
+        ///
+        @safe pure unittest {}
+
+        /****/ unittest {}
+
+        /++++/ unittest {}
+
+        /// This is a comment!
+        unittest {}
+
+        unittest {}
+    };
+
+    RollbackAllocator ra;
+    LexerConfig cf = LexerConfig("", StringBehavior.source);
+    StringCache ca = StringCache(16);
+    Module m = parseModule(getTokensForParser(src, cf, &ca), "", &ra);
+
+    final class UnittestVisitor : ASTVisitor
+    {
+        alias visit = ASTVisitor.visit;
+        bool[size_t] found;
+
+        override void visit(const Unittest test)
+        {
+            assert(test.line !in found);
+            found[test.line] = true;
+
+            switch (test.line)
+            {
+                case 3, 6, 8, 10:
+                    assert(test.comment !is null);
+                    assert(test.comment == "");
+                    break;
+
+                case 13:
+                    assert(test.comment == "This is a comment!");
+                    break;
+
+                case 15:
+                    assert(test.comment is null);
+                    break;
+
+                default:
+                    assert(false, format("Unknown line: %d", test.line));
+            }
+        }
+    }
+
+    scope visitor = new UnittestVisitor();
+    visitor.visit(m);
+    assert(visitor.found.length == 6);
+}

src/dparse/trivia.d

@@ -518,18 +518,43 @@ unittest
 string extractDdocFromTrivia(Tokens)(Tokens tokens) pure nothrow @safe
     if (isInputRange!Tokens && is(ElementType!Tokens : Token))
 {
+    bool hasDoc;
     auto ret = appender!string;
     foreach (trivia; tokens)
     {
         if (trivia.type == tok!"comment"
             && trivia.text.determineCommentType.isDocComment)
         {
+            hasDoc = true;
             if (!ret.data.empty)
                 ret.put('\n');
             unDecorateComment(trivia.text, ret);
         }
     }
-    return ret.data;
+
+    if (ret.data.length)
+        return ret.data;
+    else
+        return hasDoc ? "" : null;
+}
+
+unittest
+{
+    Token[] tokens = [
+        Token(cast(ubyte) tok!"whitespace", "\n\n", 0, 0, 0),
+        Token(cast(ubyte) tok!"comment", "///", 0, 0, 0),
+        Token(cast(ubyte) tok!"whitespace", "\n", 0, 0, 0)
+    ];
+
+    // Empty comment is non-null
+    auto comment = extractDdocFromTrivia(tokens);
+    assert(comment !is null);
+    assert(comment == "");
+
+    // Missing comment is null
+    comment = extractDdocFromTrivia(tokens[0 .. 1]);
+    assert(comment is null);
+    assert(comment == "");
 }
 
 string extractLeadingDdoc(const Token token) pure nothrow @safe
@@ -568,14 +593,17 @@ void main() {
     writeln(":)");
 }
 
+///
+unittest {}
+
 /// end of file`;
 
     LexerConfig cf;
     StringCache ca = StringCache(16);
 
     const tokens = getTokensForParser(src, cf, &ca);
 
-    assert(tokens.length == 19);
+    assert(tokens.length == 22);
 
     assert(tokens[0].type == tok!"module");
     assert(tokens[0].leadingTrivia.length == 6);
@@ -694,9 +722,30 @@ void main() {
 
     assert(tokens[18].type == tok!"}");
     assert(!tokens[18].leadingTrivia.length);
-    assert(tokens[18].trailingTrivia.length == 2);
+    assert(tokens[18].trailingTrivia.length == 1);
     assert(tokens[18].trailingTrivia[0].type == tok!"whitespace");
     assert(tokens[18].trailingTrivia[0].text == "\n\n");
-    assert(tokens[18].trailingTrivia[1].type == tok!"comment");
-    assert(tokens[18].trailingTrivia[1].text == "/// end of file");
+
+    assert(tokens[19].type == tok!"unittest");
+    assert(tokens[19].leadingTrivia.length == 2);
+    assert(tokens[19].leadingTrivia[0].type == tok!"comment");
+    assert(tokens[19].leadingTrivia[0].text == "///");
+    assert(tokens[19].leadingTrivia[1].type == tok!"whitespace");
+    assert(tokens[19].leadingTrivia[1].text == "\n");
+
+    assert(tokens[19].trailingTrivia.length == 1);
+    assert(tokens[19].trailingTrivia[0].type == tok!"whitespace");
+    assert(tokens[19].trailingTrivia[0].text == " ");
+
+    assert(tokens[20].type == tok!"{");
+    assert(!tokens[20].leadingTrivia.length);
+    assert(!tokens[20].trailingTrivia.length);
+
+    assert(tokens[21].type == tok!"}");
+    assert(!tokens[21].leadingTrivia.length);
+    assert(tokens[21].trailingTrivia.length == 2);
+    assert(tokens[21].trailingTrivia[0].type == tok!"whitespace");
+    assert(tokens[21].trailingTrivia[0].text == "\n\n");
+    assert(tokens[21].trailingTrivia[1].type == tok!"comment");
+    assert(tokens[21].trailingTrivia[1].text == "/// end of file");
 }