add RequestKind.requiresSourceCode, fix #617

this is a or-combined mask of the request kinds which operate on
`request.sourceCode`. Before if a client sent a request without source
code (with empty source) to one of these commands, the server would
crash with an assertion failure, now the server returns an empty
response.

common/src/dcd/common/messages.d

@@ -78,6 +78,10 @@ enum RequestKind : ushort
 	localUse =     	 0b00000010_00000000,
 	/// Remove import directory from server
 	removeImport =   0b00000100_00000000,
+
+	/// These request kinds require source code and won't be executed if there
+	/// is no source sent
+	requiresSourceCode = autocomplete | doc | symbolLocation | search | localUse,
 	// dfmt on
 }
 

src/dcd/server/main.d

@@ -281,6 +281,16 @@ int runServer(string[] args)
 			info("Returning import path list");
 			s.sendResponse(response);
 		}
+		else
+		{
+			// these requests operate on and require source code
+
+			if ((request.kind & RequestKind.requiresSourceCode)
+				&& !request.sourceCode.length)
+			{
+				warning("Received a ", request.kind, " request without source code");
+				s.sendResponse(AutocompleteResponse.init);
+			}
 			else if (request.kind & RequestKind.autocomplete)
 			{
 				info("Getting completions");
@@ -297,6 +307,7 @@ int runServer(string[] args)
 				s.sendResponse(symbolSearch(request, cache));
 			else if (request.kind & RequestKind.localUse)
 				s.trySendResponse(findLocalUse(request, cache), "Couldnot find local usage");
+		}
 
 		sw.stop();
 		info("Request processed in ", sw.peek().total!"msecs"(), " milliseconds");

tests/tc_empty_requests/run.sh

@@ -0,0 +1,7 @@
+set -e
+set -u
+
+../../bin/dcd-client $1 -s foo < /dev/null
+../../bin/dcd-client $1 -c 1 < /dev/null
+../../bin/dcd-client $1 -d -c 1 < /dev/null
+../../bin/dcd-client $1 -u -c 1 < /dev/null