Return null cursor when creating comment

src/core/client/stream/test/postComment.spec.tsx

@@ -39,7 +39,7 @@ beforeEach(() => {
             .returns({
               // TODO: add a type assertion here to ensure that if the type changes, that the test will fail
               edge: {
-                cursor: "2018-07-06T18:24:00.000Z",
+                cursor: null,
                 node: {
                   id: "comment-x",
                   author: users[0],

src/core/client/stream/test/postReply.spec.tsx

@@ -39,7 +39,7 @@ beforeEach(() => {
             })
             .returns({
               edge: {
-                cursor: "2018-07-06T18:24:00.000Z",
+                cursor: null,
                 node: {
                   id: "comment-x",
                   author: users[0],

src/core/server/graph/tenant/resolvers/mutation.ts

@@ -9,8 +9,11 @@ const Mutation: GQLMutationTypeResolver<void> = {
     const comment = await ctx.mutators.Comment.create(input);
     return {
       edge: {
-        // FIXME: (wyattjoh) when we're using a replies/respect sort, it is index based instead of date based, needs some work!
-        cursor: comment.created_at,
+        // (cvle)
+        // Depending on the sort we can't determine the accurate cursor
+        // in a performant way, so we return null instead.
+        // It seems that Relay does not directly use this value...
+        cursor: null,
         node: comment,
       },
       clientMutationId: input.clientMutationId,

src/core/server/graph/tenant/schema/schema.graphql

@@ -679,7 +679,7 @@ type CommentEdge {
   """
 
   """
-  cursor: Cursor!
+  cursor: Cursor
 }
 
 """