Allow filtering of issues by negated author in GraphQL

app/graphql/types/issues/negated_issue_filter_input_type.rb

@@ -14,6 +14,9 @@ module Types
       argument :milestone_title, [GraphQL::Types::String],
                 required: false,
                 description: 'Milestone not applied to this issue.'
+      argument :author_username, GraphQL::Types::String,
+                required: false,
+                description: "Username of a user who didn't author the issue."
       argument :assignee_usernames, [GraphQL::Types::String],
                 required: false,
                 description: 'Usernames of users not assigned to the issue.'

doc/api/graphql/reference/index.md

@@ -17548,6 +17548,7 @@ Represents an escalation rule.
 | ---- | ---- | ----------- |
 | <a id="negatedissuefilterinputassigneeid"></a>`assigneeId` | [`String`](#string) | ID of a user not assigned to the issues. |
 | <a id="negatedissuefilterinputassigneeusernames"></a>`assigneeUsernames` | [`[String!]`](#string) | Usernames of users not assigned to the issue. |
+| <a id="negatedissuefilterinputauthorusername"></a>`authorUsername` | [`String`](#string) | Username of a user who didn't author the issue. |
 | <a id="negatedissuefilterinputepicid"></a>`epicId` | [`String`](#string) | ID of an epic not associated with the issues. |
 | <a id="negatedissuefilterinputiids"></a>`iids` | [`[String!]`](#string) | List of IIDs of issues to exclude. For example, `[1, 2]`. |
 | <a id="negatedissuefilterinputiterationid"></a>`iterationId` | [`[ID!]`](#id) | List of iteration Global IDs not applied to the issue. |

spec/graphql/resolvers/issues_resolver_spec.rb

@@ -6,6 +6,7 @@ RSpec.describe Resolvers::IssuesResolver do
   include GraphqlHelpers
 
   let_it_be(:current_user) { create(:user) }
+  let_it_be(:reporter) { create(:user) }
 
   let_it_be(:group)         { create(:group) }
   let_it_be(:project)       { create(:project, group: group) }
@@ -27,6 +28,7 @@ RSpec.describe Resolvers::IssuesResolver do
   context "with a project" do
     before_all do
       project.add_developer(current_user)
+      project.add_reporter(reporter)
       create(:label_link, label: label1, target: issue1)
       create(:label_link, label: label1, target: issue2)
       create(:label_link, label: label2, target: issue2)
@@ -235,6 +237,14 @@ RSpec.describe Resolvers::IssuesResolver do
         it 'returns issues without the specified assignee_id' do
           expect(resolve_issues(not: { assignee_id: [assignee.id] })).to contain_exactly(issue1)
         end
+
+        context 'when filtering by negated author' do
+          let_it_be(:issue_by_reporter) { create(:issue, author: reporter, project: project, state: :opened) }
+
+          it 'returns issues without the specified author_username' do
+            expect(resolve_issues(not: { author_username: issue1.author.username })).to contain_exactly(issue_by_reporter)
+          end
+        end
       end
 
       describe 'sorting' do