Add mutation to update merge requests

This adds a mutation capable of updating title, description and
target-branch.

app/graphql/mutations/merge_requests/update.rb

+# frozen_string_literal: true
+
+module Mutations
+  module MergeRequests
+    class Update < Base
+      graphql_name 'MergeRequestUpdate'
+
+      description 'Update attributes of a merge request'
+
+      argument :title, GraphQL::STRING_TYPE,
+               required: false,
+               description: copy_field_description(Types::MergeRequestType, :title)
+
+      argument :target_branch, GraphQL::STRING_TYPE,
+               required: false,
+               description: copy_field_description(Types::MergeRequestType, :target_branch)
+
+      argument :description, GraphQL::STRING_TYPE,
+               required: false,
+               description: copy_field_description(Types::MergeRequestType, :description)
+
+      def resolve(args)
+        merge_request = authorized_find!(args.slice(:project_path, :iid))
+        attributes = args.slice(:title, :description, :target_branch).compact
+
+        ::MergeRequests::UpdateService
+          .new(merge_request.project, current_user, attributes)
+          .execute(merge_request)
+
+        errors = errors_on_object(merge_request)
+
+        {
+          merge_request: merge_request.reset,
+          errors: errors
+        }
+      end
+    end
+  end
+end

app/graphql/types/mutation_type.rb

@@ -20,6 +20,7 @@ module Types
     mount_mutation Mutations::Issues::SetDueDate
     mount_mutation Mutations::Issues::Update
     mount_mutation Mutations::MergeRequests::Create
+    mount_mutation Mutations::MergeRequests::Update
     mount_mutation Mutations::MergeRequests::SetLabels
     mount_mutation Mutations::MergeRequests::SetLocked
     mount_mutation Mutations::MergeRequests::SetMilestone

changelogs/unreleased/ajk-gql-mr-update.yml

+---
+title: Add mutation to update merge requests
+merge_request: 34748
+author:
+type: added

doc/api/graphql/reference/gitlab_schema.graphql

@@ -7321,6 +7321,61 @@ enum MergeRequestState {
   opened
 }
 
+"""
+Autogenerated input type of MergeRequestUpdate
+"""
+input MergeRequestUpdateInput {
+  """
+  A unique identifier for the client performing the mutation.
+  """
+  clientMutationId: String
+
+  """
+  Description of the merge request (Markdown rendered as HTML for caching)
+  """
+  description: String
+
+  """
+  The iid of the merge request to mutate
+  """
+  iid: String!
+
+  """
+  The project the merge request to mutate is in
+  """
+  projectPath: ID!
+
+  """
+  Target branch of the merge request
+  """
+  targetBranch: String
+
+  """
+  Title of the merge request
+  """
+  title: String
+}
+
+"""
+Autogenerated return type of MergeRequestUpdate
+"""
+type MergeRequestUpdatePayload {
+  """
+  A unique identifier for the client performing the mutation.
+  """
+  clientMutationId: String
+
+  """
+  Errors encountered during execution of the mutation.
+  """
+  errors: [String!]!
+
+  """
+  The merge request after mutation
+  """
+  mergeRequest: MergeRequest
+}
+
 type Metadata {
   """
   Revision
@@ -7607,6 +7662,11 @@ type Mutation {
   mergeRequestSetMilestone(input: MergeRequestSetMilestoneInput!): MergeRequestSetMilestonePayload
   mergeRequestSetSubscription(input: MergeRequestSetSubscriptionInput!): MergeRequestSetSubscriptionPayload
   mergeRequestSetWip(input: MergeRequestSetWipInput!): MergeRequestSetWipPayload
+
+  """
+  Update attributes of a merge request
+  """
+  mergeRequestUpdate(input: MergeRequestUpdateInput!): MergeRequestUpdatePayload
   removeAwardEmoji(input: RemoveAwardEmojiInput!): RemoveAwardEmojiPayload
   removeProjectFromSecurityDashboard(input: RemoveProjectFromSecurityDashboardInput!): RemoveProjectFromSecurityDashboardPayload
   runDastScan(input: RunDASTScanInput!): RunDASTScanPayload

doc/api/graphql/reference/gitlab_schema.json

@@ -20432,6 +20432,152 @@
           ],
           "possibleTypes": null
         },
+        {
+          "kind": "INPUT_OBJECT",
+          "name": "MergeRequestUpdateInput",
+          "description": "Autogenerated input type of MergeRequestUpdate",
+          "fields": null,
+          "inputFields": [
+            {
+              "name": "projectPath",
+              "description": "The project the merge request to mutate is in",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "ID",
+                  "ofType": null
+                }
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "iid",
+              "description": "The iid of the merge request to mutate",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "String",
+                  "ofType": null
+                }
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "title",
+              "description": "Title of the merge request",
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "targetBranch",
+              "description": "Target branch of the merge request",
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "description",
+              "description": "Description of the merge request (Markdown rendered as HTML for caching)",
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "clientMutationId",
+              "description": "A unique identifier for the client performing the mutation.",
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "defaultValue": null
+            }
+          ],
+          "interfaces": null,
+          "enumValues": null,
+          "possibleTypes": null
+        },
+        {
+          "kind": "OBJECT",
+          "name": "MergeRequestUpdatePayload",
+          "description": "Autogenerated return type of MergeRequestUpdate",
+          "fields": [
+            {
+              "name": "clientMutationId",
+              "description": "A unique identifier for the client performing the mutation.",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
+            {
+              "name": "errors",
+              "description": "Errors encountered during execution of the mutation.",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "LIST",
+                  "name": null,
+                  "ofType": {
+                    "kind": "NON_NULL",
+                    "name": null,
+                    "ofType": {
+                      "kind": "SCALAR",
+                      "name": "String",
+                      "ofType": null
+                    }
+                  }
+                }
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
+            {
+              "name": "mergeRequest",
+              "description": "The merge request after mutation",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "MergeRequest",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            }
+          ],
+          "inputFields": null,
+          "interfaces": [
+
+          ],
+          "enumValues": null,
+          "possibleTypes": null
+        },
         {
           "kind": "OBJECT",
           "name": "Metadata",
@@ -22266,6 +22412,33 @@
               "isDeprecated": false,
               "deprecationReason": null
             },
+            {
+              "name": "mergeRequestUpdate",
+              "description": "Update attributes of a merge request",
+              "args": [
+                {
+                  "name": "input",
+                  "description": null,
+                  "type": {
+                    "kind": "NON_NULL",
+                    "name": null,
+                    "ofType": {
+                      "kind": "INPUT_OBJECT",
+                      "name": "MergeRequestUpdateInput",
+                      "ofType": null
+                    }
+                  },
+                  "defaultValue": null
+                }
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "MergeRequestUpdatePayload",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
             {
               "name": "removeAwardEmoji",
               "description": null,

doc/api/graphql/reference/index.md

@@ -1100,6 +1100,16 @@ Autogenerated return type of MergeRequestSetWip
 | `errors` | String! => Array | Errors encountered during execution of the mutation. |
 | `mergeRequest` | MergeRequest | The merge request after mutation |
 
+## MergeRequestUpdatePayload
+
+Autogenerated return type of MergeRequestUpdate
+
+| Name  | Type  | Description |
+| ---   |  ---- | ----------  |
+| `clientMutationId` | String | A unique identifier for the client performing the mutation. |
+| `errors` | String! => Array | Errors encountered during execution of the mutation. |
+| `mergeRequest` | MergeRequest | The merge request after mutation |
+
 ## Metadata
 
 | Name  | Type  | Description |

spec/graphql/mutations/merge_requests/update_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Mutations::MergeRequests::Update do
+  let(:merge_request) { create(:merge_request) }
+  let(:user) { create(:user) }
+
+  subject(:mutation) { described_class.new(object: nil, context: { current_user: user }, field: nil) }
+
+  specify { expect(described_class).to require_graphql_authorizations(:update_merge_request) }
+
+  describe '#resolve' do
+    let(:attributes) { { title: 'new title', description: 'new description', target_branch: 'new-branch' } }
+    let(:mutated_merge_request) { subject[:merge_request] }
+
+    subject do
+      mutation.resolve(project_path: merge_request.project.full_path, iid: merge_request.iid, **attributes)
+    end
+
+    it 'raises an error if the resource is not accessible to the user' do
+      expect { subject }.to raise_error(Gitlab::Graphql::Errors::ResourceNotAvailable)
+    end
+
+    context 'when the user can update the merge request' do
+      before do
+        merge_request.project.add_developer(user)
+      end
+
+      it 'applies all attributes' do
+        expect(mutated_merge_request).to eq(merge_request)
+        expect(mutated_merge_request).to have_attributes(attributes)
+        expect(subject[:errors]).to be_empty
+      end
+
+      context 'the merge request is invalid' do
+        before do
+          merge_request.allow_broken = true
+          merge_request.update!(source_project: nil)
+        end
+
+        it 'returns error information, and changes were not applied' do
+          expect(mutated_merge_request).not_to have_attributes(attributes)
+          expect(subject[:errors]).not_to be_empty
+        end
+      end
+
+      context 'our change is invalid' do
+        let(:attributes) { { target_branch: 'this is not a branch' } }
+
+        it 'returns error information, and changes were not applied' do
+          expect(mutated_merge_request).not_to have_attributes(attributes)
+          expect(subject[:errors]).not_to be_empty
+        end
+      end
+
+      context 'when passing subset of attributes' do
+        let(:attributes) { { title: 'no, this title' } }
+
+        it 'only changes the mentioned attributes' do
+          expect { subject }.not_to change { merge_request.reset.description }
+
+          expect(mutated_merge_request).to have_attributes(attributes)
+        end
+      end
+    end
+  end
+end