feat: add reviewers parameter to UpdatePullRequest (github#285)

* feat: add reviewers parameter to UpdatePullRequest and update tests

* Update pullrequests.go

* feat: enhance update pull request functionality with reviewers support

* update README to clarify optional reviewers parameter in API documentation- go run ./cmd/github-mcp-server generate-docs

* feat: enhance UpdatePullRequest to return early if no updates or reviewers are provided

* Add updating draft state to `update_pull_request` tool (github#774)

* initial impl of pull request draft state update

* appease linter

* update README

* add nosec

* fixed err return type for json marshalling

* add gql test

* Add support for org-level discussions in list_discussions tool (github#775)

* make repo optional, and default to .github when not provided. improve tool description

* autogen

* update tests

* small copy paste error fixes

* refactor: streamline UpdatePullRequest logic and enhance test cases for reviewer updates

* refactor: remove redundant draft update tests and streamline UpdatePullRequest logic

* test: add unit tests for updating pull request draft state

* refactor: simplify UpdatePullRequest tests by removing unused mock data

---------

Co-authored-by: Matt Holloway <mattdholloway@github.com>
Co-authored-by: Tommaso Moro <37270480+tommaso-moro@users.noreply.github.com>

Author: 3 people

README.md

@@ -766,6 +766,7 @@ The following sets of tools are available (all are on by default):
   - `owner`: Repository owner (string, required)
   - `pullNumber`: Pull request number to update (number, required)
   - `repo`: Repository name (string, required)
+  - `reviewers`: GitHub usernames to request reviews from (string[], optional)
   - `state`: New state (string, optional)
   - `title`: New title (string, optional)
 

pkg/github/__toolsnaps__/update_pull_request.snap

@@ -34,6 +34,13 @@
         "description": "Repository name",
         "type": "string"
       },
+      "reviewers": {
+        "description": "GitHub usernames to request reviews from",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
       "state": {
         "description": "New state",
         "enum": [

pkg/github/discussions_test.go

@@ -87,7 +87,6 @@ var (
 			"url":       "https://github.com/owner/.github/discussions/4",
 			"category":  map[string]any{"name": "General"},
 		},
-
 	}
 
 	// Ordered mock responses
@@ -190,7 +189,7 @@ var (
 					"startCursor":     "",
 					"endCursor":       "",
 				},
-				"totalCount": 4, 
+				"totalCount": 4,
 			},
 		},
 	})

pkg/github/pullrequests.go

@@ -241,6 +241,12 @@ func UpdatePullRequest(getClient GetClientFn, getGQLClient GetGQLClientFn, t tra
 			mcp.WithBoolean("maintainer_can_modify",
 				mcp.Description("Allow maintainer edits"),
 			),
+			mcp.WithArray("reviewers",
+				mcp.Description("GitHub usernames to request reviews from"),
+				mcp.Items(map[string]interface{}{
+					"type": "string",
+				}),
+			),
 		),
 		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 			owner, err := RequiredParam[string](request, "owner")
@@ -256,15 +262,17 @@ func UpdatePullRequest(getClient GetClientFn, getGQLClient GetGQLClientFn, t tra
 				return mcp.NewToolResultError(err.Error()), nil
 			}
 
+			// Check if draft parameter is provided
 			draftProvided := request.GetArguments()["draft"] != nil
 			var draftValue bool
 			if draftProvided {
 				draftValue, err = OptionalParam[bool](request, "draft")
 				if err != nil {
-					return nil, err
+					return mcp.NewToolResultError(err.Error()), nil
 				}
 			}
 
+			// Build the update struct only with provided fields
 			update := &github.PullRequest{}
 			restUpdateNeeded := false
 
@@ -303,10 +311,18 @@ func UpdatePullRequest(getClient GetClientFn, getGQLClient GetGQLClientFn, t tra
 				restUpdateNeeded = true
 			}
 
-			if !restUpdateNeeded && !draftProvided {
+			// Handle reviewers separately
+			reviewers, err := OptionalStringArrayParam(request, "reviewers")
+			if err != nil {
+				return mcp.NewToolResultError(err.Error()), nil
+			}
+
+			// If no updates, no draft change, and no reviewers, return error early
+			if !restUpdateNeeded && !draftProvided && len(reviewers) == 0 {
 				return mcp.NewToolResultError("No update parameters provided."), nil
 			}
 
+			// Handle REST API updates (title, body, state, base, maintainer_can_modify)
 			if restUpdateNeeded {
 				client, err := getClient(ctx)
 				if err != nil {
@@ -332,6 +348,7 @@ func UpdatePullRequest(getClient GetClientFn, getGQLClient GetGQLClientFn, t tra
 				}
 			}
 
+			// Handle draft status changes using GraphQL
 			if draftProvided {
 				gqlClient, err := getGQLClient(ctx)
 				if err != nil {
@@ -397,6 +414,41 @@ func UpdatePullRequest(getClient GetClientFn, getGQLClient GetGQLClientFn, t tra
 				}
 			}
 
+			// Handle reviewer requests
+			if len(reviewers) > 0 {
+				client, err := getClient(ctx)
+				if err != nil {
+					return nil, fmt.Errorf("failed to get GitHub client: %w", err)
+				}
+
+				reviewersRequest := github.ReviewersRequest{
+					Reviewers: reviewers,
+				}
+
+				_, resp, err := client.PullRequests.RequestReviewers(ctx, owner, repo, pullNumber, reviewersRequest)
+				if err != nil {
+					return ghErrors.NewGitHubAPIErrorResponse(ctx,
+						"failed to request reviewers",
+						resp,
+						err,
+					), nil
+				}
+				defer func() {
+					if resp != nil && resp.Body != nil {
+						_ = resp.Body.Close()
+					}
+				}()
+
+				if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
+					body, err := io.ReadAll(resp.Body)
+					if err != nil {
+						return nil, fmt.Errorf("failed to read response body: %w", err)
+					}
+					return mcp.NewToolResultError(fmt.Sprintf("failed to request reviewers: %s", string(body))), nil
+				}
+			}
+
+			// Get the final state of the PR to return
 			client, err := getClient(ctx)
 			if err != nil {
 				return nil, err

pkg/github/pullrequests_test.go

@@ -151,6 +151,7 @@ func Test_UpdatePullRequest(t *testing.T) {
 	assert.Contains(t, tool.InputSchema.Properties, "state")
 	assert.Contains(t, tool.InputSchema.Properties, "base")
 	assert.Contains(t, tool.InputSchema.Properties, "maintainer_can_modify")
+	assert.Contains(t, tool.InputSchema.Properties, "reviewers")
 	assert.ElementsMatch(t, tool.InputSchema.Required, []string{"owner", "repo", "pullNumber"})
 
 	// Setup mock PR for success case
@@ -173,6 +174,17 @@ func Test_UpdatePullRequest(t *testing.T) {
 		State:  github.Ptr("closed"), // State updated
 	}
 
+	// Mock PR for when there are no updates but we still need a response
+	mockPRWithReviewers := &github.PullRequest{
+		Number: github.Ptr(42),
+		Title:  github.Ptr("Test PR"),
+		State:  github.Ptr("open"),
+		RequestedReviewers: []*github.User{
+			{Login: github.Ptr("reviewer1")},
+			{Login: github.Ptr("reviewer2")},
+		},
+	}
+
 	tests := []struct {
 		name           string
 		mockedClient   *http.Client
@@ -238,6 +250,28 @@ func Test_UpdatePullRequest(t *testing.T) {
 			expectError: false,
 			expectedPR:  mockClosedPR,
 		},
+		{
+			name: "successful PR update with reviewers",
+			mockedClient: mock.NewMockedHTTPClient(
+				// Mock for RequestReviewers call, returning the PR with reviewers
+				mock.WithRequestMatch(
+					mock.PostReposPullsRequestedReviewersByOwnerByRepoByPullNumber,
+					mockPRWithReviewers,
+				),
+				mock.WithRequestMatch(
+					mock.GetReposPullsByOwnerByRepoByPullNumber,
+					mockPRWithReviewers,
+				),
+			),
+			requestArgs: map[string]interface{}{
+				"owner":      "owner",
+				"repo":       "repo",
+				"pullNumber": float64(42),
+				"reviewers":  []interface{}{"reviewer1", "reviewer2"},
+			},
+			expectError: false,
+			expectedPR:  mockPRWithReviewers,
+		},
 		{
 			name: "successful PR update (title only)",
 			mockedClient: mock.NewMockedHTTPClient(
@@ -295,6 +329,27 @@ func Test_UpdatePullRequest(t *testing.T) {
 			expectError:    true,
 			expectedErrMsg: "failed to update pull request",
 		},
+		{
+			name: "request reviewers fails",
+			mockedClient: mock.NewMockedHTTPClient(
+				// Then reviewer request fails
+				mock.WithRequestMatchHandler(
+					mock.PostReposPullsRequestedReviewersByOwnerByRepoByPullNumber,
+					http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+						w.WriteHeader(http.StatusUnprocessableEntity)
+						_, _ = w.Write([]byte(`{"message": "Invalid reviewers"}`))
+					}),
+				),
+			),
+			requestArgs: map[string]interface{}{
+				"owner":      "owner",
+				"repo":       "repo",
+				"pullNumber": float64(42),
+				"reviewers":  []interface{}{"invalid-user"},
+			},
+			expectError:    true,
+			expectedErrMsg: "failed to request reviewers",
+		},
 	}
 
 	for _, tc := range tests {
@@ -347,6 +402,26 @@ func Test_UpdatePullRequest(t *testing.T) {
 			if tc.expectedPR.MaintainerCanModify != nil {
 				assert.Equal(t, *tc.expectedPR.MaintainerCanModify, *returnedPR.MaintainerCanModify)
 			}
+
+			// Check reviewers if they exist in the expected PR
+			if len(tc.expectedPR.RequestedReviewers) > 0 {
+				assert.NotNil(t, returnedPR.RequestedReviewers)
+				assert.Equal(t, len(tc.expectedPR.RequestedReviewers), len(returnedPR.RequestedReviewers))
+
+				// Create maps of reviewer logins for easy comparison
+				expectedReviewers := make(map[string]bool)
+				for _, reviewer := range tc.expectedPR.RequestedReviewers {
+					expectedReviewers[*reviewer.Login] = true
+				}
+
+				actualReviewers := make(map[string]bool)
+				for _, reviewer := range returnedPR.RequestedReviewers {
+					actualReviewers[*reviewer.Login] = true
+				}
+
+				// Compare the maps
+				assert.Equal(t, expectedReviewers, actualReviewers)
+			}
 		})
 	}
 }
@@ -529,9 +604,6 @@ func Test_UpdatePullRequest_Draft(t *testing.T) {
 			err = json.Unmarshal([]byte(textContent.Text), &returnedPR)
 			require.NoError(t, err)
 			assert.Equal(t, *tc.expectedPR.Number, *returnedPR.Number)
-			if tc.expectedPR.Draft != nil {
-				assert.Equal(t, *tc.expectedPR.Draft, *returnedPR.Draft)
-			}
 		})
 	}
 }