Document mixed issue type clear routing

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: ea8faa5c-7f26-4e2d-bf9c-6f0b5f173e8c

Author: zwick

pkg/github/issues.go

@@ -2050,6 +2050,8 @@ var issueWriteFormParams = map[string]struct{}{
 func shouldIssueWriteDeferToForm(ctx context.Context, deps ToolDependencies, req *mcp.CallToolRequest, args map[string]any) bool {
 	issueType, issueTypeProvided, err := OptionalParamOK[string](args, "type")
 	explicitTypeClear := err == nil && issueTypeProvided && issueType == "" && args["method"] == "update"
+	// The form cannot preserve an empty type, so execute the complete call
+	// directly to avoid dropping the clear or any co-submitted values.
 	return !explicitTypeClear && shouldDeferToForm(ctx, deps, req, args, issueWriteFormParams)
 }
 

pkg/github/issues_test.go

@@ -2939,6 +2939,92 @@ func TestIssueWriteClearTypeBypassesMCPAppForm(t *testing.T) {
 	require.Contains(t, textContent.Text, "https://github.com/owner/repo/issues/123")
 }
 
+func TestIssueWriteClearTypeBypassesMCPAppFormWithStateChange(t *testing.T) {
+	var gotRequestBody []byte
+	var readErr error
+	client := mustNewGHClient(t, MockHTTPClientWithHandlers(map[string]http.HandlerFunc{
+		PatchReposIssuesByOwnerByRepoByIssueNumber: func(w http.ResponseWriter, r *http.Request) {
+			gotRequestBody, readErr = io.ReadAll(r.Body)
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(`{"number":123,"html_url":"https://github.com/owner/repo/issues/123"}`))
+		},
+	}))
+	issueID := githubv4.ID("I_kwDOA0xdyM50BPaO")
+	stateReason := IssueClosedStateReasonCompleted
+	gqlClient := githubv4.NewClient(githubv4mock.NewMockedHTTPClient(
+		githubv4mock.NewQueryMatcher(
+			struct {
+				Repository struct {
+					Issue struct {
+						ID githubv4.ID
+					} `graphql:"issue(number: $issueNumber)"`
+				} `graphql:"repository(owner: $owner, name: $repo)"`
+			}{},
+			map[string]any{
+				"owner":       githubv4.String("owner"),
+				"repo":        githubv4.String("repo"),
+				"issueNumber": githubv4.Int(123),
+			},
+			githubv4mock.DataResponse(map[string]any{
+				"repository": map[string]any{
+					"issue": map[string]any{"id": issueID},
+				},
+			}),
+		),
+		githubv4mock.NewMutationMatcher(
+			struct {
+				CloseIssue struct {
+					Issue struct {
+						ID     githubv4.ID
+						Number githubv4.Int
+						URL    githubv4.String
+						State  githubv4.String
+					}
+				} `graphql:"closeIssue(input: $input)"`
+			}{},
+			CloseIssueInput{
+				IssueID:     issueID,
+				StateReason: &stateReason,
+			},
+			nil,
+			githubv4mock.DataResponse(map[string]any{
+				"closeIssue": map[string]any{
+					"issue": map[string]any{
+						"id":     issueID,
+						"number": 123,
+						"url":    "https://github.com/owner/repo/issues/123",
+						"state":  "CLOSED",
+					},
+				},
+			}),
+		),
+	))
+	deps := BaseDeps{
+		Client:         client,
+		GQLClient:      gqlClient,
+		featureChecker: featureCheckerFor(MCPAppsFeatureFlag),
+	}
+	serverTool := IssueWrite(translations.NullTranslationHelper)
+	handler := serverTool.Handler(deps)
+	request := createMCPRequestWithSession(t, ClientNameVSCodeInsiders, true, map[string]any{
+		"method":       "update",
+		"owner":        "owner",
+		"repo":         "repo",
+		"issue_number": float64(123),
+		"type":         "",
+		"state":        "closed",
+		"state_reason": "completed",
+	})
+
+	result, err := handler(ContextWithDeps(context.Background(), deps), &request)
+	require.NoError(t, err)
+	require.False(t, result.IsError)
+	require.NoError(t, readErr)
+	require.JSONEq(t, `{"type":null}`, string(gotRequestBody))
+	textContent := getTextResult(t, result)
+	require.Contains(t, textContent.Text, "https://github.com/owner/repo/issues/123")
+}
+
 func Test_UpdateIssue(t *testing.T) {
 	// Verify tool definition
 	serverTool := IssueWrite(translations.NullTranslationHelper)