Add error handling to completion callbacks

mcp.go

@@ -115,7 +115,10 @@ func handleSetTaskSuccess(s *Service, ctx context.Context, args setTaskSuccessAr
 		return nil, fmt.Errorf("failed to get project: %w", err)
 	}
 
-	nextTask := project.SetTaskSuccess(args.TaskID, args.Result, args.Notes)
+	nextTask, err := project.SetTaskSuccess(args.TaskID, args.Result, args.Notes)
+	if err != nil {
+		return nil, fmt.Errorf("completion callback error: %w", err)
+	}
 
 	response := &taskResponse{
 		TaskID:   args.TaskID,
@@ -132,7 +135,10 @@ func handleSetTaskFailure(s *Service, ctx context.Context, args setTaskFailureAr
 		return nil, fmt.Errorf("failed to get project: %w", err)
 	}
 
-	nextTask := project.SetTaskFailure(args.TaskID, args.Error, args.Notes)
+	nextTask, err := project.SetTaskFailure(args.TaskID, args.Error, args.Notes)
+	if err != nil {
+		return nil, fmt.Errorf("completion callback error: %w", err)
+	}
 
 	response := &taskResponse{
 		TaskID:   args.TaskID,

taskcp.go

@@ -40,7 +40,7 @@ type Task struct {
 	projectID          string
 	mcpService         string
 	nextTaskID         string
-	completionCallback func(task *Task)
+	completionCallback func(task *Task) error
 }
 
 func New(mcpService string) *Service {
@@ -70,7 +70,7 @@ func (s *Service) GetProject(id string) (*Project, error) {
 	return project, nil
 }
 
-func (p *Project) InsertTaskBefore(beforeID string, instructions string, completionCallback func(task *Task)) *Task {
+func (p *Project) InsertTaskBefore(beforeID string, instructions string, completionCallback func(task *Task) error) *Task {
 	task := p.newTask(instructions, completionCallback, beforeID)
 
 	if p.nextTaskID == "" && beforeID == "" {
@@ -97,29 +97,39 @@ func (p *Project) GetNextTask() *Task {
 	return task
 }
 
-func (p *Project) SetTaskSuccess(id string, result string, notes string) *Task {
+func (p *Project) SetTaskSuccess(id string, result string, notes string) (*Task, error) {
 	task := p.Tasks[id]
 	task.State = TaskStateSuccess
 	task.Result = result
 	task.Notes = notes
-	task.completionCallback(task)
+
+	err := task.completionCallback(task)
+	if err != nil {
+		return nil, err
+	}
+
 	p.nextTaskID = task.nextTaskID
 
-	return p.GetNextTask()
+	return p.GetNextTask(), nil
 }
 
-func (p *Project) SetTaskFailure(id string, error string, notes string) *Task {
+func (p *Project) SetTaskFailure(id string, error string, notes string) (*Task, error) {
 	task := p.Tasks[id]
 	task.State = TaskStateFailure
 	task.Error = error
 	task.Notes = notes
-	task.completionCallback(task)
+
+	err := task.completionCallback(task)
+	if err != nil {
+		return nil, err
+	}
+
 	p.nextTaskID = task.nextTaskID
 
-	return p.GetNextTask()
+	return p.GetNextTask(), nil
 }
 
-func (p *Project) newTask(instructions string, completionCallback func(task *Task), nextTaskID string) *Task {
+func (p *Project) newTask(instructions string, completionCallback func(task *Task) error, nextTaskID string) *Task {
 	task := &Task{
 		ID:                 uuid.New().String(),
 		State:              TaskStatePending,
@@ -159,4 +169,3 @@ func (t *Task) FailurePrompt() string {
 %s.set_task_failure(project_id="%s", task_id="%s", error="<error message>", notes="<optional notes>")`,
 		t.mcpService, t.projectID, t.ID)
 }
-

taskcp_test.go

@@ -1,6 +1,7 @@
 package taskcp_test
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/gopatchy/taskcp"
@@ -12,7 +13,7 @@ func TestTaskPrompts(t *testing.T) {
 	service := taskcp.New("my_service")
 	project := service.AddProject()
 	
-	task := project.InsertTaskBefore("", "Write unit tests", func(task *taskcp.Task) {})
+	task := project.InsertTaskBefore("", "Write unit tests", func(task *taskcp.Task) error { return nil })
 	
 	successPrompt := task.SuccessPrompt()
 	require.Contains(t, successPrompt, "my_service.set_task_success")
@@ -29,11 +30,11 @@ func TestPlaceholderExpansion(t *testing.T) {
 	service := taskcp.New("my_service")
 	project := service.AddProject()
 	
-	task1 := project.InsertTaskBefore("", "Please complete this task. {SUCCESS_PROMPT}", func(task *taskcp.Task) {})
+	task1 := project.InsertTaskBefore("", "Please complete this task. {SUCCESS_PROMPT}", func(task *taskcp.Task) error { return nil })
 	require.Contains(t, task1.Instructions, "my_service.set_task_success")
 	require.NotContains(t, task1.Instructions, "{SUCCESS_PROMPT}")
 	
-	task2 := project.InsertTaskBefore("", "Try this risky operation. {FAILURE_PROMPT}", func(task *taskcp.Task) {})
+	task2 := project.InsertTaskBefore("", "Try this risky operation. {FAILURE_PROMPT}", func(task *taskcp.Task) error { return nil })
 	require.Contains(t, task2.Instructions, "my_service.set_task_failure")
 	require.NotContains(t, task2.Instructions, "{FAILURE_PROMPT}")
 }
@@ -44,27 +45,56 @@ func TestTaskFlow(t *testing.T) {
 	
 	var completed []string
 	
-	task1 := project.InsertTaskBefore("", "First task", func(task *taskcp.Task) {
+	task1 := project.InsertTaskBefore("", "First task", func(task *taskcp.Task) error {
 		completed = append(completed, task.ID)
+		return nil
 	})
 	
-	task2 := project.InsertTaskBefore("", "Second task", func(task *taskcp.Task) {
+	task2 := project.InsertTaskBefore("", "Second task", func(task *taskcp.Task) error {
 		completed = append(completed, task.ID)
+		return nil
 	})
 	
 	current := project.GetNextTask()
 	require.NotNil(t, current)
 	require.Equal(t, task1.ID, current.ID)
 	
-	next := project.SetTaskSuccess(current.ID, "Task 1 done", "")
+	next, err := project.SetTaskSuccess(current.ID, "Task 1 done", "")
+	require.NoError(t, err)
 	require.NotNil(t, next)
 	require.Equal(t, task2.ID, next.ID)
 	require.Equal(t, taskcp.TaskStateRunning, next.State)
 	
-	next2 := project.SetTaskFailure(next.ID, "Task 2 failed", "Error details")
+	next2, err := project.SetTaskFailure(next.ID, "Task 2 failed", "Error details")
+	require.NoError(t, err)
 	require.Nil(t, next2)
 	
 	require.Equal(t, []string{task1.ID, task2.ID}, completed)
 	require.Equal(t, taskcp.TaskStateSuccess, project.Tasks[task1.ID].State)
 	require.Equal(t, taskcp.TaskStateFailure, project.Tasks[task2.ID].State)
 }
+
+func TestCallbackError(t *testing.T) {
+	service := taskcp.New("test_service")
+	project := service.AddProject()
+	
+	expectedErr := fmt.Errorf("callback error")
+	
+	task := project.InsertTaskBefore("", "Task with error callback", func(task *taskcp.Task) error {
+		return expectedErr
+	})
+	
+	current := project.GetNextTask()
+	require.NotNil(t, current)
+	require.Equal(t, task.ID, current.ID)
+	
+	// Test error propagation on success
+	_, err := project.SetTaskSuccess(current.ID, "Result", "")
+	require.Error(t, err)
+	require.Equal(t, expectedErr, err)
+	
+	// Test error propagation on failure
+	_, err = project.SetTaskFailure(current.ID, "Task failed", "")
+	require.Error(t, err)
+	require.Equal(t, expectedErr, err)
+}