Wasp Operations Skill

Quick Reference

When to use this skill:

• Creating new queries or actions
• Implementing backend operations
• Working with operations.ts files
• Setting up client-server communication
• Need auth checks, permissions, or validation patterns

Key concepts:

• Queries: Read operations using useQuery hook
• Actions: Write operations using direct async/await (NOT useAction by default)
• Type annotations: CRITICAL for context.entities access
• Auto-invalidation: Queries refetch when actions with same entities complete

---

Complete Workflow

1. Define in main.wasp

Location: app/main.wasp

Query declaration (READ operations):

query getTasks {
  fn: import { getTasks } from "@src/server/tasks/operations",
  entities: [Task]  // REQUIRED for context.entities + auto-invalidation
}

query getTask {
  fn: import { getTask } from "@src/server/tasks/operations",
  entities: [Task]
}

Action declaration (WRITE operations):

action createTask {
  fn: import { createTask } from "@src/server/tasks/operations",
  entities: [Task]  // Same entities as getTasks → auto-invalidates getTasks!
}

action updateTask {
  fn: import { updateTask } from "@src/server/tasks/operations",
  entities: [Task]  // Auto-invalidates getTasks query
}

action deleteTask {
  fn: import { deleteTask } from "@src/server/tasks/operations",
  entities: [Task]  // Auto-invalidates getTasks query
}

Critical rules:

• ✅ Use @src/ prefix in main.wasp imports (NOT relative paths)
• ✅ List ALL entities accessed in entities: [...] array
• ✅ Same entities in query + action = auto-invalidation

---

2. Implement in operations.ts

Location: app/src/{feature}/operations.ts (one file per feature)

Required imports:

import { HttpError } from "wasp/server";
import type {
  GetTasks,
  GetTask,
  CreateTask,
  UpdateTask,
  DeleteTask,
} from "wasp/server/operations";
import type { Task } from "wasp/entities";

Import rules:

• ✅ wasp/server for HttpError
• ✅ wasp/server/operations for type annotations
• ✅ wasp/entities for entity types
• ❌ NEVER use @wasp/... (wrong prefix)
• ❌ NEVER use @src/... in .ts files (use relative paths)

---

3. Pattern Library

Query Pattern: Get All (with filtering)

/**
 * Get all tasks for authenticated user
 *
 * Features:
 * - Auth check
 * - Optional filtering
 * - Returns array
 */
export const getTasks: GetTasks<
  { status?: string }, // Args type
  Task[] // Return type
> = async (args, context) => {
  // 1. ALWAYS check auth first (MANDATORY)
  if (!context.user) throw new HttpError(401);

  // 2. Build query with optional filters
  const where: any = { userId: context.user.id };
  if (args.status) {
    where.status = args.status;
  }

  // 3. Query with context.entities (enabled by type annotation + entities in main.wasp)
  return context.entities.Task.findMany({
    where,
    orderBy: { createdAt: "desc" },
    include: {
      // Include related entities to avoid N+1 queries
      user: {
        select: { id: true, username: true },
      },
    },
  });
};

Key points:

• Type annotation GetTasks<Args, Return> is CRITICAL
• Without type annotation: context.entities is undefined!
• Auth check is FIRST line (security requirement)
• Use Prisma include for relations (avoid N+1 queries)

---

Query Pattern: Get Single (with permission check)

/**
 * Get single task by ID
 *
 * Features:
 * - Auth check
 * - Resource existence check (404)
 * - Permission check (403)
 * - Returns single entity or throws
 */
export const getTask: GetTask<
  { id: string }, // Args type
  Task // Return type
> = async (args, context) => {
  // 1. Auth check
  if (!context.user) throw new HttpError(401);

  // 2. Fetch resource
  const taskRecord = await context.entities.Task.findUnique({
    where: { id: args.id },
    include: {
      user: {
        select: { id: true, username: true },
      },
    },
  });

  // 3. Check existence (404)
  if (!taskRecord) {
    throw new HttpError(404, "Task not found");
  }

  // 4. Check permission (403)
  if (taskRecord.userId !== context.user.id) {
    throw new HttpError(403, "Not authorized to access this task");
  }

  // 5. Return resource
  return taskRecord;
};

Error sequence (CRITICAL):

1. 401 Unauthorized: No user (unauthenticated)
2. 404 Not Found: Resource doesn't exist
3. 403 Forbidden: User lacks permission
4. 400 Bad Request: Invalid input

Always check in this order!

---

Action Pattern: Create (with validation)

/**
 * Create new task
 *
 * Features:
 * - Auth check
 * - Input validation
 * - Auto-invalidates getTasks query
 * - Returns created entity
 */
export const createTask: CreateTask<
  { description: string; status?: string }, // Args type
  Task // Return type
> = async (args, context) => {
  // 1. Auth check
  if (!context.user) throw new HttpError(401);

  // 2. Validate input
  if (!args.description?.trim()) {
    throw new HttpError(400, "Description is required");
  }

  if (args.description.length > 500) {
    throw new HttpError(400, "Description must be 500 characters or less");
  }

  // 3. Create entity
  const taskRecord = await context.entities.Task.create({
    data: {
      description: args.description.trim(),
      status: args.status || "TODO",
      userId: context.user.id,
    },
  });

  // 4. Return created entity
  // Note: getTasks query auto-refetches if entities match in main.wasp
  return taskRecord;
};

Auto-invalidation magic:

• createTask has entities: [Task]
• getTasks has entities: [Task]
• When createTask completes → getTasks auto-refetches!
• No manual cache invalidation needed

---

Action Pattern: Update (with validation + permission)

/**
 * Update existing task
 *
 * Features:
 * - Auth check
 * - Resource existence check
 * - Permission check
 * - Input validation
 * - Partial updates
 */
export const updateTask: UpdateTask<
  { id: string; data: { description?: string; status?: string } },
  Task
> = async (args, context) => {
  // 1. Auth check
  if (!context.user) throw new HttpError(401);

  // 2. Fetch existing resource
  const taskRecord = await context.entities.Task.findUnique({
    where: { id: args.id },
  });

  // 3. Check existence (404)
  if (!taskRecord) {
    throw new HttpError(404, "Task not found");
  }

  // 4. Check permission (403)
  if (taskRecord.userId !== context.user.id) {
    throw new HttpError(403, "Not authorized to update this task");
  }

  // 5. Validate input (if provided)
  if (args.data.description !== undefined) {
    if (!args.data.description.trim()) {
      throw new HttpError(400, "Description cannot be empty");
    }
    if (args.data.description.length > 500) {
      throw new HttpError(400, "Description must be 500 characters or less");
    }
  }

  // 6. Update entity
  const updatedTask = await context.entities.Task.update({
    where: { id: args.id },
    data: {
      ...(args.data.description && {
        description: args.data.description.trim(),
      }),
      ...(args.data.status && { status: args.data.status }),
    },
  });

  // 7. Return updated entity
  return updatedTask;
};

Partial update pattern:

• Use spread operator with conditional fields
• Validate only provided fields
• Preserve existing values if not updated

---

Action Pattern: Delete (with permission check)

/**
 * Delete task
 *
 * Features:
 * - Auth check
 * - Resource existence check
 * - Permission check
 * - Returns deleted entity
 */
export const deleteTask: DeleteTask<{ id: string }, Task> = async (
  args,
  context,
) => {
  // 1. Auth check
  if (!context.user) throw new HttpError(401);

  // 2. Fetch existing resource
  const taskRecord = await context.entities.Task.findUnique({
    where: { id: args.id },
  });

  // 3. Check existence (404)
  if (!taskRecord) {
    throw new HttpError(404, "Task not found");
  }

  // 4. Check permission (403)
  if (taskRecord.userId !== context.user.id) {
    throw new HttpError(403, "Not authorized to delete this task");
  }

  // 5. Delete entity
  const deletedTask = await context.entities.Task.delete({
    where: { id: args.id },
  });

  // 6. Return deleted entity
  return deletedTask;
};

---

4. Use in Client Code

Location: app/src/{feature}/components/*.tsx

Required imports:

import {
  useQuery,
  createTask,
  updateTask,
  deleteTask,
} from "wasp/client/operations";

Query usage (useQuery hook):

function TasksPage() {
  // Use useQuery hook for queries
  const {
    data: tasks,      // Task[] | undefined
    isLoading,        // boolean
    error             // Error | undefined
  } = useQuery(getTasks, { status: 'TODO' })  // Optional args

  // Handle loading state
  if (isLoading) return <div>Loading...</div>

  // Handle error state
  if (error) return <div>Error: {error.message}</div>

  // Handle empty state
  if (!tasks || tasks.length === 0) return <div>No tasks</div>

  // Render data
  return (
    <div>
      {tasks.map((task) => (
        <TaskItem key={task.id} task={task} />
      ))}
    </div>
  )
}

Action usage (direct async/await - DEFAULT):

function TaskForm() {
  const handleCreate = async (description: string) => {
    try {
      // ✅ CORRECT - Direct call (default approach)
      await createTask({ description, status: "TODO" });
      toast.success("Task created");
      // Wasp auto-refetches getTasks query!
    } catch (err) {
      toast.error(err instanceof Error ? err.message : "Failed to create task");
    }
  };

  const handleUpdate = async (id: string, data: any) => {
    try {
      await updateTask({ id, data });
      toast.success("Task updated");
    } catch (err) {
      toast.error(err instanceof Error ? err.message : "Failed to update task");
    }
  };

  const handleDelete = async (id: string) => {
    try {
      await deleteTask({ id });
      toast.success("Task deleted");
    } catch (err) {
      toast.error(err instanceof Error ? err.message : "Failed to delete task");
    }
  };

  // ... rest of component
}

CRITICAL: DO NOT use useAction by default!

// ❌ WRONG - useAction by default
const createTaskFn = useAction(createTask);
await createTaskFn(data);
// Blocks auto-invalidation, adds unnecessary complexity

// ✅ CORRECT - Direct call
await createTask(data);
// Simpler AND enables auto-invalidation

ONLY use useAction for optimistic UI updates (advanced):

// Advanced pattern - optimistic updates
const deleteTaskFn = useAction(deleteTask, {
  optimisticUpdates: [
    {
      getQuerySpecifier: () => [getTasks],
      updateQuery: (oldTasks, { id }) => {
        return oldTasks.filter((task) => task.id !== id);
      },
    },
  ],
});

const handleOptimisticDelete = async (id: string) => {
  try {
    // UI updates immediately (optimistic)
    // Query refetches in background (actual)
    await deleteTaskFn({ id });
    toast.success("Task deleted");
  } catch (err) {
    // Optimistic update reverted if error
    toast.error("Failed to delete task");
  }
};

When to use optimistic updates:

• Critical user experience (perceived speed)
• Action highly likely to succeed
• Complex UI state needs immediate feedback

---

5. Restart Wasp (MANDATORY)

After adding/modifying operations in main.wasp:

# Stop current wasp process (Ctrl+C), then safe-start (multi-worktree safe)
../scripts/safe-start.sh

Why restart is needed:

• Type definitions regenerate only on restart
• New operation types won't be available until restart
• Changes to entities list require restart

Common error if you forget:

Cannot find module 'wasp/server/operations'
  or
Property 'Task' does not exist on type 'Context'

Fix: Stop wasp (Ctrl+C) and run ../scripts/safe-start.sh (multi-worktree safe)

---

Advanced Patterns

Pattern: Complex Permission Check

/**
 * Check if user can access resource based on multiple criteria
 */
async function canAccessTask(
  userId: string,
  taskId: string,
  context: any,
): Promise<boolean> {
  const taskRecord = await context.entities.Task.findUnique({
    where: { id: taskId },
    include: {
      project: {
        include: {
          members: true,
        },
      },
    },
  });

  if (!taskRecord) return false;

  // Owner can access
  if (taskRecord.userId === userId) return true;

  // Project members can access
  if (taskRecord.project?.members.some((m: any) => m.userId === userId)) {
    return true;
  }

  // Organization admins can access
  const userRole = await getUserOrgRole(userId, task.organizationId, context);
  if (["OWNER", "ADMIN"].includes(userRole)) return true;

  return false;
}

// Usage in operation
export const getTask: GetTask<{ id: string }, Task> = async (args, context) => {
  if (!context.user) throw new HttpError(401);

  const hasAccess = await canAccessTask(context.user.id, args.id, context);
  if (!hasAccess) throw new HttpError(403, "Not authorized");

  return context.entities.Task.findUnique({ where: { id: args.id } });
};

---

Pattern: Input Validation with Zod

import { z } from "zod";

const CreateTaskSchema = z.object({
  description: z.string().min(1, "Description required").max(500, "Too long"),
  status: z.enum(["TODO", "IN_PROGRESS", "DONE"]).optional(),
  dueDate: z.string().datetime().optional(),
});

export const createTask: CreateTask = async (args, context) => {
  if (!context.user) throw new HttpError(401);

  try {
    const validated = CreateTaskSchema.parse(args);
    return await context.entities.Task.create({
      data: { ...validated, userId: context.user.id },
    });
  } catch (error) {
    if (error instanceof z.ZodError) {
      const messages = error.errors.map(
        (e) => `${e.path.join(".")}: ${e.message}`,
      );
      throw new HttpError(400, messages.join(", "));
    }
    throw error;
  }
};

Benefits:

• Type-safe validation
• Clear error messages
• Reusable schemas
• Complex validation rules

---

Pattern: Pagination

export const getTasks: GetTasks<
  { page?: number; pageSize?: number },
  { tasks: Task[]; total: number; hasMore: boolean }
> = async (args, context) => {
  if (!context.user) throw new HttpError(401);

  const page = args.page || 0;
  const pageSize = args.pageSize || 20;

  const [tasks, total] = await Promise.all([
    context.entities.Task.findMany({
      where: { userId: context.user.id },
      skip: page * pageSize,
      take: pageSize,
      orderBy: { createdAt: "desc" },
    }),
    context.entities.Task.count({
      where: { userId: context.user.id },
    }),
  ]);

  return {
    tasks,
    total,
    hasMore: (page + 1) * pageSize < total,
  };
};

Key points:

• Use skip and take for pagination
• Run count query in parallel with Promise.all
• Return metadata (total, hasMore) for UI

---

Pattern: Bulk Operations

export const deleteMultipleTasks: DeleteMultipleTasks<
  { ids: string[] },
  { count: number }
> = async (args, context) => {
  if (!context.user) throw new HttpError(401);

  // Verify user owns all tasks
  const tasks = await context.entities.Task.findMany({
    where: { id: { in: args.ids } },
  });

  const unauthorized = tasks.filter((task) => task.userId !== context.user.id);
  if (unauthorized.length > 0) {
    throw new HttpError(403, "Not authorized to delete some tasks");
  }

  // Bulk delete
  const result = await context.entities.Task.deleteMany({
    where: {
      id: { in: args.ids },
      userId: context.user.id,
    },
  });

  return { count: result.count };
};

Security note:

• ALWAYS verify permissions for ALL items
• Use deleteMany only after permission check
• Return count for UI feedback

---

Common Errors & Solutions

Error: "Cannot find module 'wasp/...'"

Cause: Using wrong import prefix or forgot to restart

Solutions:

1. Use wasp/... NOT @wasp/...
2. Restart wasp: ../scripts/safe-start.sh (multi-worktree safe)
3. Verify entity declared in main.wasp

// ❌ WRONG
import { Task } from "@wasp/entities";

// ✅ CORRECT
import { Task } from "wasp/entities";

---

Error: "Property 'Task' does not exist on type 'Context'"

Cause: Missing type annotation or entity not listed in main.wasp

Solutions:

1. Add type annotation: GetTasks<Args, Return>
2. Add entity to main.wasp: entities: [Task]
3. Restart wasp

// ❌ WRONG - No type annotation
export const getTasks = async (args, context) => {
  return context.entities.Task.findMany(); // context.entities is undefined!
};

// ✅ CORRECT - With type annotation
export const getTasks: GetTasks<void, Task[]> = async (args, context) => {
  return context.entities.Task.findMany(); // Works!
};

---

Error: Operation not auto-invalidating

Cause: Query and action have different entities lists

Solution: Use same entities in both

// ❌ WRONG - Different entities
query getTasks {
  entities: [Task]
}
action createTask {
  entities: [Task, User]  // Extra entities prevent auto-invalidation
}

// ✅ CORRECT - Same entities
query getTasks {
  entities: [Task]
}
action createTask {
  entities: [Task]  // Matches query → auto-invalidation works!
}

---

Error: "Not authorized" but user is logged in

Cause: Using wrong helper to access auth fields

Solution: Use Wasp helpers for email/username

// ❌ WRONG - Direct access
if (context.user.email === 'admin@example.com') { ... }  // UNDEFINED!

// ✅ CORRECT - Use helper
import { getEmail } from 'wasp/auth'

const email = getEmail(context.user)
if (email === 'admin@example.com') { ... }  // Works!

---

Critical Rules Checklist

✅ MUST DO:

1. Add type annotations

   • GetQuery<Args, Return>
   • CreateAction<Args, Return>
   • Without types: context.entities is undefined!

2. Check auth FIRST

   • if (!context.user) throw new HttpError(401)
   • First line of every operation
   • Security requirement

3. List entities in main.wasp

   • Required for context.entities access
   • Enables auto-invalidation between queries/actions
   • Add ALL entities accessed

4. Use direct await for actions (default)

   • await createTask(data) (simple, enables auto-invalidation)
   • NOT useAction(createTask) (only for optimistic UI)

5. Restart after main.wasp changes

   • Stop wasp (Ctrl+C)
   • Run ../scripts/safe-start.sh (multi-worktree safe)
   • Types only regenerate on restart

6. Follow error sequence

   • 401: Not authenticated
   • 404: Resource not found
   • 403: Not authorized
   • 400: Bad request

7. Avoid N+1 queries

   • Use Prisma include for relations
   • Fetch related data in single query

8. Validate input

   • Check required fields
   • Check length constraints
   • Use Zod for complex validation

❌ NEVER DO:

1. Skip type annotations

   • Result: context.entities undefined
   • Error: Cannot access entities

2. Skip auth check

   • Result: Security vulnerability
   • Anyone can access operations

3. Use useAction by default

   • Result: Blocks auto-invalidation
   • Adds unnecessary complexity

4. Forget to restart

   • Result: Types not updated
   • Imports fail

5. Use @wasp/ prefix

   • Correct: wasp/entities
   • Wrong: @wasp/entities

6. Use @src/ in .ts/.tsx files

   • Correct: ../../utils/helper
   • Wrong: @src/utils/helper

7. Access user.email directly

   • Correct: getEmail(user)
   • Wrong: user.email (undefined!)

8. Mix up enum imports

   • Types: import type { UserRole } from 'wasp/entities'
   • Values: import { UserRole } from '@prisma/client'

---

Complete Examples Reference

See .claude/templates/operations-patterns.ts for copy-paste ready examples:

• Lines 1-150: Query patterns (get all, get single, filtered queries)
• Lines 151-300: Action patterns (create, update, delete)
• Lines 301-450: Client-side usage (useQuery, direct calls, optimistic UI)
• Lines 451-594: Advanced patterns (permissions, validation, pagination, bulk ops)

---

Quick Decision Tree

Need to fetch data from server?
├─ YES → Create QUERY
│   1. Add query block to main.wasp
│   2. Implement with GetQuery<Args, Return> type
│   3. Use useQuery hook in client
│
└─ NO → Need to modify data?
    └─ YES → Create ACTION
        1. Add action block to main.wasp
        2. Implement with CreateAction<Args, Return> type
        3. Use direct await in client (NOT useAction)

---

Summary

This skill provides complete Wasp operations implementation guidance.

Key takeaways:

1. Type annotations are CRITICAL (enables context.entities)
2. Auth check is MANDATORY first line (security)
3. Use direct await for actions (NOT useAction by default)
4. Same entities in query + action = auto-invalidation
5. Restart after main.wasp changes (types regenerate)

When stuck:

• Check if type annotation added
• Verify entities listed in main.wasp
• Confirm ../scripts/safe-start.sh restarted after changes (multi-worktree safe)
• Review error sequence (401 → 404 → 403 → 400)
• Use helpers for auth fields (getEmail, getUsername)

For complete examples: See .claude/templates/operations-patterns.ts