Why Field-level permissions in GraphQL? - Purpose & Use Cases

The Big Idea

What if you could share data safely without worrying about who sees what?

The Scenario

Imagine you have a big spreadsheet with sensitive info like salaries and personal contacts mixed with general data. You want to share it with your team, but only let some people see certain columns.

The Problem

Manually hiding or sharing parts of the spreadsheet is slow and risky. You might forget to hide a column or accidentally share sensitive info. It's hard to keep track and update permissions as people join or leave.

The Solution

Field-level permissions let you set rules so only the right people see the right data fields automatically. This keeps sensitive info safe without extra work every time you share or update data.

Before vs After

✗ Before

if(user.role == 'admin') { show salary; } else { hide salary; }

✓ After

type User @auth(rules: [{ allow: owner }]) { salary: Int @auth(rules: [{ allow: groups, groups: ["Admin"] }]) }

What It Enables

It enables secure, automatic control over who can see each piece of data, making sharing safe and simple.

Real Life Example

A company's HR system shows employee names to all staff but only lets managers see salaries and personal details, all controlled automatically by field-level permissions.

Key Takeaways

Manual data sharing risks exposing sensitive info.

Field-level permissions automate who sees what data.

This keeps data safe and sharing easy.

Practice

1. What is the main purpose of field-level permissions in GraphQL?

easy

A. To cache query results

B. To control access to individual data fields

C. To define the schema structure

D. To speed up query execution

Solution

1. Step 1: Understand the concept of field-level permissions

   Field-level permissions restrict who can see or edit specific fields in data, protecting sensitive information.

2. Step 2: Identify the main purpose

   The main goal is to control access to individual data fields, not to speed up queries or define schema structure.

3. Final Answer:

   To control access to individual data fields -> Option B

4. Quick Check:

   Field-level permissions = control access [OK]

Hint: Focus on access control for each field, not overall schema [OK]

Common Mistakes:

• Confusing permissions with schema design
• Thinking it speeds up queries
• Assuming it caches data

2. Which of the following is the correct way to apply a field-level permission directive in a GraphQL schema?

easy

A. type User { email: String @auth(role: "admin") }

B. type User { email: String auth(role: "admin") }

C. type User { email: String @auth[role="admin"] }

D. type User { email: String #auth(role: "admin") }

Solution

1. Step 1: Recall GraphQL directive syntax

   Directives use the @directiveName(arguments) format placed after the field type.

2. Step 2: Match the correct syntax

   type User { email: String @auth(role: "admin") } uses @auth(role: "admin") correctly. Options A, B, and D have syntax errors or wrong symbols.

3. Final Answer:

   type User { email: String @auth(role: "admin") } -> Option A

4. Quick Check:

   Directive syntax = @name(args) [OK]

Hint: Remember directives start with @ and use parentheses [OK]

Common Mistakes:

• Omitting the @ symbol
• Using brackets [] instead of parentheses ()
• Commenting out the directive

3. Given this GraphQL query and schema with field-level permissions:

type User { id: ID! name: String email: String @auth(role: "admin") }

If a user with role "user" runs:

{ user { id name email } }

What will be the result?

medium

A. { "data": { "user": { "id": "1", "name": "Alice", "email": "[e-mail]" } } }

B. { "data": { "user": { "id": "1", "name": "Alice", "email": null } } }

C. Error: Unauthorized to access field 'email'

D. { "data": { "user": { "id": "1", "name": "Alice" } } }

Solution

1. Step 1: Understand the permission on the email field

   The @auth(role: "admin") directive restricts email access to admin role only.

2. Step 2: Predict query result for a user role

   The user role is not admin, so email field is omitted from the response, not returned as null or error.

3. Final Answer:

   { "data": { "user": { "id": "1", "name": "Alice" } } } -> Option D

4. Quick Check:

   Unauthorized fields are omitted, not null or error [OK]

Hint: Unauthorized fields are hidden, not null or error [OK]

Common Mistakes:

• Expecting null instead of omitted field
• Expecting an error response
• Assuming all fields return regardless of role

4. You wrote this schema snippet:

type User { id: ID! name: String email: String @auth(role: admin) }

Why does this cause an error when applying field-level permissions?

medium

A. The role value admin should be a string in quotes

B. The @auth directive is not allowed on fields

C. ID! type cannot have directives

D. The email field must be nullable to use permissions

Solution

1. Step 1: Check the directive argument syntax

   Directive arguments must be valid GraphQL values; strings require quotes.

2. Step 2: Identify the error in role argument

   The role value admin is unquoted, causing a syntax error. It should be "admin".

3. Final Answer:

   The role value admin should be a string in quotes -> Option A

4. Quick Check:

   Directive args strings need quotes [OK]

Hint: Always put string arguments in quotes inside directives [OK]

Common Mistakes:

• Forgetting quotes around string arguments
• Thinking directives can't be on fields
• Assuming non-null types disallow directives

5. You want to allow users to see their own email field but only admins to see others' emails. Which field-level permission setup achieves this?

hard

A. Use @auth(role: "admin") on email field only

B. Make email field public and filter in resolver

C. Use a custom directive checking if user is owner or admin

D. Remove email field from schema and add a separate query

Solution

1. Step 1: Analyze the requirement

   Users can see their own email; admins can see all emails. This needs conditional logic.

2. Step 2: Evaluate options for conditional access

   Use a custom directive checking if user is owner or admin uses a custom directive to check ownership or admin role, fitting the requirement precisely.

3. Step 3: Why other options fail

   Use @auth(role: "admin") on email field only restricts email only to admins, blocking users from their own email. Make email field public and filter in resolver exposes email publicly, unsafe. Remove email field from schema and add a separate query complicates schema unnecessarily.

4. Final Answer:

   Use a custom directive checking if user is owner or admin -> Option C

5. Quick Check:

   Conditional access needs custom logic [OK]

Hint: Use custom directives for complex permission logic [OK]

Common Mistakes:

• Using simple role checks only
• Exposing sensitive fields publicly
• Overcomplicating schema with extra queries