Schema visibility control in GraphQL - Step-by-Step Execution

Concept Flow - Schema visibility control

Define full schema

↓

Apply visibility rules

↓

Filter schema elements

↓

Expose filtered schema to client

↓

Client queries visible schema only

Start with the full schema, apply rules to hide or show parts, then expose only visible parts to clients.

Execution Sample

GraphQL

type Query {
  publicData: String
  privateData: String @private
}

schemaVisibility: {
  privateData: false
}

This schema hides 'privateData' field from clients by marking it private and setting visibility to false.

Execution Table

Step	Schema Element	Visibility Rule	Visible to Client	Reason
1	Query type	No rule	Yes	Root type always visible
2	publicData field	No rule	Yes	No visibility restriction
3	privateData field	@private directive	No	Marked private, visibility false
4	Expose schema	Filtered	Only publicData visible	privateData filtered out
5	Client query	Sees only publicData	Yes	privateData hidden

💡 All schema elements processed; privateData hidden due to visibility rule

Variable Tracker

Schema Element	Initial Visibility	After Rule Applied	Final Visibility
Query type	Visible	Visible	Visible
publicData	Visible	Visible	Visible
privateData	Visible	Hidden	Hidden

Key Moments - 2 Insights

Why is 'privateData' not visible to the client even though it is defined in the schema?

Because the visibility rule '@private' and schemaVisibility setting false hide it, as shown in execution_table step 3 and 4.

Does the root Query type ever get hidden by visibility rules?

No, the root Query type remains visible to allow clients to query public fields, as shown in execution_table step 1.

Visual Quiz - 3 Questions

Look at the execution table, which schema element is hidden from the client?

A Query type

B privateData field

C publicData field

D None

💡 Hint

Check execution_table row 3 where privateData is marked not visible

At which step does the schema get filtered to hide private fields?

A Step 4

B Step 3

C Step 1

D Step 5

💡 Hint

Look at execution_table step 4 where schema is exposed filtered

If the '@private' directive is removed from 'privateData', what happens to its visibility?

A It remains hidden

B Query type becomes hidden

C It becomes visible

D publicData becomes hidden

💡 Hint

Refer to variable_tracker where visibility changes after rule applied

Concept Snapshot

Schema visibility control in GraphQL:
- Define full schema with all fields
- Use directives like @private to mark hidden fields
- Apply visibility rules to filter schema
- Expose only visible parts to clients
- Clients can query only visible schema elements

Full Transcript

Schema visibility control means starting with a full GraphQL schema and then applying rules to hide some parts from clients. For example, fields marked with a @private directive can be hidden by setting their visibility to false. The system filters out these hidden fields before sending the schema to clients. This way, clients only see and can query the parts of the schema that are allowed. The root Query type always stays visible so clients have an entry point. This process ensures sensitive or internal data is not exposed unintentionally.

Practice

1. What is the main purpose of schema visibility control in GraphQL?

easy

A. To limit what parts of the schema users can see or access

B. To speed up query execution by caching results

C. To automatically generate schema documentation

D. To convert GraphQL queries into SQL queries

Solution

1. Step 1: Understand schema visibility control concept

   Schema visibility control is about restricting access to parts of the GraphQL schema based on user roles or permissions.

2. Step 2: Identify the main goal

   The goal is to protect sensitive data and tailor the API by limiting what users can see or use.

3. Final Answer:

   To limit what parts of the schema users can see or access -> Option A

4. Quick Check:

   Schema visibility control = limit schema access [OK]

Hint: Focus on access limits, not performance or docs [OK]

Common Mistakes:

• Confusing visibility control with caching
• Thinking it auto-generates docs
• Assuming it converts queries to SQL

2. Which of the following is a correct way to hide a field in a GraphQL schema using a directive?

easy

A. @deprecated(reason: "hidden") on the field

B. @private on the query operation

C. @skip(if: false) on the schema type

D. @hide(if: true) on the field definition

Solution

1. Step 1: Understand directive usage for visibility

   Directives like @hide(if: true) can be used on fields to conditionally hide them based on logic.

2. Step 2: Evaluate options

   @private is not a standard directive; @skip(if: false) means do not skip (show field); @deprecated marks fields as deprecated but does not hide them.

3. Final Answer:

   @hide(if: true) on the field definition -> Option D

4. Quick Check:

   Use conditional directives like @hide to control visibility [OK]

Hint: Look for conditional directive on field, not operation [OK]

Common Mistakes:

• Using @deprecated to hide fields
• Applying directives on queries instead of fields
• Misunderstanding @skip logic

3. Given this schema snippet with a visibility directive:

type User {
  id: ID!
  email: String @hide(if: $isGuest)
  name: String
}

What fields will a guest user see if $isGuest is true?

medium

A. id and name only

B. id, email, and name

C. email and name only

D. id and email only

Solution

1. Step 1: Analyze the directive condition

   The @hide(if: $isGuest) directive hides the email field when $isGuest is true.

2. Step 2: Determine visible fields for guest

   Since $isGuest is true, email is hidden. The visible fields are id and name.

3. Final Answer:

   id and name only -> Option A

4. Quick Check:

   @hide(if: true) hides field = id and name visible [OK]

Hint: True condition hides field, so exclude it [OK]

Common Mistakes:

• Including hidden fields in output
• Confusing @hide with @skip
• Ignoring variable values in directives

4. You wrote this directive to hide a field:

email: String @hide(if: isGuest)

But the field is always visible. What is the likely error?

medium

A. Using @hide on a field is not supported

B. Missing $ before variable name in directive condition

C. The field type String cannot have directives

D. The directive should be @skip, not @hide

Solution

1. Step 1: Check variable usage in directive

   GraphQL variables in directives must be prefixed with $. Here, isGuest is missing $.

2. Step 2: Understand impact of missing $

   Without $, the directive condition is invalid or always false, so the field is never hidden.

3. Final Answer:

   Missing $ before variable name in directive condition -> Option B

4. Quick Check:

   Variables need $ prefix in directives [OK]

Hint: Always prefix variables with $ in directives [OK]

Common Mistakes:

• Forgetting $ before variable in directive
• Assuming @hide is unsupported
• Thinking directives can't be on scalar fields

5. You want to create a GraphQL API that shows users' email only to admins and hides it from regular users. Which approach best implements this schema visibility control?

hard

A. Return null for email in resolver for regular users without schema changes

B. Remove the email field from the schema entirely

C. Use @hide(if: $isNotAdmin) on the email field and pass $isNotAdmin from server context

D. Use @deprecated directive on email field for regular users

Solution

1. Step 1: Identify requirement for conditional visibility

   The email field should be visible only to admins, so visibility depends on user role.

2. Step 2: Evaluate options for controlling visibility

   Use a directive like @hide(if: $isNotAdmin) on the email field and pass $isNotAdmin from server context. This uses a directive with a variable from server context to hide email for non-admins, which is the correct schema visibility control method.

3. Step 3: Understand why other options fail

   Removing the field removes it for all users; @deprecated only marks as outdated; returning null hides data but not schema field.

4. Final Answer:

   Use @hide(if: $isNotAdmin) on the email field and pass $isNotAdmin from server context -> Option C

5. Quick Check:

   Use conditional directives with server variables for visibility [OK]

Hint: Use directives with server variables for role-based hiding [OK]

Common Mistakes:

• Removing fields instead of hiding conditionally
• Using @deprecated to hide fields
• Returning null but not hiding schema field