Schema linting in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main purpose of schema linting in GraphQL?

Schema linting helps developers by:

• A. Checking the schema for errors and style issues before deployment
• B. Automatically generating queries from the schema
• C. Running queries faster by optimizing the schema
• D. Encrypting the schema for security

A Checking the schema for errors and style issues before deployment

B Automatically generating queries from the schema

C Running queries faster by optimizing the schema

D Encrypting the schema for security

💡 Hint

Think about what 'linting' usually means in programming.

Schema linting is the process of checking the GraphQL schema for mistakes or style problems before it is used. It helps catch errors early.

❓ query_result

intermediate

What error will this GraphQL schema linting tool report?

Given this schema snippet:

type User { id: ID! name: String! age: Int }

The linting tool requires all fields to have descriptions. What is the linting error?

A Missing description for field 'age'

B Missing description for field 'name'

C Missing description for field 'id'

D No errors found

💡 Hint

Check which fields lack descriptions.

The linting tool expects every field to have a description. Since 'id' has no description, it reports that error first.

📝 Syntax

advanced

Which schema snippet will cause a linting syntax error?

Identify the schema snippet that will fail linting due to syntax issues:

A type Query { user(id: ID!): User type User { id: ID! name: String! }

B type Query { user(id: ID!): User } type User { id: ID! name: String! }

C type Query { user(id: ID!): User } type User { id: ID! name: String! age: Int }

D type Query { user(id: ID!): User } type User { id: ID! name: String! } enum Role { ADMIN USER }

💡 Hint

Look for missing braces or keywords.

Option A is missing a closing brace for the Query type, causing a syntax error during linting.

❓ optimization

advanced

How can schema linting improve GraphQL API performance?

Choose the best explanation for how schema linting can indirectly improve API performance:

A By automatically caching all queries defined in the schema

B By encrypting schema fields to speed up data retrieval

C By compressing the schema file size to reduce network load

D By detecting inefficient schema designs that cause slow queries

💡 Hint

Think about how errors or bad designs affect query speed.

Linting can find schema design issues like deeply nested fields or missing indexes that slow down queries, helping developers fix them.

🔧 Debug

expert

Why does this schema linting tool report a duplicate type error?

Given these schema definitions:

type Product { id: ID! name: String! } type Product { sku: String! price: Float! }

What is the cause of the linting error?

A The 'Product' type is missing a description

B The 'Product' type is defined twice with different fields

C The 'Product' type fields have conflicting types

D The schema is missing a Query type

💡 Hint

Check if type names are unique in the schema.

GraphQL schemas cannot have two types with the same name. Defining 'Product' twice causes a duplicate type error during linting.

Practice

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

easy

A. To generate database tables automatically

B. To execute queries faster

C. To check the schema for mistakes and style issues

D. To encrypt data in the schema

Solution

1. Step 1: Understand schema linting role

   Schema linting is used to find errors and style problems in GraphQL schemas.

2. Step 2: Compare with other options

   Options B, C, and D describe unrelated tasks like query speed, database creation, or encryption.

3. Final Answer:

   To check the schema for mistakes and style issues -> Option C

4. Quick Check:

   Schema linting = check mistakes and style [OK]

Hint: Linting means checking code or schema for errors [OK]

Common Mistakes:

• Confusing linting with query execution
• Thinking linting creates database tables
• Assuming linting encrypts data

2. Which of the following is a correct way to define a linting rule for a GraphQL schema?

easy

A. schemaLint: off

B. lintSchema = false

C. enableLinting = 0

D. "no-unused-types": true

Solution

1. Step 1: Identify correct lint rule syntax

   Linting rules are usually defined as key-value pairs like "no-unused-types": true.

2. Step 2: Check other options for syntax errors

   Options A, B, and D use invalid or incorrect syntax for linting rules.

3. Final Answer:

   "no-unused-types": true -> Option D

4. Quick Check:

   Lint rule syntax = key: value [OK]

Hint: Lint rules use key-value pairs like "rule-name": true [OK]

Common Mistakes:

• Using assignment (=) instead of key-value pairs
• Using invalid property names
• Turning off linting with wrong syntax

3. Given this linting configuration snippet:

{
  "no-deprecated-fields": true,
  "require-description": true
}

What will happen if the schema uses a deprecated field without a description?

medium

A. Linting will pass without errors

B. Linting will report errors for both deprecated field and missing description

C. Linting will only check for missing descriptions

D. Linting will ignore deprecated fields

Solution

1. Step 1: Analyze linting rules

   "no-deprecated-fields": true means deprecated fields cause errors. "require-description": true means missing descriptions cause errors.

2. Step 2: Apply rules to schema case

   Schema has a deprecated field without description, so both rules trigger errors.

3. Final Answer:

   Linting will report errors for both deprecated field and missing description -> Option B

4. Quick Check:

   Both rules active = errors for both issues [OK]

Hint: Active lint rules cause errors for matching schema issues [OK]

Common Mistakes:

• Assuming lint ignores deprecated fields
• Thinking only one rule applies
• Believing missing description is allowed

4. You run a schema linter and get an error: Field 'userAge' is missing a description. Which fix will resolve this error?

medium

A. Add a description string above the 'userAge' field in the schema

B. Rename the field to 'ageUser'

C. Remove the 'userAge' field from the schema

D. Ignore the error and continue

Solution

1. Step 1: Understand the error meaning

   The error says the field lacks a description, so the linter expects a comment or description string.

2. Step 2: Choose the fix that adds description

   Adding a description string above the field satisfies the linter. Renaming or removing the field or ignoring the error does not fix the missing description.

3. Final Answer:

   Add a description string above the 'userAge' field in the schema -> Option A

4. Quick Check:

   Missing description = add description [OK]

Hint: Add descriptions as comments to fix missing description errors [OK]

Common Mistakes:

• Renaming field instead of adding description
• Deleting field unnecessarily
• Ignoring lint errors

5. You want to enforce that all GraphQL schema types have descriptions and no unused types exist. Which combined linting configuration achieves this?

hard

A. { "require-description": true, "no-unused-types": true }

B. { "allow-unused-types": true, "require-description": false }

C. { "no-deprecated-fields": true, "allow-unused-types": false }

D. { "require-description": false, "no-unused-types": false }

Solution

1. Step 1: Identify rules for descriptions and unused types

   "require-description": true enforces descriptions. "no-unused-types": true disallows unused types.

2. Step 2: Match configuration to requirements

   { "require-description": true, "no-unused-types": true } sets both rules to true, matching the goal. Other options disable one or both rules.

3. Final Answer:

   { "require-description": true, "no-unused-types": true } -> Option A

4. Quick Check:

   Both rules true = enforce descriptions and no unused types [OK]

Hint: Set both rules true to enforce descriptions and no unused types [OK]

Common Mistakes:

• Disabling required rules
• Confusing allow and no rules
• Partial enforcement only