GraphQL error format - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output error message format for a GraphQL query with a syntax error?

Consider a GraphQL query with a missing closing brace. What does the error response look like?

GraphQL

query { user(id: 1) { name }

A {"errors":[{"message":"Syntax Error: Expected Name, found <EOF>","locations":[{"line":1,"column":26}]}]}

B {"error":"Syntax error at line 1"}

C {"message":"Unexpected end of query"}

D {"errors":[{"msg":"Missing closing brace"}]}

💡 Hint

GraphQL errors include an 'errors' array with detailed message and location.

GraphQL returns errors as an array under 'errors' with 'message' and 'locations' keys describing the problem.

❓ query_result

intermediate

What does a GraphQL error response contain when a requested field does not exist?

If a query asks for a field 'age' on a type that does not have it, what error response is returned?

GraphQL

query { user(id: 1) { age } }

A {"message":"Invalid field age"}

B {"error":"Field age not found"}

C {"errors":[{"message":"Cannot query field \"age\" on type \"User\".","locations":[{"line":1,"column":15}]}]}

D {"errors":[{"msg":"Field age missing in schema"}]}

💡 Hint

GraphQL error messages specify the field and type causing the issue.

GraphQL errors specify the exact field and type that caused the error with location info.

📝 Syntax

advanced

Which option correctly shows the GraphQL error format for a validation error with multiple errors?

A query has two errors: a missing field and a wrong argument type. What is the correct error response format?

GraphQL

query { user(id: "abc") { name age } }

A {"errors":[{"message":"Argument \"id\" has invalid value \"abc\".","locations":[{"line":1,"column":13}]},{"message":"Cannot query field \"age\" on type \"User\".","locations":[{"line":1,"column":25}]}]}

B {"errors":[{"msg":"Invalid id argument"},{"msg":"Field age missing"}]}

C {"error":"Multiple errors found"}

D {"errors":[{"message":"id argument error"},{"message":"age field error"}]}

💡 Hint

GraphQL errors list each error with message and location in an array.

GraphQL returns multiple errors as objects in the 'errors' array with detailed messages and locations.

🧠 Conceptual

advanced

What key fields are always present in a GraphQL error object?

Select the fields that are always included in each error object returned by a GraphQL server.

A "error" and "code"

B "message" and "locations"

C "msg" and "line"

D "description" and "position"

💡 Hint

Look for the standard keys used in GraphQL error objects.

GraphQL error objects always include 'message' describing the error and 'locations' showing where it happened.

🔧 Debug

expert

Why does this GraphQL error response cause a client parsing failure?

Given this error response: {"errors":[{"message":"Field 'name' not found"}]} but the client expects 'locations' field as well, what is the issue?

A The JSON is invalid because of missing commas.

B The 'message' field is incorrectly formatted as a string instead of an object.

C The 'errors' key should be a string, not an array.

D The error object is missing the required 'locations' field, causing client parsing failure.

💡 Hint

GraphQL clients expect a consistent error object structure.

GraphQL error objects must include 'locations' to indicate where the error occurred; missing it can break clients expecting it.

Practice

1. What is the main purpose of the message field in a GraphQL error response?

easy

A. To describe what went wrong in the query

B. To show the exact line of code where the error occurred

C. To list all the fields requested in the query

D. To provide the user's authentication token

Solution

1. Step 1: Understand the role of the message field

   The message field clearly states the error description to help identify the problem.

2. Step 2: Compare with other fields

   Other fields like location show where the error happened, but message explains what the error is.

3. Final Answer:

   To describe what went wrong in the query -> Option A

4. Quick Check:

   message = error description [OK]

Hint: Message always explains the error clearly [OK]

Common Mistakes:

• Confusing message with location
• Thinking message holds query data
• Assuming message is optional

2. Which of the following is the correct structure of a GraphQL error object?

easy

A. { message: string, location: string, path: string }

B. { error: string, line: int, column: int, path: string }

C. { message: string, line: int, column: int, query: string }

D. { message: string, location: [{ line: int, column: int }], path: [string] }

Solution

1. Step 1: Recall GraphQL error object format

   GraphQL errors include message, location as an array of line and column objects, and path as an array of strings.

2. Step 2: Check each option's structure

   Only { message: string, location: [{ line: int, column: int }], path: [string] } matches the correct structure with proper types and nesting.

3. Final Answer:

   { message: string, location: [{ line: int, column: int }], path: [string] } -> Option D

4. Quick Check:

   Correct error object format = { message: string, location: [{ line: int, column: int }], path: [string] } [OK]

Hint: Look for location as array of line/column objects [OK]

Common Mistakes:

• Using location as a string
• Confusing path type with string instead of array
• Missing array brackets for location

3. Given this GraphQL error response snippet:

{"errors": [{"message": "Cannot query field 'age' on type 'User'", "locations": [{"line": 3, "column": 5}], "path": ["user", "age"]}]}

What does the path field indicate?

medium

A. The exact location in the query text where the error occurred

B. The sequence of fields leading to the error in the response data

C. The server file path where the error was logged

D. The user's file system path

Solution

1. Step 1: Understand the path field meaning

   The path shows the chain of fields in the response data that led to the error.

2. Step 2: Analyze the example path

   Here, the error is in the 'age' field inside the 'user' object, so path is ["user", "age"].

3. Final Answer:

   The sequence of fields leading to the error in the response data -> Option B

4. Quick Check:

   path = error location in response data [OK]

Hint: Path shows field chain causing error [OK]

Common Mistakes:

• Thinking path is query text location
• Confusing path with server file path
• Ignoring path as array of fields

4. You receive this GraphQL error response:

{"errors": [{"message": "Syntax Error: Expected Name, found }", "locations": [{"line": 5, "column": 10}]}]}

What is the most likely cause of this error?

medium

A. A missing or extra character in the query causing invalid syntax

B. A missing authentication token in the request headers

C. A server crash unrelated to the query

D. A network timeout error

Solution

1. Step 1: Interpret the error message

   The message says "Syntax Error: Expected Name, found }", indicating a syntax mistake in the query.

2. Step 2: Understand syntax errors in GraphQL

   Such errors happen when brackets, names, or punctuation are missing or misplaced in the query text.

3. Final Answer:

   A missing or extra character in the query causing invalid syntax -> Option A

4. Quick Check:

   Syntax error = query typo [OK]

Hint: Syntax errors mean query text is malformed [OK]

Common Mistakes:

• Assuming error is due to auth issues
• Confusing syntax error with server crash
• Ignoring location info in error

5. You want to add extra details to your GraphQL error responses for better debugging. Which field should you use to include custom error codes or metadata?

hard

A. locations

B. path

C. extensions

D. message

Solution

1. Step 1: Identify the field for extra error info

   The extensions field is designed to hold custom metadata like error codes or debugging info.

2. Step 2: Differentiate from other fields

   message is for error text, path shows error location in data, and locations shows query text position.

3. Final Answer:

   extensions -> Option C

4. Quick Check:

   extensions = custom error metadata [OK]

Hint: Use extensions for custom error details [OK]

Common Mistakes:

• Putting custom info in message
• Confusing path with metadata
• Ignoring extensions field existence