Field-level errors in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to request a field that might return an error.

GraphQL

query { user { name email [1] } }

Drag options to blanks, or click blank then click option'

Aerror

Baddress

Cage

Dphone

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a regular data field like 'age' or 'phone' instead of the error field.

The error field is used to request field-level errors in GraphQL responses.

2fill in blank

medium

Complete the code to handle errors for a nested field.

GraphQL

query { product { id name reviews [1] } }

Drag options to blanks, or click blank then click option'

Acomment

Brating

Cerror

Ddate

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting a normal data field like 'rating' or 'comment' instead of the error field.

The error field inside reviews helps capture errors related to reviews.

3fill in blank

hard

Fix the error in the query to correctly request field-level errors.

GraphQL

query { order { id total [1] } }

Drag options to blanks, or click blank then click option'

Aerror_code

BerrorMessage

Cerrors

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural or underscored versions like 'errors' or 'error_code' which are not standard.

The standard field to request field-level errors is error.

4fill in blank

hard

Fill both blanks to request a field and its error message.

GraphQL

query { user { [1] [2] } }

Drag options to blanks, or click blank then click option'

Aemail

Berror

Cmessage

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing two data fields instead of including the error field.

Request the email field and the error field to get its error message.

5fill in blank

hard

Fill all three blanks to request a nested field, its error, and the error message.

GraphQL

query { post { comments { [1] [2] { [3] } } } }

Drag options to blanks, or click blank then click option'

Atext

Berror

Cmessage

Dauthor

Attempts:

3 left

💡 Hint

Common Mistakes

Not nesting the message inside the error field.

Request the text field, the error field, and inside error the message to get detailed error info.

Practice

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

easy

A. To show exactly which field in the query caused an error

B. To speed up the query execution time

C. To encrypt the query data for security

D. To automatically fix errors in the query

Solution

1. Step 1: Understand what field-level errors represent

   Field-level errors identify the specific part of a query that failed, not the whole query.

2. Step 2: Recognize the benefit of field-level errors

   This helps apps show clear messages next to the exact problem fields, improving user experience.

3. Final Answer:

   To show exactly which field in the query caused an error -> Option A

4. Quick Check:

   Field-level errors = pinpoint error location [OK]

Hint: Field-level errors pinpoint the exact failing field [OK]

Common Mistakes:

• Thinking errors speed up queries
• Believing errors fix themselves
• Confusing errors with encryption

2. Which of the following is the correct way to represent a field-level error path in a GraphQL error response?

easy

A. "location": ["user", "email"]

B. "path": "user.email"

C. "error": "user.email"

D. "path": ["user", "email"]

Solution

1. Step 1: Identify the standard format for error paths

   GraphQL error paths are arrays showing the nested fields causing the error, e.g., ["user", "email"].

2. Step 2: Compare options to the standard format

   "path": ["user", "email"] matches the array format; others use strings or wrong keys.

3. Final Answer:

   "path": ["user", "email"] -> Option D

4. Quick Check:

   Error path = array of field names [OK]

Hint: Error paths use arrays, not dot strings [OK]

Common Mistakes:

• Using dot notation strings for paths
• Confusing 'error' with 'path' key
• Using 'location' instead of 'path'

3. Given this GraphQL error response snippet:

{"errors": [{"message": "Cannot query field 'age' on type 'User'", "path": ["user", "age"]}]}

What does the path ["user", "age"] indicate?

medium

A. The error is in the 'age' field inside the 'user' object

B. The entire 'user' object is missing

C. The query has a syntax error at the root

D. The 'age' field is null but valid

Solution

1. Step 1: Analyze the error message and path

   The message says 'Cannot query field age on type User', and the path shows the nested location: user -> age.

2. Step 2: Interpret the meaning of the path

   This means the error is specifically with the 'age' field inside the 'user' object, not the whole user or root.

3. Final Answer:

   The error is in the 'age' field inside the 'user' object -> Option A

4. Quick Check:

   Path shows exact field with error [OK]

Hint: Error path shows nested field causing issue [OK]

Common Mistakes:

• Assuming whole object is missing
• Confusing syntax errors with field errors
• Thinking null fields cause this error

4. You receive this GraphQL error response:

{"errors": [{"message": "Field 'price' must be a positive number", "path": ["product", "price"]}]}

Which fix will correctly address the field-level error?

medium

A. Ignore the error and retry the query

B. Change the 'price' value to a positive number in the query variables

C. Rename 'price' to 'cost' in the query

D. Remove the 'price' field from the query entirely

Solution

1. Step 1: Understand the error message and path

   The error says 'price' must be positive, and the path points to product -> price field.

2. Step 2: Determine the correct fix

   Fixing means providing a positive number for 'price' in the query variables, not removing or renaming the field.

3. Final Answer:

   Change the 'price' value to a positive number in the query variables -> Option B

4. Quick Check:

   Fix value to meet field rules [OK]

Hint: Fix field value to meet error message rules [OK]

Common Mistakes:

• Removing required fields
• Renaming fields without schema support
• Ignoring errors expecting auto-fix

5. You have a GraphQL query requesting nested fields:

{ user { name, posts { title, comments { text, author } } } }

If the error response shows:

{"errors": [{"message": "Cannot query field 'author' on type 'Comment'", "path": ["user", "posts", 0, "comments", 2, "author"]}]}

What does this error tell you about the query and how should you fix it?

hard

A. The 'comments' array is empty; add comments to fix the error

B. The 'posts' field is missing; add it to the query

C. The 'author' field does not exist on 'Comment'; remove or correct it in the query

D. The 'user' field is invalid; rename it to 'member'

Solution

1. Step 1: Analyze the error message and path

   The error says 'author' is not a valid field on 'Comment'. The path shows it is nested inside user -> posts -> comments at index 2.

2. Step 2: Decide the fix based on schema rules

   Since 'author' is invalid, you should remove or correct this field in the query to match the schema.

3. Final Answer:

   The 'author' field does not exist on 'Comment'; remove or correct it in the query -> Option C

4. Quick Check:

   Field error means fix or remove invalid field [OK]

Hint: Invalid field in nested path means fix query field name [OK]

Common Mistakes:

• Assuming empty arrays cause this error
• Adding missing fields not in schema
• Renaming unrelated fields