feat(input_schema): Custom error messages #567
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Pull Request Overview
This PR implements custom error messages for input schema validation, allowing developers to define field-specific error messages for validation keywords. This provides better user experience by enabling more contextual and user-friendly error messages.
Key Changes
- Added
errorMessageproperty definition to the JSON schema with support for all standard validation keywords (type, pattern, min/max constraints, etc.) - Implemented
getCustomErrorMessage()function to retrieve custom messages from the schema based on validation paths - Integrated custom error message lookup into both AJV-based validation (
parseAjvError) and pattern validation in utilities - Added comprehensive test coverage for all supported validation keywords and field types
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| packages/json_schemas/schemas/input.schema.json | Added errorMessage definition and referenced it in all property type definitions (string, array, object, integer, number, boolean, resource, any, and their sub-schema variants) |
| packages/input_schema/src/input_schema.ts | Implemented getCustomErrorMessage() function and integrated it into parseAjvError() to prioritize custom messages over default ones |
| packages/input_schema/src/utilities.ts | Integrated custom error message support for pattern validation (patternKey and patternValue) in various field types |
| test/input_schema.test.ts | Added tests to validate schema accepts custom error messages and rejects unknown keywords |
| test/utilities.client.test.ts | Added comprehensive test coverage for custom error messages across all validation keywords and field types |
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valekjo
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Nov 13, 2025
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| const pathParts = schemaPath | ||
| .replace(/^#\//, '') | ||
| .split('/') | ||
| .filter(Boolean); |
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Note: I was wondering how AJV deals with / in schemaPath and it seems it escapes it as ~1
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Yep, I tried that too :)
HonzaKirchner
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Nov 18, 2025
# Conflicts: # packages/json_schemas/schemas/input.schema.json
jancurn
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Nov 26, 2025
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Looks good (based on the description, haven't reviewed the code). Thanks Martin!
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Solves https://github.com/apify/apify-core/issues/24045 - implements option to define custom error messages within the input schema based on the specification here: #556
Few notes to the implementation:
It supports only property level validation keywords like
type,minLength,pattern,.. but no schema/object level keywords (required,additionalProperties)It supports our custom validation keywords too (
patternKeyandpatternValue)This allows to specify any validation keyword in any property. There is no check whether the property actually supports or moreover has defined the keyword. This makes the implementation much more simpler using one
errorMessagedefinition and reusing it in all the properties.This would start working out-of-the box in the UI, but we use there custom function
beautifyValidationMessageto modify the default error message for UI usecases and the custom message would just bubble through without any modification in most cases (there is regex check) - IMHO expected behavior, but mentioning it here to be sure.