gistfile1.txt

"""
Demonstration of field validator order dependency in Pydantic.

This script shows that field validators with mode='after' process fields
in definition order, meaning info.data only contains previously validated fields.
"""

from typing import Any

import pydantic

print('=' * 80)
print('DEMONSTRATION: Field Validator Order Dependency')
print('=' * 80)


class ProblematicSettings(pydantic.BaseModel):
    # These fields are defined BEFORE secret_prefix
    field_before_1: str = 'value1'
    field_before_2: str = 'value2'

    # The prefix field
    secret_prefix: str = 'PREFIX'

    # These fields are defined AFTER secret_prefix
    field_after_1: str = 'value3'
    field_after_2: str = 'value4'

    @pydantic.field_validator('*', mode='after')
    @classmethod
    def track_validation_order(cls, value: Any, info: pydantic.ValidationInfo):
        """Track which fields are available in info.data during validation."""
        if info.field_name == 'secret_prefix':
            print(f"\n✓ Validating '{info.field_name}': {value}")
            print(f'  Available in info.data: {list(info.data.keys())}')
            return value

        # Try to get secret_prefix from info.data
        prefix = info.data.get('secret_prefix', '<NOT AVAILABLE>')
        print(f"\n✓ Validating '{info.field_name}': {value}")
        print(f"  secret_prefix from info.data: '{prefix}'")
        print(f'  Available fields in info.data: {list(info.data.keys())}')

        # Simulate what would happen if we tried to use it
        if prefix == '<NOT AVAILABLE>':
            print(f"  ⚠️  WARNING: secret_prefix not yet validated! Would use None or ''")

        return value


print("\n\n1. Using field_validator with mode='after'")
print('-' * 80)
print('Creating instance with explicit values to trigger validators...')
problematic = ProblematicSettings(
    field_before_1='value1',
    field_before_2='value2',
    secret_prefix='PREFIX',
    field_after_1='value3',
    field_after_2='value4',
)


# Now demonstrate the SOLUTION with model validators
print('\n\n' + '=' * 80)


class CorrectSettings(pydantic.BaseModel):
    # Same field order as before
    field_before_1: str = 'value1'
    field_before_2: str = 'value2'
    secret_prefix: str = 'PREFIX'
    field_after_1: str = 'value3'
    field_after_2: str = 'value4'

    @pydantic.model_validator(mode='after')
    def process_all_fields(self) -> 'CorrectSettings':
        """Model validator runs after ALL fields are validated."""
        print(f'\n✓ Model validator running')
        print(f"  secret_prefix is ALWAYS available: '{self.secret_prefix}'")
        print(f'  All fields accessible: {list(self.__class__.model_fields.keys())}')
        print(f'  ✓ Can safely use secret_prefix for all fields regardless of order')
        return self


print("2. Using model_validator with mode='after'")
print('-' * 80)
print('Creating instance with explicit values...')
correct = CorrectSettings(
    field_before_1='value1',
    field_before_2='value2',
    secret_prefix='PREFIX',
    field_after_1='value3',
    field_after_2='value4',
)