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Exceptions API Reference

This page documents Pyvider's exception hierarchy and error handling patterns for provider development.

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Exception Hierarchy

graph TB
    E[Exception]
    E --> FND[FoundationError]
    FND --> PE[PyviderError]
    PE --> CE[ConversionError]
    PE --> FCE[FrameworkConfigurationError]
    PE --> PLE[PluginError]
    PE --> PVE[PyviderValueError]
    PE --> PRE[ProviderError]
    PE --> RE[ResourceError]
    PE --> FE[FunctionError]
    PE --> SE[SchemaError]
    PE --> VE[ValidationError]
    PE --> REG[ComponentRegistryError]
    PE --> SER[SerializationError]
    PE --> GE[GRPCError]

    style PE fill:#f9f,stroke:#333,stroke-width:2px
    style FND fill:#bbf,stroke:#333,stroke-width:2px

Base Exceptions

Foundation Error Hierarchy

All Pyvider exceptions inherit from FoundationError (from the provide.foundation library), which provides rich error context, automatic telemetry integration, and Terraform diagnostic generation support. You don't need to import or use FoundationError directly - use the Pyvider-specific exception classes below.

PyviderError

Base exception for all Pyvider-specific errors. Inherits from FoundationError:

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from pyvider.exceptions import PyviderError

class PyviderError(FoundationError):
    """
    Base exception for all Pyvider errors.

    Attributes:
        message: Human-readable error message
        details: Additional error context (dict)
        cause: Original exception that caused this error
    """

    def __init__(
        self,
        message: str,
        details: dict | None = None,
        cause: Exception | None = None
    ):
        self.message = message
        self.details = details or {}
        self.cause = cause
        super().__init__(message)

Provider Exceptions

ProviderError

Errors related to provider configuration and lifecycle:

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from pyvider.exceptions import ProviderError

# Provider not configured
raise ProviderError("Provider not configured with credentials")

# Invalid configuration
raise ProviderError(
    "Invalid provider configuration",
    details={"field": "region", "value": "invalid-region"}
)

# Authentication failure
raise ProviderError(
    "Authentication failed",
    details={"endpoint": "https://api.example.com"},
    cause=original_exception
)

Resource Exceptions

ResourceError

Errors during resource lifecycle operations:

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from pyvider.exceptions import ResourceError

# Resource not found
raise ResourceError(
    "Resource not found",
    details={"resource_id": "i-12345", "type": "instance"}
)

# Creation failed
raise ResourceError(
    "Failed to create resource",
    details={"reason": "Quota exceeded", "limit": 10, "current": 10}
)

# Update conflict
raise ResourceError(
    "Resource was modified outside of Terraform",
    details={"expected_version": "1.2", "actual_version": "1.3"}
)

# Delete protection
raise ResourceError(
    "Cannot delete resource with deletion protection enabled",
    details={"resource_id": "db-prod-001", "protection": True}
)

Function Exceptions

FunctionError

Errors in provider function execution:

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from pyvider.exceptions import FunctionError

# Invalid input
raise FunctionError(
    "Invalid function input",
    details={"parameter": "algorithm", "value": "unsupported"}
)

# Execution failure
raise FunctionError(
    "Function execution failed",
    details={"function": "hash_file", "reason": "File too large"}
)

Schema Exceptions

SchemaError

Schema definition and validation errors:

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from pyvider.exceptions import SchemaError

# Invalid schema
raise SchemaError(
    "Invalid schema definition",
    details={"field": "port", "issue": "Missing required validator"}
)

# Type mismatch
raise SchemaError(
    "Schema type mismatch",
    details={"expected": "string", "got": "number", "field": "name"}
)

ValidationError

Input validation failures:

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from pyvider.exceptions import ValidationError

# Required field missing
raise ValidationError(
    "Required field missing",
    details={"field": "api_key"}
)

# Invalid value
raise ValidationError(
    "Invalid field value",
    details={"field": "port", "value": 70000, "constraint": "1-65535"}
)

# Custom validation
raise ValidationError(
    "Custom validation failed",
    details={"field": "email", "reason": "Invalid email format"}
)

Registry Exceptions

RegistryError

Component registration errors:

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from pyvider.exceptions import RegistryError

# Duplicate registration
raise RegistryError(
    "Component already registered",
    details={"type": "resource", "name": "server"}
)

# Invalid component
raise RegistryError(
    "Invalid component class",
    details={"class": "MyResource", "reason": "Missing required methods"}
)

Serialization Exceptions

SerializationError

Data serialization/deserialization errors:

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from pyvider.exceptions import SerializationError

# Encoding error
raise SerializationError(
    "Failed to encode state",
    details={"type": "datetime", "value": "2024-01-01T00:00:00"},
    cause=original_exception
)

# Decoding error
raise SerializationError(
    "Failed to decode configuration",
    details={"data": raw_data, "expected_type": "dict"}
)

gRPC Exceptions

GrpcError

Protocol and communication errors:

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from pyvider.exceptions import GrpcError
import grpc

# Connection error
raise GrpcError(
    "Failed to connect to Terraform",
    details={"address": "localhost:50051"},
    cause=grpc_exception
)

# Protocol error
raise GrpcError(
    "Protocol version mismatch",
    details={"expected": "6", "got": "5"}
)

Best Practices

1. Rich Error Context

Always provide detailed context:

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# Good - Rich context
raise ResourceError(
    "Failed to create S3 bucket",
    details={
        "bucket_name": config.bucket_name,
        "region": config.region,
        "error_code": "BucketAlreadyExists",
        "suggestion": "Choose a different bucket name"
    },
    cause=boto_exception
)

# Bad - Minimal context
raise ResourceError("Bucket creation failed")

2. Exception Chaining

Preserve the original exception:

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try:
    response = await api_client.create_resource(...)
except HttpError as e:
    # Preserve original exception
    raise ResourceError(
        f"API call failed: {e.status_code}",
        details={"endpoint": e.url, "method": "POST"},
        cause=e  # Original exception preserved
    )

3. Actionable Messages

Provide guidance when possible:

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raise ValidationError(
    "Invalid instance type for selected region",
    details={
        "instance_type": "t3.micro",
        "region": "us-gov-west-1",
        "valid_types": ["t2.micro", "t2.small"],
        "suggestion": "Use t2.micro for government regions"
    }
)

4. Structured Error Handling

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async def _create_apply(self, ctx: ResourceContext) -> tuple[State | None, None]:
    """Create resource with structured error handling."""
    try:
        # Validate inputs first
        self._validate_config(ctx.config)

        # Attempt creation
        result = await self._create_resource(ctx.config)

        # Validate result
        if not result.id:
            raise ResourceError(
                "Resource created but no ID returned",
                details={"response": result}
            )

        return self._build_state(result)

    except ValidationError:
        # Re-raise validation errors as-is
        raise

    except ClientError as e:
        # Map client errors to resource errors
        if e.code == "QUOTA_EXCEEDED":
            raise ResourceError(
                "Quota exceeded for resource type",
                details={
                    "type": config.resource_type,
                    "quota": e.quota,
                    "used": e.used
                },
                cause=e
            )
        elif e.code == "PERMISSION_DENIED":
            raise ProviderError(
                "Insufficient permissions",
                details={"required_permission": e.permission},
                cause=e
            )
        else:
            raise ResourceError(
                f"Unexpected error: {e.message}",
                cause=e
            )

    except Exception as e:
        # Catch-all for unexpected errors
        raise ResourceError(
            "Unexpected error during resource creation",
            details={"config": config.__dict__},
            cause=e
        )

Custom Exceptions

Create domain-specific exceptions:

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from pyvider.exceptions import ResourceError

class QuotaExceededError(ResourceError):
    """Raised when a quota limit is exceeded."""

    def __init__(self, resource_type: str, limit: int, current: int):
        super().__init__(
            f"Quota exceeded for {resource_type}",
            details={
                "resource_type": resource_type,
                "limit": limit,
                "current": current,
                "available": limit - current
            }
        )

class ResourceLockedError(ResourceError):
    """Raised when a resource is locked and cannot be modified."""

    def __init__(self, resource_id: str, locked_by: str, locked_until: str):
        super().__init__(
            f"Resource {resource_id} is locked",
            details={
                "resource_id": resource_id,
                "locked_by": locked_by,
                "locked_until": locked_until
            }
        )

Testing Exception Handling

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import pytest
from pyvider.exceptions import ResourceError, ValidationError
from pyvider.resources.context import ResourceContext

@pytest.mark.asyncio
async def test_resource_creation_error_handling(resource):
    """Test that errors are properly handled."""

    # Test validation error
    with pytest.raises(ValidationError) as exc_info:
        ctx = ResourceContext(config=Resource.Config(name=""))  # Empty name
        await resource._create_apply(ctx)

    assert "Required field" in str(exc_info.value)
    assert exc_info.value.details["field"] == "name"

    # Test resource error with cause
    with pytest.raises(ResourceError) as exc_info:
        ctx = ResourceContext(config=Resource.Config(name="test", invalid_field=True))
        await resource._create_apply(ctx)

    assert exc_info.value.cause is not None
    assert "invalid_field" in exc_info.value.details

Logging Exceptions

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import structlog

logger = structlog.get_logger()

try:
    result = await operation()
except PyviderError as e:
    logger.error(
        "Operation failed",
        error_type=type(e).__name__,
        message=str(e),
        details=e.details,
        has_cause=e.cause is not None,
        exc_info=True  # Include traceback
    )
    raise

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