Feature request: Add LexResolver for simplified intent routing

[fakhtar]

Use case

Feature Request: Add LexResolver for simplified intent routing

Description

Add a LexResolver class similar to APIGatewayRestResolver that enables decorator-based routing for Amazon Lex V2 Lambda functions. This simplifies handling different intents and event types in Lex bot fulfillment/dialog code hooks.

Use Case

from aws_lambda_powertools.utilities.lex import LexResolver

app = LexResolver()

@app.fulfillment("OrderPizza")
def handle_order_pizza():
    # Handle pizza order fulfillment
    return {
        "sessionAttributes": session_attributes,
        "messages": [{
            "contentType": "PlainText",
            "content": "Your pizza order is confirmed"
        }]
    }

@app.dialog("CheckOrder")
def handle_check_order():
    # Handle order status dialog
    pass

Proposed Features

• Intent-based routing using decorators
• Separate decorators for DialogCodeHook and FulfillmentCodeHook
• Access to session attributes via resolver context
• Type hints and response validation
• Error handling with appropriate Lex response formats
• Middleware support similar to APIGatewayRestResolver

Benefits

• Reduces boilerplate code
• Cleaner separation of concerns
• Type-safe handling of Lex events
• Consistent with existing Powertools patterns

Implementation Notes

• Follow similar pattern to APIGatewayRestResolver
• Support Lambda Powertools logger and tracer integration
• Maintain compatibility with Lex V2 response formats

Solution/User Experience

Solution/User Experience

The LexResolver would provide a clean, intuitive API for routing Lex events:

from aws_lambda_powertools.utilities.lex import LexResolver

app = LexResolver()

@app.fulfillment("OrderPizza")
def handle_pizza_order(session_attributes: dict):
    return {
        "sessionAttributes": {**session_attributes, "order_status": "confirmed"},
        "messages": [{
            "contentType": "PlainText",
            "content": "Your pizza order is confirmed"
        }]
    }

@app.dialog("CheckDelivery", required_slots=["order_id"])
def handle_delivery_check(session_attributes: dict):
    return {
        "sessionAttributes": session_attributes,
        "messages": [{
            "contentType": "PlainText",
            "content": f"Your delivery is on its way"
        }]
    }

def lambda_handler(event, context):
    return app.resolve(event, context)

Alternative solutions

Acknowledgment

• This feature request meets Powertools for AWS Lambda (Python) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Java, TypeScript, and .NET

[anafalcao]

Hey @fakhtar ! Thank you for your feature request for a LexResolver. We appreciate your detailed suggestion and will evaluate it carefully in our next iterations. We'll get back to you soon or with any follow-up questions!

[leandrodamascena]

Assigning to me to review this issue!