azure-functions-validation 0.6.0

Validation and serialization layer for Azure Functions Python v2 programming model

Azure Functions Validation

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Validation and serialization for the Azure Functions Python v2 programming model.

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Part of the Azure Functions Python DX Toolkit → Bring FastAPI-like developer experience to Azure Functions

Why this exists

Azure Functions Python v2 handlers often drift into the same repeated problems:

• Repeated manual parsing — every handler calls req.get_json(), req.params.get(), handles ValueError individually
• Inconsistent error responses — some handlers return 400, others 422, formats vary across the project
• Missing response contracts — response payloads silently diverge from the intended schema
• No type safety — request data flows through as untyped dicts, bugs surface only at runtime

What it does

• Typed validation — body, query, path, and header parameters validated via Pydantic v2
• Automatic error responses — invalid requests get consistent 400/422 JSON error bodies
• Response model enforcement — mismatches raise ResponseValidationError (HTTP 500)
• Decorator-first API — @validate_http wraps your handler, no boilerplate needed

FastAPI comparison

Feature	FastAPI	azure-functions-validation
Request body parsing	Built-in via type hints	@validate_http(body=Model)
Query/path/header validation	Query(), Path(), Header()	@validate_http(query=Model, path=Model, headers=Model)
Response model	response_model=	@validate_http(response_model=Model)
Validation errors	Automatic 422	Automatic 422 with {"detail": [...]}
Error customization	Exception handlers	ErrorFormatter callback

Scope

• Azure Functions Python v2 programming model
• HTTP-triggered functions registered on func.FunctionApp()
• Pydantic v2-based request and response validation

This package does not target the legacy function.json-based v1 programming model.

Features

• Typed body, query, path, and header validation via @validate_http
• Automatic 400 / 422 responses with {"detail": [...]} envelope
• Response model validation — mismatches raise ResponseValidationError (HTTP 500)
• Custom per-handler error formatting via ErrorFormatter

Installation

pip install azure-functions-validation

Your Azure Functions app should also include:

azure-functions
azure-functions-validation

For local development:

git clone https://github.com/yeongseon/azure-functions-validation.git
cd azure-functions-validation
pip install -e .[dev]

Quick Start

import azure.functions as func
from pydantic import BaseModel

from azure_functions_validation import validate_http


class CreateUserRequest(BaseModel):
    name: str
    email: str


class CreateUserResponse(BaseModel):
    message: str
    status: str = "success"


app = func.FunctionApp()


@app.function_name(name="create_user")
@app.route(route="users", methods=["POST"], auth_level=func.AuthLevel.ANONYMOUS)
@validate_http(body=CreateUserRequest, response_model=CreateUserResponse)
def create_user(req: func.HttpRequest, body: CreateUserRequest) -> CreateUserResponse:
    return CreateUserResponse(message=f"Hello {body.name}")

When to use

• You have HTTP-triggered Azure Functions that accept JSON request bodies
• You want Pydantic-based validation without writing manual parsing code
• You need consistent error response formats across handlers
• You want response schema enforcement to catch contract drift

Documentation

• Project docs live under docs/
• Smoke-tested examples live under examples/
• Product requirements: PRD.md
• Design principles: DESIGN.md

Ecosystem

Part of the Azure Functions Python DX Toolkit:

Package	Role
azure-functions-validation	Request and response validation
azure-functions-openapi	OpenAPI spec and Swagger UI
azure-functions-logging	Structured logging and observability
azure-functions-doctor	Pre-deploy diagnostic CLI
azure-functions-scaffold	Project scaffolding
azure-functions-python-cookbook	Recipes and examples

Disclaimer

This project is an independent community project and is not affiliated with, endorsed by, or maintained by Microsoft.

Azure and Azure Functions are trademarks of Microsoft Corporation.

License

MIT