Overview

Recently, I faced an interesting challenge while working on a project integrating Slack Bolt with Sanic - a framework I was previously unfamiliar with, which led to some unexpected deprecation warnings and type-related issues. I'll walk you through how I tackled the issue, the lessons I learned, and the precise code changes that resolved the problem.

What Are Sanic and Slack Bolt?

Sanic

Sanic is a high-performance, asynchronous web framework in Python. Designed to be fast, it takes advantage of Python's asyncio capabilities to handle large volumes of requests efficiently. Its minimalistic design makes it suitable for lightweight web applications, microservices, and API layers.

Slack Bolt

Slack Bolt is a framework for building Slack apps. It abstracts the complexities of Slack's APIs, allowing developers to focus on creating interactive and event-driven Slack applications. With Bolt, you can manage commands, shortcuts, events, and more with ease.

The Challenge

While implementing the integration, I encountered several warnings related to Sanic's cookie handling when running tests and handling requests. Here's an example of the warnings I saw:

DeprecationWarning: [DEPRECATION] Setting cookie values using the dict pattern has been deprecated.DeprecationWarning: [DEPRECATION] Accessing cookies from the CookieJar by dict key is deprecated.TypeError: Argument "path" to "add_cookie" of "BaseHTTPResponse" has incompatible type "Optional[Any]"; expected "str"

The root cause was the use of Sanic's old dict-based cookie handling syntax, which is no longer recommended as of Sanic v23.3. Instead, the newadd_cookie method must be used to ensure compatibility and eliminate these warnings.

The Solution

The key change was replacing the dict-based cookie handling with theadd_cookie method, ensuring that all cookie parameters passed were of the correct type.

Here’s the updated code snippet:

# Iterate over cookies and add them using Sanic's add_cookie methodforcookieinbolt_resp.cookies():forkey,cincookie.items():# Convert "expires" field if providedexpire_value=c.get("expires")expires=datetime.strptime(expire_value,"%a, %d %b %Y %H:%M:%S %Z")ifexpire_valueelseNone# Convert "max-age" if providedmax_age=int(c["max-age"])ifc.get("max-age")elseNone# Ensure values are of the correct type before passing to add_cookiepath=str(c.get("path"))ifc.get("path")else"/"domain=str(c.get("domain"))ifc.get("domain")elseNone# Add cookie with Sanic's add_cookie methodresp.add_cookie(key=key,value=c.value,expires=expires,path=path,domain=domain,max_age=max_age,secure=True,httponly=True,)

Replaced Dict-Based Syntax: The old approach relied on direct manipulation ofresp.cookies using dict syntax, which is deprecated. Instead, we usedresp.add_cookie() to set cookies in a forward-compatible way.

Ensured Proper Data Types: Parameters like path and domain were sometimesNone or not strings. We explicitly converted these values tostrings or set defaults ("/" for path, None for domain) before passing them to add_cookie.

Handled Optional Cookie Fields: expires was parsed into adatetime object if provided, using the format"%a, %d %b %Y %H:%M:%S %Z".
max-age was converted to an integer if available.

These changes resolved all warnings and errors, ensuring the integration adhered to Sanic's modern practices.

Final Thoughts

Since I had no prior experience with Sanic, understanding its documentation was critical. Learning how Sanic handles cookies and requests helped me realize why the old syntax was problematic and how the newadd_cookie method works.

Integrating Slack Bolt with Sanic turned out to be a rewarding challenge. Not only did it improve my understanding of Sanic, but it also emphasized the importance of staying up-to-date with framework best practices. If you're facing similar issues, I hope this blog post provides clarity and helps you solve your problem more efficiently.