PostHog/posthog

Clean up error handling across the board; need to make sure it's consistent everything and consistent with how we were handling errors in Django

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#30,174 opened on Mar 19, 2025

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 (10 comments) (0 reactions) (1 assignee)Python (16,704 stars) (988 forks)batch import
feature/feature-flagsgood first issueteam/flags-platform

Description

More context: when I first shipped the feature-flags rust service (at src/rust/feature-flags), I used thiserror for error-handling because I like how you could define typed enums with automatic trait implementations. It was my first time writing a rust application, and it seemed like a cool tool.

I was wrong. I mean, thiserror worked, but it led to a bunch of overkill that I don't really need – a bunch of extra error handling code that doesn't do much but exists to satisfy the compiler. thiserror is great for writing rust libraries, but anyhow is a much better choice for rust applications.

So, this task is to basically port all of the error handling in the feature-flags module to use anyhow instead of thiserror, while still keeping the client interface (i.e. the actual responses the app sends to anyone calling the /flags endpoint) the same.

Contributor guide

Tech stack
rust
Domain
backendapi
Issue type
refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Rust programmingthiserror and anyhow cratesPostHog codebase familiarity
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55
Research direction
The task is to replace thiserror with anyhow for error handling in the feature flags Rust service at src/rust/feature flags. Ensure the client interface (response format of /flags endpoint) remains unchanged. Review existing comments for any additional context. Examine the current error handling in that module and replace thiserror derive macros with anyhow's Result and Context. Test the changes to ensure no breakage.