michalmuskala/jason

Better error message on invalid `@derive Jason.Encoder` options

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#183 opened on Feb 10, 2024

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 (1 comment) (0 reactions) (0 assignees)Elixir (1,676 stars) (177 forks)batch import
enhancementhelp wanted

Description

Current behavior

When passing an invalid option, eg:

@derive {Jason.Encoder, invalid: [:__meta__]}

It returns the following error: cannot encode metadata from the :__meta__ field for CrosswordsApi.Users.User to JSON.

Expected behavior

Could the error be explicit that expect or only should be passed as valid options only?

Contributor guide

Tech stack
None
Domain
developer experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Elixir basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
The issue is about improving error messages in Jason's `@derive` macro for invalid options like `:invalid`. Look in the repository's source code, likely `lib/jason/encoder.ex`, for where the current error is raised. Modify the code to check for valid options (`:only` or `:except`) and output a clear message. The change is localized and requires understanding of Elixir's `@derive` mechanism.