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narrow-bare-rescue

Narrows bare Elixir rescue clauses to explicit exception types so programmer bugs propagate.

537|38|Updated Feb 12, 2026
Search Tags:#Refactoring#Elixir#exception#rescue#Phoenix#Error handling#Code Audit
One-click install
npx skills add https://github.com/oliver-kriska/claude-elixir-phoenix --skill narrow-bare-rescue
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: narrow-bare-rescue
Source: https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/codex/skills/narrow-bare-rescue
Command: npx skills add https://github.com/oliver-kriska/claude-elixir-phoenix --skill narrow-bare-rescue

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Bare rescue _ -> clauses in Elixir swallow every exception, including UndefinedFunctionError from typos and KeyError from misspelled map keys, turning real bugs into silent {:error, :generic} fallbacks. This Skill audits those rescues and rewrites them to catch only the exception types the code path can actually raise.

Core Features & Use Cases

  • Rescue auditing: Finds bare rescue _ -> and rescue e -> sites across a single file, a directory, or the whole project, skipping already-typed rescues.
  • Verified exception taxonomy: Ships reference tables of exact exception types per work category (Jason, Ecto/Postgrex, Req, ExAws, ExCmd, Money/Decimal, Plug, LiveView HEEx, NimbleCSV), including gotchas like Phoenix.LiveView.Tokenizer.ParseError and internal NimbleCSV structs.
  • Refactoring patterns: Provides module-attribute hoisting for repeated rescue sets, Oban log-and-reraise with __STACKTRACE__, is_exception/1 replacements, large-cleanup partitioning, and a Credo check to prevent regressions.
  • Use Case: Run it on lib/my_app/ to convert every bare rescue into a typed list, then verify with mix compile --warnings-as-errors and the affected tests.

Quick Start

Ask the AI to audit and narrow all bare rescue clauses in lib/my_app/util/ using the narrow-bare-rescue skill, then compile and run the affected tests.

Frequently Asked Questions about narrow-bare-rescue

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I fix bare rescue clauses in Elixir?▼

Replace `rescue _ ->` with `rescue _ in [ExceptionType1, ExceptionType2] ->` listing only the exceptions the body can actually raise. Trace each call in the try or def body, consult a verified exception taxonomy, then run mix compile --warnings-as-errors to catch typos in module names.

Why is rescue _ -> dangerous in Elixir?▼

A bare rescue catches every exception, including programmer bugs like UndefinedFunctionError from typos and KeyError from misspelled map keys. The result is a silent fallback such as {:error, :generic} instead of a stack trace, hiding bugs from tests and error reporters.

Which exceptions should I rescue for Ecto and Postgrex?▼

Typical sets include Ecto.NoResultsError, Ecto.InvalidChangesetError, Ecto.ConstraintError, Ecto.StaleEntryError, Ecto.Query.CastError, Postgrex.Error, and DBConnection.ConnectionError. Add ArgumentError for bulk insert_all validation failures, and verify names with grep for defexception in deps.

Which exceptions should never appear in a narrowed rescue list?▼

Exclude UndefinedFunctionError, CompileError, BadFunctionError, and BadArityError because catching them hides programmer bugs that must propagate. FunctionClauseError and ArgumentError are exceptions only when raised as legitimate data signals, such as String.to_existing_atom on unknown input.

How do I log and reraise correctly in an Oban worker?▼

Narrow the rescue to the real failure types, log the message, then call reraise e, __STACKTRACE__ rather than reraise e, []. Preserving the original stack trace keeps Oban retry metadata and error reporters pointing at the true origin of the failure.

What are the limits of narrowing bare rescues?▼

The approach does not touch already-typed rescues, catch clauses for throws and exits, or replace try/rescue with with-based error tuples. It also must not be applied blindly, since dropping a genuinely raised exception is a behavioral regression.

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