rails-antipatterns

Rails Antipatterns

Comprehensive catalog of named Rails antipatterns sourced from Rails Antipatterns (Pytel & Saleh) and the 37signals/DHH idiom. Use these as diagnostic tools when reviewing code for structural smells — each antipattern has a name, detection heuristic, and idiomatic Rails fix.

These are not abstract principles. They are concrete, named problems with concrete, named solutions. Apply them by recognizing the shape of the code, not by keyword matching.

Antipattern Reference

Antipattern	Reference	Detect When
Fat Model / God Object	references/fat-model-god-object.md	AR model >300 lines mixing responsibilities
Callback Hell	references/callback-hell.md	tangled before_/after_ side-effect chains
Voyeuristic Model	references/voyeuristic-model.md	Law of Demeter train wrecks
Anemic Domain Model	references/anemic-domain-model.md	behavior in services, models as attribute bags
Spaghetti SQL	references/spaghetti-sql.md	raw queries scattered outside scopes
Fat Controller	references/fat-controller.md	business logic in controllers
Non-RESTful Actions	references/non-restful-actions.md	custom actions instead of new resources
Homemade Keys & Routes	references/homemade-keys-and-routes.md	hand-built URL patterns bypassing resources
Bloated Session	references/bloated-session.md	AR objects or state stuffed in session
PHP-itis Views	references/php-itis-views.md	conditionals/loops/queries in ERB
N+1 in Views	references/n-plus-one-in-views.md	per-row queries during iteration
God Helper Module	references/god-helper-module.md	ApplicationHelper as dumping ground
Service Object Soup	references/service-object-soup.md	*Service class proliferation
Premature Abstraction & DI	references/premature-abstraction-and-di.md	DI/interfaces purely for testability
Mock-Heavy Tests	references/mock-heavy-tests.md	stubbing collaborators that could be fixtures
Migration Smells	references/migration-smells.md	irreversible migrations, mixed schema/data

Sweep Mode

When invoked as a sweep, scan the changed code for each antipattern in the table above. For each detected smell, dispatch one subagent per antipattern reference that matches. Each subagent loads this skill, reads the matched reference, and reviews the code against that antipattern. Aggregate findings.

Dispatch one parallel subagent per antipattern. No file gating — smells can hide anywhere. See dispatching-parallel-agents for the dispatch primitive.

Each subagent receives:

• The target (diff, file paths, or working-tree scope)
• The single antipattern reference to load

Each subagent returns either:

• Findings: file:line citations with a one-line note tying the code to the smell
• No smell detected: a single line so the orchestrator can drop it from the aggregate

Group surviving findings by antipattern, then by file. For each finding cite file:line and the relevant rule from the named reference. Skip antipatterns where no reviewer flagged anything — don't list "no findings" rows.

If invoked from code-review-orchestration as a sub-orchestrator, return the structured findings list rather than narrative prose; the parent will integrate with its own posting protocol.

Constraints

• Apply fixes idiomatically. The goal is vanilla Rails — Concerns, AR verbs, scopes, helpers, jobs — not new abstraction layers.
• When a smell is found, recommend the least invasive fix that resolves it. Don't gold-plate.
• Cite the specific antipattern name and reference file for every finding so the reader can learn the pattern.
• Do not invent new antipatterns. Only flag smells that match one of the 16 named patterns above.
• A long file or complex class is not automatically a smell — look for the named shape: mixed responsibilities, leaking queries, violating conventions, etc.