Core Pattern Finder

Search Drupal core for implementation patterns and return file references.

Activation

Activate when you detect:

• "How does core do X?"
• "Find core example of X"
• "Show me core's implementation of X"
• Need a reference implementation for a Drupal pattern

Quick Reference

Check these common patterns first before searching:

Forms

Pattern	Path
ConfigFormBase	core/modules/system/src/Form/SiteInformationForm.php
FormBase	core/modules/node/src/Form/NodeForm.php
ConfirmFormBase	core/modules/node/src/Form/NodeDeleteForm.php
EntityForm	core/modules/user/src/ProfileForm.php

Entities

Pattern	Path
Content Entity	core/modules/node/src/Entity/Node.php
Config Entity	core/modules/field/src/Entity/FieldConfig.php
Entity List Builder	core/modules/node/src/NodeListBuilder.php

Services

Pattern	Path
Entity Type Manager	core/lib/Drupal/Core/Entity/EntityTypeManager.php
Plugin Manager	core/lib/Drupal/Core/Block/BlockManager.php
Event Subscriber	core/modules/system/src/EventSubscriber/ConfigCacheTag.php

Plugins

Pattern	Path
Block Plugin	core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
Field Formatter	core/modules/text/src/Plugin/Field/FieldFormatter/TextDefaultFormatter.php
Field Widget	core/modules/text/src/Plugin/Field/FieldWidget/TextareaWidget.php
Condition Plugin	core/modules/system/src/Plugin/Condition/RequestPath.php

Controllers

Pattern	Path
ControllerBase	core/modules/system/src/Controller/SystemController.php
Entity Controller	core/modules/node/src/Controller/NodeController.php

Workflow

1. Check Quick Reference

If pattern matches table above, return that path immediately.

2. Search Core

If not in quick reference, search using these strategies:

For class/interface patterns:

Use Grep with pattern: "class {PatternName}" or "interface {PatternName}"
Path: core/

For specific implementations:

Use Grep with pattern: "extends {BaseClass}" or "implements {Interface}"
Path: core/modules/

For service patterns:

Use Glob with pattern: core/modules/*/src/*Manager.php
or: core/lib/Drupal/Core/*/*.php

3. Read and Extract Key Sections

Once file found, use Read tool and identify:

• Key methods to study
• Relevant line numbers
• Dependencies injected

4. Return Structured Response

Format your response as:

## Core Pattern: {Pattern Name}

### Primary Example
`{file_path}`

**Key methods:**
- `{method1}()` (line {X}): {what it does}
- `{method2}()` (line {Y}): {what it does}

**Dependencies:**
- {service_name}: {purpose}

### Additional Examples
- `{path2}` - {variation description}
- `{path3}` - {variation description}

### Usage Notes
{Any gotchas or important considerations}

Stop Points

STOP and ask user:

• If pattern is ambiguous (multiple interpretations)
• If no matching pattern found in core
• Before reading more than 3 files (ask which to prioritize)