react18 legacy context

Provides the complete migration pattern for React legacy context API (contextTypes, childContextTypes, getChildContext) to the modern createContext API. Use this skill whenever migrating legacy context in class components - this is always a cross-file migration requiring the provider AND all consumers to be updated together. Use it before touching any contextTypes or childContextTypes code, becaus

github-copilot

Der Skill

# React 18 Legacy Context Migration

Legacy context (`contextTypes`, `childContextTypes`, `getChildContext`) was deprecated in React 16.3 and warns in React 18.3.1. It is **removed in React 19**.

## This Is Always a Cross-File Migration

Unlike most other migrations that touch one file at a time, context migration requires coordinating:
1. Create the context object (usually a new file)
2. Update the **provider** component
3. Update **every consumer** component

Missing any consumer leaves the app broken - it will read from the wrong context or get `undefined`.

## Migration Steps (Always Follow This Order)

```
Step 1: Find the provider (childContextTypes + getChildContext)
Step 2: Find ALL consumers (contextTypes)
Step 3: Create the context file
Step 4: Update the provider
Step 5: Update each consumer (class components → contextType, function components → useContext)
Step 6: Verify - run the app, check no legacy context warnings remain
```

## Scan Commands

```bash
# Find all providers
grep -rn "childContextTypes\|getChildContext" src/ --include="*.js" --include="*.jsx" | grep -v "\.test\."

# Find all consumers
grep -rn "contextTypes\s*=" src/ --include="*.js" --include="*.jsx" | grep -v "\.test\."

# Find this.context usage (may be legacy or modern - check which)
grep -rn "this\.context\." src/ --include="*.js" --include="*.jsx" | grep -v "\.test\."
```

## Reference Files

- **`references/single-context.md`** - complete migration for one context (theme, auth, etc.) with provider + class consumer + function consumer
- **`references/multi-context.md`** - apps with multiple legacy contexts (nested providers, multiple consumers of different contexts)
- **`references/context-file-template.md`** - the standard file structure for a new context module

So wird es eingerichtet

1. Open the tool and start a new conversation, project or template.
2. Paste the text below wherever the tool keeps standing instructions
   — usually called system prompt, instructions, or persona.
3. Save it so it applies to every run rather than a single message.

Hat es bei Ihnen geklappt?

Woher es stammt

GitHub, Inc. and contributors MIT Das Original

GitHub, Inc.