feat: throw error when maxRedirections is used with undici.request()

The maxRedirections option was removed in v7 but no error was thrown when users tried to use it, making migration confusing. Now throws a clear error message directing users to use the redirect interceptor instead.

Fixes #4310

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Matteo Collina <hello@matteocollina.com>

Author: mcollina

CLAUDE.md

@@ -0,0 +1,110 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Key Commands
+
+**Testing:**
+- `npm run test` - Full test suite (JavaScript + TypeScript)
+- `npm run test:unit` - Core unit tests
+- `npm run test:fetch` - Fetch API tests
+- `npm run test:websocket` - WebSocket tests
+- `npm run test:h2` - HTTP/2 tests
+- `npm run test:cache` - Cache-related tests
+- `npm run test:interceptors` - Interceptor tests
+- `npm run test:wpt` - Web Platform Tests
+- `npm run test:node-test` - Node.js specific tests
+
+**Single test runs:**
+- `borp -p "test/specific-test.js"` - Run a specific test file
+- `borp -p "test/category/*.js"` - Run tests in a category
+
+**Linting & Quality:**
+- `npm run lint` - ESLint check
+- `npm run lint:fix` - Auto-fix linting issues
+- `npm run coverage` - Generate test coverage report
+
+**Build:**
+- `npm run build:node` - Build bundled fetch for Node.js
+- `npm run build:wasm` - Build WebAssembly components (requires Docker)
+
+## Architecture Overview
+
+Undici is an HTTP/1.1 client with Fetch API implementation for Node.js, structured around several core concepts:
+
+### Dispatcher Pattern
+The foundation is the `Dispatcher` abstract class that defines the interface for making HTTP requests. All HTTP clients implement this pattern:
+
+- **Agent** - Multi-host connection pooler (default global dispatcher)
+- **Client** - Single-host HTTP/1.1 client with connection pooling  
+- **Pool** - Connection pool for a single origin
+- **BalancedPool** - Load balancer across multiple pools
+- **ProxyAgent/EnvHttpProxyAgent** - Proxy-aware dispatchers
+- **RetryAgent** - Automatic retry logic wrapper
+
+### Core Components
+
+**lib/core/** - Fundamental utilities:
+- `connect.js` - Low-level connection establishment
+- `request.js` - Request object implementation  
+- `util.js` - Parsing and validation utilities
+- `errors.js` - Error definitions
+
+**lib/api/** - High-level API implementations:
+- `api-request.js` - Basic request/response
+- `api-stream.js` - Streaming interface
+- `api-pipeline.js` - Pipeline interface
+
+**lib/web/** - Web standards implementations:
+- `fetch/` - Complete Fetch API implementation
+- `websocket/` - WebSocket client
+- `eventsource/` - EventSource implementation
+- `cache/` - Cache API
+- `cookies/` - Cookie handling
+
+### HTTP Parser
+Uses a WebAssembly build of llhttp parser located in `lib/llhttp/`. The sources are in `deps/llhttp/` and can be rebuilt with `npm run build:wasm`.
+
+### Interceptor System
+Interceptors wrap dispatchers to add functionality:
+- `redirect` - Automatic redirect handling
+- `retry` - Retry failed requests
+- `cache` - HTTP caching
+- `dns` - DNS resolution caching
+- `dump` - Request/response logging
+
+### Testing Structure
+- `test/` - Main test directory
+- `test/wpt/` - Web Platform Tests
+- `test/fetch/` - Fetch API tests
+- `test/websocket/` - WebSocket tests
+- `test/node-test/` - Node.js integration tests
+- Test runner: `borp` (not Jest for most tests)
+
+## Development Notes
+
+**Standards Compliance:**
+- Implements Fetch Standard with Node.js adaptations
+- WebSocket per RFC 6455
+- HTTP/1.1 per RFC 9110
+- Supports HTTP/2 via h2c-client
+
+**Key Files to Know:**
+- `index.js` - Main entry point, exports all APIs
+- `lib/global.js` - Global dispatcher management
+- `lib/dispatcher/agent.js` - Default multi-host client
+- `lib/web/fetch/index.js` - Fetch implementation entry
+- `package.json` - Contains all npm script definitions
+
+**Code Style:**
+- Uses neostandard (ESLint config)
+- No trailing commas in objects/arrays
+- TypeScript definitions in `types/` directory
+
+**Git Commits:**
+- Always use `git commit -s` to add signoff when committing changes
+
+**WebAssembly Components:**
+- HTTP parser is WebAssembly-based
+- Requires Docker to rebuild
+- Pre-built binaries included in `lib/llhttp/`

lib/core/request.js

@@ -42,7 +42,8 @@ class Request {
     reset,
     expectContinue,
     servername,
-    throwOnError
+    throwOnError,
+    maxRedirections
   }, handler) {
     if (typeof path !== 'string') {
       throw new InvalidArgumentError('path must be a string')
@@ -86,6 +87,10 @@ class Request {
       throw new InvalidArgumentError('invalid throwOnError')
     }
 
+    if (maxRedirections != null) {
+      throw new InvalidArgumentError('maxRedirections is not supported, use the redirect interceptor')
+    }
+
     this.headersTimeout = headersTimeout
 
     this.bodyTimeout = bodyTimeout

test/request.js

@@ -177,6 +177,20 @@ describe('DispatchOptions#expectContinue', () => {
   })
 })
 
+describe('DispatchOptions#maxRedirections', () => {
+  test('Should throw if maxRedirections option is used', async t => {
+    t = tspl(t, { plan: 1 })
+
+    await t.rejects(request({
+      method: 'GET',
+      origin: 'http://somehost.xyz',
+      maxRedirections: 5
+    }), /maxRedirections is not supported, use the redirect interceptor/)
+
+    await t.completed
+  })
+})
+
 describe('DispatchOptions#reset', () => {
   test('Should throw if invalid reset option', async t => {
     t = tspl(t, { plan: 1 })