Type Doctor

Type Doctor diagnoses potential TypeScript performance issues by analyzing type checking traces.

Overview

Type Doctor analyzes TypeScript trace files to identify expressions that take too long to type-check. It helps you find performance bottlenecks in your TypeScript codebase by pinpointing slow type checking operations.

Installation

bun install

Build the CLI:

bun run build

Usage

Generating a Trace File

First, generate a trace file from your TypeScript project:

tsc --generateTrace trace.json

Running Type Doctor

Analyze a trace file:

bun cmd/cli.ts trace.json

Or use the compiled binary:

./bin/td trace.json

Options

• --checkTimeMsWarn <ms>: Set the warning threshold in milliseconds for a single expression check (default: 500)
• --checkTimeMsError <ms>: Set the error threshold in milliseconds for a single expression check (default: 1000). Must be greater than checkTimeMsWarn
• -a, --annotate: Enable GitHub Actions annotations (also enabled automatically in CI)
• -d, --debug: Enable debug logging
• -h, --help: Show help message

Examples

Analyze with a custom error threshold:

bun cmd/cli.ts --checkTimeMsError 50 trace.json

Analyze with custom warning and error thresholds:

bun cmd/cli.ts --checkTimeMsWarn 200 --checkTimeMsError 500 trace.json

Enable GitHub Actions annotations:

bun cmd/cli.ts -a trace.json

Enable debug logging:

bun cmd/cli.ts -d trace.json

Requirements

• Bun runtime
• TypeScript 5.x (peer dependency)
• A tsconfig.json file in your project root

Development

# Install dependencies
bun install

# Build the CLI
bun run build

# Run tests (if available)
bun test