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pantheon-ai/typescript-advanced

Comprehensive TypeScript guidance covering compiler configuration, advanced types, utility types, type guards, strict mode workflows, and documentation patterns; use when configuring tsconfig, designing complex generics, making illegal states unrepresentable, fixing type errors, or writing testable and maintainable type-safe APIs.

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compiler-performance.mdreferences/

TypeScript Compiler Performance

Performance Optimization Strategies

Incremental Compilation

Enable caching for faster rebuilds:

{
  "compilerOptions": {
    "incremental": true,
    "tsBuildInfoFile": ".tsbuildinfo"
  }
}

Benefits:

  • Only recompile changed files
  • 2-5x faster on subsequent builds
  • Minimal disk usage (~few KB)

Project References

For monorepos and large projects:

{
  "compilerOptions": {
    "composite": true,
    "declaration": true
  },
  "references": [
    { "path": "../shared" }
  ]
}

Benefits:

  • Parallel compilation
  • Incremental builds across projects
  • Better IDE performance
  • Enforced dependency boundaries

Build with:

tsc --build
tsc --build --watch # Watch mode
tsc --build --force # Clean rebuild

Skip Type Checking for Libraries

Skip checking node_modules:

{
  "compilerOptions": {
    "skipLibCheck": true
  }
}

Trade-offs:

  • Faster compilation (~30-50%)
  • May miss errors in type definitions
  • Safe if dependencies are well-typed

Reduce Checked Files

{
  "include": ["src/**/*"],
  "exclude": [
    "node_modules",
    "dist",
    "**/*.test.ts",
    "**/*.spec.ts"
  ]
}

Alternative: Separate test configuration

// tsconfig.build.json (for production)
{
  "extends": "./tsconfig.json",
  "exclude": ["**/*.test.ts", "**/*.spec.ts"]
}

Limit Type Instantiation Depth

Prevent runaway type computation:

{
  "compilerOptions": {
    "noErrorTruncation": false, // Truncate long error messages
    "maxNodeModuleJsDepth": 0   // Don't infer types from .js files
  }
}

Type System Performance

Avoid Deep Nesting

// Slow: Deep recursion
type DeepPartial<T> = {
  [P in keyof T]?: T[P] extends object
    ? DeepPartial<T[P]>
    : T[P];
};

// Limit recursion depth
type DeepPartial<T, Depth extends number = 5> = Depth extends 0
  ? T
  : {
      [P in keyof T]?: T[P] extends object
        ? DeepPartial<T[P], Prev[Depth]>
        : T[P];
    };

type Prev = [never, 0, 1, 2, 3, 4, 5];

Simplify Union Types

// Slow: Large union (100s of members)
type Color = "red" | "blue" | "green" | ... // 100+ values

// Fast: Use string index
type Color = string;
const COLORS = {
  red: "#ff0000",
  blue: "#0000ff",
  // ...
} as const;
type Color = keyof typeof COLORS;

Cache Complex Types

// Slow: Recalculate every time
function process<T>(value: ComplexType<ComplexType<T>>) {}

// Fast: Cache intermediate type
type CachedComplex<T> = ComplexType<ComplexType<T>>;
function process<T>(value: CachedComplex<T>) {}

Use Type Aliases for Reuse

// Recalculates type each time
function a(value: { id: string; name: string; age: number }) {}
function b(value: { id: string; name: string; age: number }) {}

// Fast: Reuse type
type User = { id: string; name: string; age: number };
function a(value: User) {}
function b(value: User) {}

Build Tool Integration

Parallel Type Checking

Use fork-ts-checker-webpack-plugin or similar:

// webpack.config.js
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');

module.exports = {
  plugins: [
    new ForkTsCheckerWebpackPlugin({
      async: true, // Non-blocking
      typescript: {
        configFile: 'tsconfig.json'
      }
    })
  ]
};

Use swc or esbuild for Transpilation

Only use TypeScript for type checking:

# Type check
tsc --noEmit

# Transpile (fast)
esbuild src/index.ts --bundle --outfile=dist/index.js
# or
swc src -d dist

Benefits:

  • 10-100x faster transpilation
  • TypeScript only for types
  • Best of both worlds

Watch Mode Optimization

{
  "compilerOptions": {
    "assumeChangesOnlyAffectDirectDependencies": true
  },
  "watchOptions": {
    "excludeDirectories": ["**/node_modules", "dist"],
    "excludeFiles": ["**/*.test.ts"]
  }
}

IDE Performance

Reduce IntelliSense Scope

{
  "exclude": [
    "node_modules",
    "dist",
    "build",
    "coverage",
    ".cache"
  ]
}

Disable Automatic Type Acquisition

{
  "compilerOptions": {
    "types": [] // Only include explicit @types packages
  }
}

Use @ts-nocheck for Problematic Files

// @ts-nocheck
// Large generated file or vendor code

Profiling and Diagnostics

Trace Type Checking

tsc --generateTrace trace
# Analyze with: https://ui.perfetto.dev/

Measure Compilation Time

tsc --diagnostics
# or more detail
tsc --extendedDiagnostics

Output includes:

  • Files checked
  • Time per phase
  • Memory usage
  • Cache hits

Find Slow Types

tsc --generateTrace trace --extendedDiagnostics

Look for:

  • High instantiation counts
  • Deep recursion
  • Large union types

Best Practices

  1. Enable incremental compilation - 2-5x faster rebuilds
  2. Use project references - For monorepos
  3. Enable skipLibCheck - Safe for most projects
  4. Separate type checking from transpilation - Use esbuild/swc
  5. Limit recursion depth - Prevent runaway types
  6. Cache complex types - Reuse type aliases
  7. Exclude tests from production builds - Faster builds
  8. Use watch mode options - Fewer unnecessary checks
  9. Profile slow compilations - Use --generateTrace
  10. Keep dependencies updated - Better typed libraries

Performance Budget

Compilation times to aim for:

  • Small project (<100 files): <2s
  • Medium project (<500 files): <10s
  • Large project (<2000 files): <30s
  • Monorepo: <60s with project references

If slower:

  1. Enable incremental compilation
  2. Add project references
  3. Profile with --generateTrace
  4. Simplify complex types
  5. Reduce checked files

Common Bottlenecks

  • No incremental compilation - Enable incremental: true
  • Checking all node_modules - Enable skipLibCheck: true
  • No project references - Add for monorepos
  • Deep type recursion - Limit recursion depth
  • Large unions - Use string index signatures
  • Checking test files in production - Separate config
  • Overly complex mapped types - Simplify or cache

Install with Tessl CLI

npx tessl i pantheon-ai/typescript-advanced@0.1.1

references

compiler-module-resolution.md

compiler-performance.md

compiler-strict-mode.md

compiler-tsconfig.md

docs-adr-templates.md

docs-framework-docs.md

docs-jsdoc-patterns.md

docs-typedoc-config.md

guards-assertion-functions.md

guards-basic.md

guards-branded-types.md

guards-discriminated-unions.md

guards-exhaustiveness.md

guards-generic.md

guards-inference-infer.md

guards-inference-return.md

patterns-advanced-generics.md

patterns-api-client.md

patterns-branded-types.md

patterns-builder.md

patterns-deep-readonly.md

patterns-dependency-injection.md

patterns-event-emitter.md

patterns-form-validation.md

patterns-plugin-system.md

patterns-recursive-types.md

patterns-state-machine.md

patterns-type-safe-module.md

practices-illegal-states.md

practices-module-patterns.md

practices-runtime-validation.md

practices-type-first.md

types-conditional.md

types-generics.md

types-index-signatures.md

types-mapped.md

types-narrowing.md

types-template-literals.md

types-type-assertions.md

types-unions-intersections.md

utilities-custom-mapped-types.md

utilities-extract-exclude.md

utilities-key-remapping.md

utilities-nonnullable-awaited.md

utilities-partial-required.md

utilities-pick-omit.md

utilities-readonly-record.md

utilities-returntype-parameters.md

SKILL.md

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