Optimizing Build Times and Incremental Compilation in TypeScript

Table of Contents

• Introduction to Build Optimization
• Understanding Incremental Compilation
• Enabling Incremental Compilation in TypeScript
• Optimizing Build Times with tsconfig.json
• Using Build Caching in TypeScript Projects
• Leveraging External Tools for Faster Builds (e.g., Nx, Turborepo)
• Best Practices for Build Optimization in TypeScript
• Conclusion

Introduction to Build Optimization

As projects grow in size, build times become a significant part of the developer experience. In TypeScript projects, the TypeScript compiler (tsc) can be relatively slow when dealing with large codebases, particularly when performing full recompilation of all files on each change.

Optimizing build times and leveraging incremental compilation is crucial for improving developer productivity and ensuring quick feedback loops.

Key Areas to Focus on:

1. Incremental Compilation: Only recompiling the parts of the code that have changed.
2. Caching: Reusing previously built outputs to avoid redundant compilation.
3. Parallelization: Running build tasks concurrently to take advantage of multi-core CPUs.
4. Reducing Scope: Limiting the number of files TypeScript needs to analyze.

Understanding Incremental Compilation

Incremental Compilation refers to the process where TypeScript only recompiles the parts of the codebase that have changed since the last build, rather than recompiling the entire project. This significantly reduces build times, particularly in large projects with many files.

Incremental compilation works by maintaining a record of files that have been successfully compiled and their dependencies. The next time a build is triggered, TypeScript can skip over unchanged files and only focus on files that have been modified or are indirectly affected by the changes.

Enabling Incremental Compilation in TypeScript

TypeScript supports incremental compilation out-of-the-box. To enable it, you need to add the incremental flag to your tsconfig.json configuration file.

Example tsconfig.json for Incremental Compilation:

{
  "compilerOptions": {
    "incremental": true,
    "tsBuildInfoFile": "./.tsbuildinfo",  // Store incremental build info here
    "outDir": "./dist",                   // Output directory for compiled files
    "module": "ESNext",                   // Module system
    "target": "ESNext",                   // Target ECMAScript version
    "strict": true,                       // Enable strict type-checking
    "esModuleInterop": true,              // Allow interop with CommonJS modules
    "skipLibCheck": true                  // Skip type-checking of declaration files
  }
}

Key Points:

• incremental: true: This flag enables incremental builds.
• tsBuildInfoFile: This specifies the location where TypeScript stores the build state. It’s used to keep track of which files need to be recompiled.
• outDir: Specifies where the compiled output will be stored.

When incremental compilation is enabled, TypeScript will generate a .tsbuildinfo file in the specified location. This file keeps track of file dependencies, timestamps, and hash values, allowing TypeScript to detect which files need to be recompiled.

Optimizing Build Times with tsconfig.json

In addition to enabling incremental compilation, you can further optimize build times by configuring your tsconfig.json file to better suit large projects.

Common TypeScript Compiler Options for Faster Builds:

• skipLibCheck: This option skips type-checking of declaration files (*.d.ts), which can greatly speed up the build process. "skipLibCheck": true
• exclude and include: Limit the scope of files TypeScript needs to analyze. For example, exclude test files from the build if they aren’t part of the main production code. "exclude": ["node_modules", "dist", "test"], "include": ["src/**/*"]
• noEmitOnError: Set this to false to allow TypeScript to emit JavaScript even if there are type errors (only recommended for certain cases where errors don’t break the application). "noEmitOnError": false
• isolatedModules: This option ensures that TypeScript compiles files in isolation (without cross-file analysis), improving build times when using Babel or other JavaScript compilers in the project. "isolatedModules": true
• skipDefaultLibCheck: Skips type checking of the default library files (lib.d.ts), further speeding up the build process in certain cases. "skipDefaultLibCheck": true

Using Build Caching in TypeScript Projects

One of the most powerful ways to optimize build times is by leveraging build caching. This allows the build system to store the output of previous builds and reuse it in subsequent builds to avoid redundant work.

TypeScript’s Built-in Caching with tsc --build

You can use TypeScript’s --build mode (tsc -b) to enable build caching. This mode is specifically designed for incremental builds in large projects.

• --build Mode: This command enables TypeScript’s caching mechanism for large projects. tsc --build

This will cache the build outputs and only recompile files that have changed since the last successful build.

Integrating with Build Tools (Nx, Turborepo)

Both Nx and Turborepo support caching and parallelization out of the box, helping you scale builds across multiple apps and libraries within a monorepo.

Example: Nx Caching

Nx provides a powerful build caching mechanism, allowing you to save build outputs and reuse them across different tasks. Nx caches build results and test results, ensuring that only the affected projects are rebuilt.

To enable Nx caching, make sure the nx.json configuration file includes the following:

{
  "affected": {
    "defaultBase": "main"
  },
  "tasksRunnerOptions": {
    "default": {
      "runner": "@nrwl/workspace/tasks-runners/default",
      "options": {
        "cacheableOperations": ["build", "test"]
      }
    }
  }
}

Example: Turborepo Caching

Turborepo uses a similar caching strategy with its own turbo.json configuration. Tasks like build and test can be cached and run in parallel for faster results.

{
  "pipeline": {
    "build": {
      "dependsOn": ["^build"],
      "outputs": ["dist/**"]
    },
    "test": {
      "dependsOn": ["build"]
    }
  }
}

Turborepo caches build outputs across multiple pipelines, minimizing redundant work across projects.

Leveraging External Tools for Faster Builds (Nx, Turborepo)

In addition to TypeScript’s native incremental compilation, you can enhance your build system by leveraging external tools such as Nx and Turborepo. These tools are optimized for monorepos and support advanced features like parallel task execution, caching, and dependency graph analysis.

• Nx provides detailed project graphs, allowing you to visualize dependencies and optimize your build strategy.
• Turborepo emphasizes speed and parallelization, enabling concurrent task execution and reducing build times.

By using these tools, you can further optimize TypeScript builds and manage large codebases more efficiently.

Best Practices for Build Optimization in TypeScript

1. Enable Incremental Compilation: Always enable the incremental option in tsconfig.json for faster builds.
2. Optimize tsconfig.json: Use options like skipLibCheck, noEmitOnError, and isolatedModules to reduce unnecessary processing.
3. Use Build Caching: Leverage TypeScript’s build caching or external tools like Nx and Turborepo to cache build outputs and avoid redundant compilation.
4. Limit File Scope: Use the exclude and include options to limit the scope of files TypeScript needs to analyze.
5. Split Large Projects: If possible, split large projects into smaller, more manageable sub-projects or libraries to optimize build times.

Conclusion

Optimizing build times is crucial for maintaining a fast and efficient development workflow, especially in large TypeScript projects. By enabling incremental compilation, configuring TypeScript for faster builds, and leveraging caching and parallelization tools like Nx and Turborepo, you can significantly improve build performance. With these best practices, your TypeScript development process will become faster, more efficient, and more scalable.