Build mode
- TypeScript course
- Expert
- Lesson 13/35
- 4 min
Learn project building with tsc --build.
What is build mode?
tsc --build is a mode that compiles projects in dependency order and uses an incremental cache. Referenced projects need composite: true to be buildable; incremental: true lowers rebuild cost with a .tsbuildinfo file.
// tsconfig.json
{
"compilerOptions": {
"composite": true,
"incremental": true,
"outDir": "dist"
}
}Build mode recompiles only changed projects, so it speeds up large monorepos.
composite and incremental
composite: true makes a project referenceable by others; it also forces declaration and outDir. incremental: true writes build info to a .tsbuildinfo file and processes only changed files on subsequent builds.
{
"compilerOptions": {
"composite": true,
"incremental": true,
"declaration": true,
"outDir": "dist"
}
}A non-composite project cannot be referenced; build mode errors out.
Practice Validate build config
Write a validateBuildConfig function that checks a config object's composite and incremental fields and pushes to an errors array when missing. Print the error count for the config { composite: true, incremental: true }.
Starter code
// validateBuildConfig: build modu için config'i doğrula
// composite ve incremental alanlarını kontrol et
// eksikse hata dizisine ekle
// hata sayısını yazdırSample solution
function validateBuildConfig(config: { composite?: boolean; incremental?: boolean }): string[] {
const errors: string[] = [];
if (!config.composite) errors.push("composite must be true");
if (!config.incremental) errors.push("incremental recommended");
return errors;
}
const config = { composite: true, incremental: true };
console.log(validateBuildConfig(config).length);Expected output
0
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 In what order does `tsc --build` compile?
- Only the root project
- Random order, in parallel
- In dependency order, rebuilding changed projects Correct answer
- Alphabetically, all projects
Explanation: Build mode first resolves dependencies, then compiles in dependency order and rebuilds only changed projects; it is not alphabetical or random.
2 Enable composite
{
"compilerOptions": {
"composite": ____,
"declaration": true
}
}{
"compilerOptions": {
"composite": true,
"declaration": true
}
}Explanation: The composite flag takes a boolean true value; false disables referenceability, and null and "yes" are not valid.
3 Build mode parts
| Term | Meaning |
|---|---|
tsc --build |
compiles projects in dependency order |
composite: true |
enables referenceability |
incremental: true |
enables .tsbuildinfo cache |
.tsbuildinfo |
incremental build info |