Support `tsc --build --noEmit`

[segevfiner]

Suggestion

🔍 Search Terms

tsc --build --noEmit build noEmit

List of keywords you searched for before creating this issue. Write them down here so that others can find this suggestion more easily and help provide feedback.

✅ Viability Checklist

My suggestion meets these guidelines:

• [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code
• [x] This wouldn't change the runtime behavior of existing JavaScript code
• [x] This could be implemented without emitting different JS based on the types of the expressions
• [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• [x] This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

Allow tsc --build --noEmit, the relevant types can be emitted to the tsbuildinfo for incremental building. This is very useful to allow type checking only for projects using project references and working with a bundler. e.g. A create-vue project, which currently has to resort to hackery such as vue-tsc --noEmit -p tsconfig.vitest.json --composite false which is not as accurate as type checking each project individually.

📃 Motivating Example

tsc --build --noEmit is now supported, allowing to only run type checking for projects using project references that don't also build types using tsc.

💻 Use Cases

Type checking only, for projects using other build tools than tsc but still using project references for each of configuration.

[sheetalkamat]

tsc --build --noEmit is supported unless a project references another project which would make it difficult to support since its depending on d.ts output file from the referenced project.

[segevfiner]

Note that referenced projects were not allowed to specify noEmit in TS<5, but they are allowed now, although the behavior in terms of type checking is unclear, seems like it skips them or something of that sort.

[thebanjomatic]

I encountered this problem as well recently. You can specify noEmit: true in the tsconfig.js, but you can't pass it via the command-line. Support for --emitDeclarationOnly was added in this PR: https://github.com/microsoft/TypeScript/issues/51164 would it be reasonable to add --noEmit as well?

[david-alpert-nl]

I got here because I am attempting to run tsc --noEmit for type checking since my build tooling (vite) explicitly transpiles only and does not validate type consistency.

I find that tsc --noEmit does what I want but emits no progress while it's running. when I tried to add --verbose it says that the progress update is only supported with --build but that --build and --noEmit are not permitted together

tsc --verbose --noemit 
error TS5093: Compiler option '--verbose' may only be used with '--build'.

tsc --build --verbose --noemit
error TS5094: Compiler option '--noemit' may not be used with '--build'.

[Zzzen]

We are handling a sizable project where approximately 30% of the time is spent on transform and emit tasks. This duration could be decreased if this functionality is incorporated.

Projects in scope:                        100
Projects built:                            95
Aggregate Files:                       415465
Aggregate Lines of Library:           3727607
Aggregate Lines of Definitions:      25912137
Aggregate Lines of TypeScript:        2453924
Aggregate Lines of JavaScript:            844
Aggregate Lines of JSON:               111484
Aggregate Lines of Other:                   0
Aggregate Identifiers:               37850747
Aggregate Symbols:                   33949727
Aggregate Types:                      3646787
Aggregate Instantiations:            14245043
Aggregate Memory used:               3977596K
Aggregate Assignability cache size:   1965511
Aggregate Identity cache size:          96331
Aggregate Subtype cache size:          121867
Aggregate Strict subtype cache size:   116815
Aggregate I/O Read time:                1.57s
Aggregate Parse time:                  16.50s
Aggregate ResolveModule time:          14.52s
Aggregate ResolveTypeReference time:    0.51s
Aggregate ResolveLibrary time:          0.24s
Aggregate Program time:                56.92s
Aggregate Bind time:                    8.03s
Aggregate Check time:                 227.75s
Aggregate transformTime time:          33.99s
Aggregate commentTime time:             2.28s
Aggregate Source Map time:              2.16s
Aggregate printTime time:              59.12s
Aggregate Emit time:                   59.28s
Aggregate I/O Write time:               4.87s
Config file parsing time:               0.64s
Up-to-date check time:                  0.00s
Build time:                           371.55s

[proyectoramirez]

I am equally finding a need for this option. I am working on a large codebase with project references, and I am having issues related to this. We have had refactors that cause typechecking issues due to old dist files being left behind.

This could be solved with --build --noEmit, since we only need the typechecking signal from tsc. The files are otherwise all bundled via webpack

[aminpaks]

We're looking for something similar but for type checking a single composite project without generating any output (maybe except for tsconfig.tsbuildinfo). Currently a composite project can't turn off declarations.