Incremental --build, then delete generated js file, then another incremental --build does not recreate js file

[mmorearty]

TypeScript Version: 3.4.0-dev.20190326

Search Terms:

incremental

Code

tsconfig.json:

{
  "compilerOptions": {
    "incremental": true
  }
}

x.ts:

console.log("hello");

Expected behavior:

• $ tsc --build
• x.js has been generated
• $ rm x.js
• $ tsc --build

Expected: x.js has been regenerated

Actual behavior:

x.js still does not exist

Related Issues:

Did not find any.

[sheetalkamat]

Hmm the root cause of this is that in general our incremental build (BuilderProgram) isn't equipped to deal with missing output file as indication to build but changed file as more like it. Need to think about what we can do here. Till then the workaround is to run --clean and then build or add comment or something into the file whose output needs to be generated.
Note that this didn't originate with just --incremental, this would be same behavior when you followed same pattern but were running tsc --build --watch from first step (even without --incremental in compiler options)

FYI @RyanCavanaugh @DanielRosenwasser

[irakliy81]

A separate, but possibly related issue: deleting source .ts files does not remove the related .js files. Right now, to address this, I clean the output directory before every compilation - but this makes it impossible for me to use the --incremental flag.

[sheetalkamat]

@irakliy81 that's totally out of scope and does not work even without --incremental. Build cannot delete any output file unless you specify clean (which will also delete output files of config specified at that moment)

[sdwvit]

👍
Also experienced this bug:
We had a piece of code which imported a recently deleted file error in one of the dev-branches, and since we use caching of buildinfo in CI, parallel branch builds started to experience this missing file too. However, the error was different than just 'module not found', it was another type error from patient-0 branch.

[irakliy81]

@sheetalkamat - yes, I wouldn't expect it to work without --incremental flag since in that case there is no info stored about the previous build. But with the --incremental flag, it should be possible to remove output files if the source files have been removed.

A separate question: how do you specify clean? It doesn't seem to be a valid compiler option.

[milesj]

@irakliy81 --clean

[irakliy81]

@milesj - thanks! But it doesn't seem to be listed here: https://www.typescriptlang.org/docs/handbook/compiler-options.html and if I try to set it in VS Code I get "unknown compiler option" error. Am I missing something?

[milesj]

It's part of project references. Not sure if it's available outside of that, nor as a compiler option. https://www.typescriptlang.org/docs/handbook/project-references.html

[sdwvit]

any plans on fixing this? cc @sheetalkamat

it kills the point of caching build info in CI

[RyanCavanaugh]

For clarity: What/who is deleting the output files and why?

[sheetalkamat]

There are multiple workarounds for this issue.

1. Run tsc --b --clean
2. Delete .tsbuildinfo file as well

Its not clear why only .js file is deleted