`build_js(watch = TRUE)` keeps rebuilding on Windows

[dmenne]

Steps to reproduce

Run build_js(watch = TRUE) on a fresh Rhino project.

What happened?

Rhino keeps rebuilding the JS even when no changes are being introduced to the sources. This leads to high CPU utilization.

yarn run v1.22.18
$ webpack --watch
asset app.min.js 580 bytes [compared for emit] [minimized] (name: main)
runtime modules 670 bytes 3 modules
../../app/js/index.js 704 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 942 ms
asset app.min.js 580 bytes [emitted] [minimized] (name: main)
runtime modules 670 bytes 3 modules
../../app/js/index.js 704 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 184 ms
asset app.min.js 580 bytes [emitted] [minimized] (name: main)
runtime modules 670 bytes 3 modules
../../app/js/index.js 704 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 138 ms
asset app.min.js 580 bytes [emitted] [minimized] (name: main)
runtime modules 670 bytes 3 modules
../../app/js/index.js 704 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 149 ms
asset app.min.js 580 bytes [emitted] [minimized] (name: main)

Expected behavior

Rhino should rebuild the file once after changes are detected and keep waiting for more changes.

Rhino diagnostics

Windows 10 x64 build 19044 R version 4.2.0 (2022-04-22 ucrt) rhino: 1.0.0 node: v16.15.0 yarn: 1.22.18

Comments

Most likely a Windows problem. Otherwise, yarns works fine.

[kamilzyla]

This behavior is expected. The watch = TRUE argument to rhino::build_js() tells it to "keep the process running and rebuilding JS whenever source files change" (see our docs). Just run rhino::build_js() (watch is FALSE by default).

[dmenne]

Be assured that I read the docs. The expected behavior is that nothing is done when there are no changes, but it keeps rebuilding even without any changes.

[kamilzyla]

@dmenne Oh, perhaps I misunderstood. To be clear: rhino::build_js(watch = TRUE) is expected to run forever, but it should only rebuild when changes are detected in the sources.

Can you please confirm: On your system it keeps running and rebuilding even without adding any changes to the files? Does it lead to high CPU utilization?

[dmenne]

Yes, and yes (20% on a fast 6-core AMD). Not an RStudio problem, same on console R

[kamilzyla]

Thanks @dmenne for confirming, we'll investigate - I'm reopening the issue.

[vibalre]

I can confirm that rhino::build_js(watch = TRUE) keeps rebuilding JS even without any changes to ../../app/js/index.js in a new rhino project.

> rhino::build_js(watch = TRUE)
yarn run v1.22.19
$ webpack --watch
Browserslist: caniuse-lite is outdated. Please run:
  npx browserslist@latest --update-db
  Why you should do it regularly: https://github.com/browserslist/browserslist#browsers-data-updating
Browserslist: caniuse-lite is outdated. Please run:
  npx browserslist@latest --update-db
  Why you should do it regularly: https://github.com/browserslist/browserslist#browsers-data-updating
asset app.min.js 15 bytes [compared for emit] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 629 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 187 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 210 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 193 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 190 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 168 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 203 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 197 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]
webpack 5.69.0 compiled successfully in 171 ms
asset app.min.js 15 bytes [emitted] [minimized] (name: main)
../../app/js/index.js 1 bytes [built] [code generated]

Rhino Diagnostics

> rhino::diagnostics()
Windows 10 x64 build 22621
R version 4.2.1 (2022-06-23 ucrt)
rhino: 1.1.1
node: v18.9.0
yarn: 1.22.19