Some additional context: I am using WebStorm 2021.3.2 on Windows 10. I am using the built in JavaScript debugger, and when breakpoints are hit, a new file with a path of "localhost" opens and execution breaks, despite the breakpoints being set in the file on disk. This screenshot should demonstrate - the tab on the bottom is the same as the tab on top, except it is referring to a file on from the localhost webserver, and not my disk (C:\ drive):

that's strange, have never seen such issues when using the built-in web server for files hosting. Do you use any kind of transpiling/beautifying/etc. or the code in runtime exactly matches the one on disk? Can you repeat the issue in a new project?

I just now realized I was using url "https://localhost:63341" - after switching to just "http://localhost:63341" the issue has not appeared again. What effect does using https and clicking thru the insecure site warning on a browser have over using http on localhost?

Not sure... It works for me (in 2021.3.2) when using https://localhost:63342 URL

Is there any diagnostic data I could collect and/or view that would help me determine what is going on? I am still observing this behavior, regardless of http/https prefix on localhost url.

Please enable js.debugger.wip.log in Registry (Help | Find action..., type Registry... to locate it) by setting it to path to some temporary file like /tmp/wip.json, recreate the issue and provide this log along with the idea.log (Help > Show Log in ...). Note that the debug log will be re-written on each debugger start, so it's important to copy the log right after reproducing the issue

Note: please don't paste logs content here, upload them to some file server and share a link

Ok thank you, Elena. Helpful as always! I will enable this today and post back later this week with any relevant findings.

I was able to reproduce the issue while the js debugger log was enabled. I wasn't really able to interpret anything in the file; I have uploaded it here to share:

https://1drv.ms/u/s!AptI9iioFTxo1Z4pL0RZNyGiiOKZEw?e=vvwcZE

This screenshot illustrates the exact files where the issue was observed. in "assets\...\analyze-functions.js" I have set a breakpoint. However, WebStorm opens up a file via the "localhost:63341\...\analyze-functions.js" web server link. Code execution stops at the same pace the breakpoint was placed in that file. I'm unsure if this is the intended behaviors according to a setting or configuration I may have, but it seems to be randomly occurring. I do not observe this behavior every time. Sometimes the breakpoint will be hit on the file in which it was placed, and sometimes the file is opened via the localhost link.

didn't find any notion of a script with this name in the log... But looks as if you have at least some of your source scripts bundled with webpack - is it true? This can be a sourcemaps issue then - it the debugger can't resolve the original script from sourcemaps, the runtime version will be opened instead

I am not using webpack or any other transpilers or preprocessors, and no code minification. I am observing this behavior in a static website, using the built in WebStorm "JavaScript Debug" Run/Debug configuration.