[heft] rspack-plugin configuration loader incorrectly determines there is no configuration file

[UberMouse]

Summary

Due to this code in the heft-rspack-plugin it will silently ignore some classes of errors loading the configuration file, saying instead that there is no config file found.

At the very least if the config file imports a depedency that is not found it will trigger the issue, I think also errors evaluating the configuration cause the issue but I don't remember now. Possibly this issue only happens with .mjs files as well.

Repro steps

1. have heft-rspack-plugin setup in a package
2. import some invalid dependency in the config file
3. run heft configured to use the plugin

Expected result: some sort of error about how loading the config file failed

Actual result: config file not found

Details

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@rushstack/heft version?	0.75.0
Operating system?	NixOS
Node.js version (node -v)?	22.14.0

[iclanton]

@bmiddha - Would you take a look at this?