llvm dev - Jan 2021 - Handling platform-specific spellings of the same error in lit tests

Hello,

There are different spellings of the same error based on the platform. For
example,

Windows: no such file or directory
Linux:   No such file or directory
z/OS:    EDC5129I No such file or directory.

So far, these have been handled in lit tests using a regex like so: {{[Nn]}}o
such file or directory

Instead of making this regex more complicated when adding support for more
spellings, an alternative solution was proposed in my patch
https://reviews.llvm.org/D95246. This was to use a lit substitution for error
messages based on the host platform.

//RUN: ..... | FileCheck -DFILE=%t -DMSG=%errc_ENOENT %s
//CHECK:  error: '[[FILE]]': [[MSG]]

If there are any alternative solutions or feedback on this approach, please
reply here or on the patch.

Thanks in advance,
Abhina