Dealing with reserved file names under MS Windows

[lefou]

In PR #2959 I run into a hard diagnose issue with file names on MS Windows.

Here is a excerpt from an official Win32 documentation:

• Do not use the following reserved names for the name of a file:

CON, PRN, AUX, NUL, COM0, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, COM¹, COM², COM³, LPT0, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, LPT9, LPT¹, LPT², and LPT³. Also avoid these names followed immediately by an extension; for example, NUL.txt and NUL.tar.gz are both equivalent to NUL. For more information, see Namespaces.

I think we should discuss a nice way to deal with it in Mill. Mill currently assumes all legal class names are supported. But having a target named con can fail on Windows with a uninformative error message. Since we create metadata files unter out/ like con.json, con.log and con.dest, which would all be illegal under a Windows file system namespace.

[lefou]

A rather simple and generic way could be to append a single character to all or only those reserved names. For example an underscore (_). Or the more Windows typical tilde (~). Resulting in names like con~.json, con~.json and con~.dest.