They would not have to write code like `current-source-directory'.

Also note that such affected users had broken code when running the
real file.

`local-file' with absolute paths always did `(canonicalize-path (dirname`
and does not change.
`dirname' being called in a special case of `current-source-directory',
`canonicalize-path' as part of `absolute-file-name'.

Could we finish this bug report by applying your nice test code, but
changing only `absolute-dirname' to do (canonicalize-path (dirname))
in all cases?

Then either add no news item, or write the above?

Regards,
Florian