This issue is fun. Firstly, it does impact the upstream build. I reproduced
our Homebrew build outside of Homebrew, and the symlinking the symlinks
breaks there.
The way npm's `make install` works is to install everything into the
prefix specified, in this case libexec/npm, and then it creates symlinks
from libexec/npm/lib/node_modules/npm/man/man*/npm* to libexec/npm/share/man*/npm*.
For some reason, those symlinks break, both inside and outside of Homebrew, albeit
slightly differently. Outside of Homebrew they break in the symlinking the
symlinks stage. Inside of Homebrew they break in `make install`. Who even knows why.
This issue also doesn't reproduce constantly.
Sometimes it ["just works"](https://farm3.staticflickr.com/2066/5807458526_dc54025065_z.jpg).
Exactly what variables cause it to work and what causes it to break, who knows. I looked into
different shells, different versions of npm, different OS X versions - None of it seemed to matter.
The workaround is just to symlink the solid, tangible manpages that exist in
libexec/npm/lib/node_modules/npm/man/man* rather than symlinking the symlinks
that exist in libexec/npm/share/man/*.
As reported in https://github.com/Homebrew/homebrew/issues/39823#issue-77146790
in some cases the `make install` stage of `npm` seems to symlink inside the buildpath,
even though we're setting the prefix to libexec/npm and have encountered no other
issues with retention of build paths.
The problem *seems* to be that ln_sf itself is storing the paths. If I do it outside
of Homebrew, I get this:
```
ln -sf share/man/man1/* /Users/Dominyk/Downloads/package/TEST1/hmm/share/man/man1
ls -l /Users/Dominyk/Downloads/package/TEST1/hmm/share/man/man1/npm-config.1
/Users/Dominyk/Downloads/package/TEST1/hmm/share/man/man1/npm-config.1 -> share/man/man1/npm-config.1
```
Which obviously creates dead symlinks in /Users/Dominyk/Downloads/package/TEST1/hmm/share/man/man1/*.
If I switch over to using GNU's `ln` instead of OS X's default, and use this command instead:
`gln -sfr share/man/man1/* /Users/Dominyk/Downloads/package/TEST1/hmm/share/man/man1` I get:
```
/Users/Dominyk/Downloads/package/TEST1/hmm/share/man/man1/npm-config.1 -> ../../../../../man/man1/npm-config.1
```
And it seems to work. To my knowledge, BSD `ln` doesn't contain the relative option.
ClosesHomebrew/homebrew#39823ClosesHomebrew/homebrew#39947.
Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
