Progress towards #10766
I thought that #10768 achieved, but when I went to use this stuff (in
Hydra), turns out it did not. (Those `using FooConfig;` lines were not
working --- they are so finicky!) This PR gets the job done, and adds
some trivial unit tests to make sure I did what I intended.
I had to add add a header to expose `SSHStoreConfig`, after which the
preexisting `ssh-store-config.*` were very confusingly named files, so I
renamed them to `common-ssh-store-config.hh` to match the type defined
therein.
This makes it possible to certain discern failures from empty
snippets, which I think is an ok review comment.
Maybe it should do so for swapped column indexes too, but I'm not
sure.
I don't think it matters in the grand scheme. We don't even have
a real use case for `nullopt` now anyway.
Since we don't have a use case, I'm not applying this logic to
higher level functions yet.
Unfortunately these don't render correctly, because they go into the
markdown renderer, instead of the terminal.
```
nix-repl> :doc lib.version
Attribute '[35;1mversion[0m'
… defined at [35;1m/home/user/h/nixpkgs/lib/default.nix:73:40[0m
```
We could switch that to go direct to the terminal, but then we should
do the same for the primops, to get a consistent look.
Reverting for now.
This reverts commit 3413e0338cbee1c7734d5cb614b5325e51815cde.
... at call sites that are may be in the hot path.
I do not know how clever the compiler gets at these sites.
My primary concern is to not regress performance and I am confident
that this achieves it the easy way.
When the separator is empty, no difference is observable.
Note that concatStringsSep has centralized definitions. This adds the
required definitions. Alternatively, `strings-inline.hh` could be
included at call sites.
Considering that `value` was probably parsed with tokenizeString
prior, it's unlikely to contain empty strings, and we have no
reason to remove them either.
Empty attributes are probably not well supported, but the least we
could do is leave a hint.
Attribute path rendering and parsing should be done according to
Nix expression syntax in my opinion.
(System) features are unlikely to be empty strings, but when they
come in through structuredAttrs, they probably can.
I don't think this means we should drop them, but most likely they
will be dropped after this because next time they'll be parsed with
tokenizeString.
TODO: We should forbid empty features.
I don't think it's completely impossible, but I can't construct
one easily as derivationStrict seems to (re)tokenize the outputs
attribute, dropping the empty output.
It's not a scenario we have to account for here.
Bug not reported in 6 years, but here you go.
Also it is safe to switch to normal concatStringsSep behavior
because tokenizeString does not produce empty items.
The empty attribute name should not be dropped from attribute paths.
Rendering attribute paths with concatStringsSep is lossy and wrong,
but this is just a first improvement while dealing with the
dropEmptyInitThenConcatStringsSep problem.
