The point of this is to be able to do `meta.homepage = src.meta.homepage;`
instead of the usual copy-paste for the packages that are hosted
on these hosting services.
Instead it is provided to the user who can choose whether or not
to include it in the final derivati. Example of including would
be:
```nix
callPackage ... (self: { inherit (self.extras) extraThing; })
```
These extras are also available downstream without being built by
default. This is achieved with `passthru`.
- Only they are added to the optional build path (share/agda)
- Only they are are passed as an include dir (share/agda)
- Only they are propigatedBuildInputs
Instead, discover it automatically when building the package.
This makes `buildRustPackage` more future-proof with respect to changes
in how `cargo` generates the hash.
Also, it fixes broken builds in i686 because apparently, cargo generates
a different registry index hash in this architecture (compared to
x86-64).
This is unused, future users can just use override `buildFlags`
and extend/replace as needed. `includeDirs` is provided for this
purpose.
We should add `dirOf self.everythingFile` rather than `.`, but
`dirOf` breaks on relative paths so that is not an option.
This makes buildRustPackage portable to non-Linux platforms.
Additionally, now we also save the `Cargo.lock` file into the fetch output, so
that we don't have to run $cargoUpdateHook again just before building.
... in a more generic way.
With this commit, if you need to patch a registry package to make it
work with Nix, you just need to add a script to patch-registry-deps
in the same style as the `pkg-config` script.
Instead, move that code into buildRustPackage.
The setup hook was only doing part of the work anyway, and having it in
a separate place was obscuring what was really going on.
Emacs will call package-initialize itself, if required, or the user will
call it in their initialization file. There is no reason to call it in
the wrapper and doing so only increases start-up time.
It turns out that `cargo`, with respect to registry dependencies, was
ignoring the package versions locked in `Cargo.lock` because we changed
the registry index URL.
Therefore, every time `rustRegistry` would be updated, we'd always try
to use the latest version available for every dependency and as a result
the deps' SHA256 hashes would almost always have to be changed.
To fix this, now we do a string substitution in `Cargo.lock` of the
`crates.io` registry URL with our URL. This should be safe because our
registry is just a copy of the `crates.io` registry at a certain point
in time.
Since now we don't always use the latest version of every dependency,
the build of `cargo` actually started to fail because two of the
dependencies specified in its `Cargo.lock` file have build failures.
To fix the latter problem, I've added a `cargoUpdateHook` variable that
gets ran both when fetching dependencies and just before building the
program. The purpose of `cargoUpdateHook` is to do any ad-hoc updating
of dependencies necessary to get the package to build. The use of the
'--precise' flag is needed so that cargo doesn't try to fetch an even
newer version whenever `rustRegistry` is updated (and therefore have to
change depsSha256 as a consequence).
