[bug#47187] [PATCH] gnu: Add c-lightning.

[ZmnSCPxj]

Good morning Leo,

> > Yes, it is true that there is something of a requirement of a strict
> > behavior here, I suppose it is possible to use `git-fetch` instead of
> > `url-fetch` for our external libraries.
>
> Yes you can use git-fetch, to make sure we are on the same page, are
> you speaking of strict behavior requirements like for Bitcoin Core's
> consensus code?

Well we need to produce signatures and transactions that pass Bitcoin Core 
signature validation at least, so it is best to use a version of `libsecp256k1` 
(which produces signatures) that we know works, as well as `libwally-core` 
(which produces transactions).
I would personally use the `libsecp256k1` version that `libwally-core` vendors 
in as well, since there may be specific interactions between `libwally-core` 
and `libsecp256k1` that may be different if we use the Bitcoin Core version of 
`libsecp256k1`.

For `libsodium`, at least the hashing has to work correctly, but I think it is 
simple enough that strict behavior requirements are not so onerous.
Indeed, we usually get this from the OS (but we need a later feature than that 
available on some old Ubuntu versions, which is why it got vendored in), so I 
should probably "just" add it as an input.

>
> > How do I generate `guix hash` for `git-fetch`ed `source`s?
>
> Actually what I do is put a wrong hash in and then copy the "actual
> hash" from the error. I havent found another way but this definitely
> feels subpar and prevents much verification before putting in the hash,
> better suggestions welcome.

Haha I shall do so as well.

>
> > However it also means that every release of C-Lightning I have to go
> > double-check what git commit to use for each library (though `jsmn`
> > and `libbacktrace` at least seem very stable).
> > But it looks to me that unvendoring will require more extensive
> > patching of the `Makefile` and an even larger maintenance burden on
> > Guix side?
>
> Unvendoring is more or less a policy because we must be able to audit
> each piece of software separately for freedom issues (licenses,
> violations to the GNU FSDG), and it eases work for security-patching
> also.

I understand.

This will require a largish amount of work I think.

Would this technique be acceptable?

* `add-before 'configure 'unvendor-externals`
  * `rm -rf` the vendored externals.
  * `ln -s` the needed `.h` and `.la`/`.a`/`.so` files from the `inputs` to the 
expected paths within the `external/` directory.

?

> > Please do, I am not very familiar with any Python infrastructure and
> > am primarily a C programmer here, I just barely hack together some
> > kind of test in Python.
>
> If you can list the Python dependencies and their version I can look at
> packaging them.

We have a `requirements.txt` file which contains this, I duplicate below:

```
# Dependencies required to build and test c-lightning
https://github.com/ElementsProject/libwally-core/releases/download/release_0.8.0/wallycore-0.8.0-cp36-cp36m-linux_x86_64.whl;
 'linux' in sys_platform and python_version == '3.6'
https://github.com/ElementsProject/libwally-core/releases/download/release_0.8.0/wallycore-0.8.0-cp37-cp37m-linux_x86_64.whl;
 'linux' in sys_platform and python_version == '3.7'
https://github.com/ElementsProject/libwally-core/releases/download/release_0.8.0/wallycore-0.8.0-cp37-cp37m-macosx_10_14_x86_64.whl;
 sys_platform == 'darwin' and python_version == '3.7'
mrkd ~= 0.1.6
Mako ~= 1.1.3

# Dependencies from pyln-client
Sphinx ~= 3.4.0
flake8==3.7.8
recommonmark>=0.7.*
sphinx-rtd-theme==0.4.2
sphinxcontrib-websupport==1.1.0
tqdm==4.32.2

# Dependencies from pyln-testing
Flask==1.1.*
cheroot==8.5.*
ephemeral-port-reserve==1.1.1
filelock==3.0.*
flaky ~= 3.7.0
psutil==5.7.*
psycopg2-binary==2.8.*
pytest-rerunfailures==9.1.1
pytest-timeout ~= 1.4.2
pytest-xdist ~= 2.2.0
pytest==6.1.*
python-bitcoinlib==0.11.*

# Dependencies from pyln-proto
base58 ~= 2.0.1
bitstring ~= 3.1.6
coincurve ~= 13.0.0
cryptography ~= 3.2
mypy ~= 0.790
pysocks ~= 1.7.1

# Dependencies from pyln-spec
# None
```

Incidentally, we also install some Python modules.
How do I "properly" export the Python modules within Guix?

Regards,
ZmnSCPxj