fetchPypi can result in 404 CURL errors

[CMCDragonkai]

Issue description

Attempting to use fetchPypi on image-match https://pypi.org/project/image-match/ results in:

trying https://pypi.io/packages/source/i/image-match/image-match-1.1.2.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   122  100   122    0     0   1876      0 --:--:-- --:--:-- --:--:--  1876
100   282  100   282    0     0    744      0 --:--:-- --:--:-- --:--:--   744
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404

Example expression:

{
  pkgs ? import ./pkgs.nix
}:
  with pkgs;
  let
    python = python36;
  in
    python.pkgs.buildPythonPackage rec {
      pname = "image-match";
      version = "1.1.2";

      src = python.pkgs.fetchPypi {
        inherit pname version;
        sha256 = "0dxbbb63bkqp1jhwxpsw9398n5h213rh00q622bippvrzynm3i9n";
      };

      propagatedBuildInputs = (with python.pkgs; [
        scikitimage
        six
      ]);

      doCheck = false;
    }

I don't think the upstream files.pythonhosted.org is reliable.

Steps to reproduce

nix-build

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.

 - system: `"x86_64-linux"`
 - host os: `Linux 4.17.6, Form Bay ML, noversion`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.0.4`
 - nixpkgs: `/nix/nixpkgs`

[FRidh]

PyPI does not enforce normalized names for the download files so there is not anything we can do here aside from using the filename as pname.
pypi/conveyor#12

[CMCDragonkai]

Is the solution to just use fetchFromGitHub then?

[FRidh]

If you want to fetch from PyPI then that is clear no solution. If you're fine with using GitHub, then you can use that indeed. Like I said, if you want to use fetchPypi you have to explicitly pass a different pname.

[CMCDragonkai]

I see. Btw, what is the difference between using pname and name for the derivation? It appears to do the same thing for buildPythonApplication at least. I've begun to rely on the existence of a derivation's name when overriding them for other things.

[FRidh]

name is deprecated. One should pass pname and version separately.

[CMCDragonkai]

I meant for the drv itself. Did you mean fetchPypi or the entire drv? Or did you mean all drvs should be using pname now? Or only for buildPythonApplication and buildPythonPackage?

[FRidh]

buildPython* should use pname and version, not name.

For fetchPypi you can pass different pname if needed.