conan2nix

... so we can build google-orbit on nixos

NixOS/nixpkgs#94555

status

proof of concept

sample output

nix-conan-cache/abseil/20200923.3/_/_/export.nix

{ lib, stdenv, fetchurl, writeText }:
let
  url-base = "https://conan.bintray.com/v2/conans/abseil/20200923.3/_/_/revisions/b2d602ea9f45c5bb738956d0f7aafa3d";
  url-export = "${url-base}/files";
  url-package = "${url-base}/packages/b911f48570f9bb2902d9e83b2b9ebf9d376c8c56/revisions/d65ce147e5eacfc4eb61c65f3c29744b/files";
in
stdenv.mkDerivation rec {
  pname = "abseil";
  version = "20200923.3-b2d602ea9f45c5bb738956d0f7aafa3d";
  conan-reference = "abseil/20200923.3";
  conan_export-tgz = fetchurl { url = "${url-export}/conan_export.tgz"; sha256 = "1d770344954aadff19f12e3cd1be3ae687b3ed8d27c6d14a669caf554551e965"; };
  conan_sources-tgz = fetchurl { url = "${url-export}/conan_sources.tgz"; sha256 = "540293634a3b583996bd6e7fbff83c5a793e28fb463555f1119eefb094844c13"; };
  conanmanifest-txt = fetchurl { url = "${url-export}/conanmanifest.txt"; sha256 = "33fc4986b58fadc72f420b1c025cdfb456446460dbfecc90fcd5267bbd6e9c6d"; };
  conanfile-py = fetchurl { url = "${url-export}/conanfile.py"; sha256 = "57fc8d524fd61b75a619534d9d700ae00d056d76a7b2187fb909fe96dab8f314"; };
  conaninfo-txt = fetchurl { url = "${url-package}/conaninfo.txt"; sha256 = "2bd09438aeaed51559486d928d15f9929ddb7bfd87ca7d8a40694ae2afad4f1d"; };
  conan_package-tgz = fetchurl { url = "${url-package}/conan_package.tgz"; sha256 = "3938a658f83abc2360512d48dd7630f8f3ce89267bec16f282cf165240fcf8e2"; };
  conanmanifest-txt-2 = fetchurl { url = "${url-package}/conanmanifest.txt"; sha256 = "48636fbfafad647762efd3779a5b856f5ee88ad74199df9e3a3fc81a89ecad94"; };
  metadata-json = writeText "metadata.json" ''
    {"recipe": {"revision": "b2d602ea9f45c5bb738956d0f7aafa3d", "remote": "conan-center", "properties": {}, "checksums": {"conan_export.tgz": {"md5": "8a0c57a283c2ab579e676b2bc2ee6565", "sha1": "51776f21a4bc3ed9177d8663e24907efe3583ea7"}, "conanmanifest.txt": {"md5": "a4997bb29975190163371a3f81543159", "sha1": "debdb80c399f5f5d4a33b60bc2a80bddc982e42f"}, "conanfile.py": {"md5": "74addcc109f4e606abf57d75590d4540", "sha1": "a7afe538be9b315a4db92a9d7ea22921584531b8"}}}, "packages": {}}
  '';
  srcs = [conan_export-tgz conan_sources-tgz conanmanifest-txt conanfile-py conaninfo-txt conan_package-tgz conanmanifest-txt-2 metadata-json];
  phases = "checkPhase installPhase installCheckPhase distPhase";
  # path is relative to $CONAN_USER_HOME/.conan/data
  installPhase = ''
    path=abseil/20200923.3/_/_

    mkdir -p $out/$path/dl/export
    cp ${conan_export-tgz} $out/$path/dl/export/conan_export.tgz
    cp ${conan_sources-tgz} $out/$path/dl/export/conan_sources.tgz

    mkdir -p $out/$path/export
    cp ${conanmanifest-txt} $out/$path/export/conanmanifest.txt
    cp ${conanfile-py} $out/$path/export/conanfile.py


    mkdir -p $out/$path/dl/pkg/b911f48570f9bb2902d9e83b2b9ebf9d376c8c56
    cp ${conan_package-tgz} $out/$path/dl/pkg/b911f48570f9bb2902d9e83b2b9ebf9d376c8c56/conan_package.tgz

    mkdir -p $out/$path/package/b911f48570f9bb2902d9e83b2b9ebf9d376c8c56
    cp ${conaninfo-txt} $out/$path/package/b911f48570f9bb2902d9e83b2b9ebf9d376c8c56/conaninfo.txt
    cp ${conanmanifest-txt-2} $out/$path/package/b911f48570f9bb2902d9e83b2b9ebf9d376c8c56/conanmanifest.txt


    cp ${metadata-json} $out/$path/metadata.json
  '';

  meta = {
    description = "Abseil Common Libraries (C++) from Google";
    license = lib.licenses.asl20;
    homepage = "https://github.com/abseil/abseil-cpp";
    url = "https://github.com/conan-io/conan-center-index";
  };
}

build:

nix-build -E 'with import <nixpkgs> { }; callPackage ./nix-conan-cache/abseil/20200923.3/_/_/export.nix {}'

conanfile analyzer

conanfile-analyze.py is a tool for dynamic analysis of conanfile.py files

we want to extract the source URLs, so we can preload the source files and run conan offline with conan install --build missing offline

./conanfile-analyze.py ~/.conan/data/freetype-gl/79b03d9/orbitdeps/stable/export/conanfile.py
# /home/user/.conan/data/freetype-gl/79b03d9/orbitdeps/stable/export/conanfile.py
found: class FreetypeglConan (ConanFile)
fake conans.ConanFile.__init__ () {}

run conanfile.py source()
fake conans.ConanFile.run ('git clone https://github.com/rougier/freetype-gl.git',) {}
fake conans.ConanFile.run ('git checkout 79b03d9',) {'cwd': 'freetype-gl/'}
fake conans.tools.patch () {'base_path': 'freetype-gl/', 'patch_file': 'patches/001-patch.diff'}
done conanfile.py source()

cmd_history:
$ git clone https://github.com/rougier/freetype-gl.git
$ git checkout 79b03d9

git_repos = [{'url': 'https://github.com/rougier/freetype-gl.git', 'name': 'freetype-gl', 'dir': 'freetype-gl', 'owner': 'rougier', 'rev': '79b03d9'}]
get_files = []

in this example, the download link would be https://api.github.com/repos/rougier/freetype-gl/tarball/79b03d9

in nix we can use

{
  src = fetchFromGitHub {
    owner = "rougier"; repo = "freetype-gl"; rev = "79b03d9";
    sha256 = "0000000000000000000000000000000000000000000000000000"; # TODO fix checksum
  };
}

related

conan-io/conan#4668 # Cache Downloads

If you do not want to download anything all the time then you could use conan's export_sources feature
https://docs.conan.io/en/latest/reference/conanfile/attributes.html#exports-sources

conan-io/conan#6287 # Feature/download cache

Implement a download cache, which can be shared and concurrently used among different conan user homes

conan-io/conan#6754 # [question] Offline - Extracting dependency tree with conan_api (without remotes)

You might want to have a look to the generated conan.lock lockfile when you do a conan install or similar.
It has encoded the whole graph. There are other commands that will output a json with dependencies information too.
conan info poco/1.9.4@ --json=file.json
The file.json file will contain the dependencies.
The conan info command will not use the internet if the packages are already in the cache.

conan-io/conan#6727 # [question] conan info|install skips cache and tries to find package from remote instead?

I've exported a package to my local cache successfully. I've disabled the default remote because I want to work locally.

conan-io/conan#5938 # [feature] using conan offline - normaly handle existent file in tools.download (uploader_downloader.py)

conan-io/conan#5575 # [Question] Offline usage without remote

in an offline environment I would suggest copying local cache from the one installed when online
recipes like OpenSSL are downloading the sources from the internet.
So even if you have the source code for the recipe,
you will not be able to create the package locally