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#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p "python3.withPackages (ps: with ps; [ requests ])" nixpkgs-fmt
# vim: set syntax=python:
import hashlib
import json
import re
import struct
import subprocess
import requests
gen_file = "deps.nix"
repo = "facebook/sapling"
source_file = "eden/scm/setup.py"
# Fetch the latest stable release metadata from GitHub
latest = requests.get(f"https://api.github.com/repos/{repo}/releases/latest").text
latest = json.loads(latest)
# Find latest's git tag which corresponds to the Sapling version. Also needed
# is a hash of the version, so calculate that here. Taken from Sapling source
# `$root/eden/scm/setup_with_version.py`.
version = str(latest["tag_name"])
version_hash = str(
struct.unpack(">Q", hashlib.sha1(version.encode("ascii")).digest()[:8])[0]
)
# Fetch the `setup.py` source and look for instances of assets being downloaded
# from files.pythonhosted.org.
source = requests.get(
f"https://raw.githubusercontent.com/{repo}/{version}/{source_file}"
).text
matches = re.findall(
r'(https://files\.pythonhosted\.org/packages/.*?/.*?/.*?/)(.*?)(-.*?)"', source
)
# For each matched asset URL, prefetch said asset and build the corresponding
# Nix code needed to call `fetchurl` and perform symlinks in the actual build.
assets = ""
links = ""
for m in matches:
sha256 = (
subprocess.Popen(
["nix-prefetch-url", "--type", "sha256", f"{m[0]}{m[1]}{m[2]}"],
text=True,
stdout=subprocess.PIPE,
)
.stdout.read()
.strip()
)
assets += """ {} = fetchurl {{
url = "{}{}{}";
sha256 = "{}";
}};\n""".format(
m[1], m[0], m[1], m[2], sha256
)
links += " ln -s ${{{}}} {}{}\n".format(m[1], m[1], m[2])
assets = assets.strip()
links = links.strip()
# Render an autogenerated Nix file with the fetched dependency and version
# information for import in the main derivation.
out = f"""
# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
# Generated by `gen-deps`
{{ lib, fetchurl }}:
let
{assets}
in
{{
links = ''
{links}
'';
version = "{version}";
versionHash = "{version_hash}";
}}
"""
with open(gen_file, "w+") as f:
f.write(out.strip())
# Formamt the generated Nix file, which also serves as a syntax sanity check.
subprocess.run(["nixpkgs-fmt", gen_file], check=True)
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