A little python script to analyze nix build logs to aid understanding dependencies

analyze_build.py

# Author: Andreas Krohn
# Intended to help understanding dependencies by looking at (verbose) nix build outputs

import sys
import getopt
import re

def analyze(logfile):
    hashNames = dict()
    references = dict()

    scanningSection = ''
    scanning = re.compile(r'^scanning\sfor\sreferences\sinside\s\'/nix/store/([^-]+)-([^\']+)\'')
    scanEntry = re.compile(r'^found\sreference\sto\s\'([^\']+)\'')

    inputs = re.compile(r'^(u?n?referenced\sinput:|building\sof)\s\'/nix/store/([^-]+)-([^\']+)\'')

    for line in logfile:
        if scanningSection:
            m = scanEntry.match(line)
            if m:
                references[scanningSection].append(m.group(1))
                continue
            scanningSection = ''

        m = inputs.match(line)
        if m:
            hashNames[m.group(2)] = m.group(3)
            continue

        m = scanning.match(line)
        if m:
            key = m.group(1)
            if key in references:
                print(key, " already in references")
                continue
            references[key] = []
            hashNames[m.group(1)] = m.group(2)
            scanningSection = key
            continue

    for p,c in references.items():
        print(hashNames[p] if p in hashNames else p)
        for d in c:
            print(" -> ", hashNames[d] if d in hashNames else d)


def print_help():
    print("analyze_build.py -l <logfile>")

def run(argv):
    logfilepath = ""
    try:
        opts, args = getopt.getopt(argv, "hl:", ["logfile="])
    except getopt.GetoptError:
        print_help()
        sys.exit(2)

    for opt, arg in opts:
        if opt == "-h":
            print_help()
            sys.exit()
        elif opt in ("-l", "--logfile"):
            logfilepath = arg

    if not logfilepath:
        print_help()
        sys.exit(2)

    with open(logfilepath) as f:
        analyze(f)


if __name__ == '__main__':
    run(sys.argv[1:])