A bash completion script for cabal-install

complete-cabal.py

#!/usr/bin/python3

"""
Configure with

    complete -C /path/to/script cabal
"""

import os.path
import json
import collections
import subprocess
import sys
import os

def find_project():
    p = os.path.realpath('.')
    while not os.path.ismount(p):
        dist = os.path.join(p, 'dist-newstyle')
        if os.path.exists(dist):
            return dist

    return None

def list_components(project_root, type_filter=None):
    plan = json.load(open(os.path.join(project_root, "cache", "plan.json")))
    components = collections.defaultdict(lambda: 0)
    for c in plan['install-plan']:
        pkg = c['pkg-name']
        if c.get('type') == 'pre-existing':
            continue

        comp = c.get('component-name')
        if comp is None:
            continue
        if type_filter is not None and not comp.startswith(type_filter):
            continue

        components['%s:%s' % (comp, pkg)] += 1
        components[comp] += 1
        components[pkg] = 1

    return [c for c,v in components.items() if v == 1]

valid_modes = {
    'new-build': None,
    'new-run': 'exe',
    'new-test': 'test',
    'new-bench': 'bench'
}

def main():
    # determine mode
    prev = os.environ['COMP_LINE'].split()
    mode = None
    type_filter = None
    for opt in prev:
        x = valid_modes.get(opt)
        if x is not None:
            mode = opt
            type_filter = x
            break

    # Find components
    prefix = sys.argv[2]
    proj = find_project()
    if proj is None: raise RuntimeError("no project found")
    comps = list_components(proj, type_filter)

    opts = subprocess.check_output(['cabal', '--list-options']).decode('UTF-8').split()
    # Exclude modes if one was already given
    if mode is not None:
        opts = [ opt for opt in opts if opt.startswith('-') ]

    # Build completions
    for opt in opts + comps:
        if opt.startswith(prefix):
            print(opt)

if __name__ == '__main__':
    main()