Lowest common directory

Question

i have this list in Ansible w dummy folder names:

  - /tmp/another/six
  - /tmp/another/five
  - /hi/ho/one/abc
  - /hi/ho/two/abc
  - /something

i want to create a new list, based on the lowest common directory name.
e.g. for

 - /tmp/another/six
 - /tmp/another/five

the common name is /tmp/another.
e.g. for

  - /hi/ho/one/abc
  - /hi/ho/two/abc 

it is: /hi/ho.

example output of the first example list:

  - /tmp/another
  - /hi/ho
  - /something

i tried something along the lines of: the_list | map('dirname') | unique | min.
but ofc, didn't provide me w the expected results.

Answer 1

With the help of 'a friend', I've written this Ansible plugin:

from ansible.errors import AnsibleFilterError
import os

def lowest_common_directories(paths):
    if not isinstance(paths, list):
        raise AnsibleFilterError('Input should be a list of paths')
    paths = [os.path.normpath(path) for path in paths]
    common_dirs = {}

    for i, path in enumerate(paths):
        has_common = False
        for j in range(len(paths)):
            if i != j:
                common_path = os.path.commonpath([path, paths[j]])
                if common_path != '/':
                    has_common = True
                    if common_path in common_dirs:
                        common_dirs[common_path].add(path)
                        common_dirs[common_path].add(paths[j])
                    else:
                        common_dirs[common_path] = {path, paths[j]}
        
        if not has_common:
            common_dirs[path] = {path}

    final_common_dirs = set()
    for common in sorted(common_dirs, key=lambda x: len(x)):
        if all(not c.startswith(common + '/') for c in final_common_dirs):
            final_common_dirs.add(common)

    return list(final_common_dirs)

class FilterModule(object):
    """ Ansible custom filter plugin """
    def filters(self):
        return {
            'lowest_common_dirs': lowest_common_directories
        }

Call with:

- debug:
    msg: "{{ the_paths | lowest_common_dirs }}"

Provides me w the desired result.