Taskwarrior hook script that adds a "blocks:" pseudo-attribute for adding/modifying tasks.

on-modify.blocks_attr.py

#!/usr/bin/env python
#
# Adds the ability to add / modify tasks using a "blocks:" attribute,
# the opposite of "depends:".
#
# This script acts as an on-modify, on-add and on-launch hook at the same time.
#
### SETUP
# Save this file as
#   ~/.task/hooks/on-modify.blocks_attr.py
# change to that directory:
#   $ cd ~/.task/hooks
# make the script executable:
#   $ chmod +x on-modify.blocks_attr.py
# then create symlinks to that file with the other hook names:
#   $ ln -s on-modify.blocks_attr.py on-add.blocks_attr.py
#   $ ln -s on-modify.blocks_attr.py on-launch.blocks_attr.py
#
# Now tell Taskwarrior about the "blocks" attribute:
#   $ task config uda.blocks.type string
#   $ task config uda.blocks.label Blocks
#
# And we're ready to go!
#
# bf@id:~$ t add a
# Created task 1.
#
# bf@id:~$ t add b
# Created task 2.
#
# bf@id:~$ t add c blocks:1
# Created task 3.
#
# bf@id:~$ t 2 mod blocks:1
# Modifying task 2 'b'.
# Modified 1 task.
#
# bf@id:~$ t
# [t next]
#
# ID Age Deps Description Urg 
#  2 18s      b              8
#  3 8s       c              8
#  1 29s 2 3  a             -5
#

import json
import os
import subprocess
import sys

# Adjust this if "task" is not regular Taskwarrior.
TASK = 'task'
# Adjust path if needed. It is a temporary file managed by the hook.
SHIMFILE = "%s/.task/hooks/blocks_shim.txt" % os.getenv('HOME')

def on_launch():
    try:
        with open(SHIMFILE, 'r') as f:
            shim = f.readlines()
    except IOError:
        sys.exit(0)
    while shim:
        line = shim.pop(0).rstrip()
        if not line:
            continue
        if subprocess.call(line.split()) != 0:
            # Error handling by escalating to the user :)
            print("%s ERROR: First line in %s is failing to run!" % (sys.argv[0], SHIMFILE))
            print("Feel free to delete the file, or edit its contents to resolve the problem.")
            shim = [line + '\n'] + shim
            break
    if shim:
        with open(SHIMFILE, 'w') as f:
            f.write(''.join(shim))
        sys.exit(1)
    else:
        os.remove(SHIMFILE)

def handle_blocks_attribute(new):
    if 'blocks' in new:
        with open(SHIMFILE, "a") as f:
            # This needs error handling. If a later hook aborts, the UUID is invalid.
            f.write("%s rc.hooks=off rc.confirmation=no rc.bulk=10000 rc.verbose=nothing %s mod dep:%s\n" % (TASK, new['blocks'], new['uuid']))
        del new['blocks']
    print(json.dumps(new))

old = sys.stdin.readline()
new = sys.stdin.readline()

if not old:
    on_launch()
elif not new:
    handle_blocks_attribute(json.loads(old))
else:
    handle_blocks_attribute(json.loads(new))

note: hooks with helpful metadata (like this one) might mention that taskwarrior v2.3.x+ is required for hooks functionality.

note: The gist works with both python (aka python3) & legacy python (aka python2). That's nice!

Thanks @wbsch for this great script.

I'm using Taskwarrior on several computers, including on Ubuntu on top of the Windows Linux Subsystem (WSL).

I'd like to point out for future users that you may need to specify the #!/usr/bin/env python shebang as #!/usr/bin/env python3, depending on your Linux distribution and version of python available.

I've made the following addition to allow the syntax to support unblock by prefixing the parent id with a '-' ;

        # This needs error handling. If a later hook aborts, the UUID is invalid.
        if not '-' in new['blocks'] :
            f.write("%s rc.hooks=off rc.confirmation=no rc.bulk=10000 rc.verbose=nothing %s mod dep:%s\n" % (TASK, new['blocks'], new['uuid']))
        else :
            f.write("%s rc.hooks=off rc.confirmation=no rc.bulk=10000 rc.verbose=nothing %s mod dep:%s\n" % (TASK, new['blocks'][1:], '-'+new['uuid']))

There are 2 issues (with 2.5.1):

• There is no way to remove a block: task 2 modify blocks: does not remove the dependencies
• Re-running task 2 modify blocks:1 says Modified 1 task when nothing was modified