how to debug python click cli application?

This is not well documented, but you can call your command functions directly, and thus can run the code in a debugger:

Sample Code:

import click

@click.command()
@click.option('--my_arg', default=1, help='a number')
def my_command(my_arg):
    click.echo("my_arg='%d'" % my_arg)

if __name__ == '__main__':
    my_command(['--my_arg', '3'])

Result:

my_arg='3'

I'm a couple years late to the party, but in case anyone else comes here looking for an answer like I just did:

Calling your function with CliRunner.invoke() will return a "Result" object with an "exc_info" attribute. You can feed that to traceback.print_exception() like so:

runner = CliRunner()
result = runner.invoke(my_command)
traceback.print_exception(*result.exc_info)

The setup.py generates:

• console_script.exe
• console_script-script.py

from cmdline:

console_app --help

expands out to the IDE configuration cmd:

python <absolute path to>\console_app-script.py --help

Tested in PyCharm 2018.2 - you can set and hit breakpoints and preserve the expected cmdline/arg paradigm.

I have found that writing tests is a great way to debug Click CLI applications: http://click.pocoo.org/5/testing/

Start really simple with your function and a test, then add to it, making sure the test tells you what you need it to...

Also, setting defaults helps:

def run_files(input_file='/path/to/input_file', output_file='/path/to/output_file'): click.echo(input_file, output_file)

I also generally set up logging and log everything when I begin:

logging.basicConfig(format='%(levelname)s %(message)s', level=logging.DEBUG)

Then sprinkle these throughout (IU have utilities with timestamp stuff, but this is not required):

logging.info('[{0}] Blah blah selected...'.format(
             utils.get_timestamp()))

You can do this with print or click.echo too.

You can use pdb like this, put inside the code you want to debug:

import pdb
pdb.set_trace()

For example:

import click

@click.command()
def hello():
    msg = "hi"
    num = 3

    import pdb
    pdb.set_trace()

    click.echo('Hello1!')
    click.echo('Hello2!')
    click.echo(msg + num)

if __name__ == '__main__':
    hello()

Then you can use pdb:

$ python hello.py 
> /home/eduardo/w/ifpb/cozer/hello.py(11)hello()
-> click.echo('Hello1!')
(Pdb) msg
'hi'
(Pdb) num
3
(Pdb) msg = hello
(Pdb) b 13
Breakpoint 1 at /home/eduardo/w/ifpb/cozer/hello.py:13
(Pdb) c
Hello1!
Hello2!
> /home/eduardo/w/ifpb/cozer/hello.py(13)hello()
-> click.echo(msg + num)
(Pdb) c
Traceback (most recent call last):
  File "hello.py", line 16, in <module>
    hello()
  File "/home/eduardo/w/ifpb/cozer/venv/lib/python3.5/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/home/eduardo/w/ifpb/cozer/venv/lib/python3.5/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/eduardo/w/ifpb/cozer/venv/lib/python3.5/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/eduardo/w/ifpb/cozer/venv/lib/python3.5/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "hello.py", line 13, in hello
    click.echo(msg + num)
TypeError: unsupported operand type(s) for +: 'Command' and 'int'

After the error we can try again a solution:

$ python hello.py 
> /home/eduardo/w/ifpb/cozer/hello.py(11)hello()
-> click.echo('Hello1!')
(Pdb) msg
'hi'
(Pdb) num
3
(Pdb) b 13
Breakpoint 1 at /home/eduardo/w/ifpb/cozer/hello.py:13
(Pdb) c
Hello1!
Hello2!
> /home/eduardo/w/ifpb/cozer/hello.py(13)hello()
-> click.echo(msg + num)
(Pdb) num = str(num)
(Pdb) c
hi3