Function run_if

pipcl.py:2726–2956

Runs a command only if the output file is not up to date. Args: command: The command to run. We write this and a hash of argv[0] into a file .cmd so that we know to run a command if the command itself has changed. out: Pa

( command, out, *prerequisites, caller=1)

def run_if( command, out, *prerequisites, caller=1):
    '''
    Runs a command only if the output file is not up to date.

    Args:
        command:
            The command to run. We write this and a hash of argv[0] into a file
            <out>.cmd so that we know to run a command if the command itself
            has changed.
        out:
            Path of the output file.

        prerequisites:
            List of prerequisite paths or true/false/None items. If an item
            is None it is ignored, otherwise if an item is not a string we
            immediately return it cast to a bool. We recurse into directories,
            effectively using the newest file in the directory.

    Returns:
        True if we ran the command, otherwise None.


    If the output file does not exist, the command is run:

        >>> verbose(1)
        1
        >>> log_line_numbers(0)
        >>> out = 'run_if_test_out'
        >>> if os.path.exists( out):
        ...     os.remove( out)
        >>> if os.path.exists( f'{out}.cmd'):
        ...     os.remove( f'{out}.cmd')
        >>> run_if( f'touch {out}', out, caller=0)
        pipcl.py:run_if(): Running command because: File does not exist: 'run_if_test_out'
        pipcl.py:run_if(): Running: touch run_if_test_out
        True

    If we repeat, the output file will be up to date so the command is not run:

        >>> run_if( f'touch {out}', out, caller=0)
        pipcl.py:run_if(): Not running command because up to date: 'run_if_test_out'

    If we change the command, the command is run:

        >>> run_if( f'touch {out};', out, caller=0)
        pipcl.py:run_if(): Running command because: Command has changed:
        pipcl.py:run_if():     @@ -1,2 +1,2 @@
        pipcl.py:run_if():      touch
        pipcl.py:run_if():     -run_if_test_out
        pipcl.py:run_if():     +run_if_test_out;
        pipcl.py:run_if(): 
        pipcl.py:run_if(): Running: touch run_if_test_out;
        True

    If we add a prerequisite that is newer than the output, the command is run:

        >>> time.sleep(1)
        >>> prerequisite = 'run_if_test_prerequisite'