Source code for src.core.errors

"""Custom-defined exceptions.

The following custom-defined exceptions are defined in this module.

    InstrumentInUseError
        Raised when a user attempts to delete an instrument which is still
        used by an action in the sequence.
        
    InvalidInputError
        Raised when a user enters an input value which is not of the right
        type.
"""

import logging

log = logging.getLogger('transport')

class InstrumentInUseError(Exception):
    """Error for when an attempt is made to delete a still-bound instrument.
    
    Parameters
    ----------
    actions : list of Action
        A list of the actions which require the instrument the user is
        trying to delete.
    """
    
    def __init__(self, actions):
        """Create a new InstrumentInUseError."""
        super(InstrumentInUseError, self).__init__('The instrument is in use.')
        self.actions = actions
        super(InstrumentInUseError, self).__init__('The instrument is in use.')
        
class InvalidInputError(Exception):
    """An error raised when an action cannot coerce an input to the right type.
    
    This exception subsumes TypeError and ValueError so that they can be
    caught more easily by programs which set input values for actions, and
    so that it is easier for those programs to know precisely whence the
    error comes.
    
    Parameters
    ----------
    msg : str
        The message generated by the object which raises the exception.
    valueName : str
        The description of the input or output parameter for which an invalid
        value was received.
    val : str
        The invalid input supplied for the parameter.
    """
    def __init__(self, msg, valueName, val):
        """Create a new InvalidInputError."""
        self.val = val
        self.valueName = valueName
        string = ('The field [%s] requires %s, which "%s" is not. '
                  'Please try again.')

        if 'string to float' in msg:
            self.msg = string % (valueName, 'a floating-point number', val)
        else:
            self.msg = string % (valueName, 'an integer', val) 
        
        self.args = (self.msg, )
        super(InvalidInputError, self).__init__(self.msg)

class GeneralExperimentError(Exception):
    """An exception generated in response to miscellaneous problems.
    
    Parameters
    ----------
    items : list of tuple of str
        A list of tuples. Each tuple contains information about one error in
        the form of two strings. The first is the severity and may be either
        'warning', which will allow the experiment to proceed if the user
        commands it, or 'error', which will not allow the experiment to
        proceed. The second is a message about the error.
        
    Attributes
    ----------
    msg : str
        A basic string: 'Errors have been found.'
    items : list of tuple of str
        The same as `items` from the Parameters section.
    errorCount : int
        The number of elements of `items` which are 'error's rather than
        mere 'warning's.
    """
    
    def __init__(self, items):
        """Create a new GeneralExperimentError"""
        self.msg = 'Errors have been found.'
        self.items = items
        self.errorCount = 0
        for item in items:
            if item[0] == 'error':
                self.errorCount += 1
        self.args = (self.msg, self.items, self.errorCount)
        super(GeneralExperimentError, self).__init__(self.msg)


class Null(object):
    """Fake VISA driver.
    
    This class is here so that the program will run even on a computer without
    VISA drivers installed.
    """
    
    def __init__(self, *args, **kwargs):
        """Do nothing."""
        log.error(('No VISA drivers: Cannot create object. Args=[%s]. '
                   'Kwargs=[%s]'), args, kwargs)
    def __call__(self, *args, **kwargs):
        """Cannot call method, so do nothing."""
        log.error('No VISA drivers: Cannot call method.')
        return self
    def __getattribute__(self, *args, **kwargs):
        """Cannot get attribute, so do nothing."""
        try:
            if args[0] == '__bases__':
                return []
        except IndexError:
            pass
        log.error('No VISA drivers: Cannot get attribute. %s', args)
        return self
    def __setattr__(self, name, value):
        """Cannot set attribute, so do nothing."""
        log.error('No VISA drivers: Cannot set attribute.')
    def __delattr__(self, name):
        """Cannot delete attribute, so do nothing."""
        log.error('No VISA drivers: Cannot delete attribute.')