def Transform(self, func_name, active=0):
"""Parses one or more transform calls and returns a _Transform call object.
The initial '(' has already been consumed by the caller.
Args:
func_name: The name of the first transform function.
active: The transform active level, None for always active.
Returns:
The _Transform object containing the ordered list of transform calls.
"""
here = self.GetPosition()
calls = _Transform()
map_transform = 0
while True:
transform = self._ParseTransform(func_name,
active=active,
map_transform=map_transform)
if transform.func == resource_transform.TransformAlways:
active = None # Always active.
func_name = None
elif transform.func == resource_transform.TransformMap:
map_transform = int(transform.args[0]) if transform.args else 1
func_name = None
elif transform.func == resource_transform.TransformIf:
if len(transform.args) != 1:
raise resource_exceptions.ExpressionSyntaxError(
'Conditional filter expression expected [{0}].'.format(
self.Annotate(here)))
calls.SetConditional(transform.args[0])
elif transform.func == resource_transform.TransformSynthesize:
transform.func = self._ParseSynthesize(transform.args)
transform.args = []
transform.kwargs = {}
calls.Add(transform)
else:
# always() applies to all transforms for key.
# map() applies to the next transform.
map_transform = 0
calls.Add(transform)
if not self.IsCharacter('.', eoi_ok=True):
break
call = self.Key()
here = self.GetPosition()
if not self.IsCharacter('('):
raise resource_exceptions.ExpressionSyntaxError(
'Transform function expected [{0}].'.format(
self.Annotate(here)))
if len(call) != 1:
raise resource_exceptions.UnknownTransformError(
'Unknown transform function {0} [{1}].'.format(
'.'.join(call), self.Annotate(here)))
func_name = call.pop()
return calls
def _ParseTransform(self, func_name, active=0, map_transform=None):
"""Parses a transform function call.
The initial '(' has already been consumed by the caller.
Args:
func_name: The transform function name.
active: The transform active level or None if always active.
map_transform: Apply the transform to each resource list item this many
times.
Returns:
A _TransformCall object. The caller appends these to a list that is used
to apply the transform functions.
Raises:
ExpressionSyntaxError: The expression has a syntax error.
"""
here = self.GetPosition()
func = self._defaults.symbols.get(func_name)
if not func:
raise resource_exceptions.UnknownTransformError(
'Unknown transform function {0} [{1}].'.format(
func_name, self.Annotate(here)))
args = []
kwargs = {}
doc = getattr(func, '__doc__', None)
if doc and resource_projection_spec.PROJECTION_ARG_DOC in doc:
# The second transform arg is the caller projection.
args.append(self._defaults)
if getattr(func, '__defaults__', None):
# Separate the args from the kwargs.
for arg in self.Args():
name, sep, val = arg.partition('=')
if sep:
kwargs[name] = val
else:
args.append(arg)
else:
# No kwargs.
args += self.Args()
return _TransformCall(func_name,
func,
active=active,
map_transform=map_transform,
args=args,
kwargs=kwargs)