Treat tag search as case insensitive

[nyetsche]

It'd be useful to have a flag that when filtering on tags, can match case-insensitively. Ideally everyone follows the rules...but it's also easy enough to get a mix of cases.

It seems that c7n/filters/core.py is where to fix that:

279         elif self.op:
280             op = OPERATORS[self.op]
281             return op(r, v)
282         elif r == self.v:
283             return True

but I'm not sure the best way to make that a parameter/flag. Add an element to the 'properties' definition, 'type': 'boolean'?

[kapilt]

value_type is where we're moving to do pre transforms before compares

[kapilt]

did you want case insensitive on the tag key or value or both

[nyetsche]

Both I suppose. If I understand your previous comment, it's going to be something like:

value_type = [ string, string_insenstive, bool ]

in the configuration file? (Very loose pseudocode there)

[kapilt]

so for now (its mixed up in some other work on a pull request #299), its just doing the value. syntax looks like

 type: value
 key: "tag:SomeTag"
 value: rabbit
 value_type: normalize

would match "Rabbit "

[nyetsche]

If there are tags that are not being searched for, this code:

        if self.k.startswith('tag:'):
            tk = self.k.split(':', 1)[1]
            r = None
            for t in i.get("Tags", []):
                if t.get('Key') == tk:
                    r = t.get('Value')
                    break

sets r to None, which then causes an attribute error on value:

    def process_value_type(self, sentinel, value):
        if self.vtype == 'normalize':
            return sentinel, value.strip().lower()

My fix was to change that to:

        if self.vtype == 'normalize':
            try:
                return sentinel, value.strip().lower()
            except AttributeError:
                return sentinel, None

Is a pull request better?