[augeas-devel] XML lens parse_error with XML document using single quotes

[David Lutterkort]

On Tue, 2011-11-08 at 00:40 -0500, Francis Giraldeau wrote:
> You're right. This is a limitation of the current lens. Here is the
> comment from the lens:
> 
> (* if we hide the quotes, then we can only accept single or double 
>    quotes otherwise a put ambiguity is raised *)
> 
> The put ambiguity is raised because for the same tree, two lenses match.
> One way to overcome this would be to accept malformed files, where a
> quote may not be balanced i.e. att="var'. 
> 
> let example = [ key /[a-z]+/ . dels "=" . del /["']/ "\"" .
> store /[a-z]*/ . del /["']/ "\"" ]
> 
> Maybe a lens like the square lens, but that acts as a del with
> characters at extremity? Or quotient lens?

I agree .. since handling quoted strings is such a common thing, and
always a big headache, I think having a lens dedicated to it would be
very helpful. I guess we should have made square a little more
complicated, namely,

        square l1 l2 l3 = l1 . l2 . l3

with the additional constraint that whatever matches l1 must be
identical to what matches l3 in the get direction.

We could also add a special-purpose builtin dedicated to handling quoted
strings, i.e. something like

        quoted R1 D1 R2 D2 L = del R1 D1 . L . del R2 D2

with the same constraint as square.

Of course, I'd prefer the first option, but I am not sure how hard it
would be to implement.

David