Hi Alexey,
Simple answer is that overlapping is disabled by default. If you want
to allow overlapping, you have to use a separate parseRoutesNoChecking
function, which is not exported from Yesod by default (you have to
look in web-routes-quasi).
Michael
On Thu, Jun 23, 2011 at 11:42 PM, Alexey Khudyakov
Hello!
I thought about routes and overlapping. I'm not talking about actual implementation but rather trying to construct simple model.
First of all what is overlapping in routes? Simplest definition is routes do not overlap if any URL match to one route or do not match. Bad thing it couldn't be checked statically. Using for example Eric's routes.
/add /#Int
This routes do not overlap. We can make this conclusion because we know SinglePiece instance of Int. Overlapping checker could not have this information.
Better definition is. Routes do not overlap is any URL could be mapped to one or zero routes assuming that SinglePiece match any piece.
Now lets consider case of unlimited overlapping. Routes are matched from top to bottom. First route to match is selected. If singlePiece or multiPiece field fails then next route is matched. So it's very similar to pattern matching in haskell functions.
It has a problem though. There may be inconsitencies. For example:
/ HomeR /#String StrR /#Int IntR
Then roundtrip (route → URL → route) for IntR becomes:
IntR 42 → "/42" → StrR "42"
IMHO overlapping should be disabled by default. Should it be possible to enable overlapping? How should it be resolved. Method above seems to be most intuitive (at least for me).
P.S. I didn't touch subsites and multipiece parts for simplicity.
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