Auto-redirect to canonical URLs

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Originally reported by: Anonymous

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The canonical URL scheme looks like this:

• / -> cpg.root.index()
• /index -> cpg.root.index()
• /a/ -> cpg.root.a.index()
• /a/b -> cpg.root.a.b()

In other words, objects always have trailing slashes, methods never have trailing slashes.

CP2 should enforce this scheme by automatically doing an external redirect if the incoming request URI isn't "correct". For example, if the user requests /a, CP2 should redirect to /a/ before actually calling cpg.root.a.index().

If we do this, request handler classes can safely use relative HTML links to refer to their own (or their parent/child objects') methods.

See: http://sourceforge.net/mailarchive/message.php?msg_id=9558209

Reported by hmans

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• Bitbucket: https://bitbucket.org/cherrypy/cherrypy/issue/2

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Original comment by Anonymous:

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After some discussion on cherrypy-devel, we're considering making this a configuration option.

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Original comment by sja (Bitbucket: sja, GitHub: sja):

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See #4 for a patch that fixes this.

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Original comment by sja (Bitbucket: sja, GitHub: sja):

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Should URIs with virtual path parameters have a trailing slash?

My patch strips trailing slashes from such URLs, because I thought the most common case would be someting like /user/12, where "12" logically represents a file, or a leaf in the tree.

But what should happen when we have urls such as /articles/2004/, which returns a list of articles from the given year? Is this an index/folder? Should it have a trailing slash? If so, how do we distinguish between the former and the latter case?

Perhaps we could add a trailing slash when the list of parameters is incomplete. For example:

#!python
class Articles:
    def default(self, year, month=None, day=None, number=None):
        ...

Given the previous method definition, these are the possible valid urls:

/articles/2004/
/articles/2004/12/
/articles/2004/12/5/
/articles/2004/12/5/2

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Original comment by sja (Bitbucket: sja, GitHub: sja):

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I've posted an updated patch which implements the behavior I've just described in #4.

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Original comment by sja (Bitbucket: sja, GitHub: sja):

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There are a couple open issues with my latest implementation.

#!python
class A:
    def b(self, c=None):
        ...

In this case, b is a method, hence it will not have a trailing slash in the url (/a/b). But b allows a virtual path parameter (/a/b/45), so it's logically not a leaf, but an index... should it have a trailing slash when the parameter is unspecified?

#!python
class Articles:
    # colorScheme is meant as a query string parameter
    def default(self, year, month=None, day=None, number=None, colorScheme=1):
        ...

If a method is defined as in this example, the URL of an article will have a trailing slash (/2004/12/5/3/), though it problably should not.

A workaround is to define the method thus:

#!python
    def default(self, year, month=None, day=None, number=None, **parameters):
        ...

Personally I like this better because it creates a cleaner distinction between normal parameters and query string arguments.