[Ur] Abstract type for 'id' attributes?

[Karn Kallio]

On Tuesday, August 30, 2011 06:45:10 PM Adam Chlipala wrote:
> Currently, Ur/Web supports an 'id' attribute on any XML element.  I
> added this when someone requested support for the <label> tag.
> 
> Currently, 'id' attributes have type [string].  This freaks me out
> somewhat, since it's anti-modular; different functions written by
> different people might need to coordinate to avoid duplicating IDs.  The
> use of IDs is convenient for FFI JavaScript code that wants to get
> handles to DOM nodes.
> 
> So, I'm thinking of adding an abstract type of IDs, with only one
> built-in operation: "generate fresh ID."  Every tag's 'id' attribute
> would change to take a value of this type.  Under the hood, these would
> just be strings, making for easy FFI integration.
> 
> Does anyone object to the idea?  Any other feedback?

No objection, I think it is a good idea.  For integration with external CSS 
and FFI Ecmascript, would it be possible to have a second operation that takes 
a "suggestion" string and generates an id having that as the under the hood 
value if it is not already taken?  Already taken "suggestions" then cause an 
error if given again, or alternatively are ignored or modified.  Without some 
sort of mechanism for controlling or mapping id string values I think it will 
generally be impossible to use external resources (eg style sheets on another 
server or under control of some other team).

> 
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