[stringtemplate-interest] StringTemplate type proxies

[Sam Harwell]

My program is not strictly a code generation tool. I've added my code
generation abilities as a front-end to a set of data structures maintained
by another program component. Due to a requirement to match the output of
another code generation tool, I'm forced to sort items in specific ways that
aren't the same as the way the data structures are internally maintained. I
was left with two choices: duplicate and extend the original program logic
(and be forced to maintain two copies), or use proxies wrap the problematic
objects to make them usable.

 

This is a somewhat similar problem to generating code based on the
Reflection API while under restriction to use special sort orders, etc.

 

My templates also have a single "entry point" for a given task - I provide
the complete model (or the necessary subset) as input and let the template
produce whatever is needed from it. I find that this separation is much
easier to analyze and maintain.

 

Sam

 

From: Terence Parr [mailto:parrt at cs.usfca.edu] 
Sent: Monday, December 13, 2010 9:08 PM
To: Sam Harwell
Cc: 'stringtemplate-interest'
Subject: Re: [stringtemplate-interest] StringTemplate type proxies

 

Hi Sam, I'm still trying to figure out how I get away without this.  I'm
leary of adding features when I haven't ever needed them.

 

Ter

On Dec 13, 2010, at 2:55 PM, Sam Harwell wrote:





I implemented this in the C# port of ST, and submitted it in changelist
7307. I also updated the way items are registered so registrations apply to
derived types and interface implementations. Here is the order in which the
search is performed (the * indicates "until null"):

 

1.       Search current template

2.       Search enclosing template*

3.       Search group

4.       Search super group*

 

Here is the order in which a match for type T is found. This check is
performed at each step of the above process until a match is found (with
some key optimizations in place to keep it from going slow).

 

1.       Check for a registration for T (exact match).

2.       Check each registration K at the current level - if T is derived
from class K or implements interface K, then it is a candidate. If this step
reveals candidates,

a.       If there is exactly one candidate, it is chosen as a weak match and
the process is complete.

b.      For each pair of candidates T1!=T2, if T2 is derived from class T1
or implements interface T1, then T2 is a strictly stronger match and T1 is
removed from the set of candidates.

c.       The filtering process always leaves 1 or more candidates. If only 1
candidate remains, it is chosen as the weak match and the process is
complete.

d.      If >1 candidates remain, an AmbiguousMatchException is thrown.

 

From: stringtemplate-interest-bounces at antlr.org
[mailto:stringtemplate-interest-bounces at antlr.org] On Behalf Of Sam Harwell
Sent: Sunday, December 12, 2010 9:41 PM
To: stringtemplate-interest
Subject: [stringtemplate-interest] StringTemplate type proxies

 

I recently started using StringTemplate for a significant code generation
project. I'm quite happy with the way things are progressing, but I'm
noticing there are several times where I have to add a new property to my
code objects just so StringTemplate can produce the desired output. In a
manner similar to attribute renderers, I believe the addition of type
proxies would be extremely beneficial. Suppose the user registers a type
proxy for type T. The type proxy exposes the following method:

 

object createProxy(object value);

 

Whenever an attribute resolves to a value of type T, the proxy's
createProxy() method is called. Attributes on the object are resolved
against the value returned by the proxy.

 

Any thoughts on this?

 

Thanks,

Sam

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