On Aug 17, 2010, at 1:39 PM, Jesse A Wolfe wrote:
Doesn't this convert classes, definitions, et al from parse-time
constructs into compile-time constructs?
Not exactly. We've added a new phase.
Parsing is now a side-effect-free function from .pp files to AST
trees.
After that, in the new phase, we create the hostclass and definition
objects *from the ASTs*.
After that we compile the rest of the AST. This process has access
to the full TypeCollection from the start, same as it had before.
Having parsing be a function from .pp file to AST tree means that we
can be much smarter about caching, and staleness. It might improve
our memory footprint, because the AST interpretation of a .pp file
doesn't change between environments.
It also gives us the power to query .pp files about what hostclasses
they define, without involving the larger mechanisms of the
TypeCollection or the Environment.
It seems to me that this is basically the "Multi-pass compiler"
pattern.
So it looks like we now just read the code in, convert to AST, and
immediately create the types from the AST - it's not like we create a
single AST and then find all of the AST Type instances and instantiate
them. When you mentioned phases, my concern was initially that the
AST->Type conversion was triggered by a compile or something, but it
looks like it's triggered by type loading, like it used to be.
That is, with this patch in place can I still get a list of classes
after parsing but not compiling?
Yes. There's just one new method call to get the list of classes. To
put it into the multi-pass metaphor, you need only invoke the first
pass of the compiler.
Looks like asking questions from puppetmasterd via the API should
still work then.
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