I'm happy with how this ended up turning out---I was able to accomplish this
without having to introduce any additional state to the parser (I _removed_
a state, actually) by tweaking NIR a bit in a previous commit.
We can't update the system test yet, though, because nested templates are
not yet supported by asg::air::tpl; that'll come next. If you try, you'll
be greeted with this error presently (which is worth showing since you'll
never see it unless you're hacking TAMER):
,=====[ ./tests/xmli/template/ logs ]======
|
| thread 'main' panicked at 'not yet implemented: internal error:
| note: nested tpl open
| --> ./tests/xmli/template/src.xml:129:5
| |
| 129 | <t:inner-short />
| | -------------- note: for this template
|
|
| !!! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ !!!
| !!! THIS IS AN UNFINISHED FEATURE IN TAMER !!!
| !!! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ !!!
| !!! This message means that TAMER has encountered an !!!
| !!! unrecoverable error that forced it to terminate !!!
| !!! processing. !!!
| !!! !!!
| !!! TAMER has attempted to provide you with contextual !!!
| !!! information above that might allow you to work around !!!
| !!! this problem until it can be fixed. !!!
| !!! !!!
| !!! Please report this error, including the above !!!
| !!! diagnostic output beginning with 'internal error:'. !!!
| !!! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ !!!
| ', src/asg/air/tpl.rs:207:55
| note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
| Command exited with non-zero status 101
| 0/165fault 0/8io 3528rss 14/2ctx
| /home/[...]/tame/tamer/target/debug/tamec -o ./tests/xmli/template/out.xmli --emit xmlo ./tests/xmli/template/src.xml
|
`====[ end ./tests/xmli/template/ logs ]====
DEV-13708
This adds explicit variants for shorthand template application. This is
less cryptic, and we'll be able to check for the close directly during
desugaring.
DEV-13708
This represents a significant departure from how the XSLT-based TAME handles
the `@values@` param, but it will end up having the same effect. It builds
upon prior work, utilizing the fact that referencing a template in TAMER
will expand it.
The problem is this: allowing trees in `Meta` would add yet another
container; we have `Pkg` and `Tpl` already. This was the same problem with
template application---I didn't want to add support for binding arguments
separately, and so re-used templates themselves, reaching the generalization
I just mentioned above.
`Meta` is intended to be a lexical metasyntatic variable. That keeps its
implementation quite simple. But if we start allowing trees, that gets
rather complicated really quickly, and starts to require much more complex
AIR parser state.
But we can accomplish the same behavior by desugaring into an existing
container---a template---and placing the body within it. Then, in the
future, we'll parse `param-copy` into a simple `Air::RefIdent`, which will
expand the closed template and produce the same result as it does today in
the XSLT-based system.
This leaves open issues of closure (variable binding) in complex scenarios,
such as in templates that introduce metavariables to be utilized by the
body. That's never a practice I liked, but we'll see how things evolve.
Further, this does not yet handle nested template applications.
But this saved me a ton of work. Desugaring is much simpler.
The question is going to be how the XSLT-based compiler responds to this for
large packages with thousands of template applications. I'll have to see
if it's worth the hit at that time, or if we should inline it when
generating the `xmli` file, producing the same `@values@` as
before. But as it stands at this moment, the output is _not_ compatible
with the current compiler, as it expects `@values@` to be a tree, so a
modification would have to be made there.
DEV-13708
I had intended for this to be a full vertical slice initially, but AIR's
parser is going to need enough work that it'll muddy this patch a bit too
much.
This keeps the desugaring simple, which is what I was hoping for.
The next step is to load it into the graph and emit regenerated longhand
sources.
I also don't like how the namespace prefix is just being ignored for
shorthand param desugaring. This is also the case in the XSLT-based
compiler, but this violates TAMER's principle that it should parse every bit
of information; nothing should be ignored. If something does not contribute
useful information, then it is not a useful construct and ought to be
rejected.
DEV-13708
This moves translation from NirToAir into TplShortDesugar, and changes the
output from AIR to NIR.
This is going to be much easier to reason about as a desugaring
operation (and indeed that's always how TAME has implemented it, in XSLT);
this keeps the complexity isolated.
Ideally, NirToAir wouldn't even accept tokens that it can't handle, but
that's going to take quite a bit more work and I don't have the time right
now. Instead, we'll fail at runtime with some hopefully-useful
information. It shouldn't actually happen in practice.
DEV-13708
Mike Gerwitz