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 invokes clippy as part of `make check` now, which I had previously
avoided doing (I'll elaborate on that below).
This commit represents the changes needed to resolve all the warnings
presented by clippy. Many changes have been made where I find the lints to
be useful and agreeable, but there are a number of lints, rationalized in
`src/lib.rs`, where I found the lints to be disagreeable. I have provided
rationale, primarily for those wondering why I desire to deviate from the
default lints, though it does feel backward to rationalize why certain lints
ought to be applied (the reverse should be true).
With that said, this did catch some legitimage issues, and it was also
helpful in getting some older code up-to-date with new language additions
that perhaps I used in new code but hadn't gone back and updated old code
for. My goal was to get clippy working without errors so that, in the
future, when others get into TAMER and are still getting used to Rust,
clippy is able to help guide them in the right direction.
One of the reasons I went without clippy for so long (though I admittedly
forgot I wasn't using it for a period of time) was because there were a
number of suggestions that I found disagreeable, and I didn't take the time
to go through them and determine what I wanted to follow. Furthermore, it
was hard to make that judgment when I was new to the language and lacked
the necessary experience to do so.
One thing I would like to comment further on is the use of `format!` with
`expect`, which is also what the diagnostic system convenience methods
do (which clippy does not cover). Because of all the work I've done trying
to understand Rust and looking at disassemblies and seeing what it
optimizes, I falsely assumed that Rust would convert such things into
conditionals in my otherwise-pure code...but apparently that's not the case,
when `format!` is involved.
I noticed that, after making the suggested fix with `get_ident`, Rust
proceeded to then inline it into each call site and then apply further
optimizations. It was also previously invoking the thread lock (for the
interner) unconditionally and invoking the `Display` implementation. That
is not at all what I intended for, despite knowing the eager semantics of
function calls in Rust.
Anyway, possibly more to come on that, I'm just tired of typing and need to
move on. I'll be returning to investigate further diagnostic messages soon.
This removes quite a bit of work, and work that was difficult to reason
about. While I'm disappointed that that hard work is lost (aside from
digging it up in the commit history), I am happy that it was able to be
removed, because the extra complexity and cognitive burden was significant.
This removes more `memcpy`s than the sum state could have hoped to, since
aggregation is no longer necessary. Given that, there is a slight
performacne improvement. The re-introduction of required and duplicate
checks later on should be more efficient than this was, and so this should
be a net win overall in the end.
DEV-13346
This handles the bulk of the integration of the new `attr_parse_stream!` as
a replacement for `attr_parse!`, which moves from aggregate attribute
objects to a stream of attribute-derived tokens. Rationale for this change
is in the preceding commit messages.
The first striking change here is how it affects the test cases: nearly all
`Incomplete`s are removed. Note that the parser has an existing
optimization whereby `Incomplete` with lookahead causes immediate recursion
within `Parser`, since those situations are used only for control flow and
to keep recursion out of `ParseState`s.
Next: this removes types from `nir::parse`'s grammar for attributes. The
types will instead be derived from NIR tokens later in the lowering
pipeline. This simplifies NIR considerably, since adding types into the mix
at this point was taking an already really complex lowering phase and making
it ever more difficult to reason about and get everything working together
the way that I needed.
Because of `attr_parse_stream!`, there are no more required attribute
checks. Those will be handled later in the lowering pipeline, if they're
actually needed in context, with possibly one exception: namespace
declarations. Those are really part of the document and they ought to be
handled _earlier_ in the pipeline; I'll do that at some point. It's not
required for compilation; it's just required to maintain compliance with the
XML spec.
We also lose checks for duplicate attributes. This is also something that
ought to be handled at the document level, and so earlier in the pipeline,
since XML cares, not us---if we get a duplicate attribute that results in an
extra NIR token, then the next parser will error out, since it has to check
for those things anyway.
A bunch of cleanup and simplification is still needed; I want to get the
initial integration committed first. It's a shame I'm getting rid of so
much work, but this is the right approach, and results in a much simpler
system.
DEV-13346
This was a substantial change. Design and rationale are documented on
`AttrFieldSum` and related as part of this change, so please review the diff
for more information there.
If you're a Ryan employee, DEV-13209 gives plenty of profiling information,
including raw data and visualizations from kcachegrind. For everyone else:
you're able to easy produce your own from this commit and the previous and
comparing the `__memcpy_avk_unaligned_erms` calls. The reduction is
significant in this commit (~90%), and the number of Parsers invoking it has
been reduced. Rust has been able to optimize more aggressively, and
compound some of those optimizations, with the smaller `NirParseState`
width.
It also worth noting that `malloc` calls do not change at all between
these two changes, so when we refer to memory, we're referring to
pre-allocated memory on the stack, as TAMER was designed to utilize.
DEV-13209
This introduces the concept of sugared NIR and provides the boilerplate for
a desugaring pass. The earlier commits dealing with cleaning up the
lowering pipeline were to support this work, in particular to ensure that
reporting and recovery properly applied to this lowering operation without
adding a ton more boilerplate.
DEV-13158
A type alias was added for BC before errors were hoisted out in a previous
commit, but they are unnecessary because of the associated type on
`ParseState`.
This also corrects the long-existing issue of using generated identifiers in
tests.
DEV-7145
This moves `paste::paste!` up a line and reduces a level of indentation,
since it's so squished. Aside from docblock reformatting, there are no
other changes.
DEV-7145
This slims out the macro even further. It does result in an
awkwardly-placed `PhantomData` because I don't want to add another variant
that isn't actually used (since they represent states).
DEV-7145
This is in preparation for hoisting out the common states, as was done with
the Sum NT in a previous commit.
I also think that organizing states in this way is more clear. The previous
embedding of the variants named after the NTs themselves was because the
parser was storing the child state within it, before the introduction of the
superstate trampoline.
DEV-7145
Everything except for one state was already accounted for. We can now have
confidence that the parser will never panic due to state transitions (beyond
legitimate error conditions).
There are some `unreachable!`s to contend with still.
DEV-7145
This is the same as the previous commits, but for non-sum NTs.
This also extracts errors into a separate module, which I had hoped to do in
a separate commit, but it's not worth separating them. My _original_ reason
for doing so was debugging (I'll get into that below), but I had wanted to
trim down `ele.rs` anyway, since that mess is large and a lot to grok.
My debugging was trying to figure out why Rust was failing to derive
`PartialEq` on `NtError` because of `AttrParseError`. As it turns out,
`AttrParseError::InvalidValue` was failing, thus the introduction of the
`PartialEq` trait bound on `AttrParseState::ValueError`. Figuring this out
required implementing `PartialEq` myself without `derive` (well, using LSP,
which did all the work for me).
I'm not sure why this was not failing previously, which is a bit of a
concern, though perhaps in the context of the macro-expanded code, Rust was
able to properly resolve the types.
DEV-7145
The `ele_parse!` macro is a monstrosity, and expands into many different
identifiers. The hope is that chipping away at things like this will not
only make the template easier to understand by framing portions of the
problem in terms of more traditional Rust code, but will also hopefully
reduce compile times by reducing the amount of code that is expanded by the
macro.
DEV-7145
This includes when on the last state / expecting a close.
Previously, there were a couple major issues:
1. After parsing an NT, we can't allow preemption because we must emit a
dead state so that we can remove the NT from the stack, otherwise
they'll never close (until the parent does) and that results in
unbounded stack growth for a lot of siblings. Therefore, we cannot
preempt on `Text`, which causes the NT to receive it, emit a dead
state, transition away from the NT, and not accept another NT of the
same type after `Text`.
2. When encountering an unknown element, the error message stated that a
closing tag was expected rather than one of the elements accepted by the
final NT.
For #1, this was solved by allowing the parent to transition back to the NT
if it would have been matched by the previous NT. A future change may
therefore allow us to remove repetition handling entirely and allow the
parent to deal with it (maybe).
For #2, the trouble is with the parser generator macro---we don't have a
good way of knowing the last NT, and the last NT may not even exist if none
was provided. This solution is a compromise, after having tried and failed
at many others; I desperately need to move on, and this results in the
correct behavior and doesn't sacrifice performance. But it can be done
better in the future.
It's also worth noting for #2 that the behavior isn't _entirely_ desirable,
but in practice it is mostly correct. Specifically, if we encounter an
unknown token, we're going to blow through all NTs until the last one, which
will be forced to handle it. After that, we cannot return to a previous NT,
and so we've forefitted the ability to parse anything that came before it.
NIR's grammar is such that sequences are rare and, if present, there's
really only ever two NTs, and so this awkward behavior will rarely cause
practical issues. With that said, it ought to be improved in the future,
but let's wait to see if other parts of the lowering pipeline provide more
appropriate places to handle some of these things (even though it really
ought to be handled at the grammar level).
But I'm well out of time to spend on this. I have to move on.
DEV-7145
`ele_parse!` was recently converted to accept zero-or-more for every NT to
simplify the parser-generator, since NIR isn't going to be able to
accurately determine whether child requirements are met anyway (because of
the template system).
This ensures that `Close` can be accepted when we're expecting an
element. It also adds a test for a scenario that's causing me some trouble
in stashed code so that I can ensure that it doesn't break.
DEV-7145
This sets the maximum depth to 64, which is still arbitrary, but
unfortunately the sum types introduce multiple levels of nesting, in
particular for template applications, so nested applications can result in a
fairly large stack.
I have various ideas to improve upon that---limited a bit in that repetition
as it is current implemented inhibits tail calls---but they're not worth
doing just yet relative to other priorities. The impact of this change is
not significant.
DEV-7145
This removes support for configurable repetition.
What? Why?
As it turns out, the complexity that repetition adds is quite significant
and is not worth the effort. The truth is that NIR is going to have to
allow zero-or-more matches on virtually everything _anyway_ because template
application is allowed virtually anywhere---it is not possible to fully
statically analyze TAME's sources because templates can expand into just
about anything. Given that, AIR (or something down the line) is going to
have to supply the necessary invariants instead.
It does suck, though, that this removes a lot of code that I fairly recently
wrote, and spent a decent amount of time on. But it's important to know
when to cut your losses.
Perhaps I could have planned better, but deriving this whole system as been
quite the experiment.
DEV-7145
If attributes fail to parse (e.g. missing required attribute) and parsing
reaches a dead state, this will recover by ignoring the entire element. It
previously panicked with a TODO.
DEV-7145
These were initially used to prevent conflicts with generated variants, but
we are no longer generating such variants since they're being jumped to via
the trampoline.
DEV-7145
I'm starting to clean up some TODOs, and this was a glaring one causing
panics when encountered. The recovery for this is simple, because we have
no choice: just stop parsing; leave it to the next lowering operation(s) to
complain that we didn't provide what was necessary. They'll have to,
anyway, since templates mean that NIR cannot ever have enough information to
guarantee that a document is well-formed, relative to what would expand from
the template.
DEV-7145
This allows for a construction like this:
```
ele_parse! {
[...]
StmtX := QN_X {
[...]
};
StmtY := QN_Y {
[...]
};
ExprA := QN_A {
[...]
};
ExprB := QN_B {
[...]
};
Expr := (A | B);
Stmt := (StmtX | StmtY);
// This previously was not allowed:
StmtOrExpr := (Stmt | Expr);
}
```
There were initially two barriers to doing so:
1. Efficiently matching; and
2. Outputting diagnostic information about the union of all expected
elements.
The first was previously resolved with the introduction of `NT::matches`,
which is macro-expanded in a way that Rust will be able to optimize a
bit. Worst case, it's effectively a linear search, but our Sum NTs are not
that deep in practice, so I don't expect that to be a concern.
The concern that I was trying to avoid was heap-allocated `NodeMatcher`s to
avoid recursive data structures, since that would have put heap access in a
very hot code path, which is not an option.
That left problem #2, which ended up being the harder problem. The solution
was detailed in the previous commit, so you should look there, but it
amounts to being able to format individual entries as if they were a part
of a list by making them a function of not just the matcher itself, but also
the number of items in (recursively) the sum type and the position of the
matcher relative to that list. The list length is easily
computed (recursively) at compile-time using `const`
functions (`NT::matches_n`).
And with that, NIR can be abstracted in sane ways using Sum NTs without a
bunch of duplication that would have been a maintenance burden and an
inevitable source of bugs (from having to duplicate NT references).
DEV-7145
This allows using a `[attr]` special form to stream attributes as they are
encountered rather than aggregating a static attribute list. This is
necessary in particular for short-hand template application and short-hand
function application, since the attribute names are derived from template
and function parameter lists, which are runtime values.
The syntax for this is a bit odd since there's a semi-useless and confusing
`@ {} => obj` still, but this is only going to be used by a couple of NTs
and it's not worth the time to clean this up, given the rather significant
macro complexity already.
DEV-7145
This uses the same mechanism that was introduced for handling `Text` nodes
in mixed content, allowing for arbitrary element `Open` matches for
preemption by the superstate.
This will be used to allow for template expansion virtually
anywhere. Unlike the existing TAME, it'll even allow for it at the root,
though whether that's ultimately permitted is really depending on how I
approach template expansion; it may fail during a later lowering operation.
This is interesting because this approach is only possible because of the
CPS-style trampoline implementation. Previously, with the composition-based
approach, each and every parser would have to perform this check, like we
had to previously with `Text` nodes.
As usual, this is still adding to the mess a bit, and it'll need some future
cleanup.
DEV-7145
This introduces the concept of superstate node preemption generally, which I
hope to use for template application as well, since templates can appear in
essentially any (syntatically valid, for XML) position.
This implements mixed content handling by defining the mapping on the
superstate itself, which really simplifies the problem but foregoes
fine-grained text handling. I had hoped to avoid that, but oh well.
This pushes the responsibility of whether text is semantically valid at that
position to NIR->AIR lowering (which we're not transition to yet), which is
really the better place for it anyway, since this is just the grammar. The
lowering to AIR will need to validate anyway given that template expansion
happens after NIR.
Moving on!
DEV-7145
This was accepting an early EOF when the active child `ParseState` was in an
accepting state, because it was not ensuring that anything on the stack was
also accepting.
Ideally, there should be nothing on the stack, and hopefully in the future
that's what happens. But with how things are today, it's important that, if
anything is on the stack, it is accepting.
Since `is_accepting` on the superstate is only called during finalization,
and because the check terminates early, and because the stack practically
speaking will only have a couple things on it max (unless we're in tail
position in a deeply nested tree, without TCO [yet]), this shouldn't be an
expensive check.
Implementing this did require that we expose `Context` to `is_accepting`,
which I had hoped to avoid having to do, but here we are.
DEV-7145
Along with this change we also had to change how we handle dead states in
the superstate. So there were two problems here:
1. Sum states were not yielding a dead state after recovery, which meant
that parsing was unable to continue (we still have a `todo!`); and
2. The superstate considered it an error when there was nothing left on
the stack, because I assumed that ought not happen.
Regarding #2---it _shouldn't_ happen, _unless_ we have extra input after we
have completed parsing. Which happens to be the case for this test case,
but more importantly, we shouldn't be panicing with errors about TAMER bugs
if somebody puts extra input after a closing root tag in a source file.
DEV-7145
This does two things:
1. Places the expected list on a separate help line as a footnote where
it'll be a bit more tolerable when it inevitably overflows the terminal
width in certain contexts (we may wrap in the future); and
2. Removes angled brackets from the element names so that they (a) better
correspond with the span which highlights only the element name and (b)
do not imply that the elements take no attributes.
DEV-7145
When we match a QName against a namespace, we ought to store the matching
QName to use (a) in error messages and (b) to make available as a
binding. The former is necessary for sensible errors (rather than saying
that it's e.g. expecting a closing `t:*`) and the latter is necessary for
e.g. getting the template name out of `t:foo`.
DEV-7145
This allows matching on a namespace prefix by providing a `Prefix` instead
of a `QName`. This works, but is missing a couple notable things (and
possibly more):
1. Tracking the QName that is _actually_ matched so that it can be used in
messages stating what the expected closing tag is; and
2. Making that QName available via a binding.
This will be used to match on `t:*` in NIR. If you're wondering how
attribute parsing is supposed to work with that (of course you're wondering
that, random person reading this)---that'll have to work differently for
those matches, since template shorthand application contains argument names
as attributes.
DEV-7145
This introduces `NodeMatcher`, with the intent of introducing wildcard QName
matches for e.g. `t:*` nodes. It's not yet clear if I'll expand this to
support text nodes yet, or if I'll convert text nodes into elements to
re-use the existing system (which I had initially planned on doing, but
didn't because of the work and expense (token expansion) involved in the
conversion).
DEV-7145
I need to move on, and there are (a) a couple different ways to proceed that
I want to mull over and (b) upcoming changes that may influence my decision
one way or another.
DEV-7145
This will utilize the superstate's error object in place of nested errors,
which was the result of the previous composition-based delegation.
As you can see, all we had to do was remove the special handling of these
errors; the existing delegation setup continues to handle the types properly
with no change. The composition continues to work for `*Attr_`.
The alternative was to box inner errors, since they're far from the hot code
path, but that's clearly unnecessary.
To be clear: this is necessary to allow for recursive grammars in
`ele_parse` without creating recursive data structures in Rust.
DEV-7145
Comments ought not have any more semantic meaning than whitespace. Other
languages may have conventions that allow for various types of things in
comments, like annotations, but those are symptoms of language
limitations---we control the source language here.
DEV-7145
This properly integrates the trampoline into `ele_parse!`. The
implementation leaves some TODOs, most notably broken mixed text handling
since we can no longer intercept those tokens before passing to the
child. That is temporarily marked as incomplete; see a future commit.
The introduced test `ParseState`s were to help me reason about the system
intuitively as I struggled to track down some type errors in the monstrosity
that is `ele_parse!`. It will fail to compile if those invariants are
violated. (In the end, the problems were pretty simple to resolve, and the
struggle was the type system doing its job in telling me that I needed to
step back and try to reason about the problem again until it was intuitive.)
This keeps around the NT states for now, which are quickly used to
transition to the next NT state, like a couple of bounces on a trampoline:
NT -> Dead -> Parent -> Next NT
This could be optimized in the future, if it's worth doing.
This also makes no attempt to implement tail calls; that would have to come
after fixing mixed content and really isn't worth the added complexity
now. I (desperately) need to move on, and still have a bunch of cleanup to
do.
I had hoped for a smaller commit, but that was too difficult to do with all
the types involved.
DEV-7145
I had previously used `Context` to hold the parser configuration for
repetition, since that was the easier option. But I now want to utilize the
`Context` for a stack for the superstate trampoline, and I don't want to
have to deal with the awkwardness of the repetition in doing so, since it
requires that the configuration be created during delegation, rather than
just being passed through to all child parsers.
This adds to a mess that needs cleaning up, but I'll do that after
everything is working.
DEV-7145
And here's the thing that I've been dreading, partly because of the
`macro_rules` issues involved. But, it's not too terrible.
This module was already large and complex, and this just adds to it---it's
in need of refactoring, but I want to be sure it's fully working and capable
of handling NIR before I go spending time refactoring only to undo it.
_This does not yet use trampolining in place of the call stack._ That'll
come next; I just wanted to get the macro updated, the superstate generated,
and tests passing. This does convert into the
superstate (`ParseState::Super`), but then converts back to the original
`ParseState` for BC with the existing composition-based delegation. That
will go away and will then use the equivalent of CPS, using the
superstate+`Parser` as a trampoline. This will require an explicit stack
via `Context`, like XIRF. And it will allow for tail calls, with respect to
parser delegation, if I decide it's worth doing.
The root problem is that source XML requires recursive parsing (for
expressions and statements like `<section>`), which results in recursive
data structures (`ParseState` enum variants). Resolving this with boxing is
not appropriate, because that puts heap indirection in an extremely hot code
path, and may also inhibit the aggressive optimizations that I need Rust to
perform to optimize away the majority of the lowering pipeline.
Once this is sorted out, this should be the last big thing for the
parser. This unfortunately has been a nagging and looming issue for months,
that I was hoping to avoid, and in retrospect that was naive.
DEV-7145
"Mixed content" is the XML term representing element nodes mixed with text
nodes. For example, `foo <strong>bar</strong> baz` is mixed.
TAME supports text nodes as documentation, intended to be in a literate
style but never fully realized. In any case, we need to permit them, and I
wanted to do more than just ignore the nodes.
This takes a different approach than typical parser delegation---it has the
parent parser _preempt_ the child by intercepting text before delegation
takes place, rather than having the child reject the token (or possibly
interpret it itself!) and have to handle an error or dead state.
And while this makes it more confusing in terms of state machine stitching,
it does make sense, in the sense that the parent parser is really what
"owns" the text node---the parser is delegating _element_ parsing only, take
asserts authority when necessary to take back control where it shouldn't be
delegated.
DEV-7145
Previously a `Depth` was provided only for `Open` and `Close`. This depth
information, for example, will be used by NIR to quickly determine whether a
given parser ought to assert ownership of a text/comment token rather than
delegating it.
This involved modifying a number of test cases, but it's worth repeating in
these commits that this is intentional---I've been bit in the past using
`..` in contexts where I really do want to know if variant fields change so
that I can consider whether and how that change may affect the code
utilizing that variant.
DEV-7145
Recent changes regarding whitespace were all to support this change (though
it was also needed for XIRF, pre- and post-root).
Now I'll have to conted with how I want to handle text nodes in various
circumstances, in terms of `ele_parse!`.
DEV-7145
This teaches XIRF to optionally refine Text into RefinedText, which
determines whether the given SymbolId represents entirely whitespace.
This is something I've been putting off for some time, but now that I'm
parsing source language for NIR, it is necessary, in that we can only permit
whitespace Text nodes in certain contexts.
The idea is to capture the most common whitespace as preinterned
symbols. Note that this heuristic ought to be determined from scanning a
codebase, which I haven't done yet; this is just an initial list.
The fallback is to look up the string associated with the SymbolId and
perform a linear scan, aborting on the first non-whitespace character. This
combination of checks should be sufficiently performant for now considering
that this is only being run on source files, which really are not all that
large. (They become large when template-expanded.) I'll optimize further
if I notice it show up during profiling.
This also frees XIR itself from being concerned by Whitespace. Initially I
had used quick-xml's whitespace trimming, but it messed up my span
calculations, and those were a pain in the ass to implement to begin with,
since I had to resort to pointer arithmetic. I'd rather avoid tweaking it.
tameld will not check for whitespace, since it's not important---xmlo files,
if malformed, are the fault of the compiler; we can ignore text nodes except
in the context of code fragments, where they are never whitespace (unless
that's also a compiler bug).
Onward and yonward.
DEV-7145
We need to be able to export generated identifiers. Trying to figure out a
syntax for this was a bit tricky considering how much is generated, so I
just settled on something that's reasonably clear and easy to parse with
`macro_rules!`.
I had intended to just make everything public by default and encapsulate
using private modules, but that then required making everything else that it
uses public (e.g. error and token objects), which would have been a bizarre
thing to do in e.g. test cases.
DEV-7145
Mike Gerwitz