// XIR element parser generator
//
// Copyright (C) 2014-2022 Ryan Specialty Group, LLC.
//
// This file is part of TAME.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see .
//! Element parser generator for parsing of [XIRF](super::super::flat).
use arrayvec::ArrayVec;
use std::fmt::Display;
use crate::{
diagnostic_panic,
fmt::{DisplayWrapper, TtQuote},
parse::{
ClosedParseState, Context, ParseState, Transition, TransitionResult,
},
xir::{Prefix, QName},
};
#[cfg(doc)]
use crate::{ele_parse, parse::Parser};
/// A parser accepting a single element.
pub trait EleParseState: ParseState {}
/// Element parser configuration.
///
/// This configuration is set on a nonterminal reference using square
/// brackets
/// (e.g. `Foo[*]`).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub struct EleParseCfg {
/// Whether to allow zero-or-more repetition for this element.
///
/// This is the Kleene star modifier (`*`).
pub repeat: bool,
}
// This is an implementation detail for the internal state of EleParseState.
impl From for () {
fn from(_: EleParseCfg) -> Self {
()
}
}
/// Maximum level of nesting for source XML trees.
///
/// Technically this is the maximum level of nesting for _parsing_ those
/// trees,
/// which may end up being less than this value.
///
/// This should be set to something reasonable,
/// but is not an alternative to coming up with code conventions that
/// disallow ridiculous levels of nesting.
/// TAME does have a lot of nesting with primitives,
/// but that nesting is easily abstracted with templates.
/// Templates may expand into ridiculous levels of nesting---this
/// has no impact on the template expansion phase.
///
/// Note that this is assuming that this parser is used only for TAME
/// sources.
/// If that's not the case,
/// this can be made to be configurable like XIRF.
pub const MAX_DEPTH: usize = 16;
/// Parser stack for trampoline.
///
/// This can be used as a call stack for parsers while avoiding creating
/// otherwise-recursive data structures with composition-based delegation.
/// However,
/// it is more similar to CPS,
/// in that the parser popped off the stack need not be the parser that
/// initiated the request and merely represents the next step in
/// a delayed computation.
/// If such a return context is unneeded,
/// a [`ParseState`] may implement tail calls by simply not pushing itself
/// onto the stack before requesting transfer to another [`ParseState`].
#[derive(Debug, Default)]
pub struct StateStack(ArrayVec);
pub type StateStackContext = Context>;
// Note that public visibility is needed because `ele_parse` expands outside
// of this module.
impl StateStack {
/// Request a transfer to another [`ParseState`],
/// expecting that control be returned to `ret` after it has
/// completed.
///
/// This can be reasoned about like calling a thunk:
/// the return [`ParseState`] is put onto the stack,
/// the target [`ParseState`] is used for the state transition to
/// cause [`Parser`] to perform the call to it,
/// and when it is done
/// (e.g. a dead state),
/// `ret` will be pop'd from the stack and we'll transition back to
/// it.
/// Note that this method is not responsible for returning;
/// see [`Self::ret_or_dead`] to perform a return.
///
/// However,
/// the calling [`ParseState`] is not responsible for its return,
/// unlike a typical function call.
/// Instead,
/// this _actually_ more closely resembles CPS
/// (continuation passing style),
/// and so [`ele_parse!`] must be careful to ensure that stack
/// operations are properly paired.
/// On the upside,
/// if something is erroneously `ret`'d,
/// the parser is guaranteed to be in a consistent state since the
/// entire state has been reified
/// (but the input would then be parsed incorrectly).
///
/// Note that tail calls can be implemented by transferring control
/// without pushing an entry on the stack to return to,
/// but that hasn't been formalized \[yet\] and requires extra care.
pub fn transfer_with_ret(
&mut self,
Transition(ret): Transition,
target: TransitionResult,
) -> TransitionResult
where
SA: ParseState,
ST: ParseState,
{
let Self(stack) = self;
// TODO: Global configuration to (hopefully) ensure that XIRF will
// actually catch this.
if stack.is_full() {
// TODO: We need some spans here and ideally convert the
// parenthetical error message into a diagnostic footnote.
// TODO: Or should we have a special error type that tells the
// parent `Parser` to panic with context?
diagnostic_panic!(
vec![],
"maximum parsing depth of {} exceeded while attempting \
to push return state {} \
(expected XIRF configuration to prevent this error)",
MAX_DEPTH,
TtQuote::wrap(ret),
);
}
stack.push(ret.into());
target
}
/// Attempt to return to a previous [`ParseState`] that transferred
/// control away from itself,
/// otherwise yield a dead state transition to `deadst`.
///
/// Conceptually,
/// this is like returning from a function call,
/// where the function was invoked using [`Self::transfer_with_ret`].
/// However,
/// this system is more akin to CPS
/// (continuation passing style);
/// see [`Self::transfer_with_ret`] for important information.
///
/// If there is no state to return to on the stack,
/// then it is assumed that we have received more input than expected
/// after having completed a full parse.
pub fn ret_or_dead(
&mut self,
lookahead: S::Token,
deadst: S,
) -> TransitionResult {
let Self(stack) = self;
// This should certainly never happen unless there is a bug in the
// `ele_parse!` parser-generator,
// since it means that we're trying to return to a caller that
// does not exist.
match stack.pop() {
Some(st) => Transition(st).incomplete().with_lookahead(lookahead),
None => Transition(deadst).dead(lookahead),
}
}
/// Test every [`ParseState`] on the stack against the predicate `f`.
pub fn all(&self, f: impl Fn(&S) -> bool) -> bool {
let Self(stack) = self;
stack[..].iter().all(f)
}
}
/// Match some type of node.
#[derive(Debug, PartialEq, Eq)]
pub enum NodeMatcher {
/// Static [`QName`] with a simple equality check.
QName(QName),
/// Any element with a matching [`Prefix`].
Prefix(Prefix),
}
impl NodeMatcher {
/// Match against the provided [`QName`].
pub fn matches(&self, qname: QName) -> bool {
match self {
Self::QName(qn_match) if qn_match == &qname => true,
Self::Prefix(prefix) if Some(*prefix) == qname.prefix() => true,
_ => false,
}
}
}
impl From for NodeMatcher {
fn from(qname: QName) -> Self {
Self::QName(qname)
}
}
impl From for NodeMatcher {
fn from(prefix: Prefix) -> Self {
Self::Prefix(prefix)
}
}
impl Display for NodeMatcher {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
use crate::xir::fmt::XmlPrefixAnyLocal;
match self {
Self::QName(qname) => Display::fmt(qname, f),
Self::Prefix(prefix) => XmlPrefixAnyLocal::fmt(prefix, f),
}
}
}
#[macro_export]
macro_rules! ele_parse {
(
$vis:vis enum $super:ident;
// Attr has to be first to avoid ambiguity with `$rest`.
$(type AttrValueError = $evty:ty;)?
type Object = $objty:ty;
$($rest:tt)*
) => {
ele_parse! {@!next $vis $super
$(type AttrValueError = $evty;)?
type Object = $objty;
$($rest)*
}
ele_parse!(@!super_sum <$objty> $vis $super $($rest)*);
};
(@!next $vis:vis $super:ident
// Attr has to be first to avoid ambiguity with `$rest`.
$(type AttrValueError = $evty:ty;)?
type Object = $objty:ty;
$($rest:tt)*
) => {
ele_parse!(@!nonterm_decl <$objty, $($evty)?> $vis $super $($rest)*);
};
(@!nonterm_decl <$objty:ty, $($evty:ty)?>
$vis:vis $super:ident $nt:ident := $($rest:tt)*
) => {
ele_parse!(@!nonterm_def <$objty, $($evty)?> $vis $super $nt $($rest)*);
};
(@!nonterm_def <$objty:ty, $($evty:ty)?>
$vis:vis $super:ident $nt:ident $qname:ident $(($($ntp:tt)*))?
{ $($matches:tt)* }; $($rest:tt)*
) => {
ele_parse!(@!ele_expand_body <$objty, $($evty)?>
$vis $super $nt $qname ($($($ntp)*)?) $($matches)*
);
ele_parse! {@!next $vis $super
$(type AttrValueError = $evty;)?
type Object = $objty;
$($rest)*
}
};
(@!nonterm_def <$objty:ty, $($evty:ty)?>
$vis:vis $super:ident $nt:ident
($ntref_first:ident $(| $ntref:ident)+); $($rest:tt)*
) => {
ele_parse!(@!ele_dfn_sum <$objty>
$vis $super $nt [$ntref_first $($ntref)*]
);
ele_parse! {@!next $vis $super
$(type AttrValueError = $evty;)?
type Object = $objty;
$($rest)*
}
};
(@!nonterm_decl <$objty:ty, $($evty:ty)?> $vis:vis $super:ident) => {};
// Expand the provided data to a more verbose form that provides the
// context necessary for state transitions.
(@!ele_expand_body <$objty:ty, $($evty:ty)?>
$vis:vis $super:ident $nt:ident $qname:ident ($($ntp:tt)*)
@ { $($attrbody:tt)* } => $attrmap:expr,
$(/$(($close_span:ident))? => $closemap:expr,)?
// Special forms (`[sp](args) => expr`).
$(
[$special:ident]$(($($special_arg:ident),*))?
=> $special_map:expr,
)?
// Nonterminal references are provided as a list.
// A configuration specifier can be provided,
// currently intended to support the Kleene star.
$(
$ntref:ident $([$ntref_cfg:tt])?,
)*
) => {
ele_parse! {
@!ele_dfn_body <$objty, $($evty)?> $vis $super $nt $qname ($($ntp)*)
@ { $($attrbody)* } => $attrmap,
/$($($close_span)?)? => ele_parse!(@!ele_close $($closemap)?),
$([$special]$(($($special_arg),*))? => $special_map,)?
<> {
$(
$ntref,
)*
}
// Generate state transitions of the form `(S) -> (S')`.
-> {
@ ->
$(
($nt::$ntref, $ntref) [$($ntref_cfg)?],
($nt::$ntref) ->
)* ($nt::ExpectClose_, ()) [],
}
}
};
// No explicit Close mapping defaults to doing nothing at all
// (so yield Incomplete).
(@!ele_close) => {
crate::parse::ParseStatus::Incomplete
};
(@!ele_close $close:expr) => {
crate::parse::ParseStatus::Object($close)
};
// NT[*] modifier.
(@!ntref_cfg *) => {
crate::xir::parse::EleParseCfg {
repeat: true,
}
};
// No bracketed modifier following NT.
(@!ntref_cfg) => {
crate::xir::parse::EleParseCfg {
repeat: false,
}
};
// Delegation when the destination type is `()`,
// indicating that the next state is not a child NT
// (it is likely the state expecting a closing tag).
(@!ntref_delegate
$stack:ident, $ret:expr, (), $_target:expr, $done:expr
) => {
$done
};
// Delegate to a child parser by pushing self onto the stack and
// yielding to one of the child's states.
// This uses a trampoline,
// which avoids recursive data structures
// (due to `ParseState` composition/stitching)
// and does not grow the call stack.
(@!ntref_delegate
$stack:ident, $ret:expr, $ntnext_st:ty, $target:expr, $_done:expr
) => {
$stack.transfer_with_ret(
Transition($ret),
$target,
)
};
(@!ele_dfn_body <$objty:ty, $($evty:ty)?>
$vis:vis $super:ident $nt:ident $qname:ident
($($qname_matched:pat, $open_span:pat)?)
// Attribute definition special form.
@ {
// We must lightly parse attributes here so that we can retrieve
// the field identifiers that may be later used as bindings in
// `$attrmap`.
$(
$(#[$fattr:meta])*
$field:ident: ($($fmatch:tt)+) => $fty:ty,
)*
} => $attrmap:expr,
// Close expression
// (defaulting to Incomplete via @!ele_expand_body).
/$($close_span:ident)? => $closemap:expr,
// Non-whitespace text nodes can be mapped into elements with the
// given QName as a preprocessing step,
// allowing them to reuse the existing element NT system.
$([text]($text:ident, $text_span:ident) => $text_map:expr,)?
// Nonterminal references.
<> {
$(
$ntref:ident,
)*
}
-> {
@ -> ($ntfirst:path, $ntfirst_st:ty) [$($ntfirst_cfg:tt)?],
$(
($ntprev:path) -> ($ntnext:path, $ntnext_st:ty) [$($ntnext_cfg:tt)?],
)*
}
) => {
paste::paste! {
crate::attr_parse! {
vis($vis);
$(type ValueError = $evty;)?
struct [<$nt AttrsState_>] -> [<$nt Attrs_>] {
$(
$(#[$fattr])*
$field: ($($fmatch)+) => $fty,
)*
}
}
#[doc=concat!("Parser for element [`", stringify!($qname), "`].")]
#[derive(Debug, PartialEq, Eq)]
$vis enum $nt {
#[doc=concat!(
"Expecting opening tag for element [`",
stringify!($qname),
"`]."
)]
Expecting_(crate::xir::parse::EleParseCfg),
/// Recovery state ignoring all remaining tokens for this
/// element.
RecoverEleIgnore_(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::xir::OpenSpan,
crate::xir::flat::Depth
),
// Recovery completed because end tag corresponding to the
// invalid element has been found.
RecoverEleIgnoreClosed_(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::xir::CloseSpan
),
/// Recovery state ignoring all tokens when a `Close` is
/// expected.
///
/// This is token-agnostic---it
/// may be a child element,
/// but it may be text,
/// for example.
CloseRecoverIgnore_(
(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::span::Span,
crate::xir::flat::Depth
),
crate::span::Span
),
/// Parsing element attributes.
Attrs_(
(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::span::Span,
crate::xir::flat::Depth
),
[<$nt AttrsState_>]
),
$(
$ntref(
(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::span::Span,
crate::xir::flat::Depth
),
),
)*
ExpectClose_(
(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::span::Span,
crate::xir::flat::Depth
),
),
/// Closing tag found and parsing of the element is
/// complete.
Closed_(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::span::Span
),
}
impl From for $nt {
fn from(repeat: crate::xir::parse::EleParseCfg) -> Self {
Self::Expecting_(repeat)
}
}
impl crate::xir::parse::EleParseState for $nt {}
impl $nt {
/// Matcher describing the node recognized by this parser.
#[allow(dead_code)] // used by sum parser
fn matcher() -> crate::xir::parse::NodeMatcher {
crate::xir::parse::NodeMatcher::from($qname)
}
/// Yield the expected depth of child elements,
/// if known.
#[allow(dead_code)] // used by text special form
fn child_depth(&self) -> Option {
match self {
$ntfirst((_, _, _, depth)) => Some(depth.child_depth()),
$(
$ntnext((_, _, _, depth)) => Some(depth.child_depth()),
)*
_ => None,
}
}
}
impl std::fmt::Display for $nt {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
use crate::{
fmt::{DisplayWrapper, TtQuote},
xir::fmt::{TtOpenXmlEle, TtCloseXmlEle},
};
match self {
Self::Expecting_(_) => write!(
f,
"expecting opening tag {}",
TtOpenXmlEle::wrap(Self::matcher()),
),
Self::RecoverEleIgnore_(_, name, _, _)
| Self::RecoverEleIgnoreClosed_(_, name, _) => write!(
f,
"attempting to recover by ignoring element \
with unexpected name {given} \
(expected {expected})",
given = TtQuote::wrap(name),
expected = TtQuote::wrap(Self::matcher()),
),
Self::CloseRecoverIgnore_((_, qname, _, depth), _) => write!(
f,
"attempting to recover by ignoring input \
until the expected end tag {expected} \
at depth {depth}",
expected = TtCloseXmlEle::wrap(qname),
),
Self::Attrs_(_, sa) => std::fmt::Display::fmt(sa, f),
Self::ExpectClose_((_, qname, _, depth)) => write!(
f,
"expecting closing element {} at depth {depth}",
TtCloseXmlEle::wrap(qname)
),
Self::Closed_(_, qname, _) => write!(
f,
"done parsing element {}",
TtQuote::wrap(qname),
),
$(
// TODO: A better description.
Self::$ntref(_) => {
write!(
f,
"preparing to transition to \
parser for next child element(s)"
)
},
)*
}
}
}
#[derive(Debug, PartialEq)]
$vis enum [<$nt Error_>] {
/// An element was expected,
/// but the name of the element was unexpected.
UnexpectedEle_(crate::xir::QName, crate::span::Span),
/// Unexpected input while expecting an end tag for this
/// element.
///
/// The span corresponds to the opening tag.
CloseExpected_(
crate::xir::QName,
crate::span::Span,
crate::xir::flat::XirfToken,
),
Attrs_(crate::xir::parse::AttrParseError<[<$nt AttrsState_>]>),
}
impl From]>>
for [<$nt Error_>]
{
fn from(
e: crate::xir::parse::AttrParseError<[<$nt AttrsState_>]>
) -> Self {
[<$nt Error_>]::Attrs_(e)
}
}
impl std::error::Error for [<$nt Error_>] {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
// TODO
None
}
}
impl std::fmt::Display for [<$nt Error_>] {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
use crate::{
fmt::{DisplayWrapper, TtQuote},
xir::fmt::{TtOpenXmlEle, TtCloseXmlEle},
};
match self {
Self::UnexpectedEle_(name, _) => write!(
f,
"unexpected {unexpected} (expecting {expected})",
unexpected = TtOpenXmlEle::wrap(name),
expected = TtOpenXmlEle::wrap($nt::matcher()),
),
Self::CloseExpected_(qname, _, tok) => write!(
f,
"expected {}, but found {}",
TtCloseXmlEle::wrap(qname),
TtQuote::wrap(tok)
),
Self::Attrs_(e) => std::fmt::Display::fmt(e, f),
}
}
}
impl crate::diagnose::Diagnostic for [<$nt Error_>] {
fn describe(&self) -> Vec {
use crate::{
diagnose::Annotate,
fmt::{DisplayWrapper, TtQuote},
parse::Token,
xir::fmt::{TtCloseXmlEle},
};
match self {
Self::UnexpectedEle_(_, ospan) => ospan.error(
format!(
"expected {ele_name} here",
ele_name = TtQuote::wrap($nt::matcher())
)
).into(),
Self::CloseExpected_(qname, span, tok) => vec![
span.note("element starts here"),
tok.span().error(format!(
"expected {}",
TtCloseXmlEle::wrap(qname),
)),
],
Self::Attrs_(e) => e.describe(),
}
}
}
impl crate::parse::ParseState for $nt {
type Token = crate::xir::flat::XirfToken<
crate::xir::flat::RefinedText
>;
type Object = $objty;
type Error = [<$nt Error_>];
type Context = crate::xir::parse::StateStackContext;
type Super = $super;
fn parse_token(
self,
tok: Self::Token,
#[allow(unused_variables)] // used only if child NTs
stack: &mut Self::Context,
) -> crate::parse::TransitionResult {
use crate::{
parse::{EmptyContext, Transition, Transitionable},
xir::{
EleSpan,
flat::XirfToken,
parse::parse_attrs,
},
};
// Used only by _some_ expansions.
#[allow(unused_imports)]
use crate::xir::flat::Text;
use $nt::{
Attrs_, Expecting_, RecoverEleIgnore_,
CloseRecoverIgnore_, RecoverEleIgnoreClosed_,
ExpectClose_, Closed_
};
match (self, tok) {
(
Expecting_(cfg),
XirfToken::Open(qname, span, depth)
) if $nt::matcher().matches(qname) => {
Transition(Attrs_(
(cfg, qname, span.tag_span(), depth),
parse_attrs(qname, span)
)).incomplete()
},
(
Closed_(cfg, ..),
XirfToken::Open(qname, span, depth)
) if cfg.repeat && Self::matcher().matches(qname) => {
Transition(Attrs_(
(cfg, qname, span.tag_span(), depth),
parse_attrs(qname, span)
)).incomplete()
},
(
Expecting_(cfg),
XirfToken::Open(qname, span, depth)
) => {
Transition(RecoverEleIgnore_(cfg, qname, span, depth)).err(
[<$nt Error_>]::UnexpectedEle_(qname, span.name_span())
)
},
(
RecoverEleIgnore_(cfg, qname, _, depth_open),
XirfToken::Close(_, span, depth_close)
) if depth_open == depth_close => {
Transition(
RecoverEleIgnoreClosed_(cfg, qname, span)
).incomplete()
},
(Attrs_(meta @ (_, qname, _, _), sa), tok) => {
sa.delegate_until_obj::(
tok,
EmptyContext,
|sa| Transition(Attrs_(meta, sa)),
|| unreachable!("see ParseState::delegate_until_obj dead"),
|#[allow(unused_variables)] sa, attrs| {
let obj = match attrs {
// Attribute field bindings for `$attrmap`
[<$nt Attrs_>] {
$(
$field,
)*
} => {
// Optional `OpenSpan` binding
let _ = qname; // avoid unused warning
$(
use crate::xir::parse::attr::AttrParseState;
let $qname_matched = qname;
let $open_span = sa.element_span();
)?
$attrmap
},
};
// Lookahead is added by `delegate_until_obj`.
ele_parse!(@!ntref_delegate
stack,
$ntfirst(meta),
$ntfirst_st,
Transition(
Into::<$ntfirst_st>::into(
ele_parse!(@!ntref_cfg $($ntfirst_cfg)?)
)
).ok(obj),
Transition($ntfirst(meta)).ok(obj)
)
}
)
},
$(
($ntprev(meta), tok) => {
ele_parse!(@!ntref_delegate
stack,
$ntnext(meta),
$ntnext_st,
Transition(
Into::<$ntnext_st>::into(
ele_parse!(@!ntref_cfg $($ntnext_cfg)?)
)
).incomplete().with_lookahead(tok),
Transition($ntnext(meta)).incomplete().with_lookahead(tok)
)
},
)*
// XIRF ensures proper nesting,
// so we do not need to check the element name.
(
ExpectClose_((cfg, qname, _, depth))
| CloseRecoverIgnore_((cfg, qname, _, depth), _),
XirfToken::Close(_, span, tok_depth)
) if tok_depth == depth => {
$(
let $close_span = span;
)?
$closemap.transition(Closed_(cfg, qname, span.tag_span()))
},
(ExpectClose_(meta @ (_, qname, otspan, _)), unexpected_tok) => {
use crate::parse::Token;
Transition(
CloseRecoverIgnore_(meta, unexpected_tok.span())
).err([<$nt Error_>]::CloseExpected_(qname, otspan, unexpected_tok))
}
// We're still in recovery,
// so this token gets thrown out.
(st @ (RecoverEleIgnore_(..) | CloseRecoverIgnore_(..)), _) => {
Transition(st).incomplete()
},
// TODO: Use `is_accepting` guard if we do not utilize
// exhaustiveness check.
(st @ (Closed_(..) | RecoverEleIgnoreClosed_(..)), tok) => {
Transition(st).dead(tok)
}
todo => todo!("{todo:?}"),
}
}
fn is_accepting(&self, _: &Self::Context) -> bool {
matches!(*self, Self::Closed_(..) | Self::RecoverEleIgnoreClosed_(..))
}
}
}
};
(@!ele_dfn_sum <$objty:ty> $vis:vis $super:ident $nt:ident [$($ntref:ident)*]) => {
$(
// Provide a (hopefully) helpful error that can be corrected
// rather than any obscure errors that may follow from trying
// to compose parsers that were not generated with this macro.
assert_impl_all!($ntref: crate::xir::parse::EleParseState);
)*
paste::paste! {
#[doc=concat!(
"Parser expecting one of ",
$("[`", stringify!($ntref), "`], ",)*
"."
)]
#[derive(Debug, PartialEq, Eq)]
$vis enum $nt {
Expecting_(crate::xir::parse::EleParseCfg),
/// Recovery state ignoring all remaining tokens for this
/// element.
RecoverEleIgnore_(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::xir::OpenSpan,
crate::xir::flat::Depth,
),
RecoverEleIgnoreClosed_(
crate::xir::parse::EleParseCfg,
crate::xir::QName,
crate::xir::CloseSpan
),
/// Inner element has been parsed and is dead;
/// this indicates that this parser is also dead.
Done_,
}
impl std::fmt::Display for $nt {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
use crate::{
fmt::{DisplayWrapper, ListDisplayWrapper, TtQuote},
xir::fmt::EleSumList,
};
let ntrefs = [
$(
$ntref::matcher(),
)*
];
let expected = EleSumList::wrap(&ntrefs);
match self {
Self::Expecting_(_) => {
write!(f, "expecting {expected}")
},
Self::RecoverEleIgnore_(_, name, _, _)
| Self::RecoverEleIgnoreClosed_(_, name, _) => write!(
f,
"attempting to recover by ignoring element \
with unexpected name {given} \
(expected {expected})",
given = TtQuote::wrap(name),
),
Self::Done_ => write!(f, "done parsing {expected}"),
}
}
}
impl From for $nt {
fn from(repeat: crate::xir::parse::EleParseCfg) -> Self {
Self::Expecting_(repeat)
}
}
#[derive(Debug, PartialEq)]
$vis enum [<$nt Error_>] {
UnexpectedEle_(crate::xir::QName, crate::span::Span),
}
impl std::error::Error for [<$nt Error_>] {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
// TODO
None
}
}
impl std::fmt::Display for [<$nt Error_>] {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
use crate::{
fmt::DisplayWrapper,
xir::fmt::TtOpenXmlEle,
};
match self {
Self::UnexpectedEle_(qname, _) => {
write!(f, "unexpected {}", TtOpenXmlEle::wrap(qname))
},
}
}
}
impl crate::diagnose::Diagnostic for [<$nt Error_>] {
fn describe(&self) -> Vec {
use crate::{
diagnose::Annotate,
fmt::{DisplayWrapper, ListDisplayWrapper, TtQuote},
xir::fmt::EleSumList,
};
let ntrefs = [
$(
$ntref::matcher(),
)*
];
let expected = EleSumList::wrap(&ntrefs);
match self {
Self::UnexpectedEle_(qname, span) => {
span
.error(format!(
"element {name} cannot appear here",
name = TtQuote::wrap(qname),
))
.with_help(format!("expecting {expected}"))
.into()
},
}
}
}
impl crate::parse::ParseState for $nt {
type Token = crate::xir::flat::XirfToken<
crate::xir::flat::RefinedText
>;
type Object = $objty;
type Error = [<$nt Error_>];
type Context = crate::xir::parse::StateStackContext;
type Super = $super;
fn parse_token(
self,
tok: Self::Token,
stack: &mut Self::Context,
) -> crate::parse::TransitionResult {
use crate::{
parse::Transition,
xir::{
flat::XirfToken,
parse::EleParseCfg,
},
};
use $nt::{
Expecting_, RecoverEleIgnore_,
RecoverEleIgnoreClosed_, Done_
};
match (self, tok) {
$(
(
Expecting_(cfg),
XirfToken::Open(qname, span, depth)
) if $ntref::matcher().matches(qname) => {
ele_parse!(@!ntref_delegate
stack,
match cfg.repeat {
true => Expecting_(cfg),
false => Done_,
},
$ntref,
Transition(
$ntref::from(
EleParseCfg::default()
)
).incomplete().with_lookahead(
XirfToken::Open(qname, span, depth)
),
unreachable!("TODO: remove me (ntref_delegate done)")
)
},
)*
// An unexpected token when repeating ends
// repetition and should not result in an error.
(Expecting_(cfg), tok) if cfg.repeat => {
Transition(Done_).dead(tok)
}
(Expecting_(cfg), XirfToken::Open(qname, span, depth)) => {
use crate::xir::EleSpan;
Transition(RecoverEleIgnore_(cfg, qname, span, depth)).err(
// Use name span rather than full `OpenSpan`
// since it's specifically the name that
// was unexpected,
// not the fact that it's an element.
[<$nt Error_>]::UnexpectedEle_(qname, span.name_span())
)
},
// XIRF ensures that the closing tag matches the opening,
// so we need only check depth.
(
RecoverEleIgnore_(cfg, qname, _, depth_open),
XirfToken::Close(_, span, depth_close)
) if depth_open == depth_close => {
Transition(RecoverEleIgnoreClosed_(cfg, qname, span)).incomplete()
},
(st @ RecoverEleIgnore_(..), _) => {
Transition(st).incomplete()
},
(
st @ (Done_ | RecoverEleIgnoreClosed_(..)),
tok
) => Transition(st).dead(tok),
todo => todo!("sum {todo:?}"),
}
}
fn is_accepting(&self, _: &Self::Context) -> bool {
match self {
Self::RecoverEleIgnoreClosed_(..) | Self::Done_ => true,
_ => false,
}
}
}
}
};
// Generate superstate sum type.
//
// This is really annoying because we cannot read the output of another
// macro,
// and so we have to do our best to re-parse the body of the
// original `ele_parse!` invocation without duplicating too much
// logic,
// and we have to do so in a way that we can aggregate all of
// those data.
(@!super_sum <$objty:ty> $vis:vis $super:ident
$(
// NT definition is always followed by `:=`.
$nt:ident :=
// Identifier if an element NT.
$($_i:ident)?
// Parenthesis for a sum NT,
// or possibly the span match for an element NT.
// So: `:= QN_IDENT(span)` or `:= (A | B | C)`.
$( ($($_p:tt)*) )?
// Braces for an element NT body.
$( {$($_b:tt)*} )?
// Element and sum NT both conclude with a semicolon,
// which we need to disambiguate the next `$nt`.
;
)*
) => {
paste::paste! {
/// Superstate representing the union of all related parsers.
///
/// This [`ParseState`] allows sub-parsers to independently
/// the states associated with their own subgraph,
/// and then yield a state transition directly to a state of
/// another parser.
/// This is conceptually like CPS (continuation passing style),
/// where this [`ParseState`] acts as a trampoline.
///
/// This [`ParseState`] is required for use with [`Parser`];
/// see [`ClosedParseState`] for more information.
#[derive(Debug, PartialEq, Eq)]
$vis enum $super {
$(
$nt($nt),
)*
}
// Default parser is the first NT.
impl Default for $super {
fn default() -> Self {
use $super::*;
ele_parse!(@!ntfirst $($nt)*)(
crate::xir::parse::EleParseCfg::default().into()
)
}
}
$(
impl From<$nt> for $super {
fn from(st: $nt) -> Self {
$super::$nt(st)
}
}
)*
impl std::fmt::Display for $super {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
match self {
$(
Self::$nt(e) => std::fmt::Display::fmt(e, f),
)*
}
}
}
/// Superstate error object representing the union of all
/// related parsers' errors.
#[derive(Debug, PartialEq)]
$vis enum [<$super Error_>] {
$(
$nt([<$nt Error_>]),
)*
}
$(
impl From<[<$nt Error_>]> for [<$super Error_>] {
fn from(e: [<$nt Error_>]) -> Self {
[<$super Error_>]::$nt(e)
}
}
)*
impl std::error::Error for [<$super Error_>] {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
// TODO
None
}
}
impl std::fmt::Display for [<$super Error_>] {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
match self {
$(
Self::$nt(e) => std::fmt::Display::fmt(e, f),
)*
}
}
}
impl crate::diagnose::Diagnostic for [<$super Error_>] {
fn describe(&self) -> Vec {
match self {
$(
Self::$nt(e) => e.describe(),
)*
}
}
}
impl crate::parse::ParseState for $super {
type Token = crate::xir::flat::XirfToken<
crate::xir::flat::RefinedText
>;
type Object = $objty;
type Error = [<$super Error_>];
type Context = crate::xir::parse::StateStackContext;
fn parse_token(
self,
tok: Self::Token,
stack: &mut Self::Context,
) -> crate::parse::TransitionResult {
use crate::{
parse::Transition,
xir::flat::{XirfToken, RefinedText},
};
match (self, tok) {
// Depth check is unnecessary since _all_ xir::parse
// parsers
// (at least at the time of writing)
// ignore whitespace and comments,
// so may as well return early.
// TODO: I'm ignoring _all_ text for now to
// proceed with development; fix.
(
st,
XirfToken::Text(RefinedText::Whitespace(..), _)
| XirfToken::Text(RefinedText::Unrefined(..), _) // XXX
| XirfToken::Comment(..)
) => {
Transition(st).incomplete()
}
$(
// Pass token directly to child until it reports
// a dead state,
// after which we return to the `ParseState`
// atop of the stack.
(Self::$nt(st), tok) => st.delegate_child(
tok,
stack,
|deadst, tok, stack| {
stack.ret_or_dead(tok, deadst)
},
),
)*
}
}
fn is_accepting(&self, stack: &Self::Context) -> bool {
// This is short-circuiting,
// starting at the _bottom_ of the stack and
// moving upward.
// The idea is that,
// is we're still in the middle of parsing,
// then it's almost certain that the [`ParseState`] on
// the bottom of the stack will not be in an
// accepting state,
// and so we can stop checking early.
// In most cases,
// if we haven't hit EOF early,
// the stack should be either empty or consist of only
// the root state.
//
// After having considered the stack,
// we can then consider the active `ParseState`.
stack.all(|st| st.is_inner_accepting(stack))
&& self.is_inner_accepting(stack)
}
}
impl $super {
/// Whether the inner (active child) [`ParseState`] is in an
/// accepting state.
fn is_inner_accepting(
&self,
ctx: &::Context
) -> bool {
use crate::parse::ParseState;
match self {
$(
Self::$nt(st) => st.is_accepting(ctx),
)*
}
}
}
}
};
(@!ntfirst $ntfirst:ident $($nt:ident)*) => {
$ntfirst
}
}
#[cfg(test)]
mod test;