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//! Provides a lazily parsing iterator over a SQL source.
use std::ops::{Deref, Range};
use super::{Error, Location, MetaTracker, Metadata, ParserInner, Token, TokenType};
use crate::ast::Statement;
/// A parsing error while [iterating](super::iter) a source's statements.
#[derive(Debug)]
pub struct IterError<'s> {
/// The section / slice of the (full) source that failed to parse into a
/// [Statement] and is consequently skipped by the originating iterator.
pub skipped: SourceSlice<'s>,
/// The parser error itself
///
/// Note: location data referred by the the error corresponds to the full
/// source being parsed.
pub error: Error,
}
impl<'s> From<IterError<'s>> for Error {
fn from(value: IterError) -> Self {
value.error
}
}
/// The source section that failed to parse and was skipped.
///
/// Served by [Iter].
#[derive(Debug)]
pub struct SourceSlice<'s> {
/// the (skipped) text extracted from the (full) source
pub text: &'s str,
/// the location span of `slice` (within the full source)
pub span: Range<Location>,
}
impl<'s> Deref for SourceSlice<'s> {
type Target = str;
fn deref(&self) -> &Self::Target {
self.text
}
}
// ----------------------------------------------------------------------------
/// The type of items published by a [statment iterator](Iter).
pub type IterItem<'s, ID> = std::result::Result<Statement<'s, ID>, IterError<'s>>;
/// An iterator over [statments](Statement), skipping unparsable source
/// sections.
pub trait Iter<'s, ID>: Iterator<Item = IterItem<'s, ID>> {
/// Retrieves temporary access to metadata.
fn metadata(&self) -> &impl Metadata<'s, NodeId = ID>;
/// Consumes this iterator returning all collected metadata so far.
fn into_metadata(self) -> impl Metadata<'s, NodeId = ID>;
}
struct IterImpl<'s, M: MetaTracker<'s>> {
parser: ParserInner<'s, M>,
last_pos: usize,
last_loc: Location,
}
impl<'s, M: MetaTracker<'s>> IterImpl<'s, M> {
fn new(parser: ParserInner<'s, M>) -> Self {
Self {
last_pos: parser.tokens.position(),
last_loc: parser.tokens.location(),
parser,
}
}
}
impl<'s, M> Iter<'s, M::NodeId> for IterImpl<'s, M>
where
M: MetaTracker<'s>,
{
fn metadata(&self) -> &impl Metadata<'s, NodeId = M::NodeId> {
self.parser.meta_tracker.metadata()
}
fn into_metadata(self) -> impl Metadata<'s, NodeId = M::NodeId> {
self.parser.meta_tracker.finish()
}
}
impl<'s, M> Iterator for IterImpl<'s, M>
where
M: MetaTracker<'s>,
{
type Item = IterItem<'s, <<M as MetaTracker<'s>>::Metadata as Metadata<'s>>::NodeId>;
fn next(&mut self) -> Option<Self::Item> {
match self.parser.parse_statement_().transpose() {
Some(Err(error)) => {
// ~ advance the token stream right after the next semicolon and
// return the error along with skipped section
loop {
match self.parser.next_token() {
Err(_)
| Ok(None)
| Ok(Some(Token {
ttype: TokenType::Semicolon,
..
})) => break,
_ => {
// ~ keep going
}
}
}
// ~ do not associate the skippped comments with the next token
self.parser.meta_tracker.on_node_end();
// ~ extract the piece of text we skipped
let (last_pos, last_loc) = (self.last_pos, self.last_loc);
let (next_pos, next_loc) =
(self.parser.tokens.position(), self.parser.tokens.location());
let skipped = SourceSlice {
text: &self.parser.tokens.source_range(last_pos..next_pos),
span: last_loc..next_loc,
};
self.last_pos = next_pos;
self.last_loc = next_loc;
Some(Err(IterError { skipped, error }))
}
Some(Ok(stmt)) => {
// ~ advance the parser past any comment so that they get
// registered and can be served as "trailing" comments to the
// last token in `stmt`
self.last_pos = self.parser.tokens.position();
self.last_loc = self.parser.tokens.location();
if let Ok((pos, loc)) = self.parser.skip_comments() {
self.last_pos = pos;
self.last_loc = loc;
} else {
// XXX push back the error to serve it on the next `.next()` call
}
Some(Ok(stmt))
}
None => None,
}
}
}
impl<'s, M> ParserInner<'s, M>
where
M: MetaTracker<'s> + 's,
{
/// Turns this parser into a lazily parsing statement iterator.
pub(super) fn into_iter(self) -> impl Iter<'s, M::NodeId, Item = IterItem<'s, M::NodeId>> {
IterImpl::new(self)
}
}
#[cfg(test)]
mod tests {
use pretty_assertions::assert_eq;
use std::borrow::Cow;
use super::*;
use crate::{
ast::{Node, QueryBlock, QuerySelect, StatementType},
parser::{Comment, CommentStyle, DefaultTracker, Location, VoidTracker},
scanner::Scanner,
};
fn unpack_select<'s, ID>(
stmt: Statement<'s, ID>,
) -> (QuerySelect<'s, ID>, Option<Node<(), ID>>) {
let StatementType::Select(select) = stmt.statement else {
panic!("not a select statement")
};
let QueryBlock::Select(select) = select.query.body.block else {
panic!("not a plain select query");
};
(select, stmt.terminator)
}
#[test]
fn test_iter_with_invalid_statements() {
// ~ three empty statements
let mut iter = ParserInner::new(
Scanner::new("/*one*/; /*two*/ bad; /*three*/; /*appendage*/"),
VoidTracker,
)
.into_iter();
assert!(matches!(
iter.next(),
Some(Ok(Statement {
statement: StatementType::Empty,
terminator: Some(Node((), _))
}))
));
assert!(matches!(
iter.next(),
Some(Err(
IterError {
skipped,
error: Error::Unexpected {
unexpected: Cow::Owned(unexpected),
expected: "a statement",
loc: Location { line: 1, col: 18 },
}
}))
// ~ we expect the "trailing /*two*/" comment be consumed and not
// reported as "skipped", as its tracked for the preceding
// statement
if unexpected == "'bad'" && &*skipped == " bad;"
));
assert!(matches!(
iter.next(),
Some(Ok(Statement {
statement: StatementType::Empty,
terminator: Some(Node((), _))
}))
));
assert!(iter.next().is_none());
}
#[test]
fn test_iter_with_comments() {
let mut iter = ParserInner::new(
Scanner::new(
r"
/*one*/ select /*two*/ /*2a*/ /*2b*/ 1 from /*three*/ dual ;
-- three and a half
/*four*/ select 2 from dual /*five*/ ;
-- six",
),
DefaultTracker::default(),
)
.into_iter();
// ~ first statement --------------------------------------------------
let stmt = iter.next().unwrap().unwrap();
let meta = iter.metadata();
let (
QuerySelect {
select_token, from, ..
},
terminator,
) = unpack_select(stmt);
// ~ first statement: `select` token
assert_eq!(
meta.comments(select_token.1),
(
&[Comment {
text: "one",
style: CommentStyle::Block,
loc: Location { line: 2, col: 1 }
},][..],
&[
Comment {
text: "two",
style: CommentStyle::Block,
loc: Location { line: 2, col: 17 },
},
Comment {
text: "2a",
style: CommentStyle::Block,
loc: Location { line: 2, col: 25 },
},
Comment {
text: "2b",
style: CommentStyle::Block,
loc: Location { line: 2, col: 32 },
}
][..]
)
);
// ~ first statement: `from` token
assert_eq!(
meta.comments(from.from_token.1),
(
&[][..],
&[Comment {
text: "three",
style: CommentStyle::Block,
loc: Location { line: 2, col: 46 }
}][..]
)
);
// ~ first statement: terminator token, i.e. `;`
assert_eq!(
meta.location(terminator.as_ref().unwrap().1),
Location { line: 2, col: 61 }
);
assert_eq!(
meta.comments(terminator.as_ref().unwrap().1),
(
&[][..],
&[
Comment {
text: " three and a half",
style: CommentStyle::Line,
loc: Location { line: 3, col: 1 },
},
Comment {
text: "four",
style: CommentStyle::Block,
loc: Location { line: 4, col: 1 },
}
][..]
)
);
// ~ second statement -------------------------------------------------
let stmt = iter.next().unwrap().unwrap();
let meta = iter.metadata();
let (QuerySelect { select_token, .. }, terminator) = unpack_select(stmt);
assert_eq!(
meta.comments(select_token.1),
(
&[
Comment {
text: " three and a half",
style: CommentStyle::Line,
loc: Location { line: 3, col: 1 },
},
Comment {
text: "four",
style: CommentStyle::Block,
loc: Location { line: 4, col: 1 }
}
][..],
&[][..]
)
);
assert_eq!(
meta.comments(terminator.unwrap().1),
(
&[Comment {
text: "five",
style: CommentStyle::Block,
loc: Location { line: 4, col: 47 },
},][..],
&[Comment {
text: " six",
style: CommentStyle::Line,
loc: Location { line: 5, col: 1 }
}][..],
)
);
// ~ no more statements expected --------------------------------------
assert!(iter.next().is_none());
}
}