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Visitor to output the list of groups that may not exist in the output
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| use regex::Regex; | |
| use regex_syntax::hir::visit; | |
| use regex_syntax::hir::Group; | |
| use regex_syntax::hir::GroupKind; | |
| use regex_syntax::hir::Hir; | |
| use regex_syntax::hir::HirKind; | |
| use regex_syntax::hir::RepetitionKind; | |
| use regex_syntax::hir::RepetitionRange; | |
| use regex_syntax::hir::Visitor; | |
| #[derive(Default)] | |
| struct MyVisitor { | |
| stack: u32, | |
| optional_groups: Vec<u32>, | |
| } | |
| impl MyVisitor { | |
| fn new() -> Self { | |
| Default::default() | |
| } | |
| } | |
| fn get_group_idx(hir: &Hir) -> Option<u32> { | |
| match hir.kind() { | |
| HirKind::Group(Group { | |
| kind: GroupKind::CaptureIndex(idx), | |
| .. | |
| }) | |
| | HirKind::Group(Group { | |
| kind: GroupKind::CaptureName { index: idx, .. }, | |
| .. | |
| }) => Some(*idx), | |
| _ => None, | |
| } | |
| } | |
| fn subexpressions_are_optional(hir: &Hir) -> bool { | |
| match hir.kind() { | |
| HirKind::Repetition(r) => match &r.kind { | |
| RepetitionKind::ZeroOrMore | RepetitionKind::ZeroOrOne => true, | |
| RepetitionKind::Range(rr) => match rr { | |
| RepetitionRange::Exactly(0) => true, | |
| RepetitionRange::AtLeast(0) => true, | |
| RepetitionRange::Bounded(0, _) => true, | |
| _ => false, | |
| }, | |
| _ => false, | |
| }, | |
| HirKind::Alternation(_) => true, | |
| _ => false, | |
| } | |
| } | |
| impl Visitor for MyVisitor { | |
| type Output = Vec<u32>; | |
| type Err = (); | |
| fn finish(self) -> Result<Self::Output, Self::Err> { | |
| Ok(self.optional_groups) | |
| } | |
| fn visit_pre(&mut self, hir: &Hir) -> Result<(), Self::Err> { | |
| if subexpressions_are_optional(hir) { | |
| self.stack += 1; | |
| } | |
| if self.stack > 0 { | |
| if let Some(idx) = get_group_idx(hir) { | |
| self.optional_groups.push(idx); | |
| } | |
| } | |
| Ok(()) | |
| } | |
| fn visit_post(&mut self, hir: &Hir) -> Result<(), Self::Err> { | |
| if subexpressions_are_optional(hir) { | |
| self.stack -= 1; | |
| } | |
| Ok(()) | |
| } | |
| } | |
| fn main() { | |
| let s = r#"((a)?|s?|d?|f?)(t|(asdf)*(?P<foo_col>(?:foo)*)((((?P<bars_col>(?:bar)+))?(asdf))))"#; | |
| let mut p = regex_syntax::Parser::new(); | |
| let hir = p.parse(s).unwrap(); | |
| let v = MyVisitor::new(); | |
| let ops = visit(&hir, v).unwrap(); | |
| println!("Optional groups: {:#?}", ops); | |
| let r = Regex::new(s).unwrap(); | |
| let v: Vec<_> = r | |
| .captures("sasdf") | |
| .unwrap() | |
| .iter() | |
| .map(|om| om.map(|m| m.as_str())) | |
| .collect(); | |
| println!("Captures: {:#?}", v); | |
| } |
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