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Diffstat (limited to 'third_party/rust/regex-syntax/src/hir/print.rs')
| -rw-r--r-- | third_party/rust/regex-syntax/src/hir/print.rs | 367 |
1 files changed, 367 insertions, 0 deletions
diff --git a/third_party/rust/regex-syntax/src/hir/print.rs b/third_party/rust/regex-syntax/src/hir/print.rs new file mode 100644 index 0000000000..b71f3897cf --- /dev/null +++ b/third_party/rust/regex-syntax/src/hir/print.rs @@ -0,0 +1,367 @@ +/*! +This module provides a regular expression printer for `Hir`. +*/ + +use std::fmt; + +use crate::hir::visitor::{self, Visitor}; +use crate::hir::{self, Hir, HirKind}; +use crate::is_meta_character; + +/// A builder for constructing a printer. +/// +/// Note that since a printer doesn't have any configuration knobs, this type +/// remains unexported. +#[derive(Clone, Debug)] +struct PrinterBuilder { + _priv: (), +} + +impl Default for PrinterBuilder { + fn default() -> PrinterBuilder { + PrinterBuilder::new() + } +} + +impl PrinterBuilder { + fn new() -> PrinterBuilder { + PrinterBuilder { _priv: () } + } + + fn build(&self) -> Printer { + Printer { _priv: () } + } +} + +/// A printer for a regular expression's high-level intermediate +/// representation. +/// +/// A printer converts a high-level intermediate representation (HIR) to a +/// regular expression pattern string. This particular printer uses constant +/// stack space and heap space proportional to the size of the HIR. +/// +/// Since this printer is only using the HIR, the pattern it prints will likely +/// not resemble the original pattern at all. For example, a pattern like +/// `\pL` will have its entire class written out. +/// +/// The purpose of this printer is to provide a means to mutate an HIR and then +/// build a regular expression from the result of that mutation. (A regex +/// library could provide a constructor from this HIR explicitly, but that +/// creates an unnecessary public coupling between the regex library and this +/// specific HIR representation.) +#[derive(Debug)] +pub struct Printer { + _priv: (), +} + +impl Printer { + /// Create a new printer. + pub fn new() -> Printer { + PrinterBuilder::new().build() + } + + /// Print the given `Ast` to the given writer. The writer must implement + /// `fmt::Write`. Typical implementations of `fmt::Write` that can be used + /// here are a `fmt::Formatter` (which is available in `fmt::Display` + /// implementations) or a `&mut String`. + pub fn print<W: fmt::Write>(&mut self, hir: &Hir, wtr: W) -> fmt::Result { + visitor::visit(hir, Writer { wtr }) + } +} + +#[derive(Debug)] +struct Writer<W> { + wtr: W, +} + +impl<W: fmt::Write> Visitor for Writer<W> { + type Output = (); + type Err = fmt::Error; + + fn finish(self) -> fmt::Result { + Ok(()) + } + + fn visit_pre(&mut self, hir: &Hir) -> fmt::Result { + match *hir.kind() { + HirKind::Empty + | HirKind::Repetition(_) + | HirKind::Concat(_) + | HirKind::Alternation(_) => {} + HirKind::Literal(hir::Literal::Unicode(c)) => { + self.write_literal_char(c)?; + } + HirKind::Literal(hir::Literal::Byte(b)) => { + self.write_literal_byte(b)?; + } + HirKind::Class(hir::Class::Unicode(ref cls)) => { + self.wtr.write_str("[")?; + for range in cls.iter() { + if range.start() == range.end() { + self.write_literal_char(range.start())?; + } else { + self.write_literal_char(range.start())?; + self.wtr.write_str("-")?; + self.write_literal_char(range.end())?; + } + } + self.wtr.write_str("]")?; + } + HirKind::Class(hir::Class::Bytes(ref cls)) => { + self.wtr.write_str("(?-u:[")?; + for range in cls.iter() { + if range.start() == range.end() { + self.write_literal_class_byte(range.start())?; + } else { + self.write_literal_class_byte(range.start())?; + self.wtr.write_str("-")?; + self.write_literal_class_byte(range.end())?; + } + } + self.wtr.write_str("])")?; + } + HirKind::Anchor(hir::Anchor::StartLine) => { + self.wtr.write_str("(?m:^)")?; + } + HirKind::Anchor(hir::Anchor::EndLine) => { + self.wtr.write_str("(?m:$)")?; + } + HirKind::Anchor(hir::Anchor::StartText) => { + self.wtr.write_str(r"\A")?; + } + HirKind::Anchor(hir::Anchor::EndText) => { + self.wtr.write_str(r"\z")?; + } + HirKind::WordBoundary(hir::WordBoundary::Unicode) => { + self.wtr.write_str(r"\b")?; + } + HirKind::WordBoundary(hir::WordBoundary::UnicodeNegate) => { + self.wtr.write_str(r"\B")?; + } + HirKind::WordBoundary(hir::WordBoundary::Ascii) => { + self.wtr.write_str(r"(?-u:\b)")?; + } + HirKind::WordBoundary(hir::WordBoundary::AsciiNegate) => { + self.wtr.write_str(r"(?-u:\B)")?; + } + HirKind::Group(ref x) => match x.kind { + hir::GroupKind::CaptureIndex(_) => { + self.wtr.write_str("(")?; + } + hir::GroupKind::CaptureName { ref name, .. } => { + write!(self.wtr, "(?P<{}>", name)?; + } + hir::GroupKind::NonCapturing => { + self.wtr.write_str("(?:")?; + } + }, + } + Ok(()) + } + + fn visit_post(&mut self, hir: &Hir) -> fmt::Result { + match *hir.kind() { + // Handled during visit_pre + HirKind::Empty + | HirKind::Literal(_) + | HirKind::Class(_) + | HirKind::Anchor(_) + | HirKind::WordBoundary(_) + | HirKind::Concat(_) + | HirKind::Alternation(_) => {} + HirKind::Repetition(ref x) => { + match x.kind { + hir::RepetitionKind::ZeroOrOne => { + self.wtr.write_str("?")?; + } + hir::RepetitionKind::ZeroOrMore => { + self.wtr.write_str("*")?; + } + hir::RepetitionKind::OneOrMore => { + self.wtr.write_str("+")?; + } + hir::RepetitionKind::Range(ref x) => match *x { + hir::RepetitionRange::Exactly(m) => { + write!(self.wtr, "{{{}}}", m)?; + } + hir::RepetitionRange::AtLeast(m) => { + write!(self.wtr, "{{{},}}", m)?; + } + hir::RepetitionRange::Bounded(m, n) => { + write!(self.wtr, "{{{},{}}}", m, n)?; + } + }, + } + if !x.greedy { + self.wtr.write_str("?")?; + } + } + HirKind::Group(_) => { + self.wtr.write_str(")")?; + } + } + Ok(()) + } + + fn visit_alternation_in(&mut self) -> fmt::Result { + self.wtr.write_str("|") + } +} + +impl<W: fmt::Write> Writer<W> { + fn write_literal_char(&mut self, c: char) -> fmt::Result { + if is_meta_character(c) { + self.wtr.write_str("\\")?; + } + self.wtr.write_char(c) + } + + fn write_literal_byte(&mut self, b: u8) -> fmt::Result { + let c = b as char; + if c <= 0x7F as char && !c.is_control() && !c.is_whitespace() { + self.write_literal_char(c) + } else { + write!(self.wtr, "(?-u:\\x{:02X})", b) + } + } + + fn write_literal_class_byte(&mut self, b: u8) -> fmt::Result { + let c = b as char; + if c <= 0x7F as char && !c.is_control() && !c.is_whitespace() { + self.write_literal_char(c) + } else { + write!(self.wtr, "\\x{:02X}", b) + } + } +} + +#[cfg(test)] +mod tests { + use super::Printer; + use crate::ParserBuilder; + + fn roundtrip(given: &str, expected: &str) { + roundtrip_with(|b| b, given, expected); + } + + fn roundtrip_bytes(given: &str, expected: &str) { + roundtrip_with(|b| b.allow_invalid_utf8(true), given, expected); + } + + fn roundtrip_with<F>(mut f: F, given: &str, expected: &str) + where + F: FnMut(&mut ParserBuilder) -> &mut ParserBuilder, + { + let mut builder = ParserBuilder::new(); + f(&mut builder); + let hir = builder.build().parse(given).unwrap(); + + let mut printer = Printer::new(); + let mut dst = String::new(); + printer.print(&hir, &mut dst).unwrap(); + + // Check that the result is actually valid. + builder.build().parse(&dst).unwrap(); + + assert_eq!(expected, dst); + } + + #[test] + fn print_literal() { + roundtrip("a", "a"); + roundtrip(r"\xff", "\u{FF}"); + roundtrip_bytes(r"\xff", "\u{FF}"); + roundtrip_bytes(r"(?-u)\xff", r"(?-u:\xFF)"); + roundtrip("☃", "☃"); + } + + #[test] + fn print_class() { + roundtrip(r"[a]", r"[a]"); + roundtrip(r"[a-z]", r"[a-z]"); + roundtrip(r"[a-z--b-c--x-y]", r"[ad-wz]"); + roundtrip(r"[^\x01-\u{10FFFF}]", "[\u{0}]"); + roundtrip(r"[-]", r"[\-]"); + roundtrip(r"[☃-⛄]", r"[☃-⛄]"); + + roundtrip(r"(?-u)[a]", r"(?-u:[a])"); + roundtrip(r"(?-u)[a-z]", r"(?-u:[a-z])"); + roundtrip_bytes(r"(?-u)[a-\xFF]", r"(?-u:[a-\xFF])"); + + // The following test that the printer escapes meta characters + // in character classes. + roundtrip(r"[\[]", r"[\[]"); + roundtrip(r"[Z-_]", r"[Z-_]"); + roundtrip(r"[Z-_--Z]", r"[\[-_]"); + + // The following test that the printer escapes meta characters + // in byte oriented character classes. + roundtrip_bytes(r"(?-u)[\[]", r"(?-u:[\[])"); + roundtrip_bytes(r"(?-u)[Z-_]", r"(?-u:[Z-_])"); + roundtrip_bytes(r"(?-u)[Z-_--Z]", r"(?-u:[\[-_])"); + } + + #[test] + fn print_anchor() { + roundtrip(r"^", r"\A"); + roundtrip(r"$", r"\z"); + roundtrip(r"(?m)^", r"(?m:^)"); + roundtrip(r"(?m)$", r"(?m:$)"); + } + + #[test] + fn print_word_boundary() { + roundtrip(r"\b", r"\b"); + roundtrip(r"\B", r"\B"); + roundtrip(r"(?-u)\b", r"(?-u:\b)"); + roundtrip_bytes(r"(?-u)\B", r"(?-u:\B)"); + } + + #[test] + fn print_repetition() { + roundtrip("a?", "a?"); + roundtrip("a??", "a??"); + roundtrip("(?U)a?", "a??"); + + roundtrip("a*", "a*"); + roundtrip("a*?", "a*?"); + roundtrip("(?U)a*", "a*?"); + + roundtrip("a+", "a+"); + roundtrip("a+?", "a+?"); + roundtrip("(?U)a+", "a+?"); + + roundtrip("a{1}", "a{1}"); + roundtrip("a{1,}", "a{1,}"); + roundtrip("a{1,5}", "a{1,5}"); + roundtrip("a{1}?", "a{1}?"); + roundtrip("a{1,}?", "a{1,}?"); + roundtrip("a{1,5}?", "a{1,5}?"); + roundtrip("(?U)a{1}", "a{1}?"); + roundtrip("(?U)a{1,}", "a{1,}?"); + roundtrip("(?U)a{1,5}", "a{1,5}?"); + } + + #[test] + fn print_group() { + roundtrip("()", "()"); + roundtrip("(?P<foo>)", "(?P<foo>)"); + roundtrip("(?:)", "(?:)"); + + roundtrip("(a)", "(a)"); + roundtrip("(?P<foo>a)", "(?P<foo>a)"); + roundtrip("(?:a)", "(?:a)"); + + roundtrip("((((a))))", "((((a))))"); + } + + #[test] + fn print_alternation() { + roundtrip("|", "|"); + roundtrip("||", "||"); + + roundtrip("a|b", "a|b"); + roundtrip("a|b|c", "a|b|c"); + roundtrip("foo|bar|quux", "foo|bar|quux"); + } +} |