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Diffstat (limited to 'third_party/rust/regex-syntax/src/parser.rs')
| -rw-r--r-- | third_party/rust/regex-syntax/src/parser.rs | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/third_party/rust/regex-syntax/src/parser.rs b/third_party/rust/regex-syntax/src/parser.rs new file mode 100644 index 0000000000..ded95b280a --- /dev/null +++ b/third_party/rust/regex-syntax/src/parser.rs @@ -0,0 +1,200 @@ +use crate::ast; +use crate::hir; + +use crate::Result; + +/// A builder for a regular expression parser. +/// +/// This builder permits modifying configuration options for the parser. +/// +/// This type combines the builder options for both the +/// [AST `ParserBuilder`](ast/parse/struct.ParserBuilder.html) +/// and the +/// [HIR `TranslatorBuilder`](hir/translate/struct.TranslatorBuilder.html). +#[derive(Clone, Debug, Default)] +pub struct ParserBuilder { + ast: ast::parse::ParserBuilder, + hir: hir::translate::TranslatorBuilder, +} + +impl ParserBuilder { + /// Create a new parser builder with a default configuration. + pub fn new() -> ParserBuilder { + ParserBuilder::default() + } + + /// Build a parser from this configuration with the given pattern. + pub fn build(&self) -> Parser { + Parser { ast: self.ast.build(), hir: self.hir.build() } + } + + /// Set the nesting limit for this parser. + /// + /// The nesting limit controls how deep the abstract syntax tree is allowed + /// to be. If the AST exceeds the given limit (e.g., with too many nested + /// groups), then an error is returned by the parser. + /// + /// The purpose of this limit is to act as a heuristic to prevent stack + /// overflow for consumers that do structural induction on an `Ast` using + /// explicit recursion. While this crate never does this (instead using + /// constant stack space and moving the call stack to the heap), other + /// crates may. + /// + /// This limit is not checked until the entire Ast is parsed. Therefore, + /// if callers want to put a limit on the amount of heap space used, then + /// they should impose a limit on the length, in bytes, of the concrete + /// pattern string. In particular, this is viable since this parser + /// implementation will limit itself to heap space proportional to the + /// length of the pattern string. + /// + /// Note that a nest limit of `0` will return a nest limit error for most + /// patterns but not all. For example, a nest limit of `0` permits `a` but + /// not `ab`, since `ab` requires a concatenation, which results in a nest + /// depth of `1`. In general, a nest limit is not something that manifests + /// in an obvious way in the concrete syntax, therefore, it should not be + /// used in a granular way. + pub fn nest_limit(&mut self, limit: u32) -> &mut ParserBuilder { + self.ast.nest_limit(limit); + self + } + + /// Whether to support octal syntax or not. + /// + /// Octal syntax is a little-known way of uttering Unicode codepoints in + /// a regular expression. For example, `a`, `\x61`, `\u0061` and + /// `\141` are all equivalent regular expressions, where the last example + /// shows octal syntax. + /// + /// While supporting octal syntax isn't in and of itself a problem, it does + /// make good error messages harder. That is, in PCRE based regex engines, + /// syntax like `\0` invokes a backreference, which is explicitly + /// unsupported in Rust's regex engine. However, many users expect it to + /// be supported. Therefore, when octal support is disabled, the error + /// message will explicitly mention that backreferences aren't supported. + /// + /// Octal syntax is disabled by default. + pub fn octal(&mut self, yes: bool) -> &mut ParserBuilder { + self.ast.octal(yes); + self + } + + /// When enabled, the parser will permit the construction of a regular + /// expression that may match invalid UTF-8. + /// + /// When disabled (the default), the parser is guaranteed to produce + /// an expression that will only ever match valid UTF-8 (otherwise, the + /// parser will return an error). + /// + /// Perhaps surprisingly, when invalid UTF-8 isn't allowed, a negated ASCII + /// word boundary (uttered as `(?-u:\B)` in the concrete syntax) will cause + /// the parser to return an error. Namely, a negated ASCII word boundary + /// can result in matching positions that aren't valid UTF-8 boundaries. + pub fn allow_invalid_utf8(&mut self, yes: bool) -> &mut ParserBuilder { + self.hir.allow_invalid_utf8(yes); + self + } + + /// Enable verbose mode in the regular expression. + /// + /// When enabled, verbose mode permits insignificant whitespace in many + /// places in the regular expression, as well as comments. Comments are + /// started using `#` and continue until the end of the line. + /// + /// By default, this is disabled. It may be selectively enabled in the + /// regular expression by using the `x` flag regardless of this setting. + pub fn ignore_whitespace(&mut self, yes: bool) -> &mut ParserBuilder { + self.ast.ignore_whitespace(yes); + self + } + + /// Enable or disable the case insensitive flag by default. + /// + /// By default this is disabled. It may alternatively be selectively + /// enabled in the regular expression itself via the `i` flag. + pub fn case_insensitive(&mut self, yes: bool) -> &mut ParserBuilder { + self.hir.case_insensitive(yes); + self + } + + /// Enable or disable the multi-line matching flag by default. + /// + /// By default this is disabled. It may alternatively be selectively + /// enabled in the regular expression itself via the `m` flag. + pub fn multi_line(&mut self, yes: bool) -> &mut ParserBuilder { + self.hir.multi_line(yes); + self + } + + /// Enable or disable the "dot matches any character" flag by default. + /// + /// By default this is disabled. It may alternatively be selectively + /// enabled in the regular expression itself via the `s` flag. + pub fn dot_matches_new_line(&mut self, yes: bool) -> &mut ParserBuilder { + self.hir.dot_matches_new_line(yes); + self + } + + /// Enable or disable the "swap greed" flag by default. + /// + /// By default this is disabled. It may alternatively be selectively + /// enabled in the regular expression itself via the `U` flag. + pub fn swap_greed(&mut self, yes: bool) -> &mut ParserBuilder { + self.hir.swap_greed(yes); + self + } + + /// Enable or disable the Unicode flag (`u`) by default. + /// + /// By default this is **enabled**. It may alternatively be selectively + /// disabled in the regular expression itself via the `u` flag. + /// + /// Note that unless `allow_invalid_utf8` is enabled (it's disabled by + /// default), a regular expression will fail to parse if Unicode mode is + /// disabled and a sub-expression could possibly match invalid UTF-8. + pub fn unicode(&mut self, yes: bool) -> &mut ParserBuilder { + self.hir.unicode(yes); + self + } +} + +/// A convenience parser for regular expressions. +/// +/// This parser takes as input a regular expression pattern string (the +/// "concrete syntax") and returns a high-level intermediate representation +/// (the HIR) suitable for most types of analysis. In particular, this parser +/// hides the intermediate state of producing an AST (the "abstract syntax"). +/// The AST is itself far more complex than the HIR, so this parser serves as a +/// convenience for never having to deal with it at all. +/// +/// If callers have more fine grained use cases that need an AST, then please +/// see the [`ast::parse`](ast/parse/index.html) module. +/// +/// A `Parser` can be configured in more detail via a +/// [`ParserBuilder`](struct.ParserBuilder.html). +#[derive(Clone, Debug)] +pub struct Parser { + ast: ast::parse::Parser, + hir: hir::translate::Translator, +} + +impl Parser { + /// Create a new parser with a default configuration. + /// + /// The parser can be run with `parse` method. The parse method returns + /// a high level intermediate representation of the given regular + /// expression. + /// + /// To set configuration options on the parser, use + /// [`ParserBuilder`](struct.ParserBuilder.html). + pub fn new() -> Parser { + ParserBuilder::new().build() + } + + /// Parse the regular expression into a high level intermediate + /// representation. + pub fn parse(&mut self, pattern: &str) -> Result<hir::Hir> { + let ast = self.ast.parse(pattern)?; + let hir = self.hir.translate(pattern, &ast)?; + Ok(hir) + } +} |