Struct regex_syntax::ParserBuilder

pub struct ParserBuilder { /* private fields */ }

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 and the HIR TranslatorBuilder.

Implementations

impl ParserBuilder

pub fn new() -> ParserBuilder

Create a new parser builder with a default configuration.

pub fn build(&self) -> Parser

Build a parser from this configuration with the given pattern.

pub fn nest_limit(&mut self, limit: u32) -> &mut ParserBuilder

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 octal(&mut self, yes: bool) -> &mut ParserBuilder

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 utf8(&mut self, yes: bool) -> &mut ParserBuilder

When disabled, translation will permit the construction of a regular expression that may match invalid UTF-8.

When enabled (the default), the translator is guaranteed to produce an expression that, for non-empty matches, will only ever produce spans that are entirely valid UTF-8 (otherwise, the translator will return an error).

Perhaps surprisingly, when UTF-8 is enabled, an empty regex or even a negated ASCII word boundary (uttered as (?-u:\B) in the concrete syntax) will be allowed even though they can produce matches that split a UTF-8 encoded codepoint. This only applies to zero-width or “empty” matches, and it is expected that the regex engine itself must handle these cases if necessary (perhaps by suppressing any zero-width matches that split a codepoint).

pub fn ignore_whitespace(&mut self, yes: bool) -> &mut ParserBuilder

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 case_insensitive(&mut self, yes: bool) -> &mut ParserBuilder

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 multi_line(&mut self, yes: bool) -> &mut ParserBuilder

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 dot_matches_new_line(&mut self, yes: bool) -> &mut ParserBuilder

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 crlf(&mut self, yes: bool) -> &mut ParserBuilder

Enable or disable the CRLF mode flag by default.

By default this is disabled. It may alternatively be selectively enabled in the regular expression itself via the R flag.

When CRLF mode is enabled, the following happens:

• Unless dot_matches_new_line is enabled, . will match any character except for \r and \n.
• When multi_line mode is enabled, ^ and $ will treat \r\n, \r and \n as line terminators. And in particular, neither will match between a \r and a \n.

pub fn line_terminator(&mut self, byte: u8) -> &mut ParserBuilder

Sets the line terminator for use with (?u-s:.) and (?-us:.).

Namely, instead of . (by default) matching everything except for \n, this will cause . to match everything except for the byte given.

If . is used in a context where Unicode mode is enabled and this byte isn’t ASCII, then an error will be returned. When Unicode mode is disabled, then any byte is permitted, but will return an error if UTF-8 mode is enabled and it is a non-ASCII byte.

In short, any ASCII value for a line terminator is always okay. But a non-ASCII byte might result in an error depending on whether Unicode mode or UTF-8 mode are enabled.

Note that if R mode is enabled then it always takes precedence and the line terminator will be treated as \r and \n simultaneously.

Note also that this doesn’t impact the look-around assertions (?m:^) and (?m:$). That’s usually controlled by additional configuration in the regex engine itself.

pub fn swap_greed(&mut self, yes: bool) -> &mut ParserBuilder

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 unicode(&mut self, yes: bool) -> &mut ParserBuilder

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 utf8 is disabled (it’s enabled by default), a regular expression will fail to parse if Unicode mode is disabled and a sub-expression could possibly match invalid UTF-8.

Trait Implementations

impl Clone for ParserBuilder

fn clone(&self) -> ParserBuilder

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ParserBuilder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ParserBuilder

fn default() -> ParserBuilder

Returns the “default value” for a type.