summaryrefslogtreecommitdiffstats
path: root/vendor/regex-syntax/src/parser.rs
blob: ded95b280afb428feda8e4ac9a8b41f75fab91c1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
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)
    }
}