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
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
// SPDX-License-Identifier: Apache-2.0 OR MIT
use alloc::{borrow::ToOwned as _, vec, vec::Vec};
use crate::cfg_expr::{
error::{ParseError, Reason},
expr::{
ExprNode, Expression, Func, InnerPredicate,
lexer::{Lexer, Token},
},
};
impl Expression {
/// Given a cfg() expression (the cfg( and ) are optional), attempts to
/// parse it into a form where it can be evaluated
pub(crate) fn parse(original: &str) -> Result<Self, ParseError> {
#[derive(Debug)]
struct FuncAndSpan {
func: Func,
parens_index: usize,
span: core::ops::Range<usize>,
predicates: Vec<InnerPredicate>,
nest_level: u8,
}
let lexer = Lexer::new(original);
// The lexer automatically trims any cfg( ), so reacquire
// the string before we start walking tokens
let original = lexer.inner;
let mut func_stack: Vec<FuncAndSpan> = Vec::with_capacity(5);
let mut expr_queue = Vec::with_capacity(5);
// Keep track of the last token to simplify validation of the token stream
let mut last_token: Option<Token<'_>> = None;
let parse_predicate = |key: (&str, core::ops::Range<usize>),
val: Option<(&str, core::ops::Range<usize>)>|
-> Result<InnerPredicate, ParseError> {
let span = key.1;
Ok(InnerPredicate { identifier: span, value: val.map(|(_, span)| span) })
};
macro_rules! token_err {
($span:expr) => {{
let expected: &[&str] = match last_token {
None => &["<key>", "all", "any", "not"],
Some(Token::All | Token::Any | Token::Not) => &["("],
Some(Token::CloseParen) => &[")", ","],
Some(Token::Comma) => &[")", "<key>"],
Some(Token::Equals) => &["\""],
Some(Token::Key(_)) => &["=", ",", ")"],
Some(Token::Value(_)) => &[",", ")"],
Some(Token::OpenParen) => &["<key>", ")", "all", "any", "not"],
};
return Err(ParseError {
original: original.into(),
span: $span,
reason: Reason::Unexpected(&expected),
});
}};
}
let mut pred_key: Option<(&str, _)> = None;
let mut pred_val: Option<(&str, _)> = None;
let mut root_predicate_count = 0;
// Basic implementation of the https://en.wikipedia.org/wiki/Shunting-yard_algorithm
'outer: for lt in lexer {
let lt = lt?;
match <.token {
Token::Key(k) => {
if matches!(last_token, None | Some(Token::OpenParen | Token::Comma)) {
pred_key = Some((k, lt.span.clone()));
} else {
token_err!(lt.span)
}
}
Token::Value(v) => {
if matches!(last_token, Some(Token::Equals)) {
// We only record the span for keys and values
// so that the expression doesn't need a lifetime
// but in the value case we need to strip off
// the quotes so that the proper raw string is
// provided to callers when evaluating the expression
pred_val = Some((v, lt.span.start + 1..lt.span.end - 1));
} else {
token_err!(lt.span)
}
}
Token::Equals => {
if !matches!(last_token, Some(Token::Key(_))) {
token_err!(lt.span)
}
}
Token::All | Token::Any | Token::Not => {
if matches!(last_token, None | Some(Token::OpenParen | Token::Comma)) {
let new_fn = match lt.token {
// the 0 is a dummy value -- it will be substituted for the real
// number of predicates in the `CloseParen` branch below.
Token::All => Func::All(0),
Token::Any => Func::Any(0),
Token::Not => Func::Not,
_ => unreachable!(),
};
if let Some(fs) = func_stack.last_mut() {
fs.nest_level += 1;
}
func_stack.push(FuncAndSpan {
func: new_fn,
span: lt.span,
parens_index: 0,
predicates: vec![],
nest_level: 0,
});
} else {
token_err!(lt.span)
}
}
Token::OpenParen => {
if matches!(last_token, Some(Token::All | Token::Any | Token::Not)) {
if let Some(ref mut fs) = func_stack.last_mut() {
fs.parens_index = lt.span.start;
}
} else {
token_err!(lt.span)
}
}
Token::CloseParen => {
if matches!(
last_token,
None | Some(Token::All | Token::Any | Token::Not | Token::Equals)
) {
token_err!(lt.span)
}
if let Some(top) = func_stack.pop() {
let key = pred_key.take();
let val = pred_val.take();
let num_predicates =
top.predicates.len() + key.is_some() as usize + top.nest_level as usize;
let func = match top.func {
Func::All(_) => Func::All(num_predicates),
Func::Any(_) => Func::Any(num_predicates),
Func::Not => {
// not() doesn't take a predicate list, but only a single predicate,
// so ensure we have exactly 1
if num_predicates != 1 {
return Err(ParseError {
original: original.into(),
span: top.span.start..lt.span.end,
reason: Reason::InvalidNot(num_predicates),
});
}
Func::Not
}
};
for pred in top.predicates {
expr_queue.push(ExprNode::Predicate(pred));
}
if let Some(key) = key {
let inner_pred = parse_predicate(key, val)?;
expr_queue.push(ExprNode::Predicate(inner_pred));
}
expr_queue.push(ExprNode::Fn(func));
// This is the only place we go back to the top of the outer loop,
// so make sure we correctly record this token
last_token = Some(Token::CloseParen);
continue 'outer;
}
// We didn't have an opening parentheses if we get here
return Err(ParseError {
original: original.into(),
span: lt.span,
reason: Reason::UnopenedParens,
});
}
Token::Comma => {
if matches!(
last_token,
None | Some(
Token::OpenParen | Token::All | Token::Any | Token::Not | Token::Equals
)
) {
token_err!(lt.span)
}
let key = pred_key.take();
let val = pred_val.take();
let inner_pred = key.map(|key| parse_predicate(key, val)).transpose()?;
match (inner_pred, func_stack.last_mut()) {
(Some(pred), Some(func)) => {
func.predicates.push(pred);
}
(Some(pred), None) => {
root_predicate_count += 1;
expr_queue.push(ExprNode::Predicate(pred));
}
_ => {}
}
}
}
last_token = Some(lt.token);
}
if let Some(Token::Equals) = last_token {
return Err(ParseError {
original: original.into(),
span: original.len()..original.len(),
reason: Reason::Unexpected(&["\"<value>\""]),
});
}
// If we still have functions on the stack, it means we have an unclosed parens
if let Some(top) = func_stack.pop() {
if top.parens_index == 0 {
Err(ParseError {
original: original.into(),
span: top.span,
reason: Reason::Unexpected(&["("]),
})
} else {
Err(ParseError {
original: original.into(),
span: top.parens_index..original.len(),
reason: Reason::UnclosedParens,
})
}
} else {
let key = pred_key.take();
let val = pred_val.take();
if let Some(key) = key {
root_predicate_count += 1;
expr_queue.push(ExprNode::Predicate(parse_predicate(key, val)?));
}
if expr_queue.is_empty() {
Err(ParseError {
original: original.into(),
span: 0..original.len(),
reason: Reason::Empty,
})
} else if root_predicate_count > 1 {
Err(ParseError {
original: original.into(),
span: 0..original.len(),
reason: Reason::MultipleRootPredicates,
})
} else {
Ok(Expression { original: original.to_owned(), expr: expr_queue })
}
}
}
}