cfg_expr/expr/parser.rs
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use crate::{
error::{ParseError, Reason},
expr::{
lexer::{Lexer, Token},
ExprNode, Expression, Func, InnerPredicate,
},
};
use smallvec::SmallVec;
impl Expression {
/// Given a `cfg()` expression (the cfg( and ) are optional), attempts to
/// parse it into a form where it can be evaluated
///
/// ```
/// assert!(cfg_expr::Expression::parse(r#"cfg(all(unix, target_arch = "x86_64"))"#).is_ok());
/// ```
pub fn parse(original: &str) -> Result<Self, ParseError> {
let lexer = Lexer::new(original);
// The lexer automatically trims any cfg( ), so reacquire
// the string before we start walking tokens
let original = lexer.inner;
#[derive(Debug)]
struct FuncAndSpan {
func: Func,
parens_index: usize,
span: std::ops::Range<usize>,
predicates: SmallVec<[InnerPredicate; 5]>,
nest_level: u8,
}
let mut func_stack = SmallVec::<[FuncAndSpan; 5]>::new();
let mut expr_queue = SmallVec::<[ExprNode; 5]>::new();
// 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, std::ops::Range<usize>),
val: Option<(&str, std::ops::Range<usize>)>|
-> Result<InnerPredicate, ParseError> {
// Warning: It is possible for arbitrarily-set configuration
// options to have the same value as compiler-set configuration
// options. For example, it is possible to do rustc --cfg "unix" program.rs
// while compiling to a Windows target, and have both unix and windows
// configuration options set at the same time. It is unwise to actually
// do this.
//
// rustc is very permissive in this regard, but I'd rather be really
// strict, as it's much easier to loosen restrictions over time than add
// new ones
macro_rules! err_if_val {
() => {
if let Some((_, vspan)) = val {
return Err(ParseError {
original: original.to_owned(),
span: vspan,
reason: Reason::Unexpected(&[]),
});
}
};
}
let span = key.1;
let key = key.0;
use super::{InnerTarget, Which};
Ok(match key {
// These are special cases in the cfg language that are
// semantically the same as `target_family = "<family>"`,
// so we just make them not special
// NOTE: other target families like "wasm" are NOT allowed
// as naked predicates; they must be specified through
// `target_family`
"unix" | "windows" => {
err_if_val!();
InnerPredicate::Target(InnerTarget {
which: Which::Family,
span: Some(span),
})
}
"test" => {
err_if_val!();
InnerPredicate::Test
}
"debug_assertions" => {
err_if_val!();
InnerPredicate::DebugAssertions
}
"proc_macro" => {
err_if_val!();
InnerPredicate::ProcMacro
}
"feature" => {
// rustc allows bare feature without a value, but the only way
// such a predicate would ever evaluate to true would be if they
// explicitly set --cfg feature, which would be terrible, so we
// just error instead
match val {
Some((_, span)) => InnerPredicate::Feature(span),
None => {
return Err(ParseError {
original: original.to_owned(),
span,
reason: Reason::Unexpected(&["= \"<feature_name>\""]),
});
}
}
}
"panic" => match val {
Some((_, vspan)) => InnerPredicate::Target(InnerTarget {
which: Which::Panic,
span: Some(vspan),
}),
None => {
return Err(ParseError {
original: original.to_owned(),
span,
reason: Reason::Unexpected(&["= \"<panic_strategy>\""]),
});
}
},
target_key if key.starts_with("target_") => {
let (val, vspan) = match val {
None => {
return Err(ParseError {
original: original.to_owned(),
span,
reason: Reason::Unexpected(&["= \"<target_cfg_value>\""]),
});
}
Some((val, vspan)) => (val, vspan),
};
macro_rules! tp {
($which:ident) => {
InnerTarget {
which: Which::$which,
span: Some(vspan),
}
};
}
let tp = match &target_key[7..] {
"abi" => tp!(Abi),
"arch" => tp!(Arch),
"feature" => {
if val.is_empty() {
return Err(ParseError {
original: original.to_owned(),
span: vspan,
reason: Reason::Unexpected(&["<feature>"]),
});
}
return Ok(InnerPredicate::TargetFeature(vspan));
}
"os" => tp!(Os),
"family" => tp!(Family),
"env" => tp!(Env),
"endian" => InnerTarget {
which: Which::Endian(val.parse().map_err(|_err| ParseError {
original: original.to_owned(),
span: vspan,
reason: Reason::InvalidInteger,
})?),
span: None,
},
"has_atomic" => InnerTarget {
which: Which::HasAtomic(val.parse().map_err(|_err| ParseError {
original: original.to_owned(),
span: vspan,
reason: Reason::InvalidHasAtomic,
})?),
span: None,
},
"pointer_width" => InnerTarget {
which: Which::PointerWidth(val.parse().map_err(|_err| ParseError {
original: original.to_owned(),
span: vspan,
reason: Reason::InvalidInteger,
})?),
span: None,
},
"vendor" => tp!(Vendor),
_ => {
return Err(ParseError {
original: original.to_owned(),
span,
reason: Reason::Unexpected(&[
"target_arch",
"target_feature",
"target_os",
"target_family",
"target_env",
"target_endian",
"target_has_atomic",
"target_pointer_width",
"target_vendor",
]),
})
}
};
InnerPredicate::Target(tp)
}
_other => InnerPredicate::Other {
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.to_owned(),
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: SmallVec::new(),
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)
} else {
if let Some(top) = func_stack.pop() {
let key = pred_key.take();
let val = pred_val.take();
// In this context, the boolean to int conversion is confusing.
#[allow(clippy::bool_to_int_with_if)]
let num_predicates = top.predicates.len()
+ if key.is_some() { 1 } else { 0 }
+ 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.to_owned(),
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.to_owned(),
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)
} else {
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.to_owned(),
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.to_owned(),
span: top.parens_index..original.len(),
reason: Reason::UnclosedParens,
})
} else {
Err(ParseError {
original: original.to_owned(),
span: top.span,
reason: Reason::Unexpected(&["("]),
})
}
} 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.to_owned(),
span: 0..original.len(),
reason: Reason::Empty,
})
} else if root_predicate_count > 1 {
Err(ParseError {
original: original.to_owned(),
span: 0..original.len(),
reason: Reason::MultipleRootPredicates,
})
} else {
Ok(Expression {
original: original.to_owned(),
expr: expr_queue,
})
}
}
}
}