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//! The condition expression used in `#[cfg(..)]` attributes.
//!
//! See: https://doc.rust-lang.org/reference/conditional-compilation.html#conditional-compilation
use std::slice::Iter as SliceIter;
use tt::SmolStr;
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum CfgExpr {
Invalid,
Atom(SmolStr),
KeyValue { key: SmolStr, value: SmolStr },
All(Vec<CfgExpr>),
Any(Vec<CfgExpr>),
Not(Box<CfgExpr>),
}
impl CfgExpr {
pub fn parse(tt: &tt::Subtree) -> CfgExpr {
next_cfg_expr(&mut tt.token_trees.iter()).unwrap_or(CfgExpr::Invalid)
}
/// Fold the cfg by querying all basic `Atom` and `KeyValue` predicates.
pub fn fold(&self, query: &dyn Fn(&SmolStr, Option<&SmolStr>) -> bool) -> Option<bool> {
match self {
CfgExpr::Invalid => None,
CfgExpr::Atom(name) => Some(query(name, None)),
CfgExpr::KeyValue { key, value } => Some(query(key, Some(value))),
CfgExpr::All(preds) => {
preds.iter().try_fold(true, |s, pred| Some(s && pred.fold(query)?))
}
CfgExpr::Any(preds) => {
preds.iter().try_fold(false, |s, pred| Some(s || pred.fold(query)?))
}
CfgExpr::Not(pred) => pred.fold(query).map(|s| !s),
}
}
}
fn next_cfg_expr(it: &mut SliceIter<tt::TokenTree>) -> Option<CfgExpr> {
let name = match it.next() {
None => return None,
Some(tt::TokenTree::Leaf(tt::Leaf::Ident(ident))) => ident.text.clone(),
Some(_) => return Some(CfgExpr::Invalid),
};
// Peek
let ret = match it.as_slice().first() {
Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) if punct.char == '=' => {
match it.as_slice().get(1) {
Some(tt::TokenTree::Leaf(tt::Leaf::Literal(literal))) => {
it.next();
it.next();
// FIXME: escape? raw string?
let value =
SmolStr::new(literal.text.trim_start_matches('"').trim_end_matches('"'));
CfgExpr::KeyValue { key: name, value }
}
_ => return Some(CfgExpr::Invalid),
}
}
Some(tt::TokenTree::Subtree(subtree)) => {
it.next();
let mut sub_it = subtree.token_trees.iter();
let mut subs = std::iter::from_fn(|| next_cfg_expr(&mut sub_it)).collect();
match name.as_str() {
"all" => CfgExpr::All(subs),
"any" => CfgExpr::Any(subs),
"not" => CfgExpr::Not(Box::new(subs.pop().unwrap_or(CfgExpr::Invalid))),
_ => CfgExpr::Invalid,
}
}
_ => CfgExpr::Atom(name),
};
// Eat comma separator
if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) = it.as_slice().first() {
if punct.char == ',' {
it.next();
}
}
Some(ret)
}
#[cfg(test)]
mod tests {
use super::*;
use mbe::ast_to_token_tree;
use syntax::ast::{self, AstNode};
fn assert_parse_result(input: &str, expected: CfgExpr) {
let (tt, _) = {
let source_file = ast::SourceFile::parse(input).ok().unwrap();
let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
ast_to_token_tree(&tt).unwrap()
};
let cfg = CfgExpr::parse(&tt);
assert_eq!(cfg, expected);
}
#[test]
fn test_cfg_expr_parser() {
assert_parse_result("#![cfg(foo)]", CfgExpr::Atom("foo".into()));
assert_parse_result("#![cfg(foo,)]", CfgExpr::Atom("foo".into()));
assert_parse_result(
"#![cfg(not(foo))]",
CfgExpr::Not(Box::new(CfgExpr::Atom("foo".into()))),
);
assert_parse_result("#![cfg(foo(bar))]", CfgExpr::Invalid);
// Only take the first
assert_parse_result(r#"#![cfg(foo, bar = "baz")]"#, CfgExpr::Atom("foo".into()));
assert_parse_result(
r#"#![cfg(all(foo, bar = "baz"))]"#,
CfgExpr::All(vec![
CfgExpr::Atom("foo".into()),
CfgExpr::KeyValue { key: "bar".into(), value: "baz".into() },
]),
);
assert_parse_result(
r#"#![cfg(any(not(), all(), , bar = "baz",))]"#,
CfgExpr::Any(vec![
CfgExpr::Not(Box::new(CfgExpr::Invalid)),
CfgExpr::All(vec![]),
CfgExpr::Invalid,
CfgExpr::KeyValue { key: "bar".into(), value: "baz".into() },
]),
);
}
}
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