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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::{fmt, slice::Iter as SliceIter};
use tt::SmolStr;
/// A simple configuration value passed in from the outside.
#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
pub enum CfgAtom {
/// eg. `#[cfg(test)]`
Flag(SmolStr),
/// eg. `#[cfg(target_os = "linux")]`
///
/// Note that a key can have multiple values that are all considered "active" at the same time.
/// For example, `#[cfg(target_feature = "sse")]` and `#[cfg(target_feature = "sse2")]`.
KeyValue { key: SmolStr, value: SmolStr },
}
impl CfgAtom {
/// Returns `true` when the atom comes from the target specification.
///
/// If this returns `true`, then changing this atom requires changing the compilation target. If
/// it returns `false`, the atom might come from a build script or the build system.
pub fn is_target_defined(&self) -> bool {
match self {
CfgAtom::Flag(flag) => matches!(&**flag, "unix" | "windows"),
CfgAtom::KeyValue { key, value: _ } => matches!(
&**key,
"target_arch"
| "target_os"
| "target_env"
| "target_family"
| "target_endian"
| "target_pointer_width"
| "target_vendor" // NOTE: `target_feature` is left out since it can be configured via `-Ctarget-feature`
),
}
}
}
impl fmt::Display for CfgAtom {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
CfgAtom::Flag(name) => write!(f, "{}", name),
CfgAtom::KeyValue { key, value } => write!(f, "{} = {:?}", key, value),
}
}
}
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum CfgExpr {
Invalid,
Atom(CfgAtom),
All(Vec<CfgExpr>),
Any(Vec<CfgExpr>),
Not(Box<CfgExpr>),
}
impl From<CfgAtom> for CfgExpr {
fn from(atom: CfgAtom) -> Self {
CfgExpr::Atom(atom)
}
}
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(&CfgAtom) -> bool) -> Option<bool> {
match self {
CfgExpr::Invalid => None,
CfgExpr::Atom(atom) => Some(query(atom)),
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('"'));
CfgAtom::KeyValue { key: name, value }.into()
}
_ => 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,
}
}
_ => CfgAtom::Flag(name).into(),
};
// Eat comma separator
if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) = it.as_slice().first() {
if punct.char == ',' {
it.next();
}
}
Some(ret)
}
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