aboutsummaryrefslogtreecommitdiff
path: root/crates/cfg/src/cfg_expr.rs
blob: 069fc01d0c7e3c89d1f7aba5268c9dadbddc59d9 (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
//! 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)
}