refactor

fix-common/src/lib.rs

@@ -0,0 +1,394 @@
+use std::borrow::Cow;
+use std::collections::BTreeMap;
+use std::fmt::{Debug, Display, Formatter, Result as FmtResult};
+use std::ops::{Deref, DerefMut};
+
+use gc_arena::Collect;
+
+#[repr(transparent)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Collect)]
+#[collect(require_static)]
+pub struct StringId(pub string_interner::symbol::SymbolU32);
+
+/// Represents a Nix symbol, which is used as a key in attribute sets.
+#[derive(Debug, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Symbol<'a>(Cow<'a, str>);
+
+pub type StaticSymbol = Symbol<'static>;
+
+impl From<String> for Symbol<'_> {
+    fn from(value: String) -> Self {
+        Symbol(Cow::Owned(value))
+    }
+}
+
+impl<'a> From<&'a str> for Symbol<'a> {
+    fn from(value: &'a str) -> Self {
+        Symbol(Cow::Borrowed(value))
+    }
+}
+
+/// Formats a string slice as a Nix symbol, quoting it if necessary.
+pub fn format_symbol<'a>(sym: impl Into<Cow<'a, str>>) -> Cow<'a, str> {
+    let sym = sym.into();
+    if Symbol::NORMAL_REGEX.test(&sym) {
+        sym
+    } else {
+        Cow::Owned(escape_quote_string(&sym))
+    }
+}
+
+impl Display for Symbol<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        if self.normal() {
+            write!(f, "{}", self.0)
+        } else {
+            write!(f, "{}", escape_quote_string(&self.0))
+        }
+    }
+}
+
+impl Symbol<'_> {
+    const NORMAL_REGEX: ere::Regex<1> = ere::compile_regex!("^[a-zA-Z_][a-zA-Z0-9_'-]*$");
+    /// Checks if the symbol is a "normal" identifier that doesn't require quotes.
+    fn normal(&self) -> bool {
+        Self::NORMAL_REGEX.test(self)
+    }
+}
+
+impl Deref for Symbol<'_> {
+    type Target = str;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+fn escape_quote_string(s: &str) -> String {
+    let mut ret = String::with_capacity(s.len() + 2);
+    ret.push('"');
+    let mut iter = s.chars().peekable();
+    while let Some(c) = iter.next() {
+        match c {
+            '\\' => ret.push_str("\\\\"),
+            '"' => ret.push_str("\\\""),
+            '\n' => ret.push_str("\\n"),
+            '\r' => ret.push_str("\\r"),
+            '\t' => ret.push_str("\\t"),
+            '$' if iter.peek() == Some(&'{') => ret.push_str("\\$"),
+            c => ret.push(c),
+        }
+    }
+    ret.push('"');
+    ret
+}
+
+/// Represents a Nix attribute set, which is a map from symbols to values.
+#[derive(Default, Clone, PartialEq)]
+pub struct AttrSet {
+    data: BTreeMap<StaticSymbol, Value>,
+}
+
+impl AttrSet {
+    pub fn new(data: BTreeMap<StaticSymbol, Value>) -> Self {
+        Self { data }
+    }
+
+    /// Gets a value by key (string or Symbol).
+    pub fn get<'a, 'sym: 'a>(&'a self, key: impl Into<Symbol<'sym>>) -> Option<&'a Value> {
+        self.data.get(&key.into())
+    }
+
+    /// Checks if a key exists in the attribute set.
+    pub fn contains_key<'a, 'sym: 'a>(&'a self, key: impl Into<Symbol<'sym>>) -> bool {
+        self.data.contains_key(&key.into())
+    }
+}
+
+impl Deref for AttrSet {
+    type Target = BTreeMap<StaticSymbol, Value>;
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+impl DerefMut for AttrSet {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.data
+    }
+}
+
+impl Debug for AttrSet {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        use Value::*;
+        write!(f, "{{")?;
+        for (k, v) in self.data.iter() {
+            write!(f, " {k:?} = ")?;
+            match v {
+                List(_) => write!(f, "[ ... ];")?,
+                AttrSet(_) => write!(f, "{{ ... }};")?,
+                v => write!(f, "{v:?};")?,
+            }
+        }
+        write!(f, " }}")
+    }
+}
+
+impl Display for AttrSet {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        use Value::*;
+        if self.data.len() > 1 {
+            writeln!(f, "{{")?;
+            for (k, v) in self.data.iter() {
+                write!(f, "  {k} = ")?;
+                match v {
+                    List(_) => writeln!(f, "[ ... ];")?,
+                    AttrSet(_) => writeln!(f, "{{ ... }};")?,
+                    v => writeln!(f, "{v};")?,
+                }
+            }
+            write!(f, "}}")
+        } else {
+            write!(f, "{{")?;
+            for (k, v) in self.data.iter() {
+                write!(f, " {k} = ")?;
+                match v {
+                    List(_) => write!(f, "[ ... ];")?,
+                    AttrSet(_) => write!(f, "{{ ... }};")?,
+                    v => write!(f, "{v};")?,
+                }
+            }
+            write!(f, " }}")
+        }
+    }
+}
+
+impl AttrSet {
+    pub fn display_compat(&self) -> AttrSetCompatDisplay<'_> {
+        AttrSetCompatDisplay(self)
+    }
+}
+
+pub struct AttrSetCompatDisplay<'a>(&'a AttrSet);
+
+impl Display for AttrSetCompatDisplay<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "{{")?;
+        for (k, v) in self.0.data.iter() {
+            write!(f, " {k} = {};", v.display_compat())?;
+        }
+        write!(f, " }}")
+    }
+}
+
+/// Represents a Nix list, which is a vector of values.
+#[derive(Default, Clone, Debug, PartialEq)]
+pub struct List {
+    data: Vec<Value>,
+}
+
+impl List {
+    pub fn new(data: Vec<Value>) -> Self {
+        Self { data }
+    }
+}
+
+impl Deref for List {
+    type Target = Vec<Value>;
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+impl DerefMut for List {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.data
+    }
+}
+
+impl Display for List {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        use Value::*;
+        if self.data.len() > 1 {
+            writeln!(f, "[")?;
+            for v in self.data.iter() {
+                match v {
+                    List(_) => writeln!(f, "  [ ... ]")?,
+                    AttrSet(_) => writeln!(f, "  {{ ... }}")?,
+                    v => writeln!(f, "  {v}")?,
+                }
+            }
+            write!(f, "]")
+        } else {
+            write!(f, "[ ")?;
+            for v in self.data.iter() {
+                match v {
+                    List(_) => write!(f, "[ ... ] ")?,
+                    AttrSet(_) => write!(f, "{{ ... }} ")?,
+                    v => write!(f, "{v} ")?,
+                }
+            }
+            write!(f, "]")
+        }
+    }
+}
+
+impl List {
+    pub fn display_compat(&self) -> ListCompatDisplay<'_> {
+        ListCompatDisplay(self)
+    }
+}
+
+pub struct ListCompatDisplay<'a>(&'a List);
+
+impl Display for ListCompatDisplay<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "[ ")?;
+        for v in self.0.data.iter() {
+            write!(f, "{} ", v.display_compat())?;
+        }
+        write!(f, "]")
+    }
+}
+
+/// Represents any possible Nix value that can be returned from an evaluation.
+#[derive(Clone, Debug, PartialEq)]
+pub enum Value {
+    /// An integer value.
+    Int(i64),
+    /// An floating-point value.
+    Float(f64),
+    /// An boolean value.
+    Bool(bool),
+    /// An null value.
+    Null,
+    /// A string value.
+    String(String),
+    /// A path value (absolute path string).
+    Path(String),
+    /// An attribute set.
+    AttrSet(AttrSet),
+    /// A list.
+    List(List),
+    /// A thunk, representing a delayed computation.
+    Thunk,
+    /// A function (lambda).
+    Func,
+    /// A primitive (built-in) operation.
+    PrimOp(String),
+    /// A partially applied primitive operation.
+    PrimOpApp(String),
+    /// A marker for a value that has been seen before during serialization, to break cycles.
+    /// This is used to prevent infinite recursion when printing or serializing cyclic data structures.
+    Repeated,
+}
+
+/// Wrapper to format a float in Nix style (C printf `%g` with precision 6).
+pub struct NixFloat(pub f64);
+
+impl Display for NixFloat {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        fmt_nix_float(f, self.0)
+    }
+}
+
+/// Format a float matching C's `printf("%g", x)` with default precision 6.
+fn fmt_nix_float(f: &mut Formatter<'_>, x: f64) -> FmtResult {
+    if !x.is_finite() {
+        return write!(f, "{x}");
+    }
+    if x == 0.0 {
+        return if x.is_sign_negative() {
+            write!(f, "-0")
+        } else {
+            write!(f, "0")
+        };
+    }
+
+    let precision: i32 = 6;
+    let exp = x.abs().log10().floor() as i32;
+
+    let formatted = if exp >= -4 && exp < precision {
+        let decimal_places = (precision - 1 - exp) as usize;
+        format!("{x:.decimal_places$}")
+    } else {
+        let sig_digits = (precision - 1) as usize;
+        let s = format!("{x:.sig_digits$e}");
+        let (mantissa, exp_part) = s
+            .split_once('e')
+            .expect("scientific notation must contain 'e'");
+        let (sign, digits) = if let Some(d) = exp_part.strip_prefix('-') {
+            ("-", d)
+        } else if let Some(d) = exp_part.strip_prefix('+') {
+            ("+", d)
+        } else {
+            ("+", exp_part)
+        };
+        if digits.len() < 2 {
+            format!("{mantissa}e{sign}0{digits}")
+        } else {
+            format!("{mantissa}e{sign}{digits}")
+        }
+    };
+
+    if formatted.contains('.') {
+        if let Some(e_pos) = formatted.find('e') {
+            let trimmed = formatted[..e_pos]
+                .trim_end_matches('0')
+                .trim_end_matches('.');
+            write!(f, "{}{}", trimmed, &formatted[e_pos..])
+        } else {
+            let trimmed = formatted.trim_end_matches('0').trim_end_matches('.');
+            write!(f, "{trimmed}")
+        }
+    } else {
+        write!(f, "{formatted}")
+    }
+}
+
+impl Display for Value {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        use Value::*;
+        match self {
+            &Int(x) => write!(f, "{x}"),
+            &Float(x) => fmt_nix_float(f, x),
+            &Bool(x) => write!(f, "{x}"),
+            Null => write!(f, "null"),
+            String(x) => write!(f, "{}", escape_quote_string(x)),
+            Path(x) => write!(f, "{x}"),
+            AttrSet(x) => write!(f, "{x}"),
+            List(x) => write!(f, "{x}"),
+            Thunk => write!(f, "«code»"),
+            Func => write!(f, "«lambda»"),
+            PrimOp(name) => write!(f, "«primop {name}»"),
+            PrimOpApp(name) => write!(f, "«partially applied primop {name}»"),
+            Repeated => write!(f, "«repeated»"),
+        }
+    }
+}
+
+impl Value {
+    pub fn display_compat(&self) -> ValueCompatDisplay<'_> {
+        ValueCompatDisplay(self)
+    }
+}
+
+pub struct ValueCompatDisplay<'a>(&'a Value);
+
+impl Display for ValueCompatDisplay<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        use Value::*;
+        match self.0 {
+            &Int(x) => write!(f, "{x}"),
+            &Float(x) => fmt_nix_float(f, x),
+            &Bool(x) => write!(f, "{x}"),
+            Null => write!(f, "null"),
+            String(x) => write!(f, "{}", escape_quote_string(x)),
+            Path(x) => write!(f, "{x}"),
+            AttrSet(x) => write!(f, "{}", x.display_compat()),
+            List(x) => write!(f, "{}", x.display_compat()),
+            Thunk => write!(f, "«thunk»"),
+            Func => write!(f, "<LAMBDA>"),
+            PrimOp(_) => write!(f, "<PRIMOP>"),
+            PrimOpApp(_) => write!(f, "<PRIMOP-APP>"),
+            Repeated => write!(f, "«repeated»"),
+        }
+    }
+}