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Diffstat (limited to 'tvix/eval/src/value/mod.rs')
| -rw-r--r-- | tvix/eval/src/value/mod.rs | 895 |
1 files changed, 895 insertions, 0 deletions
diff --git a/tvix/eval/src/value/mod.rs b/tvix/eval/src/value/mod.rs new file mode 100644 index 000000000000..f5b373e3c4ef --- /dev/null +++ b/tvix/eval/src/value/mod.rs @@ -0,0 +1,895 @@ +//! This module implements the backing representation of runtime +//! values in the Nix language. +use std::cmp::Ordering; +use std::fmt::Display; +use std::num::{NonZeroI32, NonZeroUsize}; +use std::path::PathBuf; +use std::rc::Rc; + +use lexical_core::format::CXX_LITERAL; +use serde::Deserialize; + +#[cfg(feature = "arbitrary")] +mod arbitrary; +mod attrs; +mod builtin; +mod function; +mod json; +mod list; +mod path; +mod string; +mod thunk; + +use crate::errors::{CatchableErrorKind, ErrorKind}; +use crate::opcode::StackIdx; +use crate::spans::LightSpan; +use crate::vm::generators::{self, GenCo}; +use crate::AddContext; +pub use attrs::NixAttrs; +pub use builtin::{Builtin, BuiltinResult}; +pub(crate) use function::Formals; +pub use function::{Closure, Lambda}; +pub use list::NixList; +pub use path::canon_path; +pub use string::NixString; +pub use thunk::Thunk; + +pub use self::thunk::{SharedThunkSet, ThunkSet}; + +use lazy_static::lazy_static; + +#[warn(variant_size_differences)] +#[derive(Clone, Debug, Deserialize)] +#[serde(untagged)] +pub enum Value { + Null, + Bool(bool), + Integer(i64), + Float(f64), + String(NixString), + + #[serde(skip)] + Path(Box<PathBuf>), + Attrs(Box<NixAttrs>), + List(NixList), + + #[serde(skip)] + Closure(Rc<Closure>), // must use Rc<Closure> here in order to get proper pointer equality + + #[serde(skip)] + Builtin(Builtin), + + // Internal values that, while they technically exist at runtime, + // are never returned to or created directly by users. + #[serde(skip_deserializing)] + Thunk(Thunk), + + // See [`compiler::compile_select_or()`] for explanation + #[serde(skip)] + AttrNotFound, + + // this can only occur in Chunk::Constants and nowhere else + #[serde(skip)] + Blueprint(Rc<Lambda>), + + #[serde(skip)] + DeferredUpvalue(StackIdx), + #[serde(skip)] + UnresolvedPath(Box<PathBuf>), + #[serde(skip)] + Json(serde_json::Value), + + #[serde(skip)] + FinaliseRequest(bool), + + #[serde(skip)] + Catchable(CatchableErrorKind), +} + +impl From<CatchableErrorKind> for Value { + fn from(c: CatchableErrorKind) -> Value { + Value::Catchable(c) + } +} + +impl<V> From<Result<V, CatchableErrorKind>> for Value +where + Value: From<V>, +{ + fn from(v: Result<V, CatchableErrorKind>) -> Value { + v.map_or_else(|cek| Value::Catchable(cek), |v| v.into()) + } +} + +lazy_static! { + static ref WRITE_FLOAT_OPTIONS: lexical_core::WriteFloatOptions = + lexical_core::WriteFloatOptionsBuilder::new() + .trim_floats(true) + .round_mode(lexical_core::write_float_options::RoundMode::Round) + .positive_exponent_break(Some(NonZeroI32::new(5).unwrap())) + .max_significant_digits(Some(NonZeroUsize::new(6).unwrap())) + .build() + .unwrap(); +} + +// Helper macros to generate the to_*/as_* macros while accounting for +// thunks. + +/// Generate an `as_*` method returning a reference to the expected +/// type, or a type error. This only works for types that implement +/// `Copy`, as returning a reference to an inner thunk value is not +/// possible. + +/// Generate an `as_*/to_*` accessor method that returns either the +/// expected type, or a type error. +macro_rules! gen_cast { + ( $name:ident, $type:ty, $expected:expr, $variant:pat, $result:expr ) => { + pub fn $name(&self) -> Result<$type, ErrorKind> { + match self { + $variant => Ok($result), + Value::Thunk(thunk) => Self::$name(&thunk.value()), + other => Err(type_error($expected, &other)), + } + } + }; +} + +/// Generate an `as_*_mut/to_*_mut` accessor method that returns either the +/// expected type, or a type error. +macro_rules! gen_cast_mut { + ( $name:ident, $type:ty, $expected:expr, $variant:ident) => { + pub fn $name(&mut self) -> Result<&mut $type, ErrorKind> { + match self { + Value::$variant(x) => Ok(x), + other => Err(type_error($expected, &other)), + } + } + }; +} + +/// Generate an `is_*` type-checking method. +macro_rules! gen_is { + ( $name:ident, $variant:pat ) => { + pub fn $name(&self) -> bool { + match self { + $variant => true, + Value::Thunk(thunk) => Self::$name(&thunk.value()), + _ => false, + } + } + }; +} + +/// Describes what input types are allowed when coercing a `Value` to a string +#[derive(Clone, Copy, PartialEq, Debug)] +pub enum CoercionKind { + /// Only coerce already "stringly" types like strings and paths, but also + /// coerce sets that have a `__toString` attribute. Equivalent to + /// `!coerceMore` in C++ Nix. + Weak, + /// Coerce all value types included by `Weak`, but also coerce `null`, + /// booleans, integers, floats and lists of coercible types. Equivalent to + /// `coerceMore` in C++ Nix. + Strong, +} + +impl<T> From<T> for Value +where + T: Into<NixString>, +{ + fn from(t: T) -> Self { + Self::String(t.into()) + } +} + +/// Constructors +impl Value { + /// Construct a [`Value::Attrs`] from a [`NixAttrs`]. + pub fn attrs(attrs: NixAttrs) -> Self { + Self::Attrs(Box::new(attrs)) + } +} + +/// Controls what kind of by-pointer equality comparison is allowed. +/// +/// See `//tvix/docs/value-pointer-equality.md` for details. +#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)] +pub enum PointerEquality { + /// Pointer equality not allowed at all. + ForbidAll, + + /// Pointer equality comparisons only allowed for nested values. + AllowNested, + + /// Pointer equality comparisons are allowed in all contexts. + AllowAll, +} + +impl Value { + // TODO(amjoseph): de-asyncify this (when called directly by the VM) + /// Deeply forces a value, traversing e.g. lists and attribute sets and forcing + /// their contents, too. + /// + /// This is a generator function. + pub(super) async fn deep_force( + self, + co: GenCo, + thunk_set: SharedThunkSet, + ) -> Result<Value, ErrorKind> { + // Get rid of any top-level thunks, and bail out of self-recursive + // thunks. + let value = if let Value::Thunk(ref t) = &self { + if !thunk_set.insert(t) { + return Ok(self); + } + generators::request_force(&co, self).await + } else { + self + }; + + match &value { + // Short-circuit on already evaluated values, or fail on internal values. + Value::Null + | Value::Bool(_) + | Value::Integer(_) + | Value::Float(_) + | Value::String(_) + | Value::Path(_) + | Value::Closure(_) + | Value::Builtin(_) => return Ok(value), + + Value::List(list) => { + for val in list { + if let c @ Value::Catchable(_) = + generators::request_deep_force(&co, val.clone(), thunk_set.clone()).await + { + return Ok(c); + } + } + } + + Value::Attrs(attrs) => { + for (_, val) in attrs.iter() { + if let c @ Value::Catchable(_) = + generators::request_deep_force(&co, val.clone(), thunk_set.clone()).await + { + return Ok(c); + } + } + } + + Value::Thunk(_) => panic!("Tvix bug: force_value() returned a thunk"), + + Value::Catchable(_) => return Ok(value), + + Value::AttrNotFound + | Value::Blueprint(_) + | Value::DeferredUpvalue(_) + | Value::UnresolvedPath(_) + | Value::Json(_) + | Value::FinaliseRequest(_) => panic!( + "Tvix bug: internal value left on stack: {}", + value.type_of() + ), + }; + + Ok(value) + } + + // TODO(amjoseph): de-asyncify this (when called directly by the VM) + /// Coerce a `Value` to a string. See `CoercionKind` for a rundown of what + /// input types are accepted under what circumstances. + pub async fn coerce_to_string(self, co: GenCo, kind: CoercionKind) -> Result<Value, ErrorKind> { + let value = generators::request_force(&co, self).await; + + match (value, kind) { + // coercions that are always done + tuple @ (Value::String(_), _) => Ok(tuple.0), + + // TODO(sterni): Think about proper encoding handling here. This needs + // general consideration anyways, since one current discrepancy between + // C++ Nix and Tvix is that the former's strings are arbitrary byte + // sequences without NUL bytes, whereas Tvix only allows valid + // Unicode. See also b/189. + (Value::Path(p), _) => { + // TODO(tazjin): there are cases where coerce_to_string does not import + let imported = generators::request_path_import(&co, *p).await; + Ok(imported.to_string_lossy().into_owned().into()) + } + + // Attribute sets can be converted to strings if they either have an + // `__toString` attribute which holds a function that receives the + // set itself or an `outPath` attribute which should be a string. + // `__toString` is preferred. + (Value::Attrs(attrs), kind) => { + if let Some(s) = attrs.try_to_string(&co, kind).await { + return Ok(Value::String(s)); + } + + if let Some(out_path) = attrs.select("outPath") { + return match generators::request_string_coerce(&co, out_path.clone(), kind) + .await + { + Ok(s) => Ok(Value::String(s)), + Err(c) => Ok(Value::Catchable(c)), + }; + } + + Err(ErrorKind::NotCoercibleToString { from: "set", kind }) + } + + // strong coercions + (Value::Null, CoercionKind::Strong) | (Value::Bool(false), CoercionKind::Strong) => { + Ok("".into()) + } + (Value::Bool(true), CoercionKind::Strong) => Ok("1".into()), + + (Value::Integer(i), CoercionKind::Strong) => Ok(format!("{i}").into()), + (Value::Float(f), CoercionKind::Strong) => { + // contrary to normal Display, coercing a float to a string will + // result in unconditional 6 decimal places + Ok(format!("{:.6}", f).into()) + } + + // Lists are coerced by coercing their elements and interspersing spaces + (Value::List(list), CoercionKind::Strong) => { + let mut out = String::new(); + + for (idx, elem) in list.into_iter().enumerate() { + if idx > 0 { + out.push(' '); + } + + match generators::request_string_coerce(&co, elem, kind).await { + Ok(s) => out.push_str(s.as_str()), + Err(c) => return Ok(Value::Catchable(c)), + } + } + + Ok(Value::String(out.into())) + } + + (Value::Thunk(_), _) => panic!("Tvix bug: force returned unforced thunk"), + + val @ (Value::Closure(_), _) + | val @ (Value::Builtin(_), _) + | val @ (Value::Null, _) + | val @ (Value::Bool(_), _) + | val @ (Value::Integer(_), _) + | val @ (Value::Float(_), _) + | val @ (Value::List(_), _) => Err(ErrorKind::NotCoercibleToString { + from: val.0.type_of(), + kind, + }), + + (c @ Value::Catchable(_), _) => return Ok(c), + + (Value::AttrNotFound, _) + | (Value::Blueprint(_), _) + | (Value::DeferredUpvalue(_), _) + | (Value::UnresolvedPath(_), _) + | (Value::Json(_), _) + | (Value::FinaliseRequest(_), _) => { + panic!("tvix bug: .coerce_to_string() called on internal value") + } + } + } + + // TODO(amjoseph): de-asyncify this (when called directly by the VM) + /// Compare two Nix values for equality, forcing nested parts of the structure + /// as needed. + /// + /// This comparison needs to be invoked for nested values (e.g. in lists and + /// attribute sets) as well, which is done by suspending and asking the VM to + /// perform the nested comparison. + /// + /// The `top_level` parameter controls whether this invocation is the top-level + /// comparison, or a nested value comparison. See + /// `//tvix/docs/value-pointer-equality.md` + pub(crate) async fn nix_eq( + self, + other: Value, + co: GenCo, + ptr_eq: PointerEquality, + ) -> Result<Value, ErrorKind> { + let a = match self { + Value::Thunk(ref thunk) => { + // If both values are thunks, and thunk comparisons are allowed by + // pointer, do that and move on. + if ptr_eq == PointerEquality::AllowAll { + if let Value::Thunk(t1) = &other { + if t1.ptr_eq(thunk) { + return Ok(Value::Bool(true)); + } + } + }; + + generators::request_force(&co, self).await + } + + _ => self, + }; + + let b = match other { + Value::Thunk(_) => generators::request_force(&co, other).await, + _ => other, + }; + + debug_assert!(!matches!(a, Value::Thunk(_))); + debug_assert!(!matches!(b, Value::Thunk(_))); + + let result = match (a, b) { + // Trivial comparisons + (c @ Value::Catchable(_), _) => return Ok(c), + (_, c @ Value::Catchable(_)) => return Ok(c), + (Value::Null, Value::Null) => true, + (Value::Bool(b1), Value::Bool(b2)) => b1 == b2, + (Value::String(s1), Value::String(s2)) => s1 == s2, + (Value::Path(p1), Value::Path(p2)) => p1 == p2, + + // Numerical comparisons (they work between float & int) + (Value::Integer(i1), Value::Integer(i2)) => i1 == i2, + (Value::Integer(i), Value::Float(f)) => i as f64 == f, + (Value::Float(f1), Value::Float(f2)) => f1 == f2, + (Value::Float(f), Value::Integer(i)) => i as f64 == f, + + // List comparisons + (Value::List(l1), Value::List(l2)) => { + if ptr_eq >= PointerEquality::AllowNested && l1.ptr_eq(&l2) { + return Ok(Value::Bool(true)); + } + + if l1.len() != l2.len() { + return Ok(Value::Bool(false)); + } + + for (vi1, vi2) in l1.into_iter().zip(l2.into_iter()) { + if !generators::check_equality( + &co, + vi1, + vi2, + std::cmp::max(ptr_eq, PointerEquality::AllowNested), + ) + .await? + { + return Ok(Value::Bool(false)); + } + } + + true + } + + (_, Value::List(_)) | (Value::List(_), _) => false, + + // Attribute set comparisons + (Value::Attrs(a1), Value::Attrs(a2)) => { + if ptr_eq >= PointerEquality::AllowNested && a1.ptr_eq(&a2) { + return Ok(Value::Bool(true)); + } + + // Special-case for derivation comparisons: If both attribute sets + // have `type = derivation`, compare them by `outPath`. + match (a1.select("type"), a2.select("type")) { + (Some(v1), Some(v2)) => { + let s1 = generators::request_force(&co, v1.clone()).await.to_str(); + let s2 = generators::request_force(&co, v2.clone()).await.to_str(); + + if let (Ok(s1), Ok(s2)) = (s1, s2) { + if s1.as_str() == "derivation" && s2.as_str() == "derivation" { + // TODO(tazjin): are the outPaths really required, + // or should it fall through? + let out1 = a1 + .select_required("outPath") + .context("comparing derivations")? + .clone(); + + let out2 = a2 + .select_required("outPath") + .context("comparing derivations")? + .clone(); + + let result = generators::request_force(&co, out1.clone()) + .await + .to_str()? + == generators::request_force(&co, out2.clone()) + .await + .to_str()?; + return Ok(Value::Bool(result)); + } + } + } + _ => {} + }; + + if a1.len() != a2.len() { + return Ok(Value::Bool(false)); + } + + let iter1 = a1.into_iter_sorted(); + let iter2 = a2.into_iter_sorted(); + + for ((k1, v1), (k2, v2)) in iter1.zip(iter2) { + if k1 != k2 { + return Ok(Value::Bool(false)); + } + + if !generators::check_equality( + &co, + v1, + v2, + std::cmp::max(ptr_eq, PointerEquality::AllowNested), + ) + .await? + { + return Ok(Value::Bool(false)); + } + } + + true + } + + (Value::Attrs(_), _) | (_, Value::Attrs(_)) => false, + + (Value::Closure(c1), Value::Closure(c2)) if ptr_eq >= PointerEquality::AllowNested => { + Rc::ptr_eq(&c1, &c2) + } + + // Everything else is either incomparable (e.g. internal types) or + // false. + _ => false, + }; + + Ok(Value::Bool(result)) + } + + pub fn type_of(&self) -> &'static str { + match self { + Value::Null => "null", + Value::Bool(_) => "bool", + Value::Integer(_) => "int", + Value::Float(_) => "float", + Value::String(_) => "string", + Value::Path(_) => "path", + Value::Attrs(_) => "set", + Value::List(_) => "list", + Value::Closure(_) | Value::Builtin(_) => "lambda", + + // Internal types. Note: These are only elaborated here + // because it makes debugging easier. If a user ever sees + // any of these strings, it's a bug. + Value::Thunk(_) => "internal[thunk]", + Value::AttrNotFound => "internal[attr_not_found]", + Value::Blueprint(_) => "internal[blueprint]", + Value::DeferredUpvalue(_) => "internal[deferred_upvalue]", + Value::UnresolvedPath(_) => "internal[unresolved_path]", + Value::Json(_) => "internal[json]", + Value::FinaliseRequest(_) => "internal[finaliser_sentinel]", + Value::Catchable(_) => "internal[catchable]", + } + } + + gen_cast!(as_bool, bool, "bool", Value::Bool(b), *b); + gen_cast!(as_int, i64, "int", Value::Integer(x), *x); + gen_cast!(as_float, f64, "float", Value::Float(x), *x); + gen_cast!(to_str, NixString, "string", Value::String(s), s.clone()); + gen_cast!(to_path, Box<PathBuf>, "path", Value::Path(p), p.clone()); + gen_cast!(to_attrs, Box<NixAttrs>, "set", Value::Attrs(a), a.clone()); + gen_cast!(to_list, NixList, "list", Value::List(l), l.clone()); + gen_cast!( + as_closure, + Rc<Closure>, + "lambda", + Value::Closure(c), + c.clone() + ); + + gen_cast_mut!(as_list_mut, NixList, "list", List); + + gen_is!(is_path, Value::Path(_)); + gen_is!(is_number, Value::Integer(_) | Value::Float(_)); + gen_is!(is_bool, Value::Bool(_)); + gen_is!(is_attrs, Value::Attrs(_)); + + // TODO(amjoseph): de-asyncify this (when called directly by the VM) + /// Compare `self` against other using (fallible) Nix ordering semantics. + /// + /// Note that as this returns an `Option<Ordering>` it can not directly be + /// used as a generator function in the VM. The exact use depends on the + /// callsite, as the meaning is interpreted in different ways e.g. based on + /// the comparison operator used. + /// + /// The function is intended to be used from within other generator + /// functions or `gen!` blocks. + pub async fn nix_cmp_ordering( + self, + other: Self, + co: GenCo, + ) -> Result<Option<Ordering>, ErrorKind> { + Self::nix_cmp_ordering_(self, other, co).await + } + + async fn nix_cmp_ordering_( + mut myself: Self, + mut other: Self, + co: GenCo, + ) -> Result<Option<Ordering>, ErrorKind> { + 'outer: loop { + match (myself, other) { + // same types + (Value::Integer(i1), Value::Integer(i2)) => return Ok(i1.partial_cmp(&i2)), + (Value::Float(f1), Value::Float(f2)) => return Ok(f1.partial_cmp(&f2)), + (Value::String(s1), Value::String(s2)) => return Ok(s1.partial_cmp(&s2)), + (Value::List(l1), Value::List(l2)) => { + for i in 0.. { + if i == l2.len() { + return Ok(Some(Ordering::Greater)); + } else if i == l1.len() { + return Ok(Some(Ordering::Less)); + } else if !generators::check_equality( + &co, + l1[i].clone(), + l2[i].clone(), + PointerEquality::AllowAll, + ) + .await? + { + // TODO: do we need to control `top_level` here? + myself = generators::request_force(&co, l1[i].clone()).await; + other = generators::request_force(&co, l2[i].clone()).await; + continue 'outer; + } + } + + unreachable!() + } + + // different types + (Value::Integer(i1), Value::Float(f2)) => return Ok((i1 as f64).partial_cmp(&f2)), + (Value::Float(f1), Value::Integer(i2)) => return Ok(f1.partial_cmp(&(i2 as f64))), + + // unsupported types + (lhs, rhs) => { + return Err(ErrorKind::Incomparable { + lhs: lhs.type_of(), + rhs: rhs.type_of(), + }) + } + } + } + } + + // TODO(amjoseph): de-asyncify this (when called directly by the VM) + pub async fn force(self, co: GenCo, span: LightSpan) -> Result<Value, ErrorKind> { + if let Value::Thunk(thunk) = self { + return thunk.force(co, span).await; + } + + Ok(self) + } + + /// Explain a value in a human-readable way, e.g. by presenting + /// the docstrings of functions if present. + pub fn explain(&self) -> String { + match self { + Value::Null => "the 'null' value".into(), + Value::Bool(b) => format!("the boolean value '{}'", b), + Value::Integer(i) => format!("the integer '{}'", i), + Value::Float(f) => format!("the float '{}'", f), + Value::String(s) => format!("the string '{}'", s), + Value::Path(p) => format!("the path '{}'", p.to_string_lossy()), + Value::Attrs(attrs) => format!("a {}-item attribute set", attrs.len()), + Value::List(list) => format!("a {}-item list", list.len()), + + Value::Closure(f) => { + if let Some(name) = &f.lambda.name { + format!("the user-defined Nix function '{}'", name) + } else { + "a user-defined Nix function".to_string() + } + } + + Value::Builtin(b) => { + let mut out = format!("the builtin function '{}'", b.name()); + if let Some(docs) = b.documentation() { + out.push_str("\n\n"); + out.push_str(docs); + } + out + } + + // TODO: handle suspended thunks with a different explanation instead of panicking + Value::Thunk(t) => t.value().explain(), + + Value::Catchable(_) => "a catchable failure".into(), + + Value::AttrNotFound + | Value::Blueprint(_) + | Value::DeferredUpvalue(_) + | Value::UnresolvedPath(_) + | Value::Json(_) + | Value::FinaliseRequest(_) => "an internal Tvix evaluator value".into(), + } + } +} + +trait TotalDisplay { + fn total_fmt(&self, f: &mut std::fmt::Formatter<'_>, set: &mut ThunkSet) -> std::fmt::Result; +} + +impl Display for Value { + fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + self.total_fmt(f, &mut Default::default()) + } +} + +/// Emulates the C++-Nix style formatting of floats, which diverges +/// significantly from Rust's native float formatting. +fn total_fmt_float<F: std::fmt::Write>(num: f64, mut f: F) -> std::fmt::Result { + let mut buf = [b'0'; lexical_core::BUFFER_SIZE]; + let mut s = lexical_core::write_with_options::<f64, { CXX_LITERAL }>( + num, + &mut buf, + &WRITE_FLOAT_OPTIONS, + ); + + // apply some postprocessing on the buffer. If scientific + // notation is used (we see an `e`), and the next character is + // a digit, add the missing `+` sign.) + let mut new_s = Vec::with_capacity(s.len()); + + if s.contains(&b'e') { + for (i, c) in s.iter().enumerate() { + // encountered `e` + if c == &b'e' { + // next character is a digit (so no negative exponent) + if s.len() > i && s[i + 1].is_ascii_digit() { + // copy everything from the start up to (including) the e + new_s.extend_from_slice(&s[0..=i]); + // add the missing '+' + new_s.push(b'+'); + // check for the remaining characters. + // If it's only one, we need to prepend a trailing zero + if s.len() == i + 2 { + new_s.push(b'0'); + } + new_s.extend_from_slice(&s[i + 1..]); + break; + } + } + } + + // if we modified the scientific notation, flip the reference + if !new_s.is_empty() { + s = &mut new_s + } + } + // else, if this is not scientific notation, and there's a + // decimal point, make sure we really drop trailing zeroes. + // In some cases, lexical_core doesn't. + else if s.contains(&b'.') { + for (i, c) in s.iter().enumerate() { + // at `.`` + if c == &b'.' { + // trim zeroes from the right side. + let frac = String::from_utf8_lossy(&s[i + 1..]); + let frac_no_trailing_zeroes = frac.trim_end_matches('0'); + + if frac.len() != frac_no_trailing_zeroes.len() { + // we managed to strip something, construct new_s + if frac_no_trailing_zeroes.is_empty() { + // if frac_no_trailing_zeroes is empty, the fractional part was all zeroes, so we can drop the decimal point as well + new_s.extend_from_slice(&s[0..=i - 1]); + } else { + // else, assemble the rest of the string + new_s.extend_from_slice(&s[0..=i]); + new_s.extend_from_slice(frac_no_trailing_zeroes.as_bytes()); + } + + // flip the reference + s = &mut new_s; + break; + } + } + } + } + + write!(f, "{}", String::from_utf8_lossy(s)) +} + +impl TotalDisplay for Value { + fn total_fmt(&self, f: &mut std::fmt::Formatter<'_>, set: &mut ThunkSet) -> std::fmt::Result { + match self { + Value::Null => f.write_str("null"), + Value::Bool(true) => f.write_str("true"), + Value::Bool(false) => f.write_str("false"), + Value::Integer(num) => write!(f, "{}", num), + Value::String(s) => s.fmt(f), + Value::Path(p) => p.display().fmt(f), + Value::Attrs(attrs) => attrs.total_fmt(f, set), + Value::List(list) => list.total_fmt(f, set), + // TODO: fancy REPL display with position + Value::Closure(_) => f.write_str("<LAMBDA>"), + Value::Builtin(builtin) => builtin.fmt(f), + + // Nix prints floats with a maximum precision of 5 digits + // only. Except when it decides to use scientific notation + // (with a + after the `e`, and zero-padded to 0 digits) + Value::Float(num) => total_fmt_float(*num, f), + + // internal types + Value::AttrNotFound => f.write_str("internal[not found]"), + Value::Blueprint(_) => f.write_str("internal[blueprint]"), + Value::DeferredUpvalue(_) => f.write_str("internal[deferred_upvalue]"), + Value::UnresolvedPath(_) => f.write_str("internal[unresolved_path]"), + Value::Json(_) => f.write_str("internal[json]"), + Value::FinaliseRequest(_) => f.write_str("internal[finaliser_sentinel]"), + + // Delegate thunk display to the type, as it must handle + // the case of already evaluated or cyclic thunks. + Value::Thunk(t) => t.total_fmt(f, set), + Value::Catchable(_) => panic!("total_fmt() called on a CatchableErrorKind"), + } + } +} + +impl From<bool> for Value { + fn from(b: bool) -> Self { + Value::Bool(b) + } +} + +impl From<i64> for Value { + fn from(i: i64) -> Self { + Self::Integer(i) + } +} + +impl From<f64> for Value { + fn from(i: f64) -> Self { + Self::Float(i) + } +} + +impl From<PathBuf> for Value { + fn from(path: PathBuf) -> Self { + Self::Path(Box::new(path)) + } +} + +fn type_error(expected: &'static str, actual: &Value) -> ErrorKind { + ErrorKind::TypeError { + expected, + actual: actual.type_of(), + } +} + +#[cfg(test)] +mod tests { + mod floats { + use crate::value::total_fmt_float; + + #[test] + fn format_float() { + let ff = vec![ + (0f64, "0"), + (1.0f64, "1"), + (-0.01, "-0.01"), + (5e+22, "5e+22"), + (1e6, "1e+06"), + (-2E-2, "-0.02"), + (6.626e-34, "6.626e-34"), + (9_224_617.445_991_227, "9.22462e+06"), + ]; + for (n, expected) in ff.iter() { + let mut buf = String::new(); + let res = total_fmt_float(*n, &mut buf); + assert!(res.is_ok()); + assert_eq!( + expected, &buf, + "{} should be formatted as {}, but got {}", + n, expected, &buf + ); + } + } + } +} |