nu_protocol/value/from_value.rs
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use crate::{
ast::{CellPath, PathMember},
engine::Closure,
NuGlob, Range, Record, ShellError, Span, Spanned, Type, Value,
};
use chrono::{DateTime, FixedOffset};
use std::{
any,
cmp::Ordering,
collections::{HashMap, VecDeque},
fmt,
path::PathBuf,
str::FromStr,
};
/// A trait for loading a value from a [`Value`].
///
/// # Derivable
/// This trait can be used with `#[derive]`.
///
/// When derived on structs with named fields, it expects a [`Value::Record`] where each field of
/// the struct maps to a corresponding field in the record.
///
/// - If `#[nu_value(rename = "...")]` is applied to a field, that name will be used as the key in
/// the record.
/// - If `#[nu_value(rename_all = "...")]` is applied on the container (struct) the key of the
/// field will be case-converted accordingly.
/// - If neither attribute is applied, the field name is used as is.
///
/// Supported case conversions include those provided by [`heck`], such as
/// "snake_case", "kebab-case", "PascalCase", and others.
/// Additionally, all values accepted by
/// [`#[serde(rename_all = "...")]`](https://serde.rs/container-attrs.html#rename_all) are valid here.
///
/// For structs with unnamed fields, it expects a [`Value::List`], and the fields are populated in
/// the order they appear in the list.
/// Unit structs expect a [`Value::Nothing`], as they contain no data.
/// Attempting to convert from a non-matching `Value` type will result in an error.
///
/// Only enums with no fields may derive this trait.
/// The expected value representation will be the name of the variant as a [`Value::String`].
///
/// - If `#[nu_value(rename = "...")]` is applied to a variant, that name will be used.
/// - If `#[nu_value(rename_all = "...")]` is applied on the enum container, the name of variant
/// will be case-converted accordingly.
/// - If neither attribute is applied, the variant name will default to
/// ["snake_case"](heck::ToSnakeCase).
///
/// Additionally, you can use `#[nu_value(type_name = "...")]` in the derive macro to set a custom type name
/// for `FromValue::expected_type`. This will result in a `Type::Custom` with the specified type name.
/// This can be useful in situations where the default type name is not desired.
///
/// # Enum Example
/// ```
/// # use nu_protocol::{FromValue, Value, ShellError, record, Span};
/// #
/// # let span = Span::unknown();
/// #
/// #[derive(FromValue, Debug, PartialEq)]
/// #[nu_value(rename_all = "COBOL-CASE", type_name = "birb")]
/// enum Bird {
/// MountainEagle,
/// ForestOwl,
/// #[nu_value(rename = "RIVER-QUACK")]
/// RiverDuck,
/// }
///
/// assert_eq!(
/// Bird::from_value(Value::string("FOREST-OWL", span)).unwrap(),
/// Bird::ForestOwl
/// );
///
/// assert_eq!(
/// Bird::from_value(Value::string("RIVER-QUACK", span)).unwrap(),
/// Bird::RiverDuck
/// );
///
/// assert_eq!(
/// &Bird::expected_type().to_string(),
/// "birb"
/// );
/// ```
///
/// # Struct Example
/// ```
/// # use nu_protocol::{FromValue, Value, ShellError, record, Span};
/// #
/// # let span = Span::unknown();
/// #
/// #[derive(FromValue, PartialEq, Eq, Debug)]
/// #[nu_value(rename_all = "kebab-case")]
/// struct Person {
/// first_name: String,
/// last_name: String,
/// #[nu_value(rename = "age")]
/// age_years: u32,
/// }
///
/// let value = Value::record(record! {
/// "first-name" => Value::string("John", span),
/// "last-name" => Value::string("Doe", span),
/// "age" => Value::int(42, span),
/// }, span);
///
/// assert_eq!(
/// Person::from_value(value).unwrap(),
/// Person {
/// first_name: "John".into(),
/// last_name: "Doe".into(),
/// age_years: 42,
/// }
/// );
/// ```
pub trait FromValue: Sized {
// TODO: instead of ShellError, maybe we could have a FromValueError that implements Into<ShellError>
/// Loads a value from a [`Value`].
///
/// This method retrieves a value similarly to how strings are parsed using [`FromStr`].
/// The operation might fail if the `Value` contains unexpected types or structures.
fn from_value(v: Value) -> Result<Self, ShellError>;
/// Expected `Value` type.
///
/// This is used to print out errors of what type of value is expected for conversion.
/// Even if not used in [`from_value`](FromValue::from_value) this should still be implemented
/// so that other implementations like `Option` or `Vec` can make use of it.
/// It is advised to call this method in `from_value` to ensure that expected type in the error
/// is consistent.
///
/// Unlike the default implementation, derived implementations explicitly reveal the concrete
/// type, such as [`Type::Record`] or [`Type::List`], instead of an opaque type.
fn expected_type() -> Type {
Type::Custom(
any::type_name::<Self>()
.split(':')
.last()
.expect("str::split returns an iterator with at least one element")
.to_string()
.into_boxed_str(),
)
}
}
// Primitive Types
impl<T, const N: usize> FromValue for [T; N]
where
T: FromValue,
{
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
let v_ty = v.get_type();
let vec = Vec::<T>::from_value(v)?;
vec.try_into()
.map_err(|err_vec: Vec<T>| ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v_ty.to_string(),
span,
help: Some(match err_vec.len().cmp(&N) {
Ordering::Less => format!(
"input list too short ({}), expected length of {N}, add missing values",
err_vec.len()
),
Ordering::Equal => {
unreachable!("conversion would have worked if the length would be the same")
}
Ordering::Greater => format!(
"input list too long ({}), expected length of {N}, remove trailing values",
err_vec.len()
),
}),
})
}
fn expected_type() -> Type {
Type::Custom(format!("list<{};{N}>", T::expected_type()).into_boxed_str())
}
}
impl FromValue for bool {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Bool { val, .. } => Ok(val),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Bool
}
}
impl FromValue for char {
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
let v_ty = v.get_type();
match v {
Value::String { ref val, .. } => match char::from_str(val) {
Ok(c) => Ok(c),
Err(_) => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v_ty.to_string(),
span,
help: Some("make the string only one char long".to_string()),
}),
},
_ => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v_ty.to_string(),
span,
help: None,
}),
}
}
fn expected_type() -> Type {
Type::String
}
}
impl FromValue for f32 {
fn from_value(v: Value) -> Result<Self, ShellError> {
f64::from_value(v).map(|float| float as f32)
}
}
impl FromValue for f64 {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Float { val, .. } => Ok(val),
Value::Int { val, .. } => Ok(val as f64),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Float
}
}
impl FromValue for i64 {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Int { val, .. } => Ok(val),
Value::Filesize { val, .. } => Ok(val),
Value::Duration { val, .. } => Ok(val),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Int
}
}
macro_rules! impl_from_value_for_int {
($type:ty) => {
impl FromValue for $type {
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
let int = i64::from_value(v)?;
const MIN: i64 = <$type>::MIN as i64;
const MAX: i64 = <$type>::MAX as i64;
#[allow(overlapping_range_endpoints)] // calculating MIN-1 is not possible for i64::MIN
#[allow(unreachable_patterns)] // isize might max out i64 number range
<$type>::try_from(int).map_err(|_| match int {
MIN..=MAX => unreachable!(
"int should be within the valid range for {}",
stringify!($type)
),
i64::MIN..=MIN => int_too_small_error(int, <$type>::MIN, span),
MAX..=i64::MAX => int_too_large_error(int, <$type>::MAX, span),
})
}
fn expected_type() -> Type {
i64::expected_type()
}
}
};
}
impl_from_value_for_int!(i8);
impl_from_value_for_int!(i16);
impl_from_value_for_int!(i32);
impl_from_value_for_int!(isize);
macro_rules! impl_from_value_for_uint {
($type:ty, $max:expr) => {
impl FromValue for $type {
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
const MAX: i64 = $max;
match v {
Value::Int { val, .. }
| Value::Filesize { val, .. }
| Value::Duration { val, .. } => {
match val {
i64::MIN..=-1 => Err(ShellError::NeedsPositiveValue { span }),
0..=MAX => Ok(val as $type),
#[allow(unreachable_patterns)] // u64 will max out the i64 number range
n => Err(ShellError::GenericError {
error: "Integer too large".to_string(),
msg: format!("{n} is larger than {MAX}"),
span: Some(span),
help: None,
inner: vec![],
}),
}
}
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Custom("non-negative int".to_string().into_boxed_str())
}
}
};
}
// Sadly we cannot implement FromValue for u8 without losing the impl of Vec<u8>,
// Rust would find two possible implementations then, Vec<u8> and Vec<T = u8>,
// and wouldn't compile.
// The blanket implementation for Vec<T> is probably more useful than
// implementing FromValue for u8.
impl_from_value_for_uint!(u16, u16::MAX as i64);
impl_from_value_for_uint!(u32, u32::MAX as i64);
impl_from_value_for_uint!(u64, i64::MAX); // u64::Max would be -1 as i64
#[cfg(target_pointer_width = "64")]
impl_from_value_for_uint!(usize, i64::MAX);
#[cfg(target_pointer_width = "32")]
impl_from_value_for_uint!(usize, usize::MAX as i64);
impl FromValue for () {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Nothing { .. } => Ok(()),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Nothing
}
}
macro_rules! tuple_from_value {
($template:literal, $($t:ident:$n:tt),+) => {
impl<$($t),+> FromValue for ($($t,)+) where $($t: FromValue,)+ {
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
match v {
Value::List { vals, .. } => {
let mut deque = VecDeque::from(vals);
Ok(($(
{
let v = deque.pop_front().ok_or_else(|| ShellError::CantFindColumn {
col_name: $n.to_string(),
span: None,
src_span: span
})?;
$t::from_value(v)?
},
)*))
},
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Custom(
format!(
$template,
$($t::expected_type()),*
)
.into_boxed_str(),
)
}
}
};
}
// Tuples in std are implemented for up to 12 elements, so we do it here too.
tuple_from_value!("[{}]", T0:0);
tuple_from_value!("[{}, {}]", T0:0, T1:1);
tuple_from_value!("[{}, {}, {}]", T0:0, T1:1, T2:2);
tuple_from_value!("[{}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3);
tuple_from_value!("[{}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4);
tuple_from_value!("[{}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5);
tuple_from_value!("[{}, {}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5, T6:6);
tuple_from_value!("[{}, {}, {}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5, T6:6, T7:7);
tuple_from_value!("[{}, {}, {}, {}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5, T6:6, T7:7, T8:8);
tuple_from_value!("[{}, {}, {}, {}, {}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5, T6:6, T7:7, T8:8, T9:9);
tuple_from_value!("[{}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5, T6:6, T7:7, T8:8, T9:9, T10:10);
tuple_from_value!("[{}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}]", T0:0, T1:1, T2:2, T3:3, T4:4, T5:5, T6:6, T7:7, T8:8, T9:9, T10:10, T11:11);
// Other std Types
impl FromValue for PathBuf {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::String { val, .. } => Ok(val.into()),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::String
}
}
impl FromValue for String {
fn from_value(v: Value) -> Result<Self, ShellError> {
// FIXME: we may want to fail a little nicer here
match v {
Value::CellPath { val, .. } => Ok(val.to_string()),
Value::String { val, .. } => Ok(val),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::String
}
}
// This impl is different from Vec<T> as it allows reading from Value::Binary and Value::String too.
// This also denies implementing FromValue for u8 as it would be in conflict with the Vec<T> impl.
impl FromValue for Vec<u8> {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Binary { val, .. } => Ok(val),
Value::String { val, .. } => Ok(val.into_bytes()),
Value::List { vals, .. } => {
const U8MIN: i64 = u8::MIN as i64;
const U8MAX: i64 = u8::MAX as i64;
let mut this = Vec::with_capacity(vals.len());
for val in vals {
let span = val.span();
let int = i64::from_value(val)?;
// calculating -1 on these ranges would be less readable
#[allow(overlapping_range_endpoints)]
#[allow(clippy::match_overlapping_arm)]
match int {
U8MIN..=U8MAX => this.push(int as u8),
i64::MIN..=U8MIN => return Err(int_too_small_error(int, U8MIN, span)),
U8MAX..=i64::MAX => return Err(int_too_large_error(int, U8MAX, span)),
};
}
Ok(this)
}
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Binary
}
}
// Blanket std Implementations
impl<T> FromValue for Option<T>
where
T: FromValue,
{
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Nothing { .. } => Ok(None),
v => T::from_value(v).map(Option::Some),
}
}
fn expected_type() -> Type {
T::expected_type()
}
}
impl<V> FromValue for HashMap<String, V>
where
V: FromValue,
{
fn from_value(v: Value) -> Result<Self, ShellError> {
let record = v.into_record()?;
let items: Result<Vec<(String, V)>, ShellError> = record
.into_iter()
.map(|(k, v)| Ok((k, V::from_value(v)?)))
.collect();
Ok(HashMap::from_iter(items?))
}
fn expected_type() -> Type {
Type::Record(vec![].into_boxed_slice())
}
}
impl<T> FromValue for Vec<T>
where
T: FromValue,
{
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::List { vals, .. } => vals
.into_iter()
.map(|v| T::from_value(v))
.collect::<Result<Vec<T>, ShellError>>(),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::List(Box::new(T::expected_type()))
}
}
// Nu Types
impl FromValue for Value {
fn from_value(v: Value) -> Result<Self, ShellError> {
Ok(v)
}
fn expected_type() -> Type {
Type::Any
}
}
impl FromValue for CellPath {
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
match v {
Value::CellPath { val, .. } => Ok(val),
Value::String { val, .. } => Ok(CellPath {
members: vec![PathMember::String {
val,
span,
optional: false,
}],
}),
Value::Int { val, .. } => {
if val.is_negative() {
Err(ShellError::NeedsPositiveValue { span })
} else {
Ok(CellPath {
members: vec![PathMember::Int {
val: val as usize,
span,
optional: false,
}],
})
}
}
x => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: x.get_type().to_string(),
span,
help: None,
}),
}
}
fn expected_type() -> Type {
Type::CellPath
}
}
impl FromValue for Closure {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Closure { val, .. } => Ok(*val),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
}
impl FromValue for DateTime<FixedOffset> {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Date { val, .. } => Ok(val),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Date
}
}
impl FromValue for NuGlob {
fn from_value(v: Value) -> Result<Self, ShellError> {
// FIXME: we may want to fail a little nicer here
match v {
Value::CellPath { val, .. } => Ok(NuGlob::Expand(val.to_string())),
Value::String { val, .. } => Ok(NuGlob::DoNotExpand(val)),
Value::Glob {
val,
no_expand: quoted,
..
} => {
if quoted {
Ok(NuGlob::DoNotExpand(val))
} else {
Ok(NuGlob::Expand(val))
}
}
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::String
}
}
impl FromValue for Range {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Range { val, .. } => Ok(*val),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Range
}
}
impl FromValue for Record {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Record { val, .. } => Ok(val.into_owned()),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
}
// Blanket Nu Implementations
impl<T> FromValue for Spanned<T>
where
T: FromValue,
{
fn from_value(v: Value) -> Result<Self, ShellError> {
let span = v.span();
Ok(Spanned {
item: T::from_value(v)?,
span,
})
}
fn expected_type() -> Type {
T::expected_type()
}
}
// Foreign Types
impl FromValue for bytes::Bytes {
fn from_value(v: Value) -> Result<Self, ShellError> {
match v {
Value::Binary { val, .. } => Ok(val.into()),
v => Err(ShellError::CantConvert {
to_type: Self::expected_type().to_string(),
from_type: v.get_type().to_string(),
span: v.span(),
help: None,
}),
}
}
fn expected_type() -> Type {
Type::Binary
}
}
// Use generics with `fmt::Display` to allow passing different kinds of integer
fn int_too_small_error(int: impl fmt::Display, min: impl fmt::Display, span: Span) -> ShellError {
ShellError::GenericError {
error: "Integer too small".to_string(),
msg: format!("{int} is smaller than {min}"),
span: Some(span),
help: None,
inner: vec![],
}
}
fn int_too_large_error(int: impl fmt::Display, max: impl fmt::Display, span: Span) -> ShellError {
ShellError::GenericError {
error: "Integer too large".to_string(),
msg: format!("{int} is larger than {max}"),
span: Some(span),
help: None,
inner: vec![],
}
}
#[cfg(test)]
mod tests {
use crate::{engine::Closure, FromValue, IntoValue, Record, Span, Type, Value};
use std::ops::Deref;
#[test]
fn expected_type_default_impl() {
assert_eq!(
Record::expected_type(),
Type::Custom("Record".to_string().into_boxed_str())
);
assert_eq!(
Closure::expected_type(),
Type::Custom("Closure".to_string().into_boxed_str())
);
}
#[test]
fn from_value_vec_u8() {
let vec: Vec<u8> = vec![1, 2, 3];
let span = Span::test_data();
let string = "Hello Vec<u8>!".to_string();
assert_eq!(
Vec::<u8>::from_value(vec.clone().into_value(span)).unwrap(),
vec.clone(),
"Vec<u8> roundtrip"
);
assert_eq!(
Vec::<u8>::from_value(Value::test_string(string.clone()))
.unwrap()
.deref(),
string.as_bytes(),
"Vec<u8> from String"
);
assert_eq!(
Vec::<u8>::from_value(Value::test_binary(vec.clone())).unwrap(),
vec,
"Vec<u8> from Binary"
);
assert!(Vec::<u8>::from_value(vec![u8::MIN as i32 - 1].into_value(span)).is_err());
assert!(Vec::<u8>::from_value(vec![u8::MAX as i32 + 1].into_value(span)).is_err());
}
}