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This Pull Request closes #1975. It's still a work in progress, but tries to go in that direction. It changes the following: - Adds a new `TryFromJs` trait, that can be derived using a new `boa_derive` crate. - Adds a new `try_js_into()` function that, similarly to the standard library `TryInto` trait Things to think about: - Should the `boa_derive` crate be re-exported in `boa_engine` using a `derive` feature, similar to how it's done in `serde`? - The current implementation only converts perfectly valid values. So, if we try to convert a big integer into an `i8`, or any floating point number to an `f32`. So, you cannot derive `TryFromJs` for structures that contain an `f32` for example (you can still manually implement the trait, though, and decide in favour of a loss of precision). Should we also provide some traits for transparent loss of precision? - Currently, you cannot convert between types, so if the JS struct has an integer, you cannot cast it to a boolean, for example. Should we provide a `TryConvertJs` trait, for example to force conversions? - Currently we only have basic types and object conversions. Should add `Array` to `Vec` conversion, for example, right? Should we also add `TypedArray` conversions? What about `Map` and `Set`? Does this step over the fine grained APIs that we were creating? Note that this still requires a bunch of documentation, tests, and validation from the dev team and from the users that requested this feature. I'm particularly interested in @lastmjs's thoughts on this API. I already added an usage example in `boa_examples/src/bin/derive.rs`. Co-authored-by: jedel1043 <jedel0124@gmail.com>pull/2769/head
Iban Eguia Moraza
2 years ago
17 changed files with 714 additions and 102 deletions
@ -0,0 +1,237 @@
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//! This module contains the [`TryFromJs`] trait, and conversions to basic Rust types.
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use crate::{Context, JsBigInt, JsNativeError, JsResult, JsValue}; |
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use num_bigint::BigInt; |
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/// This trait adds a fallible and efficient conversions from a [`JsValue`] to Rust types.
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pub trait TryFromJs: Sized { |
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/// This function tries to convert a JavaScript value into `Self`.
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fn try_from_js(value: &JsValue, context: &mut Context<'_>) -> JsResult<Self>; |
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} |
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impl JsValue { |
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/// This function is the inverse of [`TryFromJs`]. It tries to convert a [`JsValue`] to a given
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/// Rust type.
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pub fn try_js_into<T>(&self, context: &mut Context<'_>) -> JsResult<T> |
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where |
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T: TryFromJs, |
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{ |
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T::try_from_js(self, context) |
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} |
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} |
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impl TryFromJs for bool { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Boolean(b) => Ok(*b), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a boolean") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for String { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::String(s) => s.to_std_string().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("could not convert JsString to Rust string, since it has UTF-16 characters: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a String") |
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.into()), |
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} |
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} |
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} |
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impl<T> TryFromJs for Option<T> |
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where |
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T: TryFromJs, |
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{ |
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fn try_from_js(value: &JsValue, context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Null | JsValue::Undefined => Ok(None), |
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value => Ok(Some(T::try_from_js(value, context)?)), |
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} |
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} |
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} |
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impl TryFromJs for JsBigInt { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::BigInt(b) => Ok(b.clone()), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a BigInt") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for BigInt { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::BigInt(b) => Ok(b.as_inner().clone()), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a BigInt") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for JsValue { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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Ok(value.clone()) |
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} |
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} |
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impl TryFromJs for f64 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => Ok((*i).into()), |
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JsValue::Rational(r) => Ok(*r), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a f64") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for i8 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a i8: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a i8") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for u8 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a u8: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a u8") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for i16 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a i16: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a i16") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for u16 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a iu16: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a u16") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for i32 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => Ok(*i), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a i32") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for u32 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a u32: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a u32") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for i64 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => Ok((*i).into()), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a i64") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for u64 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a u64: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a u64") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for i128 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => Ok((*i).into()), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a i128") |
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.into()), |
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} |
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} |
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} |
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impl TryFromJs for u128 { |
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fn try_from_js(value: &JsValue, _context: &mut Context<'_>) -> JsResult<Self> { |
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match value { |
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JsValue::Integer(i) => (*i).try_into().map_err(|e| { |
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JsNativeError::typ() |
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.with_message(format!("cannot convert value to a u128: {e}")) |
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.into() |
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}), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to a u128") |
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.into()), |
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} |
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} |
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} |
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@ -0,0 +1,48 @@
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use boa_engine::{value::TryFromJs, Context, JsNativeError, JsResult, JsValue, Source}; |
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/// You can easily derive `TryFromJs` for structures with base Rust types.
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///
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/// By default, the conversion will only work if the type is directly representable by the Rust
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/// type.
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#[derive(Debug, TryFromJs)] |
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#[allow(dead_code)] |
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struct TestStruct { |
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inner: bool, |
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hello: String, |
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// You can override the conversion of an attribute.
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#[boa(from_js_with = "lossy_conversion")] |
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my_float: i16, |
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} |
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fn main() { |
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let js_str = r#" |
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let x = { |
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inner: false, |
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hello: "World", |
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my_float: 2.9, |
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}; |
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x; |
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"#; |
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let js = Source::from_bytes(js_str); |
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let mut context = Context::default(); |
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let res = context.eval_script(js).unwrap(); |
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let str = TestStruct::try_from_js(&res, &mut context) |
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.map_err(|e| e.to_string()) |
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.unwrap(); |
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println!("{str:?}"); |
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} |
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/// Converts the value lossly
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fn lossy_conversion(value: &JsValue, _context: &mut Context) -> JsResult<i16> { |
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match value { |
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JsValue::Rational(r) => Ok(r.round() as i16), |
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JsValue::Integer(i) => Ok(*i as i16), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to an i16") |
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.into()), |
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} |
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} |
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@ -0,0 +1,16 @@
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[package] |
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name = "boa_macros_tests" |
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description = "Testing crate for boa_macros" |
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keywords = ["javascript", "ECMASCript", "compiler", "tester"] |
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publish = false |
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version.workspace = true |
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edition.workspace = true |
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authors.workspace = true |
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license.workspace = true |
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repository.workspace = true |
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rust-version.workspace = true |
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[dev-dependencies] |
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trybuild = "1.0.80" |
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boa_macros.workspace = true |
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boa_engine.workspace = true |
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@ -0,0 +1,20 @@
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use boa_engine::{value::TryFromJs, Context, JsNativeError, JsResult, JsValue}; |
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#[derive(TryFromJs)] |
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struct TestStruct { |
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inner: bool, |
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#[boa(from_js_with = "lossy_float")] |
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my_int: i16, |
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} |
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fn main() {} |
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fn lossy_float(value: &JsValue, _context: &mut Context) -> JsResult<i16> { |
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match value { |
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JsValue::Rational(r) => Ok(r.round() as i16), |
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JsValue::Integer(i) => Ok(*i as i16), |
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_ => Err(JsNativeError::typ() |
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.with_message("cannot convert value to an i16") |
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.into()), |
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} |
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} |
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@ -0,0 +1,8 @@
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use boa_engine::value::TryFromJs; |
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#[derive(TryFromJs)] |
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struct TestStruct { |
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inner: bool, |
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} |
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fn main() {} |
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