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Make a "trampoline" crate to avoid unneeded dependencies in a proc-ma…
…cro crate
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| @@ -1,5 +1,6 @@ | ||
| [workspace] | ||
| members=[ | ||
| 'wasm-bindgen-derive-macro', | ||
| 'wasm-bindgen-derive', | ||
| 'tests' | ||
| ] |
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| [package] | ||
| name = "wasm-bindgen-derive-macro" | ||
| version = "0.0.0" | ||
| edition = "2021" | ||
| authors = ["Bogdan Opanchuk <bogdan@opanchuk.net>"] | ||
| license = "MIT" | ||
| description = "Proc-macro backend for wasm-bindgen-derive" | ||
| rust-version = "1.65.0" | ||
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|
||
| [lib] | ||
| proc-macro = true | ||
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|
||
| [dependencies] | ||
| syn = "1.0" | ||
| quote = "1.0" | ||
| proc-macro2 = "1.0" |
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| //! A proc-macro to be re-exported by `wasm-bindgen-derive`. | ||
| //! We need this trampoline to enforce the correct bounds on the `wasm-bindgen` and `js-sys` | ||
| //! dependencies, but those are technically not the dependencies of this crate, | ||
| //! but only of the code it generates. | ||
|
|
||
| #![warn(missing_docs, rust_2018_idioms, unused_qualifications)] | ||
| #![no_std] | ||
|
|
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| extern crate alloc; | ||
|
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||
| use alloc::format; | ||
| use alloc::string::ToString; | ||
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| use proc_macro::TokenStream; | ||
| use proc_macro2::{Span, TokenStream as TokenStream2}; | ||
| use quote::quote; | ||
| use syn::{parse_macro_input, Data, DeriveInput, Error}; | ||
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| macro_rules! derive_error { | ||
| ($string: tt) => { | ||
| Error::new(Span::call_site(), $string) | ||
| .to_compile_error() | ||
| .into() | ||
| }; | ||
| } | ||
|
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| /** Derives a `TryFrom<&JsValue>` for a type exported using `#[wasm_bindgen]`. | ||
| Note that: | ||
| * this derivation must be be positioned before `#[wasm_bindgen]`; | ||
| * the type must implement [`Clone`]. | ||
| * `extern crate alloc` must be declared in scope. | ||
| The macro is authored by [**@AlexKorn**](https://github.com/AlexKorn) | ||
| based on the idea of [**@aweinstock314**](https://github.com/aweinstock314). | ||
| See [this](https://github.com/rustwasm/wasm-bindgen/issues/2231#issuecomment-656293288) | ||
| and [this](https://github.com/rustwasm/wasm-bindgen/issues/2231#issuecomment-1169658111) | ||
| GitHub comments. | ||
| */ | ||
| #[proc_macro_derive(TryFromJsValue)] | ||
| pub fn derive_try_from_jsvalue(input: TokenStream) -> TokenStream { | ||
| let input: DeriveInput = parse_macro_input!(input as DeriveInput); | ||
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|
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| let name = input.ident; | ||
| let data = input.data; | ||
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| match data { | ||
| Data::Struct(_) => {} | ||
| _ => return derive_error!("TryFromJsValue may only be derived on structs"), | ||
| }; | ||
|
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||
| let wasm_bindgen_meta = input.attrs.iter().find_map(|attr| { | ||
| attr.parse_meta() | ||
| .ok() | ||
| .and_then(|meta| match meta.path().is_ident("wasm_bindgen") { | ||
| true => Some(meta), | ||
| false => None, | ||
| }) | ||
| }); | ||
| if wasm_bindgen_meta.is_none() { | ||
| return derive_error!( | ||
| "TryFromJsValue can be defined only on struct exported to wasm with #[wasm_bindgen]" | ||
| ); | ||
| } | ||
|
|
||
| let maybe_js_class = wasm_bindgen_meta | ||
| .and_then(|meta| match meta { | ||
| syn::Meta::List(list) => Some(list), | ||
| _ => None, | ||
| }) | ||
| .and_then(|meta_list| { | ||
| meta_list.nested.iter().find_map(|nested_meta| { | ||
| let maybe_meta = match nested_meta { | ||
| syn::NestedMeta::Meta(meta) => Some(meta), | ||
| _ => None, | ||
| }; | ||
|
|
||
| maybe_meta | ||
| .and_then(|meta| match meta { | ||
| syn::Meta::NameValue(name_value) => Some(name_value), | ||
| _ => None, | ||
| }) | ||
| .and_then(|name_value| match name_value.path.is_ident("js_name") { | ||
| true => Some(name_value.lit.clone()), | ||
| false => None, | ||
| }) | ||
| .and_then(|lit| match lit { | ||
| syn::Lit::Str(str) => Some(str.value()), | ||
| _ => None, | ||
| }) | ||
| }) | ||
| }); | ||
|
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||
| let wasm_bindgen_macro_invocaton = match maybe_js_class { | ||
| Some(class) => format!("wasm_bindgen(js_class = \"{}\")", class), | ||
| None => "wasm_bindgen".to_string(), | ||
| } | ||
| .parse::<TokenStream2>() | ||
| .unwrap(); | ||
|
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| let expanded = quote! { | ||
| impl #name { | ||
| pub fn __get_classname() -> &'static str { | ||
| ::core::stringify!(#name) | ||
| } | ||
| } | ||
|
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| #[#wasm_bindgen_macro_invocaton] | ||
| impl #name { | ||
| #[wasm_bindgen(js_name = "__getClassname")] | ||
| pub fn __js_get_classname(&self) -> String { | ||
| use ::alloc::borrow::ToOwned; | ||
| ::core::stringify!(#name).to_owned() | ||
| } | ||
| } | ||
|
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| impl ::core::convert::TryFrom<&::wasm_bindgen::JsValue> for #name { | ||
| type Error = String; | ||
|
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| fn try_from(js: &::wasm_bindgen::JsValue) -> Result<Self, Self::Error> { | ||
| use ::alloc::borrow::ToOwned; | ||
| use ::alloc::string::ToString; | ||
| use ::wasm_bindgen::JsCast; | ||
| use ::wasm_bindgen::convert::RefFromWasmAbi; | ||
|
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| let classname = Self::__get_classname(); | ||
|
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| if !js.is_object() { | ||
| return Err(format!("Value supplied as {} is not an object", classname)); | ||
| } | ||
|
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| let no_get_classname_msg = concat!( | ||
| "no __getClassname method specified for object; ", | ||
| "did you forget to derive TryFromJsObject for this type?"); | ||
|
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| let get_classname = ::js_sys::Reflect::get( | ||
| js, | ||
| &::wasm_bindgen::JsValue::from("__getClassname"), | ||
| ) | ||
| .or(Err(no_get_classname_msg.to_string()))?; | ||
|
|
||
| if get_classname.is_undefined() { | ||
| return Err(no_get_classname_msg.to_string()); | ||
| } | ||
|
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| let get_classname = get_classname | ||
| .dyn_into::<::js_sys::Function>() | ||
| .map_err(|err| format!("__getClassname is not a function, {:?}", err))?; | ||
|
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| let object_classname: String = ::js_sys::Reflect::apply( | ||
| &get_classname, | ||
| js, | ||
| &::js_sys::Array::new(), | ||
| ) | ||
| .ok() | ||
| .and_then(|v| v.as_string()) | ||
| .ok_or_else(|| "Failed to get classname".to_owned())?; | ||
|
|
||
| if object_classname.as_str() == classname { | ||
| // Note: using an undocumented implementation detail of `wasm-bindgen`: | ||
| // the pointer property has the name `__wbg_ptr` (since wasm-bindgen 0.2.85) | ||
| let ptr = ::js_sys::Reflect::get(js, &::wasm_bindgen::JsValue::from_str("__wbg_ptr")) | ||
| .map_err(|err| format!("{:?}", err))?; | ||
| let ptr_u32: u32 = ptr.as_f64().ok_or(::wasm_bindgen::JsValue::NULL) | ||
| .map_err(|err| format!("{:?}", err))? | ||
| as u32; | ||
| let instance_ref = unsafe { #name::ref_from_abi(ptr_u32) }; | ||
| Ok(instance_ref.clone()) | ||
| } else { | ||
| Err(format!("Cannot convert {} to {}", object_classname, classname)) | ||
| } | ||
| } | ||
| } | ||
| }; | ||
|
|
||
| TokenStream::from(expanded) | ||
| } |
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