Add importing strings as JsString (#4055)

CHANGELOG.md

@@ -72,6 +72,9 @@
 * Added an experimental Node.JS ES module target, in comparison the current `node` target uses CommonJS, with `--target experimental-nodejs-module` or when testing with `wasm_bindgen_test_configure!(run_in_node_experimental)`.
   [#4027](https://github.com/rustwasm/wasm-bindgen/pull/4027)
 
+* Added importing strings as `JsString` through `#[wasm_bindgen(static_string)] static STRING: JsString = "a string literal";`.
+  [#4055](https://github.com/rustwasm/wasm-bindgen/pull/4055)
+
 ### Changed
 
 * Stabilize Web Share API.

crates/backend/src/ast.rs

@@ -29,6 +29,8 @@ pub struct Program {
     pub inline_js: Vec<String>,
     /// Path to wasm_bindgen
     pub wasm_bindgen: Path,
+    /// Path to js_sys
+    pub js_sys: Path,
     /// Path to wasm_bindgen_futures
     pub wasm_bindgen_futures: Path,
 }
@@ -44,6 +46,7 @@ impl Default for Program {
             typescript_custom_sections: Default::default(),
             inline_js: Default::default(),
             wasm_bindgen: syn::parse_quote! { wasm_bindgen },
+            js_sys: syn::parse_quote! { js_sys },
             wasm_bindgen_futures: syn::parse_quote! { wasm_bindgen_futures },
         }
     }
@@ -160,6 +163,8 @@ pub enum ImportKind {
     Function(ImportFunction),
     /// Importing a static value
     Static(ImportStatic),
+    /// Importing a static string
+    String(ImportString),
     /// Importing a type/class
     Type(ImportType),
     /// Importing a JS enum
@@ -272,6 +277,26 @@ pub struct ImportStatic {
     pub wasm_bindgen: Path,
 }
 
+/// The type of a static string being imported
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+#[derive(Clone)]
+pub struct ImportString {
+    /// The visibility of this static string in Rust
+    pub vis: syn::Visibility,
+    /// The type specified by the user, which we only use to show an error if the wrong type is used.
+    pub ty: syn::Type,
+    /// The name of the shim function used to access this static
+    pub shim: Ident,
+    /// The name of this static on the Rust side
+    pub rust_name: Ident,
+    /// Path to wasm_bindgen
+    pub wasm_bindgen: Path,
+    /// Path to js_sys
+    pub js_sys: Path,
+    /// The string to export.
+    pub string: String,
+}
+
 /// The metadata for a type being imported
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
 #[derive(Clone)]
@@ -502,6 +527,7 @@ impl ImportKind {
         match *self {
             ImportKind::Function(_) => true,
             ImportKind::Static(_) => false,
+            ImportKind::String(_) => false,
             ImportKind::Type(_) => false,
             ImportKind::Enum(_) => false,
         }

crates/backend/src/codegen.rs

@@ -9,6 +9,7 @@ use quote::quote_spanned;
 use quote::{quote, ToTokens};
 use std::collections::{HashMap, HashSet};
 use std::sync::Mutex;
+use syn::parse_quote;
 use syn::spanned::Spanned;
 use wasm_bindgen_shared as shared;
 
@@ -846,6 +847,7 @@ impl TryToTokens for ast::ImportKind {
         match *self {
             ast::ImportKind::Function(ref f) => f.try_to_tokens(tokens)?,
             ast::ImportKind::Static(ref s) => s.to_tokens(tokens),
+            ast::ImportKind::String(ref s) => s.to_tokens(tokens),
             ast::ImportKind::Type(ref t) => t.to_tokens(tokens),
             ast::ImportKind::Enum(ref e) => e.to_tokens(tokens),
         }
@@ -1477,6 +1479,7 @@ impl<'a> ToTokens for DescribeImport<'a> {
         let f = match *self.kind {
             ast::ImportKind::Function(ref f) => f,
             ast::ImportKind::Static(_) => return,
+            ast::ImportKind::String(_) => return,
             ast::ImportKind::Type(_) => return,
             ast::ImportKind::Enum(_) => return,
         };
@@ -1641,44 +1644,19 @@ impl ToTokens for ast::Enum {
 
 impl ToTokens for ast::ImportStatic {
     fn to_tokens(&self, into: &mut TokenStream) {
-        let name = &self.rust_name;
         let ty = &self.ty;
-        let shim_name = &self.shim;
-        let vis = &self.vis;
-        let wasm_bindgen = &self.wasm_bindgen;
-
-        let abi_ret = quote! {
-            #wasm_bindgen::convert::WasmRet<<#ty as #wasm_bindgen::convert::FromWasmAbi>::Abi>
-        };
-        (quote! {
-            #[automatically_derived]
-            #vis static #name: #wasm_bindgen::JsStatic<#ty> = {
-                fn init() -> #ty {
-                    #[link(wasm_import_module = "__wbindgen_placeholder__")]
-                    #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
-                    extern "C" {
-                        fn #shim_name() -> #abi_ret;
-                    }
-
-                    #[cfg(not(all(target_arch = "wasm32", target_os = "unknown")))]
-                    unsafe fn #shim_name() -> #abi_ret {
-                        panic!("cannot access imported statics on non-wasm targets")
-                    }
-
-                    unsafe {
-                        <#ty as #wasm_bindgen::convert::FromWasmAbi>::from_abi(#shim_name().join())
-                    }
-                }
-                thread_local!(static _VAL: #ty = init(););
-                #wasm_bindgen::JsStatic {
-                    __inner: &_VAL,
-                }
-            };
-        })
+        static_import(
+            &self.vis,
+            &self.rust_name,
+            &self.wasm_bindgen,
+            ty,
+            ty,
+            &self.shim,
+        )
         .to_tokens(into);
 
         Descriptor {
-            ident: shim_name,
+            ident: &self.shim,
             inner: quote! {
                 <#ty as WasmDescribe>::describe();
             },
@@ -1689,6 +1667,61 @@ impl ToTokens for ast::ImportStatic {
     }
 }
 
+impl ToTokens for ast::ImportString {
+    fn to_tokens(&self, into: &mut TokenStream) {
+        let js_sys = &self.js_sys;
+        let actual_ty: syn::Type = parse_quote!(#js_sys::JsString);
+
+        static_import(
+            &self.vis,
+            &self.rust_name,
+            &self.wasm_bindgen,
+            &actual_ty,
+            &self.ty,
+            &self.shim,
+        )
+        .to_tokens(into);
+    }
+}
+
+fn static_import(
+    vis: &syn::Visibility,
+    name: &Ident,
+    wasm_bindgen: &syn::Path,
+    actual_ty: &syn::Type,
+    ty: &syn::Type,
+    shim_name: &Ident,
+) -> TokenStream {
+    let abi_ret = quote! {
+        #wasm_bindgen::convert::WasmRet<<#ty as #wasm_bindgen::convert::FromWasmAbi>::Abi>
+    };
+    quote! {
+        #[automatically_derived]
+        #vis static #name: #wasm_bindgen::JsStatic<#actual_ty> = {
+            fn init() -> #ty {
+                #[link(wasm_import_module = "__wbindgen_placeholder__")]
+                #[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
+                extern "C" {
+                    fn #shim_name() -> #abi_ret;
+                }
+
+                #[cfg(not(all(target_arch = "wasm32", target_os = "unknown")))]
+                unsafe fn #shim_name() -> #abi_ret {
+                    panic!("cannot access imported statics on non-wasm targets")
+                }
+
+                unsafe {
+                    <#ty as #wasm_bindgen::convert::FromWasmAbi>::from_abi(#shim_name().join())
+                }
+            }
+            thread_local!(static _VAL: #ty = init(););
+            #wasm_bindgen::JsStatic {
+                __inner: &_VAL,
+            }
+        };
+    }
+}
+
 /// Emits the necessary glue tokens for "descriptor", generating an appropriate
 /// symbol name as well as attributes around the descriptor function itself.
 struct Descriptor<'a, T> {

crates/backend/src/encode.rs

@@ -297,6 +297,7 @@ fn shared_import_kind<'a>(
     Ok(match i {
         ast::ImportKind::Function(f) => ImportKind::Function(shared_import_function(f, intern)?),
         ast::ImportKind::Static(f) => ImportKind::Static(shared_import_static(f, intern)),
+        ast::ImportKind::String(f) => ImportKind::String(shared_import_string(f, intern)),
         ast::ImportKind::Type(f) => ImportKind::Type(shared_import_type(f, intern)),
         ast::ImportKind::Enum(f) => ImportKind::Enum(shared_import_enum(f, intern)),
     })
@@ -332,6 +333,13 @@ fn shared_import_static<'a>(i: &'a ast::ImportStatic, intern: &'a Interner) -> I
     }
 }
 
+fn shared_import_string<'a>(i: &'a ast::ImportString, intern: &'a Interner) -> ImportString<'a> {
+    ImportString {
+        shim: intern.intern(&i.shim),
+        string: &i.string,
+    }
+}
+
 fn shared_import_type<'a>(i: &'a ast::ImportType, intern: &'a Interner) -> ImportType<'a> {
     ImportType {
         name: &i.js_name,

crates/cli-support/src/js/mod.rs

@@ -3067,6 +3067,19 @@ impl<'a> Context<'a> {
                 self.import_name(js)
             }
 
+            AuxImport::String(string) => {
+                assert!(kind == AdapterJsImportKind::Normal);
+                assert!(!variadic);
+                assert_eq!(args.len(), 0);
+
+                let mut escaped = String::with_capacity(string.len());
+                string.chars().for_each(|c| match c {
+                    '`' | '\\' | '$' => escaped.extend(['\\', c]),
+                    _ => escaped.extend([c]),
+                });
+                Ok(format!("`{escaped}`"))
+            }
+
             AuxImport::Closure {
                 dtor,
                 mutable,

crates/cli-support/src/wit/mod.rs

@@ -567,6 +567,7 @@ impl<'a> Context<'a> {
         match &import.kind {
             decode::ImportKind::Function(f) => self.import_function(&import, f),
             decode::ImportKind::Static(s) => self.import_static(&import, s),
+            decode::ImportKind::String(s) => self.import_string(s),
             decode::ImportKind::Type(t) => self.import_type(&import, t),
             decode::ImportKind::Enum(_) => Ok(()),
         }
@@ -803,6 +804,32 @@ impl<'a> Context<'a> {
         Ok(())
     }
 
+    fn import_string(&mut self, string: &decode::ImportString<'_>) -> Result<(), Error> {
+        let (import_id, _id) = match self.function_imports.get(string.shim) {
+            Some(pair) => *pair,
+            None => return Ok(()),
+        };
+
+        // Register the signature of this imported shim
+        let id = self.import_adapter(
+            import_id,
+            Function {
+                arguments: Vec::new(),
+                shim_idx: 0,
+                ret: Descriptor::Externref,
+                inner_ret: None,
+            },
+            AdapterJsImportKind::Normal,
+        )?;
+
+        // And then save off that this function is is an instanceof shim for an
+        // imported item.
+        self.aux
+            .import_map
+            .insert(id, AuxImport::String(string.string.to_owned()));
+        Ok(())
+    }
+
     fn import_type(
         &mut self,
         import: &decode::Import<'_>,

crates/cli-support/src/wit/nonstandard.rs

@@ -220,6 +220,9 @@ pub enum AuxImport {
     /// `JsImport`.
     Static(JsImport),
 
+    /// This import is expected to be a shim that returns an exported `JsString`.
+    String(String),
+
     /// This import is intended to manufacture a JS closure with the given
     /// signature and then return that back to Rust.
     Closure {