Support WebIDL constants

crates/backend/src/ast.rs

@@ -42,6 +42,7 @@ pub enum ImportKind {
     Static(ImportStatic),
     Type(ImportType),
     Enum(ImportEnum),
+    Const(Const),
 }
 
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
@@ -174,6 +175,24 @@ pub struct TypeAlias {
     pub src: syn::Type,
 }
 
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+pub struct Const {
+    pub vis: syn::Visibility,
+    pub name: Ident,
+    pub interface_name: Ident,
+    pub ty: syn::Type,
+    pub value: ConstValue,
+}
+
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+/// same as webidl::ast::ConstValue
+pub enum ConstValue {
+    BooleanLiteral(bool),
+    FloatLiteral(f64),
+    IntegerLiteral(i64),
+    Null,
+}
+
 impl Program {
     pub(crate) fn shared(&self) -> shared::Program {
         shared::Program {
@@ -293,6 +312,7 @@ impl ImportKind {
             ImportKind::Static(_) => false,
             ImportKind::Type(_) => false,
             ImportKind::Enum(_) => false,
+            ImportKind::Const(_) => false,
         }
     }
 
@@ -302,6 +322,7 @@ impl ImportKind {
             ImportKind::Static(ref f) => shared::ImportKind::Static(f.shared()),
             ImportKind::Type(ref f) => shared::ImportKind::Type(f.shared()),
             ImportKind::Enum(ref f) => shared::ImportKind::Enum(f.shared()),
+            ImportKind::Const(ref f) => shared::ImportKind::Const(f.shared()),
         }
     }
 }
@@ -404,3 +425,9 @@ impl StructField {
         }
     }
 }
+
+impl Const {
+    fn shared(&self) -> shared::Const {
+        shared::Const {}
+    }
+}

crates/backend/src/codegen.rs

@@ -501,6 +501,7 @@ impl ToTokens for ast::ImportKind {
             ast::ImportKind::Static(ref s) => s.to_tokens(tokens),
             ast::ImportKind::Type(ref t) => t.to_tokens(tokens),
             ast::ImportKind::Enum(ref e) => e.to_tokens(tokens),
+            ast::ImportKind::Const(ref c) => c.to_tokens(tokens),
         }
     }
 }
@@ -842,6 +843,7 @@ impl<'a> ToTokens for DescribeImport<'a> {
             ast::ImportKind::Static(_) => return,
             ast::ImportKind::Type(_) => return,
             ast::ImportKind::Enum(_) => return,
+            ast::ImportKind::Const(_) => return,
         };
         let describe_name = format!("__wbindgen_describe_{}", f.shim);
         let describe_name = Ident::new(&describe_name, Span::call_site());
@@ -958,3 +960,41 @@ impl ToTokens for ast::TypeAlias {
         }).to_tokens(into);
     }
 }
+
+impl ToTokens for ast::Const {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        use ast::ConstValue::*;
+
+        let vis = &self.vis;
+        let name = &self.name;
+        let interface_name = &self.interface_name;
+        let ty = &self.ty;
+
+        let value: TokenStream = match self.value {
+            BooleanLiteral(false) => quote!(false),
+            BooleanLiteral(true) => quote!(true),
+            // the actual type is unknown because of typedefs
+            // so we cannot use std::fxx::INFINITY
+            // but we can use type inference
+            FloatLiteral(f) if f.is_infinite() && f.is_sign_positive() => quote!(1.0 / 0.0),
+            FloatLiteral(f) if f.is_infinite() && f.is_sign_negative() => quote!(-1.0 / 0.0),
+            FloatLiteral(f) if f.is_nan() => quote!(0.0 / 0.0),
+            // again no suffix
+            // panics on +-inf, nan
+            FloatLiteral(f) => {
+                let f = Literal::f64_unsuffixed(f);
+                quote!(#f)
+            },
+            IntegerLiteral(i) => {
+                let i = Literal::i64_unsuffixed(i);
+                quote!(#i)
+            },
+            Null => unimplemented!(),
+        };
+        (quote! {
+            impl #interface_name {
+                #vis const #name: #ty = #value;
+            }
+        }).to_tokens(tokens);
+    }
+}

crates/backend/src/defined.rs

@@ -106,6 +106,7 @@ impl ImportedTypes for ast::ImportKind {
             ast::ImportKind::Function(fun) => fun.imported_types(f),
             ast::ImportKind::Type(ty) => ty.imported_types(f),
             ast::ImportKind::Enum(enm) => enm.imported_types(f),
+            ast::ImportKind::Const(c) => c.imported_types(f),
         }
     }
 }
@@ -229,6 +230,15 @@ impl ImportedTypes for ast::TypeAlias {
     }
 }
 
+impl ImportedTypes for ast::Const {
+    fn imported_types<F>(&self, f: &mut F)
+    where
+        F: FnMut(&Ident, ImportedTypeKind),
+    {
+        self.ty.imported_types(f);
+    }
+}
+
 /// Remove any methods, statics, &c, that reference types that are *not*
 /// defined.
 pub trait RemoveUndefinedImports {

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

@@ -1757,6 +1757,7 @@ impl<'a, 'b> SubContext<'a, 'b> {
             }
             shared::ImportKind::Type(_) => {}
             shared::ImportKind::Enum(_) => {}
+            shared::ImportKind::Const(_) => {}
         }
         Ok(())
     }

crates/shared/src/lib.rs

@@ -34,6 +34,7 @@ pub enum ImportKind {
     Static(ImportStatic),
     Type(ImportType),
     Enum(ImportEnum),
+    Const(Const)
 }
 
 #[derive(Deserialize, Serialize)]
@@ -124,6 +125,9 @@ pub struct StructField {
     pub comments: Vec<String>,
 }
 
+#[derive(Deserialize, Serialize)]
+pub struct Const {}
+
 pub fn new_function(struct_name: &str) -> String {
     let mut name = format!("__wbg_");
     name.extend(struct_name.chars().flat_map(|s| s.to_lowercase()));

crates/webidl/src/lib.rs

@@ -29,12 +29,12 @@ use std::path::Path;
 use backend::defined::{ImportedTypeDefinitions, RemoveUndefinedImports};
 use backend::util::{ident_ty, rust_ident, wrap_import_function};
 use failure::ResultExt;
-use heck::CamelCase;
+use heck::{CamelCase, ShoutySnakeCase};
 use quote::ToTokens;
 
 use util::{
-    create_basic_method, create_function, create_getter, create_setter, webidl_ty_to_syn_ty,
-    TypePosition,
+    create_basic_method, create_function, create_getter, create_setter, webidl_const_ty_to_syn_ty,
+    webidl_const_v_to_backend_const_v, webidl_ty_to_syn_ty, TypePosition,
 };
 
 /// Either `Ok(t)` or `Err(failure::Error)`.
@@ -297,9 +297,9 @@ impl<'a> WebidlParse<&'a str> for webidl::ast::InterfaceMember {
                 attr.webidl_parse(program, self_name)
             }
             webidl::ast::InterfaceMember::Operation(ref op) => op.webidl_parse(program, self_name),
+            webidl::ast::InterfaceMember::Const(ref c) => c.webidl_parse(program, self_name),
             // TODO
-            webidl::ast::InterfaceMember::Const(_)
-            | webidl::ast::InterfaceMember::Iterable(_)
+            webidl::ast::InterfaceMember::Iterable(_)
             | webidl::ast::InterfaceMember::Maplike(_)
             | webidl::ast::InterfaceMember::Setlike(_) => {
                 warn!("Unsupported WebIDL interface member: {:?}", self);
@@ -474,3 +474,28 @@ impl<'a> WebidlParse<()> for webidl::ast::Enum {
         Ok(())
     }
 }
+
+impl<'a> WebidlParse<&'a str> for webidl::ast::Const {
+    fn webidl_parse(
+        &self,
+        program: &mut backend::ast::Program,
+        interface_name: &'a str,
+    ) -> Result<()> {
+        let syn_ty = webidl_const_ty_to_syn_ty(&self.type_);
+        program.imports.push(backend::ast::Import {
+            module: None,
+            version: None,
+            js_namespace: None,
+            kind: backend::ast::ImportKind::Const(backend::ast::Const {
+                vis: syn::Visibility::Public(syn::VisPublic {
+                    pub_token: Default::default(),
+                }),
+                name: rust_ident(self.name.to_shouty_snake_case().as_str()),
+                interface_name: rust_ident(interface_name),
+                ty: syn_ty,
+                value: webidl_const_v_to_backend_const_v(&self.value),
+            }),
+        });
+        Ok(())
+    }
+}

crates/webidl/src/util.rs

@@ -90,6 +90,35 @@ pub fn webidl_ty_to_syn_ty(ty: &webidl::ast::Type, pos: TypePosition) -> Option<
     })
 }
 
+pub fn webidl_const_ty_to_syn_ty(ty: &webidl::ast::ConstType) -> syn::Type {
+    use webidl::ast::ConstType::*;
+
+    // similar to webidl_ty_to_syn_ty
+    match ty {
+        Boolean => ident_ty(raw_ident("bool")),
+        Byte => ident_ty(raw_ident("i8")),
+        Octet => ident_ty(raw_ident("u8")),
+        RestrictedDouble | UnrestrictedDouble => ident_ty(raw_ident("f64")),
+        RestrictedFloat | UnrestrictedFloat => ident_ty(raw_ident("f32")),
+        SignedLong => ident_ty(raw_ident("i32")),
+        SignedLongLong => ident_ty(raw_ident("i64")),
+        SignedShort => ident_ty(raw_ident("i16")),
+        UnsignedLong => ident_ty(raw_ident("u32")),
+        UnsignedLongLong => ident_ty(raw_ident("u64")),
+        UnsignedShort => ident_ty(raw_ident("u16")),
+        Identifier(ref id) => ident_ty(rust_ident(id)),
+    }
+}
+
+pub fn webidl_const_v_to_backend_const_v(v: &webidl::ast::ConstValue) -> backend::ast::ConstValue {
+    match *v {
+        webidl::ast::ConstValue::BooleanLiteral(b) => backend::ast::ConstValue::BooleanLiteral(b),
+        webidl::ast::ConstValue::FloatLiteral(f) => backend::ast::ConstValue::FloatLiteral(f),
+        webidl::ast::ConstValue::IntegerLiteral(i) => backend::ast::ConstValue::IntegerLiteral(i),
+        webidl::ast::ConstValue::Null => backend::ast::ConstValue::Null,
+    }
+}
+
 fn simple_fn_arg(ident: Ident, ty: syn::Type) -> syn::ArgCaptured {
     syn::ArgCaptured {
         pat: syn::Pat::Ident(syn::PatIdent {