web-sys: Don't remove dictionaries if required fields are removed

This commit updates the conditional binding generation for dictionaries
to ensure that a dictionary is not entirely removed if any of its
required fields are removed. If a required field is removed, however, it
cannot be constructed, so the constructor is removed.

crates/backend/src/ast.rs

@@ -292,6 +292,7 @@ pub enum ConstValue {
 pub struct Dictionary {
     pub name: Ident,
     pub fields: Vec<DictionaryField>,
+    pub ctor: bool,
 }
 
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]

crates/backend/src/codegen.rs

@@ -1282,6 +1282,18 @@ impl ToTokens for ast::Dictionary {
         let required_names2 = required_names;
         let required_names3 = required_names;
 
+        let ctor = if self.ctor {
+            quote! {
+                pub fn new(#(#required_names: #required_types),*) -> #name {
+                    let mut _ret = #name { obj: ::js_sys::Object::new() };
+                    #(_ret.#required_names2(#required_names3);)*
+                    return _ret
+                }
+            }
+        } else {
+            quote! {}
+        };
+
         let const_name = Ident::new(&format!("_CONST_{}", name), Span::call_site());
         (quote! {
             #[derive(Clone, Debug)]
@@ -1293,12 +1305,7 @@ impl ToTokens for ast::Dictionary {
 
             #[allow(clippy::all)]
             impl #name {
-                pub fn new(#(#required_names: #required_types),*) -> #name {
+                #ctor
-                    let mut _ret = #name { obj: ::js_sys::Object::new() };
-                    #(_ret.#required_names2(#required_names3);)*
-                    return _ret
-                }
-
                 #methods
             }
 

crates/backend/src/defined.rs

@@ -348,25 +348,20 @@ impl RemoveUndefinedImports for ast::Program {
         let mut changed = self.imports.remove_undefined_imports(is_defined);
         changed = self.consts.remove_undefined_imports(is_defined) || changed;
 
-        let mut dictionaries_to_remove = Vec::new();
+        for dictionary in self.dictionaries.iter_mut() {
-        for (i, dictionary) in self.dictionaries.iter_mut().enumerate() {
             let num_required =
                 |dict: &ast::Dictionary| dict.fields.iter().filter(|f| f.required).count();
             let before = num_required(dictionary);
             changed = dictionary.fields.remove_undefined_imports(is_defined) || changed;
+
+            // If a required field was removed we can no longer construct this
+            // dictionary so disable the constructor.
             if before != num_required(dictionary) {
-                log::warn!(
+                dictionary.ctor = false;
-                    "removing {} due to a required field being removed",
-                    dictionary.name
-                );
-                dictionaries_to_remove.push(i);
             }
         }
-        for i in dictionaries_to_remove.iter().rev() {
-            self.dictionaries.swap_remove(*i);
-        }
 
-        changed || dictionaries_to_remove.len() > 0
+        changed
     }
 }
 

crates/webidl/src/lib.rs

@@ -317,6 +317,7 @@ impl<'src> FirstPassRecord<'src> {
         program.dictionaries.push(ast::Dictionary {
             name: rust_ident(&camel_case_ident(def.identifier.0)),
             fields,
+            ctor: true,
         });
     }
 
@@ -784,6 +785,7 @@ impl<'src> FirstPassRecord<'src> {
         program.dictionaries.push(ast::Dictionary {
             name: rust_ident(&camel_case_ident(item.definition.identifier.0)),
             fields,
+            ctor: true,
         });
     }
 }