LibWeb: Break friendship between CSS Declaration and Parser

This means deviating slightly from the spec in order to construct a
fully-initialized Declaration instead of creating an empty one and then
poking at its internals.

DeclarationOrAtRule should probably use a Variant, but for now, making
its Declaration member optional is quick and easy.

Userland/Libraries/LibWeb/CSS/Parser/Declaration.cpp

@@ -10,7 +10,13 @@
 
 namespace Web::CSS::Parser {
 
-Declaration::Declaration() = default;
+Declaration::Declaration(FlyString name, Vector<ComponentValue> values, Important important)
+    : m_name(move(name))
+    , m_values(move(values))
+    , m_important(move(important))
+{
+}
+
 Declaration::~Declaration() = default;
 
 String Declaration::to_string() const

Userland/Libraries/LibWeb/CSS/Parser/Declaration.h

@@ -14,10 +14,8 @@
 namespace Web::CSS::Parser {
 
 class Declaration {
-    friend class Parser;
-
 public:
-    Declaration();
+    Declaration(FlyString name, Vector<ComponentValue> values, Important);
     ~Declaration();
 
     StringView name() const { return m_name; }

Userland/Libraries/LibWeb/CSS/Parser/DeclarationOrAtRule.cpp

@@ -32,7 +32,7 @@ String DeclarationOrAtRule::to_string() const
         builder.append(m_at->to_string());
         break;
     case DeclarationType::Declaration:
-        builder.append(m_declaration.to_string());
+        builder.append(m_declaration->to_string());
         break;
     }
 

Userland/Libraries/LibWeb/CSS/Parser/DeclarationOrAtRule.h

@@ -36,7 +36,7 @@ public:
     Declaration const& declaration() const
     {
         VERIFY(is_declaration());
-        return m_declaration;
+        return *m_declaration;
     }
 
     String to_string() const;
@@ -44,7 +44,7 @@ public:
 private:
     DeclarationType m_type;
     RefPtr<StyleRule> m_at;
-    Declaration m_declaration;
+    Optional<Declaration> m_declaration;
 };
 
 }

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -1932,8 +1932,10 @@ Optional<Declaration> Parser::consume_a_declaration(TokenStream<T>& tokens)
 
     // Create a new declaration with its name set to the value of the current input token
     // and its value initially set to the empty list.
-    Declaration declaration;
-    declaration.m_name = ((Token)token).ident();
+    // NOTE: We create a fully-initialized Declaration just before returning it instead.
+    FlyString declaration_name = ((Token)token).ident();
+    Vector<ComponentValue> declaration_values;
+    Important declaration_important = Important::No;
 
     // 1. While the next input token is a <whitespace-token>, consume the next input token.
     tokens.skip_whitespace();
@@ -1958,18 +1960,18 @@ Optional<Declaration> Parser::consume_a_declaration(TokenStream<T>& tokens)
         if (tokens.peek_token().is(Token::Type::EndOfFile)) {
             break;
         }
-        declaration.m_values.append(consume_a_component_value(tokens));
+        declaration_values.append(consume_a_component_value(tokens));
     }
 
     // 5. If the last two non-<whitespace-token>s in the declaration’s value are a <delim-token>
     //    with the value "!" followed by an <ident-token> with a value that is an ASCII case-insensitive
     //    match for "important", remove them from the declaration’s value and set the declaration’s
     //    important flag to true.
-    if (declaration.m_values.size() >= 2) {
+    if (declaration_values.size() >= 2) {
         // Walk backwards from the end until we find "important"
         Optional<size_t> important_index;
-        for (size_t i = declaration.m_values.size() - 1; i > 0; i--) {
-            auto value = declaration.m_values[i];
+        for (size_t i = declaration_values.size() - 1; i > 0; i--) {
+            auto value = declaration_values[i];
             if (value.is(Token::Type::Ident) && value.token().ident().equals_ignoring_case("important")) {
                 important_index = i;
                 break;
@@ -1983,7 +1985,7 @@ Optional<Declaration> Parser::consume_a_declaration(TokenStream<T>& tokens)
         if (important_index.has_value()) {
             Optional<size_t> bang_index;
             for (size_t i = important_index.value() - 1; i > 0; i--) {
-                auto value = declaration.m_values[i];
+                auto value = declaration_values[i];
                 if (value.is(Token::Type::Delim) && value.token().delim() == '!') {
                     bang_index = i;
                     break;
@@ -1994,24 +1996,24 @@ Optional<Declaration> Parser::consume_a_declaration(TokenStream<T>& tokens)
             }
 
             if (bang_index.has_value()) {
-                declaration.m_values.remove(important_index.value());
-                declaration.m_values.remove(bang_index.value());
-                declaration.m_important = Important::Yes;
+                declaration_values.remove(important_index.value());
+                declaration_values.remove(bang_index.value());
+                declaration_important = Important::Yes;
             }
         }
     }
 
     // 6. While the last token in the declaration’s value is a <whitespace-token>, remove that token.
-    while (!declaration.m_values.is_empty()) {
-        auto maybe_whitespace = declaration.m_values.last();
+    while (!declaration_values.is_empty()) {
+        auto maybe_whitespace = declaration_values.last();
         if (!(maybe_whitespace.is(Token::Type::Whitespace))) {
             break;
         }
-        declaration.m_values.take_last();
+        declaration_values.take_last();
     }
 
     // 7. Return the declaration.
-    return declaration;
+    return Declaration { move(declaration_name), move(declaration_values), move(declaration_important) };
 }
 
 // 5.4.5. Consume a list of declarations