JSSpecCompiler: Parse true, false, this, undefined, and null

Author: https://github.com/DanShaders
Commit: https://github.com/SerenityOS/serenity/commit/b800276347
Pull-request: https://github.com/SerenityOS/serenity/pull/23123
Reviewed-by: https://github.com/ADKaster ✅

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.h

@@ -134,6 +134,11 @@ protected:
 class WellKnownNode : public Expression {
 public:
     enum Type {
+        False,
+        Null,
+        This,
+        True,
+        Undefined,
         ZeroArgumentFunctionCall,
         // Update WellKnownNode::dump_tree after adding an entry here
     };

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/ASTPrinting.cpp

@@ -38,6 +38,11 @@ void ErrorNode::dump_tree(StringBuilder& builder)
 void WellKnownNode::dump_tree(StringBuilder& builder)
 {
     static constexpr StringView type_to_name[] = {
+        "False"sv,
+        "Null"sv,
+        "This"sv,
+        "True"sv,
+        "Undefined"sv,
         "ZeroArgumentFunctionCall"sv,
     };
     dump_node(builder, "WellKnownNode {}", type_to_name[m_type]);

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Parser/Lexer.cpp

@@ -158,8 +158,8 @@ void tokenize_tree(SpecificationParsingContext& ctx, TokenizerState& state, XML:
 
                     if (contents.length() >= 2 && contents.starts_with('"') && contents.ends_with('"'))
                         tokens.append({ TokenType::String, contents.substring_view(1, contents.length() - 2), move(child_location) });
-                    else if (contents == "undefined")
-                        tokens.append({ TokenType::Undefined, contents, move(child_location) });
+                    else if (contents.is_one_of("undefined", "null", "this", "true", "false"))
+                        tokens.append({ TokenType::WellKnownValue, contents, move(child_location) });
                     else
                         tokens.append({ TokenType::Identifier, contents, move(child_location) });
                     return;

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Parser/TextParser.cpp

@@ -298,6 +298,24 @@ TextParseErrorOr<Tree> TextParser::parse_expression()
             NullableTree expression;
             if (token.type == TokenType::Identifier) {
                 expression = make_ref_counted<UnresolvedReference>(token.data);
+            } else if (token.type == TokenType::WellKnownValue) {
+                static constexpr struct {
+                    StringView name;
+                    WellKnownNode::Type type;
+                } translations[] = {
+                    { "false"sv, WellKnownNode::Type::False },
+                    { "null"sv, WellKnownNode::Type::Null },
+                    { "this"sv, WellKnownNode::Type::This },
+                    { "true"sv, WellKnownNode::Type::True },
+                    { "undefined"sv, WellKnownNode::Type::Undefined },
+                };
+                for (auto [name, type] : translations) {
+                    if (token.data == name) {
+                        expression = make_ref_counted<WellKnownNode>(type);
+                        break;
+                    }
+                }
+                VERIFY(expression);
             } else if (token.type == TokenType::Number) {
                 expression = make_ref_counted<MathematicalConstant>(MUST(Crypto::BigFraction::from_string(token.data)));
             } else if (token.type == TokenType::String) {

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Parser/Token.h

@@ -48,7 +48,7 @@ constexpr i32 closing_bracket_precedence = 18;
     F(String, -1, Invalid, Invalid, Invalid, "string literal")                       \
     F(Superscript, 4, Invalid, Power, Invalid, "subscript")                          \
     F(UnaryMinus, 3, Minus, Invalid, Invalid, "unary minus")                         \
-    F(Undefined, -1, Invalid, Invalid, Invalid, "constant")                          \
+    F(WellKnownValue, -1, Invalid, Invalid, Invalid, "constant")                     \
     F(Word, -1, Invalid, Invalid, Invalid, "word")
 
 enum class TokenType {

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Tests/spec-parsing.xml

@@ -13,4 +13,24 @@
          </ol>
       </emu-alg>
    </emu-clause>
+   <emu-clause id="2" aoid="WellKnownConstants">
+      <h1><span class="secnum">2</span> WellKnownConstants ( <var>a</var> )</h1>
+      <emu-alg>
+         <ol>
+            <li>
+               If <var>a</var> is <emu-val>undefined</emu-val>, then
+               <ol>
+                  <li>Let <var>b</var> be <emu-val>null</emu-val>.</li>
+                  <li>Return <emu-val>true</emu-val>.</li>
+               </ol>
+            </li>
+            <li>Else,
+               <ol>
+                  <li>Let <var>c</var> be <emu-val>this</emu-val>.</li>
+                  <li>Return <emu-val>false</emu-val>.</li>
+               </ol>
+            </li>
+         </ol>
+      </emu-alg>
+   </emu-clause>
 </specification>

Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Tests/spec-parsing.xml.expectation

@@ -27,3 +27,22 @@ TreeList
             Var d
             Var e
 
+WellKnownConstants(a):
+TreeList
+  IfElseIfChain
+    IsOneOf
+      Var a
+      WellKnownNode Undefined
+    TreeList
+      BinaryOperation Assignment
+        Var b
+        WellKnownNode Null
+      ReturnNode
+        WellKnownNode True
+    TreeList
+      BinaryOperation Assignment
+        Var c
+        WellKnownNode This
+      ReturnNode
+        WellKnownNode False
+