LibJS: Allow functions to take arguments (#1405)

Author: https://github.com/f-eiwu
Commit: https://github.com/SerenityOS/serenity/commit/01133733dde
Pull-request: https://github.com/SerenityOS/serenity/pull/1405
Reviewed-by: https://github.com/awesomekling ✅

Libraries/LibJS/AST.cpp

@@ -24,6 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/HashMap.h>
+#include <AK/StringBuilder.h>
 #include <LibJS/AST.h>
 #include <LibJS/Function.h>
 #include <LibJS/Interpreter.h>
@@ -40,7 +42,7 @@ Value ScopeNode::execute(Interpreter& interpreter) const
 
 Value FunctionDeclaration::execute(Interpreter& interpreter) const
 {
-    auto* function = interpreter.heap().allocate<Function>(name(), body());
+    auto* function = interpreter.heap().allocate<Function>(name(), body(), parameters());
     interpreter.set_variable(m_name, Value(function));
     return Value(function);
 }
@@ -62,7 +64,18 @@ Value CallExpression::execute(Interpreter& interpreter) const
     auto* callee_object = callee.as_object();
     ASSERT(callee_object->is_function());
     auto& function = static_cast<Function&>(*callee_object);
-    return interpreter.run(function.body(), ScopeType::Function);
+
+    const size_t arguments_size = m_arguments.size();
+    ASSERT(function.parameters().size() == arguments_size);
+    HashMap<String, Value> passed_parameters;
+    for (size_t i = 0; i < arguments_size; ++i) {
+        auto name = function.parameters()[i];
+        auto value = m_arguments[i].execute(interpreter);
+        dbg() << name << ": " << value;
+        passed_parameters.set(move(name), move(value));
+    }
+
+    return interpreter.run(function.body(), move(passed_parameters), ScopeType::Function);
 }
 
 Value ReturnStatement::execute(Interpreter& interpreter) const
@@ -283,8 +296,19 @@ void BooleanLiteral::dump(int indent) const
 
 void FunctionDeclaration::dump(int indent) const
 {
+    bool first_time = true;
+    StringBuilder parameters_builder;
+    for (const auto& parameter : m_parameters) {
+        if (first_time)
+            first_time = false;
+        else
+            parameters_builder.append(',');
+
+        parameters_builder.append(parameter);
+    }
+
     print_indent(indent);
-    printf("%s '%s'\n", class_name(), name().characters());
+    printf("%s '%s(%s)'\n", class_name(), name().characters(), parameters_builder.build().characters());
     body().dump(indent + 1);
 }
 

Libraries/LibJS/AST.h

@@ -29,6 +29,7 @@
 #include <AK/NonnullOwnPtrVector.h>
 #include <AK/OwnPtr.h>
 #include <AK/String.h>
+#include <AK/Vector.h>
 #include <LibJS/Forward.h>
 #include <LibJS/Value.h>
 
@@ -115,14 +116,16 @@ private:
 
 class FunctionDeclaration : public Statement {
 public:
-    FunctionDeclaration(String name, NonnullOwnPtr<ScopeNode> body)
+    FunctionDeclaration(String name, NonnullOwnPtr<ScopeNode> body, Vector<String> parameters = {})
         : m_name(move(name))
         , m_body(move(body))
+        , m_parameters(move(parameters))
     {
     }
 
     String name() const { return m_name; }
     const ScopeNode& body() const { return *m_body; }
+    const Vector<String>& parameters() const { return m_parameters; };
 
     virtual Value execute(Interpreter&) const override;
     virtual void dump(int indent) const override;
@@ -132,6 +135,7 @@ private:
 
     String m_name;
     NonnullOwnPtr<ScopeNode> m_body;
+    const Vector<String> m_parameters;
 };
 
 class Expression : public ASTNode {
@@ -363,8 +367,9 @@ private:
 
 class CallExpression : public Expression {
 public:
-    explicit CallExpression(String name)
+    explicit CallExpression(String name, NonnullOwnPtrVector<Expression> arguments = {})
         : m_name(move(name))
+        , m_arguments(move(arguments))
     {
     }
 
@@ -377,6 +382,7 @@ private:
     virtual const char* class_name() const override { return "CallExpression"; }
 
     String m_name;
+    const NonnullOwnPtrVector<Expression> m_arguments;
 };
 
 enum class AssignmentOp {

Libraries/LibJS/Function.cpp

@@ -29,9 +29,10 @@
 
 namespace JS {
 
-Function::Function(String name, const ScopeNode& body)
+Function::Function(String name, const ScopeNode& body, Vector<String> parameters)
     : m_name(move(name))
     , m_body(body)
+    , m_parameters(move(parameters))
 {
 }
 

Libraries/LibJS/Function.h

@@ -33,11 +33,12 @@ namespace JS {
 
 class Function : public Object {
 public:
-    Function(String name, const ScopeNode& body);
+    Function(String name, const ScopeNode& body, Vector<String> parameters = {});
     virtual ~Function();
 
     const String& name() const { return m_name; }
     const ScopeNode& body() const { return m_body; }
+    const Vector<String>& parameters() const { return m_parameters; };
 
 protected:
     virtual const char* class_name() const override { return "Function"; }
@@ -47,6 +48,7 @@ private:
 
     String m_name;
     const ScopeNode& m_body;
+    const Vector<String> m_parameters;
 };
 
 }

Libraries/LibJS/Interpreter.cpp

@@ -42,9 +42,9 @@ Interpreter::~Interpreter()
 {
 }
 
-Value Interpreter::run(const ScopeNode& scope_node, ScopeType scope_type)
+Value Interpreter::run(const ScopeNode& scope_node, HashMap<String, Value> scope_variables, ScopeType scope_type)
 {
-    enter_scope(scope_node, scope_type);
+    enter_scope(scope_node, move(scope_variables), scope_type);
 
     Value last_value = js_undefined();
     for (auto& node : scope_node.children()) {
@@ -55,9 +55,9 @@ Value Interpreter::run(const ScopeNode& scope_node, ScopeType scope_type)
     return last_value;
 }
 
-void Interpreter::enter_scope(const ScopeNode& scope_node, ScopeType scope_type)
+void Interpreter::enter_scope(const ScopeNode& scope_node, HashMap<String, Value> scope_variables, ScopeType scope_type)
 {
-    m_scope_stack.append({ scope_type, scope_node, {} });
+    m_scope_stack.append({ scope_type, scope_node, move(scope_variables) });
 }
 
 void Interpreter::exit_scope(const ScopeNode& scope_node)

Libraries/LibJS/Interpreter.h

@@ -49,7 +49,7 @@ public:
     Interpreter();
     ~Interpreter();
 
-    Value run(const ScopeNode&, ScopeType = ScopeType::Block);
+    Value run(const ScopeNode&, HashMap<String, Value> scope_variables = {}, ScopeType = ScopeType::Block);
 
     Object& global_object() { return *m_global_object; }
     const Object& global_object() const { return *m_global_object; }
@@ -65,7 +65,7 @@ public:
     void collect_roots(Badge<Heap>, HashTable<Cell*>&);
 
 private:
-    void enter_scope(const ScopeNode&, ScopeType);
+    void enter_scope(const ScopeNode&, HashMap<String, Value> scope_variables, ScopeType);
     void exit_scope(const ScopeNode&);
 
     Heap m_heap;

Userland/js.cpp

@@ -71,4 +71,3 @@ int main(int argc, char** argv)
     interpreter.heap().collect_garbage();
     return 0;
 }
-