From 0e3fb39a0ab9a54d708e18bfc638fe3ec182e6d0 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Tue, 30 May 2023 09:48:23 +0330
Subject: [PATCH] LibWeb: Make 'optional BufferSource' IDL arguments actually
 optional

Previously this was compiled to require an object despite the IDL file
specifying 'optional'.
This commit makes IDLGenerator respect this modifier, and fixes the only
affected instance.
---
 .../LibWeb/BindingsGenerator/IDLGenerators.cpp  | 17 ++++++++++++++++-
 .../expected/TextDecoder/TextDecoder_decode.txt |  2 ++
 .../input/TextDecoder/TextDecoder_decode.html   | 12 ++++++++++++
 .../Libraries/LibWeb/Encoding/TextDecoder.cpp   |  7 +++++--
 .../Libraries/LibWeb/Encoding/TextDecoder.h     |  2 +-
 5 files changed, 36 insertions(+), 4 deletions(-)
 create mode 100644 Tests/LibWeb/Text/expected/TextDecoder/TextDecoder_decode.txt
 create mode 100644 Tests/LibWeb/Text/input/TextDecoder/TextDecoder_decode.html

diff --git a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
index 2b3db2a6054..b1e9c8b3433 100644
--- a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
@@ -644,13 +644,28 @@ static void generate_to_cpp(SourceGenerator& generator, ParameterType& parameter
 )~~~");
         }
     } else if (parameter.type->name() == "BufferSource") {
+        if (optional) {
+            scoped_generator.append(R"~~~(
+    Optional<JS::Handle<JS::Object>> @cpp_name@;
+    if (!@js_name@@js_suffix@.is_undefined()) {
+)~~~");
+        } else {
+            scoped_generator.append(R"~~~(
+    JS::Handle<JS::Object> @cpp_name@;
+)~~~");
+        }
         scoped_generator.append(R"~~~(
     if (!@js_name@@js_suffix@.is_object() || !(is<JS::TypedArrayBase>(@js_name@@js_suffix@.as_object()) || is<JS::ArrayBuffer>(@js_name@@js_suffix@.as_object()) || is<JS::DataView>(@js_name@@js_suffix@.as_object())))
         return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObjectOfType, "@parameter.type.name@");
 
     // TODO: Should we make this a Variant?
-    auto @cpp_name@ = JS::make_handle(&@js_name@@js_suffix@.as_object());
+    @cpp_name@ = JS::make_handle(&@js_name@@js_suffix@.as_object());
 )~~~");
+        if (optional) {
+            scoped_generator.append(R"~~~(
+        }
+)~~~");
+        }
     } else if (parameter.type->name() == "any") {
         if (variadic) {
             scoped_generator.append(R"~~~(
diff --git a/Tests/LibWeb/Text/expected/TextDecoder/TextDecoder_decode.txt b/Tests/LibWeb/Text/expected/TextDecoder/TextDecoder_decode.txt
new file mode 100644
index 00000000000..8fc16ea51f2
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/TextDecoder/TextDecoder_decode.txt
@@ -0,0 +1,2 @@
+[ABC]
+[]
diff --git a/Tests/LibWeb/Text/input/TextDecoder/TextDecoder_decode.html b/Tests/LibWeb/Text/input/TextDecoder/TextDecoder_decode.html
new file mode 100644
index 00000000000..4a2273770ce
--- /dev/null
+++ b/Tests/LibWeb/Text/input/TextDecoder/TextDecoder_decode.html
@@ -0,0 +1,12 @@
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        try {
+            let decoder = new TextDecoder("utf-8");
+            println(`[${decoder.decode(new Uint8Array([0x41, 0x42, 0x43]))}]`); // "ABC"
+            println(`[${decoder.decode()}]`);
+        } catch(e) {
+            println("ERROR: " + e.name + ": " + e.message);
+        }
+    });
+</script>
diff --git a/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp b/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
index d975b7f8b58..eb02aa78221 100644
--- a/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
+++ b/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
@@ -44,11 +44,14 @@ JS::ThrowCompletionOr<void> TextDecoder::initialize(JS::Realm& realm)
 }
 
 // https://encoding.spec.whatwg.org/#dom-textdecoder-decode
-WebIDL::ExceptionOr<DeprecatedString> TextDecoder::decode(JS::Handle<JS::Object> const& input) const
+WebIDL::ExceptionOr<DeprecatedString> TextDecoder::decode(Optional<JS::Handle<JS::Object>> const& input) const
 {
+    if (!input.has_value())
+        return TRY_OR_THROW_OOM(vm(), m_decoder.to_utf8({}));
+
     // FIXME: Implement the streaming stuff.
 
-    auto data_buffer_or_error = WebIDL::get_buffer_source_copy(*input.cell());
+    auto data_buffer_or_error = WebIDL::get_buffer_source_copy(*input->cell());
     if (data_buffer_or_error.is_error())
         return WebIDL::OperationError::create(realm(), "Failed to copy bytes from ArrayBuffer");
     auto& data_buffer = data_buffer_or_error.value();
diff --git a/Userland/Libraries/LibWeb/Encoding/TextDecoder.h b/Userland/Libraries/LibWeb/Encoding/TextDecoder.h
index 02210830ae7..e5e7c72f9ba 100644
--- a/Userland/Libraries/LibWeb/Encoding/TextDecoder.h
+++ b/Userland/Libraries/LibWeb/Encoding/TextDecoder.h
@@ -25,7 +25,7 @@ public:
 
     virtual ~TextDecoder() override;
 
-    WebIDL::ExceptionOr<DeprecatedString> decode(JS::Handle<JS::Object> const&) const;
+    WebIDL::ExceptionOr<DeprecatedString> decode(Optional<JS::Handle<JS::Object>> const&) const;
 
     DeprecatedFlyString const& encoding() const { return m_encoding; }
     bool fatal() const { return m_fatal; }