Honor source encoding argument in String#encode

include/natalie/object.hpp

@@ -223,6 +223,7 @@ class Object : public Cell {
 
     ArrayObject *as_array_or_raise(Env *);
     ClassObject *as_class_or_raise(Env *);
+    EncodingObject *as_encoding_or_raise(Env *);
     ExceptionObject *as_exception_or_raise(Env *);
     FloatObject *as_float_or_raise(Env *);
     HashObject *as_hash_or_raise(Env *);

spec/core/string/encode_spec.rb

@@ -136,7 +136,7 @@
 
   describe "when passed to, from" do
     it "returns a copy in the destination encoding when both encodings are the same" do
-      NATFIXME 'honor source encoding', exception: Encoding::UndefinedConversionError, message: /from ASCII-8BIT to UTF-8/ do
+      NATFIXME 'same encoding for source and destination', exception: SpecFailedException, message: '#<Encoding:ASCII-8BIT> should be == to #<Encoding:UTF-8>' do
         str = "あ".dup.force_encoding("binary")
         encoded = str.encode("utf-8", "utf-8")
 
@@ -172,7 +172,7 @@
     end
 
     it "returns a copy in the destination encoding when both encodings are the same" do
-      NATFIXME 'honor source encoding', exception: Encoding::UndefinedConversionError, message: /from ASCII-8BIT to UTF-8/ do
+      NATFIXME 'same encoding for source and destination', exception: SpecFailedException, message: '#<Encoding:ASCII-8BIT> should be == to #<Encoding:UTF-8>' do
         str = "あ".dup.force_encoding("binary")
         encoded = str.encode("utf-8", "utf-8", invalid: :replace)
 

spec/core/string/shared/encode.rb

@@ -127,25 +127,21 @@
 
   describe "when passed to, from" do
     it "transcodes between the encodings ignoring the String encoding" do
-      NATFIXME 'honor source encoding', exception: SpecFailedException, message: /should be ==/ do
-        str = "あ"
-        result = [0xA6, 0xD0, 0x8F, 0xAB, 0xE4, 0x8F, 0xAB, 0xB1].pack('C8')
-        result.force_encoding Encoding::EUC_JP
-        str.send(@method, "euc-jp", "ibm437").should == result
-      end
+      str = "あ"
+      result = [0xA6, 0xD0, 0x8F, 0xAB, 0xE4, 0x8F, 0xAB, 0xB1].pack('C8')
+      result.force_encoding Encoding::EUC_JP
+      str.send(@method, "euc-jp", "ibm437").should == result
     end
 
     it "calls #to_str to convert the from object to an Encoding" do
-      NATFIXME 'honor source encoding', exception: SpecFailedException, message: /should be ==/ do
-        enc = mock("string encode encoding")
-        enc.should_receive(:to_str).and_return("ibm437")
+      enc = mock("string encode encoding")
+      enc.should_receive(:to_str).and_return("ibm437")
 
-        str = "あ"
-        result = [0xA6, 0xD0, 0x8F, 0xAB, 0xE4, 0x8F, 0xAB, 0xB1].pack('C8')
-        result.force_encoding Encoding::EUC_JP
+      str = "あ"
+      result = [0xA6, 0xD0, 0x8F, 0xAB, 0xE4, 0x8F, 0xAB, 0xB1].pack('C8')
+      result.force_encoding Encoding::EUC_JP
 
-        str.send(@method, "euc-jp", enc).should == result
-      end
+      str.send(@method, "euc-jp", enc).should == result
     end
   end
 
@@ -174,53 +170,43 @@
 
   describe "when passed to, from, options" do
     it "replaces undefined characters in the destination encoding" do
-      NATFIXME 'honor source encoding', exception: Encoding::UndefinedConversionError, message: /to UTF-8 in conversion from ASCII-8BIT to UTF-8 to EUC-JP/ do
-        str = "あ?あ".force_encoding Encoding::BINARY
-        result = str.send(@method, "euc-jp", "utf-8", undef: :replace)
-        xA4xA2 = [0xA4, 0xA2].pack('CC').force_encoding('utf-8')
-        result.should == "#{xA4xA2}?#{xA4xA2}".force_encoding("euc-jp")
-      end
+      str = "あ?あ".force_encoding Encoding::BINARY
+      result = str.send(@method, "euc-jp", "utf-8", undef: :replace)
+      xA4xA2 = [0xA4, 0xA2].pack('CC').force_encoding('utf-8')
+      result.should == "#{xA4xA2}?#{xA4xA2}".force_encoding("euc-jp")
     end
 
     it "replaces invalid characters in the destination encoding" do
-      NATFIXME 'honor source encoding', exception: Encoding::UndefinedConversionError, message: /to UTF-8 in conversion from ASCII-8BIT to UTF-8 to ISO-8859-1/ do
-        xFF = [0xFF].pack('C').force_encoding('utf-8')
-        str = "ab#{xFF}c".force_encoding Encoding::BINARY
-        str.send(@method, "iso-8859-1", "utf-8", invalid: :replace).should == "ab?c"
-      end
+      xFF = [0xFF].pack('C').force_encoding('utf-8')
+      str = "ab#{xFF}c".force_encoding Encoding::BINARY
+      str.send(@method, "iso-8859-1", "utf-8", invalid: :replace).should == "ab?c"
     end
 
     it "calls #to_str to convert the to object to an encoding" do
-      NATFIXME 'honor source encoding', exception: Encoding::UndefinedConversionError, message: /to UTF-8 in conversion from ASCII-8BIT to UTF-8 to ISO-8859-1/ do
-        to = mock("string encode to encoding")
-        to.should_receive(:to_str).and_return("iso-8859-1")
+      to = mock("string encode to encoding")
+      to.should_receive(:to_str).and_return("iso-8859-1")
 
-        xFF = [0xFF].pack('C').force_encoding('utf-8')
-        str = "ab#{xFF}c".force_encoding Encoding::BINARY
-        str.send(@method, to, "utf-8", invalid: :replace).should == "ab?c"
-      end
+      xFF = [0xFF].pack('C').force_encoding('utf-8')
+      str = "ab#{xFF}c".force_encoding Encoding::BINARY
+      str.send(@method, to, "utf-8", invalid: :replace).should == "ab?c"
     end
 
     it "calls #to_str to convert the from object to an encoding" do
-      NATFIXME 'honor source encoding', exception: Encoding::UndefinedConversionError, message: /to UTF-8 in conversion from ASCII-8BIT to UTF-8 to ISO-8859-1/ do
-        from = mock("string encode to encoding")
-        from.should_receive(:to_str).and_return("utf-8")
+      from = mock("string encode to encoding")
+      from.should_receive(:to_str).and_return("utf-8")
 
-        xFF = [0xFF].pack('C').force_encoding('utf-8')
-        str = "ab#{xFF}c".force_encoding Encoding::BINARY
-        str.send(@method, "iso-8859-1", from, invalid: :replace).should == "ab?c"
-      end
+      xFF = [0xFF].pack('C').force_encoding('utf-8')
+      str = "ab#{xFF}c".force_encoding Encoding::BINARY
+      str.send(@method, "iso-8859-1", from, invalid: :replace).should == "ab?c"
     end
 
     it "calls #to_hash to convert the options object" do
-      NATFIXME 'keyword splat should call to_hash?' do
-        options = mock("string encode options")
-        options.should_receive(:to_hash).and_return({ invalid: :replace })
+      options = mock("string encode options")
+      options.should_receive(:to_hash).and_return({ invalid: :replace })
 
-        xFF = [0xFF].pack('C').force_encoding('utf-8')
-        str = "ab#{xFF}c".force_encoding Encoding::BINARY
-        str.send(@method, "iso-8859-1", "utf-8", **options).should == "ab?c"
-      end
+      xFF = [0xFF].pack('C').force_encoding('utf-8')
+      str = "ab#{xFF}c".force_encoding Encoding::BINARY
+      str.send(@method, "iso-8859-1", "utf-8", **options).should == "ab?c"
     end
   end
 

src/object.cpp

@@ -547,6 +547,12 @@ ClassObject *Object::as_class_or_raise(Env *env) {
     return static_cast<ClassObject *>(this);
 }
 
+EncodingObject *Object::as_encoding_or_raise(Env *env) {
+    if (!is_encoding())
+        env->raise("TypeError", "{} can't be coerced into Encoding", m_klass->inspect_str());
+    return static_cast<EncodingObject *>(this);
+}
+
 ExceptionObject *Object::as_exception_or_raise(Env *env) {
     if (!is_exception())
         env->raise("TypeError", "{} can't be coerced into Exception", m_klass->inspect_str());

src/string_object.cpp

@@ -1137,6 +1137,9 @@ Value StringObject::encode_in_place(Env *env, Value dst_encoding, Value src_enco
     if (!dst_encoding)
         dst_encoding = EncodingObject::get(Encoding::UTF_8);
 
+    if (!src_encoding)
+        src_encoding = m_encoding;
+
     EncodeOptions options;
     if (kwargs) {
         if (kwargs->remove(env, "universal_newline"_s))
@@ -1172,9 +1175,9 @@ Value StringObject::encode_in_place(Env *env, Value dst_encoding, Value src_enco
     }
 
     env->ensure_no_extra_keywords(kwargs);
-    auto orig_encoding = m_encoding;
-    EncodingObject *encoding_obj = EncodingObject::find_encoding(env, dst_encoding);
-    return encoding_obj->encode(env, orig_encoding, this, options);
+    EncodingObject *dst_encoding_obj = EncodingObject::find_encoding(env, dst_encoding);
+    EncodingObject *src_encoding_obj = EncodingObject::find_encoding(env, src_encoding);
+    return dst_encoding_obj->encode(env, src_encoding_obj, this, options);
 }
 
 Value StringObject::force_encoding(Env *env, Value encoding) {