From 07942550cda0e9c122c7b58f421b560bda3a11c1 Mon Sep 17 00:00:00 2001
From: ydah <t.yudai92@gmail.com>
Date: Tue, 6 Oct 2026 20:53:07 +0900
Subject: [PATCH] Reject non-ASCII BINARY strings during JSON generation

---
 ext/json/ext/generator/generator.c   | 17 +---------------
 java/src/json/ext/StringEncoder.java | 21 ++------------------
 test/json/json_generator_test.rb     | 29 +++++++++++++++-------------
 3 files changed, 19 insertions(+), 48 deletions(-)

diff --git a/ext/json/ext/generator/generator.c b/ext/json/ext/generator/generator.c
index fbef1980..45f95fb9 100644
--- a/ext/json/ext/generator/generator.c
+++ b/ext/json/ext/generator/generator.c
@@ -75,7 +75,7 @@ static void generate_json_bignum(FBuffer *buffer, struct generate_json_data *dat
 static void generate_json_float(FBuffer *buffer, struct generate_json_data *data, VALUE obj);
 static void generate_json_fragment(FBuffer *buffer, struct generate_json_data *data, VALUE obj);
 
-static int usascii_encindex, utf8_encindex, binary_encindex;
+static int usascii_encindex, utf8_encindex;
 
 NORETURN(static void) raise_generator_error_str(VALUE invalid_object, VALUE str)
 {
@@ -865,20 +865,6 @@ NOINLINE(static) VALUE convert_invalid_encoding(struct generate_json_data *data,
         }
     }
 
-    if (RB_ENCODING_GET_INLINED(str) == binary_encindex) {
-        VALUE utf8_string = rb_enc_associate_index(rb_str_dup(str), utf8_encindex);
-        switch (rb_enc_str_coderange(utf8_string)) {
-            case ENC_CODERANGE_7BIT:
-                return utf8_string;
-            case ENC_CODERANGE_VALID:
-                // For historical reason, we silently reinterpret binary strings as UTF-8 if it would work.
-                // TODO: Raise in 3.0.0
-                rb_warn("JSON.generate: UTF-8 string passed as BINARY, this will raise an encoding error in json 3.0");
-                return utf8_string;
-                break;
-        }
-    }
-
     return rb_rescue(encode_json_string_try, str, encode_json_string_rescue, str);
 }
 
@@ -2140,7 +2126,6 @@ void Init_generator(void)
 
     usascii_encindex = rb_usascii_encindex();
     utf8_encindex = rb_utf8_encindex();
-    binary_encindex = rb_ascii8bit_encindex();
 
     rb_require("json/ext/generator/state");
 
diff --git a/java/src/json/ext/StringEncoder.java b/java/src/json/ext/StringEncoder.java
index e059fc99..347635ca 100644
--- a/java/src/json/ext/StringEncoder.java
+++ b/java/src/json/ext/StringEncoder.java
@@ -13,7 +13,6 @@
 import java.nio.charset.StandardCharsets;
 
 import org.jcodings.Encoding;
-import org.jcodings.specific.ASCIIEncoding;
 import org.jcodings.specific.USASCIIEncoding;
 import org.jcodings.specific.UTF8Encoding;
 import org.jruby.Ruby;
@@ -229,28 +228,12 @@ static RubyString ensureValidEncoding(ThreadContext context, RubyString str) {
             return str;
         }
 
-        return tryWeirdEncodings(context, str, encoding);
+        return tryWeirdEncodings(context, str);
     }
 
-    private static RubyString tryWeirdEncodings(ThreadContext context, RubyString str, Encoding encoding) {
+    private static RubyString tryWeirdEncodings(ThreadContext context, RubyString str) {
         Ruby runtime = context.runtime;
 
-        RubyString utf8String;
-
-        if (encoding == ASCIIEncoding.INSTANCE) {
-            utf8String = str.strDup(runtime);
-            utf8String.setEncoding(UTF8Encoding.INSTANCE);
-            switch (utf8String.getCodeRange()) {
-                case StringSupport.CR_7BIT:
-                    return utf8String;
-                case StringSupport.CR_VALID:
-                    // For historical reason, we silently reinterpret binary strings as UTF-8 if it would work.
-                    // TODO: Raise in 3.0.0
-                    runtime.getWarnings().warn("JSON.generate: UTF-8 string passed as BINARY, this will raise an encoding error in json 3.0");
-                    return utf8String;
-            }
-        }
-
         try {
             str = (RubyString) str.encode(context, runtime.getEncodingService().convertEncodingToRubyEncoding(UTF8Encoding.INSTANCE));
         } catch (RaiseException re) {
diff --git a/test/json/json_generator_test.rb b/test/json/json_generator_test.rb
index 2fbe3f9f..80f761e7 100755
--- a/test/json/json_generator_test.rb
+++ b/test/json/json_generator_test.rb
@@ -1049,22 +1049,25 @@ def to_s
     end
   end
 
-  if defined?(JSON::Ext::Generator) and RUBY_PLATFORM != "java"
-    def test_valid_utf8_in_different_encoding
-      utf8_string = "€™"
-      wrong_encoding_string = utf8_string.b
-      # This behavior is historical. Not necessary desirable. We should deprecated it.
-      # The pure and java version of the gem already don't behave this way.
-      assert_warning(/UTF-8 string passed as BINARY, this will raise an encoding error in json 3.0/) do
-        assert_equal utf8_string.to_json, wrong_encoding_string.to_json
-      end
-
-      assert_warning(/UTF-8 string passed as BINARY, this will raise an encoding error in json 3.0/) do
-        assert_equal JSON.dump(utf8_string), JSON.dump(wrong_encoding_string)
-      end
+  def test_valid_utf8_in_binary_encoding
+    string = "€™".b.freeze
+    assert_raise(JSON::GeneratorError) { string.to_json }
+    assert_raise(JSON::GeneratorError) { JSON.dump(string) }
+    [string, [string], { string => 1 }, { value: string }].each do |object|
+      error = assert_raise(JSON::GeneratorError) { JSON.generate(object) }
+      assert_same string, error.invalid_object
+      assert_kind_of Encoding::UndefinedConversionError, error.cause
     end
   end
 
+  def test_ascii_in_binary_encoding
+    string = "ascii".b
+    assert_equal '"ascii"', string.to_json
+    assert_equal '"ascii"', JSON.dump(string)
+    assert_equal '["ascii"]', JSON.generate([string])
+    assert_equal '{"ascii":1}', JSON.generate(string => 1)
+  end
+
   def test_nonutf8_encoding
     assert_equal("\"5\u{b0}\"", "5\xb0".dup.force_encoding(Encoding::ISO_8859_1).to_json)
   end