jruby · headius · Feb 10, 2026 · Feb 10, 2026 · Feb 10, 2026
diff --git a/core/src/main/java/org/jruby/RubyData.java b/core/src/main/java/org/jruby/RubyData.java
@@ -43,6 +43,7 @@
 import static org.jruby.runtime.ThreadContext.CALL_KEYWORD_EMPTY;
 import static org.jruby.runtime.ThreadContext.clearCallInfo;
 import static org.jruby.runtime.ThreadContext.hasKeywords;
+import static org.jruby.runtime.ThreadContext.hasNonemptyKeywords;
 import static org.jruby.runtime.ThreadContext.resetCallInfo;
 import static org.jruby.runtime.invokedynamic.MethodNames.HASH;
 import static org.jruby.util.RubyStringBuilder.str;
@@ -310,7 +311,7 @@ public static IRubyObject rbNew(ThreadContext context, IRubyObject self, IRubyOb
 
             RubyHash init;
             int callInfo = resetCallInfo(context);
-            if (hasKeywords(callInfo) && (callInfo & CALL_KEYWORD_EMPTY) == 0) {
+            if (hasNonemptyKeywords(callInfo)) {
                 if (!(hashOrElt instanceof RubyHash)) {
                     throw argumentError(context, 1, 0, 0);
                 }

diff --git a/core/src/main/java/org/jruby/RubyStruct.java b/core/src/main/java/org/jruby/RubyStruct.java
@@ -71,6 +71,7 @@
 import static org.jruby.runtime.Helpers.invokedynamic;
 import static org.jruby.runtime.ObjectAllocator.NOT_ALLOCATABLE_ALLOCATOR;
 import static org.jruby.runtime.ThreadContext.hasKeywords;
+import static org.jruby.runtime.ThreadContext.hasNonemptyKeywords;
 import static org.jruby.runtime.Visibility.PRIVATE;
 import static org.jruby.runtime.invokedynamic.MethodNames.HASH;
 import static org.jruby.RubyEnumerator.SizeFn;
@@ -531,7 +532,7 @@ public IRubyObject initialize(ThreadContext context) {
 
     @JRubyMethod(visibility = PRIVATE)
     public IRubyObject initialize(ThreadContext context, IRubyObject arg0) {
-        boolean keywords = hasKeywords(ThreadContext.resetCallInfo(context));
+        boolean keywords = hasNonemptyKeywords(ThreadContext.resetCallInfo(context));
 
         if (keywords) {
             return setupStructValuesFromHash(context, (RubyHash) arg0);

diff --git a/core/src/main/java/org/jruby/runtime/ThreadContext.java b/core/src/main/java/org/jruby/runtime/ThreadContext.java
@@ -1588,6 +1588,14 @@ public static boolean hasKeywords(int callInfo) {
         return (callInfo & CALL_KEYWORD) != 0;
     }
 
+    public static boolean hasNonemptyKeywords(int callInfo) {
+        return (callInfo & CALL_KEYWORD) != 0 && !keywordsEmpty(callInfo);
+    }
+
+    public static boolean keywordsEmpty(int callInfo) {
+        return (callInfo & CALL_KEYWORD_EMPTY) != 0;
+    }
+
     @Deprecated(since = "9.3.0.0")
     public IRubyObject setBackRef(IRubyObject match) {
         if (match.isNil()) return clearBackRef();

diff --git a/spec/ruby/core/data/fixtures/classes.rb b/spec/ruby/core/data/fixtures/classes.rb
@@ -1,13 +1,20 @@
 module DataSpecs
   if Data.respond_to?(:define)
     Measure = Data.define(:amount, :unit)
+    Single = Data.define(:value)
 
     class MeasureWithOverriddenName < Measure
       def self.name
         "A"
       end
     end
 
+    class SingleWithOverriddenName < Single
+      def self.name
+        "A"
+      end
+    end
+
     class DataSubclass < Data; end
 
     MeasureSubclass = Class.new(Measure) do

diff --git a/spec/ruby/core/data/initialize_spec.rb b/spec/ruby/core/data/initialize_spec.rb
@@ -37,6 +37,17 @@
     data.unit.should == "km"
   end
 
+  it "accepts positional arguments with empty keyword arguments" do
+    data = DataSpecs::Single.new(42, **{})
+
+    data.value.should == 42
+
+    data = DataSpecs::Measure.new(42, "km", **{})
+
+    data.amount.should == 42
+    data.unit.should == "km"
+  end
+
   it "raises ArgumentError if no arguments are given" do
     -> {
       DataSpecs::Measure.new
@@ -111,6 +122,17 @@ def initialize(*, **)
       ScratchPad.recorded.should == [:initialize, [], {amount: 42, unit: "m"}]
     end
 
+      it "accepts positional arguments with empty keyword arguments" do
+        data = DataSpecs::SingleWithOverriddenName.new(42, **{})
+
+        data.value.should == 42
+
+        data = DataSpecs::MeasureWithOverriddenName.new(42, "km", **{})
+
+        data.amount.should == 42
+        data.unit.should == "km"
+      end
+
     # See https://github.com/ruby/psych/pull/765
     it "can be deserialized by calling Data.instance_method(:initialize)" do
       d1 = DataSpecs::Area.new(width: 2, height: 3)

diff --git a/spec/ruby/core/struct/fixtures/classes.rb b/spec/ruby/core/struct/fixtures/classes.rb
@@ -3,6 +3,7 @@ module StructClasses
   class Apple < Struct; end
 
   Ruby = Struct.new(:version, :platform)
+  Single = Struct.new(:value)
 
   Car = Struct.new(:make, :model, :year)
 

diff --git a/spec/ruby/core/struct/initialize_spec.rb b/spec/ruby/core/struct/initialize_spec.rb
@@ -48,4 +48,15 @@
     positional_args.version.should == keyword_args.version
     positional_args.platform.should == keyword_args.platform
   end
+
+  it "accepts positional arguments with empty keyword arguments" do
+    data = StructClasses::Single.new(42, **{})
+
+    data.value.should == 42
+
+    data = StructClasses::Ruby.new("3.2", "OS", **{})
+
+    data.version.should == "3.2"
+    data.platform.should == "OS"
+  end
 end