Kernel#sprintf: don't unconditionally grant encoding validity

The old code seems to grant strings with encoding validity when it does
not have enough information to make that call. Be defensive and claim we
don't know the code range instead.

Author: XrXr

spec/ruby/core/kernel/shared/sprintf.rb

@@ -865,6 +865,20 @@ def obj.to_str; end
     end
   end
 
+  describe "encoding" do
+    it "can produce a string with valid encoding" do
+      string = format("good day %{valid}", valid: "e")
+      string.encoding.should == Encoding::UTF_8
+      string.valid_encoding?.should be_true
+    end
+
+    it "can produce a string with invalid encoding" do
+      string = format("good day %{invalid}", invalid: "\x80")
+      string.encoding.should == Encoding::UTF_8
+      string.valid_encoding?.should be_false
+    end
+  end
+
   describe "faulty key" do
     before :all do
       @base_method = @method

src/main/java/org/truffleruby/core/format/FormatNode.java

@@ -12,11 +12,9 @@
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 
-import org.jcodings.specific.USASCIIEncoding;
 import org.truffleruby.core.array.ArrayUtils;
 import org.truffleruby.core.format.exceptions.TooFewArgumentsException;
 import org.truffleruby.core.rope.CodeRange;
-import org.truffleruby.core.rope.RopeOperations;
 import org.truffleruby.language.RubyBaseNode;
 
 import com.oracle.truffle.api.CompilerDirectives;
@@ -162,7 +160,6 @@ protected void writeByte(VirtualFrame frame, byte value) {
         final int outputPosition = getOutputPosition(frame);
         output[outputPosition] = value;
         setOutputPosition(frame, outputPosition + 1);
-        setStringCodeRange(frame, value >= 0 ? CodeRange.CR_7BIT : CodeRange.CR_VALID);
         increaseStringLength(frame, 1);
     }
 
@@ -175,9 +172,6 @@ protected void writeBytes(VirtualFrame frame, byte[] values, int valuesLength) {
         final int outputPosition = getOutputPosition(frame);
         System.arraycopy(values, 0, output, outputPosition, valuesLength);
         setOutputPosition(frame, outputPosition + valuesLength);
-        setStringCodeRange(
-                frame,
-                RopeOperations.isAsciiOnly(values, USASCIIEncoding.INSTANCE) ? CodeRange.CR_7BIT : CodeRange.CR_VALID);
         increaseStringLength(frame, valuesLength);
     }
 

src/main/java/org/truffleruby/core/format/FormatRootNode.java

@@ -52,7 +52,7 @@ public Object execute(VirtualFrame frame) {
         frame.setObject(FormatFrameDescriptor.OUTPUT_SLOT, new byte[expectedLength]);
         frame.setInt(FormatFrameDescriptor.OUTPUT_POSITION_SLOT, 0);
         frame.setInt(FormatFrameDescriptor.STRING_LENGTH_SLOT, 0);
-        frame.setInt(FormatFrameDescriptor.STRING_CODE_RANGE_SLOT, CodeRange.CR_7BIT.toInt());
+        frame.setInt(FormatFrameDescriptor.STRING_CODE_RANGE_SLOT, CodeRange.CR_UNKNOWN.toInt());
         frame.setBoolean(FormatFrameDescriptor.TAINT_SLOT, false);
         frame.setObject(FormatFrameDescriptor.ASSOCIATED_SLOT, null);