fix issue with incorrect matches for some surrogate chars (#1360)

Author: pjfanning

release-notes/CREDITS-2.x

@@ -456,3 +456,8 @@ Jared Stehler (@jaredstehler)
 Zhanghao (@zhangOranges)
  * Contributed #1305: Make helper methods of `WriterBasedJsonGenerator` non-final to allow overriding
   (2.18.0)
+
+Justin Gosselin (@jgosselin-accesso)
+ * Reported #1359: Non-surrogate characters being incorrectly combined when
+  `JsonWriteFeature.COMBINE_UNICODE_SURROGATES_IN_UTF8` is enabled
+  (2.18.2)

release-notes/VERSION-2.x

@@ -18,6 +18,10 @@ a pure JSON library.
 
 #1353: Use fastdoubleparser 1.0.90
  (fixed by @pjfanning)
+#1359: Non-surrogate characters being incorrectly combined when
+  `JsonWriteFeature.COMBINE_UNICODE_SURROGATES_IN_UTF8` is enabled
+ (reported by Justin G)
+ (fixed by @pjfanning)
 
 2.18.0 (26-Sep-2024)
 

src/main/java/com/fasterxml/jackson/core/json/UTF8JsonGenerator.java

@@ -1509,7 +1509,7 @@ private final void _writeStringSegment2(final char[] cbuf, int offset, final int
                 outputBuffer[outputPtr++] = (byte) (0x80 | (ch & 0x3f));
             } else {
                 // 3- or 4-byte character
-                if (_isSurrogateChar(ch)) {
+                if (_isStartOfSurrogatePair(ch)) {
                     final boolean combineSurrogates = Feature.COMBINE_UNICODE_SURROGATES_IN_UTF8.enabledIn(_features);
                     if (combineSurrogates && offset < end) {
                         char highSurrogate = (char) ch;
@@ -1557,7 +1557,7 @@ private final void _writeStringSegment2(final String text, int offset, final int
                 outputBuffer[outputPtr++] = (byte) (0x80 | (ch & 0x3f));
             } else {
                 // 3- or 4-byte character
-                if (_isSurrogateChar(ch)) {
+                if (_isStartOfSurrogatePair(ch)) {
                     final boolean combineSurrogates = Feature.COMBINE_UNICODE_SURROGATES_IN_UTF8.enabledIn(_features);
                     if (combineSurrogates && offset < end) {
                         char highSurrogate = (char) ch;
@@ -2247,8 +2247,9 @@ private byte[] getHexBytes() {
     }
 
     // @since 2.18
-    private boolean _isSurrogateChar(int ch) {
-        return (ch & 0xD800) == 0xD800;
+    private static boolean _isStartOfSurrogatePair(final int ch) {
+        // In 0xD800 - 0xDBFF range?
+        return (ch & 0xFC00) == 0xD800;
     }
 }
 

src/test/java/com/fasterxml/jackson/core/json/Surrogate223Test.java renamed to src/test/java/com/fasterxml/jackson/core/write/SurrogateWrite223Test.java

@@ -1,17 +1,19 @@
-package com.fasterxml.jackson.core.json;
+package com.fasterxml.jackson.core.write;
 
 import java.io.ByteArrayOutputStream;
 import java.io.StringWriter;
 import java.io.Writer;
 
 import com.fasterxml.jackson.core.*;
+import com.fasterxml.jackson.core.json.JsonWriteFeature;
 
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
-class Surrogate223Test extends JUnit5TestBase
+class SurrogateWrite223Test extends JUnit5TestBase
 {
     private final JsonFactory DEFAULT_JSON_F = newStreamFactory();
 
@@ -90,4 +92,35 @@ void surrogatesCharBacked() throws Exception
         assertToken(JsonToken.END_ARRAY, p.nextToken());
         p.close();
     }
+
+    //https://github.com/FasterXML/jackson-core/issues/1359
+    @Test
+    void checkNonSurrogates() throws Exception {
+        JsonFactory f = JsonFactory.builder()
+                .enable(JsonWriteFeature.COMBINE_UNICODE_SURROGATES_IN_UTF8)
+                .build();
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        try (JsonGenerator gen = f.createGenerator(out)) {
+            gen.writeStartObject();
+
+            // Inside the BMP, beyond surrogate block; 0xFF0C - full-width comma
+            gen.writeStringField("test_full_width", "foo" + new String(Character.toChars(0xFF0C)) + "bar");
+
+            // Inside the BMP, beyond surrogate block; 0xFE6A - small form percent
+            gen.writeStringField("test_small_form", "foo" + new String(Character.toChars(0xFE6A)) + "bar");
+
+            // Inside the BMP, before the surrogate block; 0x3042 - Hiragana A
+            gen.writeStringField("test_hiragana", "foo" + new String(Character.toChars(0x3042)) + "bar");
+
+            // Outside the BMP; 0x1F60A - emoji
+            gen.writeStringField("test_emoji", new String(Character.toChars(0x1F60A)));
+
+            gen.writeEndObject();
+        }
+        String json = out.toString("UTF-8");
+        assertTrue(json.contains("foo\uFF0Cbar"));
+        assertTrue(json.contains("foo\uFE6Abar"));
+        assertTrue(json.contains("foo\u3042bar"));
+        assertTrue(json.contains("\"test_emoji\":\"\uD83D\uDE0A\""));
+    }
 }