[java] Make JsonInput.hasNext() idempotent between elements

hasNext() consumed the comma between elements but did not clear the
'container has element' flag, so a second hasNext() before reading the
next value threw as if the comma were missing. Iterator-style callers
that probe multiple times per element saw spurious failures on valid
input like [1,2].

Author: shs96c

java/src/org/openqa/selenium/json/JsonInput.java

@@ -364,6 +364,9 @@ public boolean hasNext() {
         throw new JsonException("Unexpected ',' before first element of container. " + input);
       }
       input.read();
+      // We've moved past the separator, so we're once again expecting an element rather than
+      // another comma. Clear the flag so a repeat hasNext() before reading is a no-op.
+      clearSeenElement();
       skipWhitespace(input);
       JsonType afterComma = peek();
       // Trailing comma leniency: '[1,]' and '{"a":1,}' are accepted.
@@ -608,6 +611,13 @@ private void markElementRead() {
     }
   }
 
+  private void clearSeenElement() {
+    if (!containerHasElement.isEmpty()) {
+      containerHasElement.removeFirst();
+      containerHasElement.addFirst(false);
+    }
+  }
+
   /**
    * Read the next element from the JSON input stream, converting with the supplied mapper if it's
    * the expected string.

java/test/org/openqa/selenium/json/JsonInputTest.java

@@ -429,6 +429,39 @@ void shouldRejectLeadingCommaInArray() {
     }
   }
 
+  @Test
+  void hasNextIsIdempotentBetweenElementsInArray() {
+    // Iterator-style probing (peek/hasNext repeatedly before reading) must not falsely fail
+    // once hasNext() has already consumed the comma before the next element.
+    try (JsonInput input = newInput("[1,2]")) {
+      input.beginArray();
+      assertThat(input.hasNext()).isTrue();
+      assertThat(input.nextNumber()).isEqualTo(1L);
+      assertThat(input.hasNext()).isTrue();
+      assertThat(input.hasNext()).isTrue();
+      assertThat(input.nextNumber()).isEqualTo(2L);
+      assertThat(input.hasNext()).isFalse();
+      assertThat(input.hasNext()).isFalse();
+      input.endArray();
+    }
+  }
+
+  @Test
+  void hasNextIsIdempotentBetweenEntriesInObject() {
+    try (JsonInput input = newInput("{\"a\":1,\"b\":2}")) {
+      input.beginObject();
+      assertThat(input.hasNext()).isTrue();
+      assertThat(input.nextName()).isEqualTo("a");
+      assertThat(input.nextNumber()).isEqualTo(1L);
+      assertThat(input.hasNext()).isTrue();
+      assertThat(input.hasNext()).isTrue();
+      assertThat(input.nextName()).isEqualTo("b");
+      assertThat(input.nextNumber()).isEqualTo(2L);
+      assertThat(input.hasNext()).isFalse();
+      input.endObject();
+    }
+  }
+
   @Test
   void nullInputsShouldCoerceAsNullValues() throws IOException {
     try (InputStream is = new ByteArrayInputStream(new byte[0]);