fix: Always make sure we put valid utf8-encoded strings into attribut…

…e values (#661)

app/src/main/java/io/appium/uiautomator2/utils/XMLHelpers.java

@@ -18,6 +18,7 @@
 
 import androidx.annotation.Nullable;
 
+import java.nio.charset.StandardCharsets;
 import java.util.regex.Pattern;
 
 public abstract class XMLHelpers {
@@ -50,7 +51,18 @@ public static String toNodeName(String str) {
     @Nullable
     public static String toSafeString(@Nullable Object source, String replacement) {
         return source == null ? null : XML10_PATTERN
-                .matcher(String.valueOf(source))
+                .matcher(toSafeUtf8String(String.valueOf(source)))
                 .replaceAll(replacement);
     }
+
+    @Nullable
+    public static String toSafeUtf8String(@Nullable String source) {
+        if (source == null) {
+            return null;
+        }
+
+        // This method always replaces malformed-input and unmappable-character sequences
+        // with this charset's default replacement byte array.
+        return new String(source.getBytes(StandardCharsets.UTF_8), StandardCharsets.UTF_8);
+    }
 }

app/src/test/java/io/appium/uiautomator2/utils/XMLHelpersTests.java

@@ -34,6 +34,8 @@
 
 import static org.junit.Assert.assertEquals;
 
+import static io.appium.uiautomator2.utils.XMLHelpers.toSafeString;
+
 import android.os.SystemClock;
 
 import java.io.ByteArrayInputStream;
@@ -238,6 +240,12 @@ private static List<Element> findNodesUsingXpath1(String xml, String xpathSelect
         }
     }
 
+    @Test
+    public void createsSafeXmlString() {
+        String text = toSafeString("°C\u000b", "?");
+        assertEquals(text, "°C?");
+    }
+
     @Test
     public void parsesComplexXpath1() {
         String query = "(//android.widget.TextView[@text='some, text']/following::android.widget.ImageButton)[1]";