fix(independent-project): throw IllegalArgumentException on failed UR…

…L decoding

Previously, URLUtils.decode threw a RuntimeException when encountering invalid percent-encoded values.

Now, it throws an IllegalArgumentException, ensuring that malformed input is correctly recognized as a client error.

Test coverage added for:
- Invalid percent encoding (e.g., %zz, %2)
- Gray-area invalid UTF-8 cases (e.g., %80)
- Properly encoded values (e.g., %20, form-encoded +, Japanese characters)

Fixes quarkusio#46197

independent-projects/resteasy-reactive/common/runtime/src/main/java/org/jboss/resteasy/reactive/common/util/URLUtils.java

@@ -217,8 +217,8 @@ public static String decode(String s, Charset enc, boolean decodeSlash, boolean
         return s;
     }
 
-    private static RuntimeException failedToDecodeURL(String s, Charset enc, Throwable o) {
-        return new RuntimeException("Failed to decode URL " + s + " to " + enc, o);
+    private static IllegalArgumentException failedToDecodeURL(String s, Charset enc, Throwable o) {
+        return new IllegalArgumentException("Failed to decode URL " + s + " to " + enc, o);
     }
 
     private static byte[] expandBytes(byte[] bytes) {

independent-projects/resteasy-reactive/common/runtime/src/test/java/org/jboss/resteasy/reactive/common/util/URLUtilsTest.java

@@ -0,0 +1,50 @@
+package org.jboss.resteasy.reactive.common.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.nio.charset.StandardCharsets;
+
+import org.junit.jupiter.api.Test;
+
+class URLUtilsTest {
+    @Test
+    void decodeInvalidPercentEncoding() {
+        String incomplete = "invalid%2";
+        String invalidHex = "invalid%zz";
+
+        assertThrows(IllegalArgumentException.class,
+                () -> URLUtils.decode(incomplete, StandardCharsets.UTF_8, true, new StringBuilder()));
+        assertThrows(IllegalArgumentException.class,
+                () -> URLUtils.decode(invalidHex, StandardCharsets.UTF_8, true, new StringBuilder()));
+    }
+
+    @Test
+    void decodeGrayAreaInvalidUtf8() {
+        String invalidUtf8 = "invalid%80";
+
+        // This is a gray area: %80 is not valid in UTF-8 as a standalone byte,
+        // but Java's default decoding behavior does not throw an exception.
+        // Instead, it replaces it with a special character (�).
+        //
+        // To enforce strict decoding, CharsetDecoder with CodingErrorAction.REPORT
+        // should be used inside URLUtils.decode.
+        String decoded = URLUtils.decode(invalidUtf8, StandardCharsets.UTF_8, true, new StringBuilder());
+
+        assertEquals("invalid�", decoded); // Note: This may vary depending on the JVM.
+    }
+
+    @Test
+    void decodeValidValues() {
+        String path = "test%20path";
+        String formEncoded = "test+path";
+        String japanese = "%E3%83%86%E3%82%B9%E3%83%88"; // テスト
+
+        assertEquals("test path",
+                URLUtils.decode(path, StandardCharsets.UTF_8, true, new StringBuilder()));
+        assertEquals("test path",
+                URLUtils.decode(formEncoded, StandardCharsets.UTF_8, true, true, new StringBuilder()));
+        assertEquals("テスト",
+                URLUtils.decode(japanese, StandardCharsets.UTF_8, true, new StringBuilder()));
+    }
+}