review: support old true value for access delegation mode

polaris-service/src/main/java/org/apache/polaris/service/catalog/AccessDelegationMode.java

@@ -21,6 +21,7 @@
 import com.google.common.base.Functions;
 import java.util.Arrays;
 import java.util.EnumSet;
+import java.util.Locale;
 import java.util.Map;
 import java.util.stream.Collectors;
 
@@ -49,6 +50,14 @@ public static EnumSet<AccessDelegationMode> fromProtocolValuesList(String protoc
       return EnumSet.noneOf(AccessDelegationMode.class);
     }
 
+    // Backward-compatibility case for old clients that still use the unofficial value of `true` to
+    // request credential vending. Note that if the client requests `true` among other values it
+    // will be parsed as `UNKNOWN` (by the code below this `if`) since the client submitting
+    // multiple access modes is expected to be aware of the Iceberg REST API spec.
+    if (protocolValues.trim().toLowerCase(Locale.ROOT).equals("true")) {
+      return EnumSet.of(VENDED_CREDENTIALS);
+    }
+
     EnumSet<AccessDelegationMode> set = EnumSet.noneOf(AccessDelegationMode.class);
     Arrays.stream(protocolValues.split(",")) // per Iceberg REST Catalog spec
         .map(String::trim)

polaris-service/src/test/java/org/apache/polaris/service/catalog/AccessDelegationModeTest.java

@@ -56,4 +56,11 @@ void testUnknown() {
     assertThat(fromProtocolValuesList("abc,remote-signing"))
         .isEqualTo(EnumSet.of(REMOTE_SIGNING, UNKNOWN));
   }
+
+  @Test
+  void testLegacy() {
+    assertThat(fromProtocolValuesList("true")).isEqualTo(EnumSet.of(VENDED_CREDENTIALS));
+    assertThat(fromProtocolValuesList("true, vended-credentials"))
+        .isEqualTo(EnumSet.of(UNKNOWN, VENDED_CREDENTIALS));
+  }
 }