Fix #437 - add java.util.Optional support to empty operator

Includes TCK test.
Test validated with Tomcat's EL implementation.

spec/src/main/asciidoc/expression-language-spec-body.adoc

diff --git a/spec/src/main/asciidoc/expression-language-spec-body.adoc b/spec/src/main/asciidoc/expression-language-spec-body.adoc
index 6388ab5..2f0921c 100644
--- a/spec/src/main/asciidoc/expression-language-spec-body.adoc
+++ b/spec/src/main/asciidoc/expression-language-spec-body.adoc
@@ -1056,6 +1056,8 @@
 
 * Otherwise, if `A` is an empty `Collection`, return `true`
 
+* Otherwise, if `A` is an instance of `java.util.Optional` and `A.isEmpty()` returns `true`, return `true`
+
 * Otherwise return `false`
 
 === Conditional Operator - `A ? B : C`
@@ -3179,6 +3181,11 @@
   the import handler expects canonical class names where full class names are
   required.
 
+* https://github.com/jakartaee/expression-language/issues/437[#437]
+  Update the definition of the empty operator to include empty Optional
+  instances in the list of conditions that cause the empty operator to return
+  true.
+
 === Changes between 6.0 and 5.0
 
 * The EL API requires Java 17 as a minimum.

tck/src/main/java/com/sun/ts/tests/el/spec/emptyoperator/ELClientIT.java

diff --git a/tck/src/main/java/com/sun/ts/tests/el/spec/emptyoperator/ELClientIT.java b/tck/src/main/java/com/sun/ts/tests/el/spec/emptyoperator/ELClientIT.java
index b902a21..720ef44 100644
--- a/tck/src/main/java/com/sun/ts/tests/el/spec/emptyoperator/ELClientIT.java
+++ b/tck/src/main/java/com/sun/ts/tests/el/spec/emptyoperator/ELClientIT.java
@@ -22,6 +22,7 @@
 
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.Optional;
 
 import com.sun.ts.tests.el.common.util.ExprEval;
 import com.sun.ts.tests.el.common.util.NameValuePair;
@@ -174,6 +175,14 @@
     testCollection.clear();
   }
 
+  @Test
+  public void elEmptyOptionalTest() throws Exception {
+
+    this.testEmptyOperator(Optional.empty() , true);
+
+    this.testEmptyOperator(Optional.of("value"), false);
+  }
+
   // ---------------------------------------------------------- private methods
 
   // Test Empty operator.