WW-5086 Fixes s:set tag with empty body

Author: lukaszlenart

core/src/main/java/org/apache/struts2/components/Set.java

@@ -31,8 +31,7 @@
  * complex expression and then simply reference that variable each time rather than the complex expression. This is
  * useful in both cases: when the complex expression takes time (performance improvement) or is hard to read (code
  * readability improvement).</p>
- * <p>If the tag is used with body content, the evaluation of the value parameter is omitted. Instead, the String to
- * which the body evaluates is set as value for the scoped variable.</p>
+ * <p>If the value parameter is omitted, the String to which the body evaluates is set as value for the scoped variable.</p>
  *
  * <p>The scopes available are as follows:</p>
  * <ul>
@@ -94,11 +93,7 @@ public boolean end(Writer writer, String body) {
 
         Object o;
         if (value == null) {
-            if (body != null && !body.equals("")) {
-                o = body;
-            } else {
-                o = findValue("top");
-            }
+            o = body;
         } else {
             o = findValue(value);
         }

core/src/test/java/org/apache/struts2/views/jsp/SetTagTest.java

@@ -121,6 +121,20 @@ public void testSetTrimBody() throws JspException, IOException {
         assertEquals(beginEndSpaceString, context.get("foo"));
     }
 
+    public void testEmptyBody() throws JspException {
+        StrutsMockBodyContent mockBodyContent;
+        String variableName = "foo";
+        tag.setName(variableName);
+        tag.setValue(null);
+        mockBodyContent = new StrutsMockBodyContent(new MockJspWriter());
+        String emptyBody = "";
+        mockBodyContent.setString(emptyBody);
+        tag.setBodyContent(mockBodyContent);
+        tag.doStartTag();
+        tag.doEndTag();
+        assertEquals(emptyBody, context.get(variableName));
+    }
+
     protected void setUp() throws Exception {
         super.setUp();