WW-5782 fix(tags): document and warn that s:a href ignores nested params

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

@@ -38,15 +38,16 @@
  * <!-- START SNIPPET: javadoc -->
  * <p>
  * A tag that creates a HTML &lt;a &gt;.This tag supports the same attributes as the "url" tag,
- * including nested parameters using the "param" tag.
+ * including nested parameters using the "param" tag. Nested parameters are applied only when the URL is built
+ * from the "value" or "action" attributes; they are ignored when "href" is set.
  * </p>
  * <!-- END SNIPPET: javadoc -->
  *
  * <p><b>Examples</b></p>
  *
  * <pre>
  * <!-- START SNIPPET: example1 -->
- * &lt;s:a id="link1" href="/do-it.action"&gt;
+ * &lt;s:a id="link1" value="/do-it.action"&gt;
  *     &lt;img border="none" src="&lt;%=request.getContextPath()%&gt;/images/delete.gif"/&gt;
  *     &lt;s:param name="id" value="1"/&gt;
  * &lt;/s:a&gt;
@@ -101,6 +102,10 @@ protected void evaluateExtraParams() {
 
         if (href != null) {
             addParameter("href", ensureAttributeSafelyNotEscaped(findString(href)));
+            if (devMode && !urlParameters.isEmpty()) {
+                LOG.warn("Nested params {} are ignored because <s:a> has href [{}], use value or action to build a URL with params",
+                        urlParameters.keySet(), href);
+            }
         } else {
             //no href, build it from URL attributes
             StringWriter sw = new StringWriter();
@@ -189,7 +194,7 @@ public UrlProvider getUrlProvider() {
         return urlProvider;
     }
 
-    @StrutsTagAttribute(description = "The URL.")
+    @StrutsTagAttribute(description = "The URL. Nested param tags are not applied, use value or action to build a URL with params")
     public void setHref(String href) {
         this.href = href;
     }

core/src/site/resources/tags/a-attributes.html

@@ -123,7 +123,7 @@
         <td class="tag-attribute"></td>
         <td class="tag-attribute">false</td>
         <td class="tag-attribute">String</td>
-        <td class="tag-attribute">The URL.</td>
+        <td class="tag-attribute">The URL. Nested param tags are not applied, use value or action to build a URL with params</td>
     </tr>
     <tr>
         <td class="tag-attribute">id</td>

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

@@ -18,6 +18,8 @@
  */
 package org.apache.struts2.views.jsp;
 
+import org.apache.struts2.components.Anchor;
+import org.apache.struts2.test.LogCapture;
 import org.apache.struts2.views.jsp.ui.AnchorTag;
 import org.apache.struts2.views.jsp.ui.StrutsBodyContent;
 
@@ -1646,4 +1648,52 @@ protected void setUp() throws Exception {
         pageContext.setJspWriter(jspWriter);
     }
 
+    public void testHrefIgnoresNestedParams() throws Exception {
+        tag.setHref("/do-it.action");
+
+        try (LogCapture logs = new LogCapture(Anchor.class)) {
+            renderWithParam("id", "%{'1'}");
+
+            assertEquals(wrapWithAnchor("/do-it.action"), writer.toString());
+            assertTrue(logs.messages().toString(), logs.messages().isEmpty());
+        }
+    }
+
+    public void testHrefWithNestedParamsWarnsInDevMode() throws Exception {
+        setDevMode(true);
+        tag.setHref("/do-it.action");
+
+        try (LogCapture logs = new LogCapture(Anchor.class)) {
+            renderWithParam("id", "%{'1'}");
+
+            assertEquals(wrapWithAnchor("/do-it.action"), writer.toString());
+            assertEquals(1, logs.messages().size());
+            assertTrue(logs.messages().get(0), logs.messages().get(0).contains("[id]"));
+        }
+    }
+
+    public void testValueWithNestedParamsDoesNotWarnInDevMode() throws Exception {
+        setDevMode(true);
+        tag.setValue("/do-it.action");
+
+        try (LogCapture logs = new LogCapture(Anchor.class)) {
+            renderWithParam("id", "%{'1'}");
+
+            assertEquals(wrapWithAnchor("/do-it.action?id=1"), writer.toString());
+            assertTrue(logs.messages().toString(), logs.messages().isEmpty());
+        }
+    }
+
+    private void renderWithParam(String name, String value) throws JspException {
+        ParamTag param = new ParamTag();
+        param.setPageContext(pageContext);
+        param.setName(name);
+        param.setValue(value);
+
+        tag.doStartTag();
+        param.doStartTag();
+        param.doEndTag();
+        tag.doEndTag();
+    }
+
 }