Backporting LTS 2.541.2 (#26220)

Author: krisstern

core/src/main/java/hudson/model/Computer.java

@@ -1503,7 +1503,9 @@ public void doConfigSubmit(StaplerRequest2 req, StaplerResponse2 rsp) throws IOE
             throw new FormException(Messages.Slave_InvalidConfig_Executors(nodeName), "numExecutors");
         }
 
+        OfflineCause offlineCause = node.getTemporaryOfflineCause();
         Node result = node.reconfigure(req, req.getSubmittedForm());
+        result.setTemporaryOfflineCause(offlineCause);
         Jenkins.get().getNodesObject().replaceNode(this.getNode(), result);
 
         if (result.getNodeProperty(DiskSpaceMonitorNodeProperty.class) != null) {

test/src/test/java/hudson/model/ComputerTest.java

@@ -160,6 +160,18 @@ void computerIconDependsOnOfflineCause() throws Exception {
         assertThat(computer.getIcon(), equalTo(cause.getComputerIcon()));
     }
 
+    @Test
+    @Issue("#26146")
+    void computerTemporaryOfflineCauseStaysOnConfigRound() throws Exception {
+        var agent = j.createSlave();
+        var computer = agent.toComputer();
+        var offlineCause = new OfflineCause.UserCause(User.getOrCreateByIdOrFullName("username"), "Initial cause");
+        computer.setTemporaryOfflineCause(offlineCause);
+        j.configRoundtrip(agent);
+        agent = (DumbSlave) j.jenkins.getNode(agent.getNodeName());
+        assertThat(agent.getTemporaryOfflineCause(), equalTo(offlineCause));
+    }
+
     @Test
     @LocalData
     void removeUserDetailsFromOfflineCause() throws Exception {

war/src/main/webapp/scripts/hudson-behavior.js

@@ -1683,47 +1683,66 @@ function rowvgStartEachRow(recursive, f) {
         return;
       }
 
-      var subForms = [];
-      var start = findInFollowingTR(e, "dropdownList-container");
+      function buildSubForms(e) {
+        var subForms = [];
+        var start = findInFollowingTR(e, "dropdownList-container");
 
-      do {
-        start = start.firstElementChild;
-      } while (start && !isTR(start));
+        do {
+          start = start.firstElementChild;
+        } while (start && !isTR(start));
 
-      if (start && !start.classList.contains("dropdownList-start")) {
-        start = findFollowingTR(start, "dropdownList-start");
-      }
-      while (start != null) {
-        subForms.push(start);
-        start = findFollowingTR(start, "dropdownList-start");
+        if (start && !start.classList.contains("dropdownList-start")) {
+          start = findFollowingTR(start, "dropdownList-start");
+        }
+        while (start != null) {
+          subForms.push(start);
+          start = findFollowingTR(start, "dropdownList-start");
+        }
+        return subForms;
       }
 
+      var subForms = buildSubForms(e);
       // control visibility
       function updateDropDownList() {
         for (var i = 0; i < subForms.length; i++) {
           var show = e.selectedIndex == i;
           var f = subForms[i];
 
           if (show) {
-            renderOnDemand(f.nextElementSibling);
+            const idx = i; // capture the index so that it is not mutated in the loop
+            renderOnDemand(f.nextElementSibling, function () {
+              const current = e.selectedIndex == idx;
+              if (!current) {
+                console.warn(
+                  "renderOnDemandCallback: selection is no longer valid, rebuilding correct DOM",
+                );
+                // our form div has changed (but the index is stable) so go and re-get the new domtree
+                const subForm = buildSubForms(e)[idx];
+                updateDropDownFormRowVisibility(subForm, false);
+              }
+            });
           }
-          f.rowVisibilityGroup.makeInnerVisible(show);
-
-          // TODO: this is actually incorrect in the general case if nested vg uses field-disabled
-          // so far dropdownList doesn't create such a situation.
-          f.rowVisibilityGroup.eachRow(
-            true,
-            show
-              ? function (e) {
-                  e.removeAttribute("field-disabled");
-                }
-              : function (e) {
-                  e.setAttribute("field-disabled", "true");
-                },
-          );
+          updateDropDownFormRowVisibility(f, show);
         }
       }
 
+      function updateDropDownFormRowVisibility(f, show) {
+        f.rowVisibilityGroup.makeInnerVisible(show);
+
+        // TODO: this is actually incorrect in the general case if nested vg uses field-disabled
+        // so far dropdownList doesn't create such a situation.
+        f.rowVisibilityGroup.eachRow(
+          true,
+          show
+            ? function (e) {
+                e.removeAttribute("field-disabled");
+              }
+            : function (e) {
+                e.setAttribute("field-disabled", "true");
+              },
+        );
+      }
+
       e.onchange = updateDropDownList;
 
       updateDropDownList();