fix: add devmode warning for removing fragment markers

packages/marko/src/runtime/components/util-browser.js

@@ -170,6 +170,33 @@ function addComponentRootToKeyedElements(
   }
 }
 
+// eslint-disable-next-line no-constant-condition
+if ("MARKO_DEBUG") {
+  var warnNodeRemoved = function(event) {
+    var fragment = event.target.fragment;
+    if (fragment) {
+      var baseError = new Error(
+        "Fragment boundary marker removed.  This will cause an error when the fragment is updated."
+      );
+      fragment.___markersRemovedError = function(message) {
+        var error = new Error(message + " Boundary markers missing.");
+
+        baseError.stack = baseError.stack.replace(/.*warnNodeRemoved.*\n/, "");
+
+        // eslint-disable-next-line no-console
+        console.warn(baseError);
+        return error;
+      };
+    }
+  };
+  exports.___startDOMManipulationWarning = function() {
+    document.addEventListener("DOMNodeRemoved", warnNodeRemoved);
+  };
+  exports.___stopDOMManipulationWarning = function() {
+    document.removeEventListener("DOMNodeRemoved", warnNodeRemoved);
+  };
+}
+
 exports.___runtimeId = runtimeId;
 exports.___componentLookup = componentLookup;
 exports.___getComponentForEl = getComponentForEl;

packages/marko/src/runtime/components/util.js

@@ -69,3 +69,9 @@ exports.___isServer = true;
 exports.___attachBubblingEvent = attachBubblingEvent;
 exports.___destroyComponentForNode = function noop() {};
 exports.___destroyNodeRecursive = function noop() {};
+
+// eslint-disable-next-line no-constant-condition
+if ("MARKO_DEBUG") {
+  exports.___startDOMManipulationWarning = function noop() {};
+  exports.___stopDOMManipulationWarning = function noop() {};
+}

packages/marko/src/runtime/vdom/morphdom/fragment.js

@@ -22,6 +22,12 @@ var fragmentPrototype = {
     return this.endNode.nextSibling;
   },
   get nodes() {
+    // eslint-disable-next-line no-constant-condition
+    if ("MARKO_DEBUG") {
+      if (this.___markersRemovedError) {
+        throw this.___markersRemovedError("Cannot get fragment nodes.");
+      }
+    }
     var nodes = [];
     var current = this.startNode;
     while (current !== this.endNode) {

packages/marko/src/runtime/vdom/morphdom/index.js

@@ -670,6 +670,11 @@ function morphdom(fromNode, toNode, doc, componentsContext) {
     }
   } // END: morphEl(...)
 
+  // eslint-disable-next-line no-constant-condition
+  if ("MARKO_DEBUG") {
+    componentsUtil.___stopDOMManipulationWarning();
+  }
+
   morphChildren(fromNode, toNode, toNode.___component);
 
   detachedNodes.forEach(function(node) {
@@ -693,6 +698,11 @@ function morphdom(fromNode, toNode, doc, componentsContext) {
       }
     }
   });
+
+  // eslint-disable-next-line no-constant-condition
+  if ("MARKO_DEBUG") {
+    componentsUtil.___startDOMManipulationWarning();
+  }
 }
 
 module.exports = morphdom;