Blockly.Extensions.buildTooltipForDropdown(..): Deferred validation. (#870)

Defer tooltip message string check until after load, when all Blockly.Msg should be loaded.
Avoids validation in headless mode, due to lack of document.readyState.

core/extensions.js

@@ -88,16 +88,23 @@ Blockly.Extensions.buildTooltipForDropdown = function(dropdownName, lookupTable)
   // List of block types already validated, to minimize duplicate warnings.
   var blockTypesChecked = [];
 
-  // Validate message strings early.
-  for (var key in lookupTable) {
-    Blockly.utils.checkMessageReferences(lookupTable[key]);
+  // Check the tooltip string messages for invalid references.
+  // Wait for load, in case Blockly.Msg is not yet populated.
+  // runAfterPageLoad() does not run in a Node.js environment due to lack of
+  // document object, in which case skip the validation.
+  if (document) { // Relies on document.readyState
+    Blockly.utils.runAfterPageLoad(function() {
+      for (var key in lookupTable) {
+        Blockly.utils.checkMessageReferences(lookupTable[key]);
+      }
+    });
   }
 
   /**
    * The actual extension.
    * @this {Blockly.Block}
    */
-  return function() {
+  var extensionFn = function() {
     var thisBlock = this;
 
     if (this.type && !blockTypesChecked.includes(this.type)) {
@@ -125,6 +132,7 @@ Blockly.Extensions.buildTooltipForDropdown = function(dropdownName, lookupTable)
       return tooltip;
     });
   };
+  return extensionFn;
 };
 
 /**

core/utils.js

@@ -834,3 +834,25 @@ Blockly.utils.insertAfter_ = function(newNode, refNode) {
     parentNode.appendChild(newNode);
   }
 };
+
+/**
+ * Calls a function after the page has loaded, possibly immediately.
+ * @param {function()} fn Function to run.
+ * @throws Error Will throw if no global document can be found (e.g., Node.js).
+ */
+Blockly.utils.runAfterPageLoad = function(fn) {
+  if (!document) {
+    throw new Error('Blockly.utils.runAfterPageLoad() requires browser document.');
+  }
+  if (document.readyState === 'complete') {
+    fn();  // Page has already loaded. Call immediately.
+  } else {
+    // Poll readyState.
+    var readyStateCheckInterval = setInterval(function() {
+      if (document.readyState === 'complete') {
+          clearInterval(readyStateCheckInterval);
+          fn();
+      }
+    }, 10);
+  }
+};