Merge pull request #3477 from rkilpadi/main

Improve error message for missing type parameter

.changeset/large-flies-check.md

@@ -0,0 +1,5 @@
+---
+"jspsych": patch
+---
+
+Add informative error message when a trial is missing the `type` parameter

packages/jspsych/src/timeline/Trial.spec.ts

@@ -36,6 +36,16 @@ describe("Trial", () => {
     return trial;
   };
 
+  it("throws an error upon construction when the `type` parameter or plugin info object is undefined", () => {
+    for (const description of [{}, { type: {} }] as TrialDescription[]) {
+      expect(
+        () => new Trial(dependencies, description, timeline)
+      ).toThrowErrorMatchingInlineSnapshot(
+        "\"Plugin not recognized. Please provide a valid plugin using the 'type' parameter.\""
+      );
+    }
+  });
+
   describe("run()", () => {
     it("instantiates the corresponding plugin", async () => {
       const trial = createTrial({ type: TestPlugin });

packages/jspsych/src/timeline/Trial.ts

@@ -35,7 +35,12 @@ export class Trial extends TimelineNode {
 
     this.trialObject = deepCopy(description);
     this.pluginClass = this.getParameterValue("type", { evaluateFunctions: false });
-    this.pluginInfo = this.pluginClass["info"];
+    this.pluginInfo = this.pluginClass?.["info"];
+    if (!this.pluginInfo) {
+      throw new Error(
+        "Plugin not recognized. Please provide a valid plugin using the 'type' parameter."
+      );
+    }
 
     if (!("version" in this.pluginInfo) && !("data" in this.pluginInfo)) {
       console.warn(