fix(inspect): eliminate panic inspecting event classes (#10979)

cli/tests/unit/event_test.ts

@@ -1,5 +1,10 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
-import { assert, assertEquals, unitTest } from "./test_util.ts";
+import {
+  assert,
+  assertEquals,
+  assertStringIncludes,
+  unitTest,
+} from "./test_util.ts";
 
 unitTest(function eventInitializedWithType(): void {
   const type = "click";
@@ -127,3 +132,30 @@ unitTest(function eventInspectOutput(): void {
     assertEquals(Deno.inspect(event), outputProvider(event));
   }
 });
+
+unitTest(function inspectEvent(): void {
+  // has a customInspect implementation that previously would throw on a getter
+  assertEquals(
+    Deno.inspect(Event.prototype),
+    `Event {
+  bubbles: [Getter/Setter],
+  cancelable: [Getter/Setter],
+  composed: [Getter/Setter],
+  currentTarget: [Getter/Setter],
+  defaultPrevented: [Getter/Setter],
+  eventPhase: [Getter/Setter],
+  srcElement: [Getter/Setter],
+  target: [Getter/Setter],
+  returnValue: [Getter/Setter],
+  timeStamp: [Getter/Setter],
+  type: [Getter/Setter]
+}`,
+  );
+
+  // ensure this still works
+  assertStringIncludes(
+    Deno.inspect(new Event("test")),
+    // check a substring because one property is a timestamp
+    `Event {\n  bubbles: false,\n  cancelable: false,`,
+  );
+});

extensions/web/02_event.js

@@ -144,7 +144,7 @@
     }
 
     [Symbol.for("Deno.customInspect")](inspect) {
-      return buildCustomInspectOutput(this, EVENT_PROPS, inspect);
+      return inspect(buildFilteredPropertyInspectObject(this, EVENT_PROPS));
     }
 
     get type() {
@@ -395,9 +395,41 @@
     }
   }
 
-  function buildCustomInspectOutput(object, keys, inspect) {
-    const inspectObject = Object.fromEntries(keys.map((k) => [k, object[k]]));
-    return `${object.constructor.name} ${inspect(inspectObject)}`;
+  function buildFilteredPropertyInspectObject(object, keys) {
+    // forward the subset of properties from `object` without evaluating
+    // as evaluation could lead to an error, which is better handled
+    // in the inspect code
+    return new Proxy({}, {
+      get(_target, key) {
+        if (key === Symbol.toStringTag) {
+          return object.constructor?.name;
+        } else if (keys.includes(key)) {
+          return Reflect.get(object, key);
+        } else {
+          return undefined;
+        }
+      },
+      getOwnPropertyDescriptor(_target, key) {
+        if (!keys.includes(key)) {
+          return undefined;
+        }
+
+        return Reflect.getOwnPropertyDescriptor(object, key) ??
+          (object.prototype &&
+            Reflect.getOwnPropertyDescriptor(object.prototype, key)) ??
+          {
+            configurable: true,
+            enumerable: true,
+            value: object[key],
+          };
+      },
+      has(_target, key) {
+        return keys.includes(key);
+      },
+      ownKeys() {
+        return keys;
+      },
+    });
   }
 
   function defineEnumerableProps(
@@ -1053,14 +1085,14 @@
     }
 
     [Symbol.for("Deno.customInspect")](inspect) {
-      return buildCustomInspectOutput(this, [
+      return inspect(buildFilteredPropertyInspectObject(this, [
         ...EVENT_PROPS,
         "message",
         "filename",
         "lineno",
         "colno",
         "error",
-      ], inspect);
+      ]));
     }
   }
 
@@ -1107,12 +1139,12 @@
     }
 
     [Symbol.for("Deno.customInspect")](inspect) {
-      return buildCustomInspectOutput(this, [
+      return inspect(buildFilteredPropertyInspectObject(this, [
         ...EVENT_PROPS,
         "wasClean",
         "code",
         "reason",
-      ], inspect);
+      ]));
     }
   }
 
@@ -1134,12 +1166,12 @@
     }
 
     [Symbol.for("Deno.customInspect")](inspect) {
-      return buildCustomInspectOutput(this, [
+      return inspect(buildFilteredPropertyInspectObject(this, [
         ...EVENT_PROPS,
         "data",
         "origin",
         "lastEventId",
-      ], inspect);
+      ]));
     }
   }
 
@@ -1164,10 +1196,10 @@
     }
 
     [Symbol.for("Deno.customInspect")](inspect) {
-      return buildCustomInspectOutput(this, [
+      return inspect(buildFilteredPropertyInspectObject(this, [
         ...EVENT_PROPS,
         "detail",
-      ], inspect);
+      ]));
     }
   }
 
@@ -1187,12 +1219,12 @@
     }
 
     [Symbol.for("Deno.customInspect")](inspect) {
-      return buildCustomInspectOutput(this, [
+      return inspect(buildFilteredPropertyInspectObject(this, [
         ...EVENT_PROPS,
         "lengthComputable",
         "loaded",
         "total",
-      ], inspect);
+      ]));
     }
   }