Bug 1548098 - Pull out exception handling into a dedicated _returnError method. r=remote-protocol-reviewers,ato

This will be used in the next changeset.

Differential Revision: https://phabricator.services.mozilla.com/D30263

--HG--
extra : moz-landing-system : lando

remote/domains/content/runtime/ExecutionContext.jsm

@@ -59,24 +59,37 @@ class ExecutionContext {
       };
     }
     if (rv.throw) {
-      if (this._debuggee.executeInGlobalWithBindings("e instanceof Error", {e: rv.throw}).return) {
-        return {
-          exceptionDetails: {
-            text: this._debuggee.executeInGlobalWithBindings("e.message", {e: rv.throw}).return,
-          },
-        };
-      }
-      return {
-        exceptionDetails: {
-          exception: this._createRemoteObject(rv.throw),
-        },
-      };
+      return this._returnError(rv.throw);
     }
     return {
       result: this._createRemoteObject(rv.return),
     };
   }
 
+  /**
+   * Given a Debugger.Object reference for an Exception, return a JSON object
+   * describing the exception by following CDP ExceptionDetails specification.
+   */
+  _returnError(exception) {
+    if (this._debuggee.executeInGlobalWithBindings("exception instanceof Error",
+      {exception}).return) {
+      const text = this._debuggee.executeInGlobalWithBindings("exception.message",
+        {exception}).return;
+      return {
+        exceptionDetails: {
+          text,
+        },
+      };
+    }
+
+    // If that isn't an Error, consider the exception as a JS value
+    return {
+      exceptionDetails: {
+        exception: this._toRemoteObject(exception),
+      },
+    };
+  }
+
   /**
    * Convert a given `Debugger.Object` to a JSON string.
    *