Bug 1698554 - [devtools] Improve error logging when a request fails with a custom exception. r=nchevobbe

Like BrowsingContextTargetActor.detach which was throwing { error: wrongState }
and we were logging "(void 0)" because error.message was undefined,
while error was the thrown JS object.

Differential Revision: https://phabricator.services.mozilla.com/D107986

devtools/server/tests/browser/browser_actor_error.js

@@ -81,6 +81,14 @@ add_task(async function test_protocoljs_actor() {
         `\\(${TEST_ERRORS_ACTOR_URL}:\\d+:\\d+\\)`
     ).test(e.message);
   });
+  await Assert.rejects(testErrorsFront.throwsString(), e => {
+    return new RegExp(`ErrorString from: ${testErrorsFront.actorID}`).test(
+      e.message
+    );
+  });
+  await Assert.rejects(testErrorsFront.throwsObject(), e => {
+    return new RegExp(`foo from: ${testErrorsFront.actorID}`).test(e.message);
+  });
 
   await gClient.close();
 });

devtools/server/tests/browser/test-errors-actor.js

@@ -22,6 +22,14 @@ const testErrorsSpec = protocol.generateActorSpec({
       request: {},
       response: {},
     },
+    throwsString: {
+      request: {},
+      response: {},
+    },
+    throwsObject: {
+      request: {},
+      response: {},
+    },
   },
 });
 
@@ -31,17 +39,29 @@ const TestErrorsActor = protocol.ActorClassWithSpec(testErrorsSpec, {
     this.conn = conn;
   },
 
-  throwsComponentsException: async function() {
+  throwsComponentsException() {
     throw components.Exception("", Cr.NS_ERROR_NOT_IMPLEMENTED);
   },
 
-  throwsException: async function() {
+  throwsException() {
     return this.a.b.c;
   },
 
-  throwsJSError: async function() {
+  throwsJSError() {
     throw new Error("JSError");
   },
+
+  throwsString() {
+    // eslint-disable-next-line no-throw-literal
+    throw "ErrorString";
+  },
+
+  throwsObject() {
+    // eslint-disable-next-line no-throw-literal
+    throw {
+      error: "foo",
+    };
+  },
 });
 exports.TestErrorsActor = TestErrorsActor;
 

devtools/shared/protocol/Actor.js

@@ -94,10 +94,12 @@ class Actor extends Pool {
   writeError(error, typeName, method) {
     console.error(
       `Error while calling actor '${typeName}'s method '${method}'`,
-      error.message
+      error.message || error
     );
+    // Also log the error object as-is in order to log the server side stack
+    // nicely in the console, while the previous log will log the client side stack only.
     if (error.stack) {
-      console.error(error.stack);
+      console.error(error);
     }
 
     // Do not try to send the error if the actor is destroyed
@@ -110,7 +112,11 @@ class Actor extends Pool {
       from: this.actorID,
       // error.error -> errors created using the throwError() helper
       // error.name -> errors created using `new Error` or Components.exception
-      error: error.error || error.name || "unknownError",
+      // typeof(error)=="string" -> a method thrown like this `throw "a string"`
+      error:
+        error.error ||
+        error.name ||
+        (typeof error == "string" ? error : "unknownError"),
       message: error.message,
       // error.fileName -> regular Error instances
       // error.filename -> errors created using Components.exception