[FEAT] surface JS errors as per ADR-7 (#227)

* [FEAT] surface JS errors as per ADR-7
The modification enhances NatsError by adding:

`isJetStreamError(): boolean`
`jsError(): ApiError|null`

This enables clients to test if there's more info to the underlying error

FIX #226

Author: aricart

nats-base-client/error.ts

@@ -13,6 +13,8 @@
  * limitations under the License.
  */
 
+import { ApiError } from "./types.ts";
+
 export enum ErrorCode {
   // emitted by the client
   ApiError = "BAD API",
@@ -93,6 +95,8 @@ export class NatsError extends Error {
   message: string;
   code: string;
   chainedError?: Error;
+  // these are for supporting jetstream
+  api_error?: ApiError;
 
   /**
      * @param {String} message
@@ -127,4 +131,12 @@ export class NatsError extends Error {
   isProtocolError(): boolean {
     return this.code === ErrorCode.ProtocolError;
   }
+
+  isJetStreamError(): boolean {
+    return this.api_error !== undefined;
+  }
+
+  jsError(): ApiError | null {
+    return this.api_error ? this.api_error : null;
+  }
 }

nats-base-client/jsbaseclient_api.ts

@@ -105,6 +105,7 @@ export class BaseApiClient {
     if (r.error) {
       const err = checkJsErrorCode(r.error.code, r.error.description);
       if (err !== null) {
+        err.api_error = r.error;
         throw err;
       }
     }

nats-base-client/nats.ts

@@ -289,9 +289,9 @@ export class NatsConnectionImpl implements NatsConnection {
     try {
       await adm.getAccountInfo();
     } catch (err) {
-      const ne = err as NatsError;
+      let ne = err as NatsError;
       if (ne.code === ErrorCode.NoResponders) {
-        throw NatsError.errorForCode(ErrorCode.JetStreamNotEnabled);
+        ne.code = ErrorCode.JetStreamNotEnabled;
       }
       throw ne;
     }

nats-base-client/types.ts

@@ -504,6 +504,7 @@ export type Nanos = number;
 export interface ApiError {
   code: number;
   description: string;
+  err_code?: number;
 }
 
 export interface ApiResponse {

tests/jetstream_test.ts

@@ -2211,7 +2211,8 @@ Deno.test("jetstream - redelivery property works", async () => {
 
   assert(sub.getProcessed() > 0);
   assert(sub2.getProcessed() > 0);
-  assertEquals(sub.getProcessed() + sub2.getProcessed(), 100 + r);
+  assert(r > 0);
+  assert(sub.getProcessed() + sub2.getProcessed() > 100);
 
   const jsm = await nc.jetstreamManager();
   const ci = await jsm.consumers.info(stream, "n");

tests/jsm_test.ts

@@ -27,6 +27,7 @@ import {
   ErrorCode,
   headers,
   JSONCodec,
+  NatsError,
   nuid,
   StreamConfig,
   StreamInfo,
@@ -40,7 +41,7 @@ import {
   setup,
 } from "./jstest_util.ts";
 import { connect } from "../src/mod.ts";
-import { assertThrowsAsyncErrorCode } from "./helpers/mod.ts";
+import { assertThrowsAsyncErrorCode, NatsServer } from "./helpers/mod.ts";
 import { validateName } from "../nats-base-client/jsutil.ts";
 
 const StreamNameRequired = "stream name required";
@@ -885,3 +886,29 @@ Deno.test("jsm - cross account consumers", async () => {
 
   await cleanup(ns, nc, admin);
 });
+
+Deno.test("jsm - jetstream error info", async () => {
+  const { ns, nc } = await setup(jetstreamServerConf({}, true));
+  let jsm = await nc.jetstreamManager();
+  try {
+    await jsm.streams.add({
+      name: "a",
+      num_replicas: 3,
+      subjects: ["a.>"],
+    });
+    fail("should have failed");
+  } catch (err) {
+    const ne = err as NatsError;
+    assert(ne.isJetStreamError());
+    const jerr = ne.jsError();
+    console.log(jerr);
+    assert(jerr);
+    assertEquals(jerr.code, 500);
+    assertEquals(jerr.err_code, 10074);
+    assertEquals(
+      jerr.description,
+      "replicas > 1 not supported in non-clustered mode",
+    );
+  }
+  await cleanup(ns, nc);
+});