Harden Noswhere translation response handling and add failure diagnostics

src/translate/noswhere.js

@@ -7,7 +7,27 @@ module.exports = class NoswhereTranslator {
     constructor() {
         if (!this.#noswhereKey)
             throw new Error("expected NOSWHERE_KEY env var")
-        this.#loadTranslationLangs()
+        this.#loadTranslationLangs().catch((err) => {
+            console.error("error loading noswhere translation langs: %o", err)
+        })
+    }
+    #getRequestId(resp) {
+        return resp.headers?.get?.("x-noswhere-request") || "unknown"
+    }
+    #getBodySnippet(body) {
+        if (typeof body !== "string" || body.length === 0) return "<empty>"
+        if (body.length <= 500) return body
+        return body.slice(0, 500) + "...(truncated)"
+    }
+    async #parseResponse(resp, action) {
+        const requestId = this.#getRequestId(resp)
+        const body = await resp.text()
+        try {
+            return JSON.parse(body)
+        } catch (err) {
+            console.error("noswhere %s response parse error: status=%s ok=%s request=%s body=%o", action, resp.status, resp.ok, requestId, this.#getBodySnippet(body))
+            throw new Error(`error ${action}: invalid JSON response from Noswhere (request: ${requestId})`)
+        }
     }
     async #loadTranslationLangs() {
         let resp = await fetch(this.#noswhereURL + "/langs", {
@@ -18,9 +38,9 @@ module.exports = class NoswhereTranslator {
                 'Content-Type': 'application/json'
             }
         })
-        let data = await resp.json()
+        let data = await this.#parseResponse(resp, "getting translation langs")
         if (!resp.ok) {
-            throw new Error(`error getting translation langs: API failed with ${resp.status} ${data.error} (request: ${resp.headers.get("x-noswhere-request")})`)
+            throw new Error(`error getting translation langs: API failed with ${resp.status} ${data.error} (request: ${this.#getRequestId(resp)})`)
         }
         if (!data[this.#type]) {
             throw new Error(`type ${this.#type} not supported for translation`)
@@ -46,9 +66,9 @@ module.exports = class NoswhereTranslator {
             })
         })
 
-        let data = await resp.json()
+        let data = await this.#parseResponse(resp, "translating")
         if (!resp.ok) {
-            throw new Error(`error translating: API failed with ${resp.status} ${data.error} (request: ${resp.headers.get("x-noswhere-request")})`)
+            throw new Error(`error translating: API failed with ${resp.status} ${data.error} (request: ${this.#getRequestId(resp)})`)
         }
 
         if (data.result) {

test/noswhere.test.js

@@ -0,0 +1,91 @@
+const tap = require('tap');
+const sinon = require('sinon');
+
+const NOSWHERE_TRANSLATOR_PATH = require.resolve('../src/translate/noswhere.js');
+
+function loadNoswhereTranslator() {
+  delete require.cache[NOSWHERE_TRANSLATOR_PATH];
+  return require(NOSWHERE_TRANSLATOR_PATH);
+}
+
+function mockHeaders(requestId) {
+  return {
+    get: (name) => name === 'x-noswhere-request' ? requestId : null,
+  };
+}
+
+tap.test('NoswhereTranslator constructor logs malformed langs responses without crashing', async (t) => {
+  process.env.NOSWHERE_KEY = 'test-key';
+
+  const fetchStub = sinon.stub(global, 'fetch').resolves({
+    ok: true,
+    status: 200,
+    headers: mockHeaders('langs-req-1'),
+    text: async () => '',
+  });
+  const errorStub = sinon.stub(console, 'error');
+
+  t.teardown(() => {
+    fetchStub.restore();
+    errorStub.restore();
+    delete process.env.NOSWHERE_KEY;
+    delete require.cache[NOSWHERE_TRANSLATOR_PATH];
+  });
+
+  const NoswhereTranslator = loadNoswhereTranslator();
+  const translator = new NoswhereTranslator();
+
+  await new Promise((resolve) => setImmediate(resolve));
+
+  t.equal(translator.canTranslate('en', 'ja'), true, 'translator stays usable when langs cannot be loaded');
+  t.ok(errorStub.calledTwice, 'malformed response is logged without escaping the constructor');
+  t.match(errorStub.firstCall.args[0], /noswhere %s response parse error/, 'parse failure is logged');
+  t.match(errorStub.firstCall.args.slice(1).join(' '), /langs-req-1/, 'request id is included in log output');
+  t.match(errorStub.firstCall.args.slice(1).join(' '), /<empty>/, 'response body snippet is included in log output');
+  t.match(errorStub.secondCall.args[0], /error loading noswhere translation langs/, 'constructor catch logs the failure summary');
+});
+
+tap.test('NoswhereTranslator translate rejects malformed JSON responses with request details', async (t) => {
+  process.env.NOSWHERE_KEY = 'test-key';
+
+  const fetchStub = sinon.stub(global, 'fetch');
+  fetchStub.onFirstCall().resolves({
+    ok: true,
+    status: 200,
+    headers: mockHeaders('langs-req-2'),
+    text: async () => JSON.stringify({
+      default: {
+        from: ['en'],
+        to: ['ja'],
+      },
+    }),
+  });
+  fetchStub.onSecondCall().resolves({
+    ok: true,
+    status: 200,
+    headers: mockHeaders('translate-req-1'),
+    text: async () => '{"result"',
+  });
+  const errorStub = sinon.stub(console, 'error');
+
+  t.teardown(() => {
+    fetchStub.restore();
+    errorStub.restore();
+    delete process.env.NOSWHERE_KEY;
+    delete require.cache[NOSWHERE_TRANSLATOR_PATH];
+  });
+
+  const NoswhereTranslator = loadNoswhereTranslator();
+  const translator = new NoswhereTranslator();
+
+  await new Promise((resolve) => setImmediate(resolve));
+
+  await t.rejects(
+    translator.translate('en', 'ja', 'hello'),
+    /error translating: invalid JSON response from Noswhere \(request: translate-req-1\)/,
+    'translate surfaces a helpful parse error'
+  );
+  t.equal(errorStub.calledOnce, true, 'translate parse failures are logged');
+  t.match(errorStub.firstCall.args.slice(1).join(' '), /translate-req-1/, 'translate log includes request id');
+  t.match(errorStub.firstCall.args.slice(1).join(' '), /{"result"/, 'translate log includes body snippet');
+});