fix(nitro): skip default error logging when evlog records the request

.changeset/nitro-no-duplicate-error-log.md

@@ -0,0 +1,5 @@
+---
+'evlog': patch
+---
+
+Stop Nitro and Nuxt from printing an error a second time when evlog already records it. In production, an unhandled error or a `fatal` one produced both the wide event and Nitro's `[request error] [unhandled]` block with its stack. evlog's error handler now skips Nitro's default logging whenever the request has a wide event. Nitro still logs the error when evlog is disabled, the route is excluded, or the plugin is not registered.

packages/evlog/src/nitro-v3/errorHandler.ts

@@ -6,6 +6,7 @@ import {
   buildPlainNitroErrorBody,
   isSensitiveNitroError,
   isExpectedEvlogError,
+  isRecordedByEvlog,
   serializeEvlogErrorResponse,
   shouldSerializeNitroErrorAsJson,
   shouldSuppressNitroDevOverlay,
@@ -49,7 +50,7 @@ export default defineErrorHandler(async (error, event, ctx: NitroErrorHandlerCon
 
   const suppressOverlay = shouldSuppressNitroDevOverlay()
 
-  if (!suppressOverlay && !isExpectedEvlogError(evlogError)) {
+  if (!suppressOverlay && !isExpectedEvlogError(evlogError) && !isRecordedByEvlog(event.req.context)) {
     await ctx.defaultHandler(error, event, { silent: false })
   }
 

packages/evlog/src/nitro.ts

@@ -124,6 +124,16 @@ export function isExpectedEvlogError(evlogError: Error | null): boolean {
   return evlogError !== null && extractErrorStatus(evlogError) < 500
 }
 
+/**
+ * Whether the evlog plugin records this request's error in its wide event, so
+ * Nitro's default `[request error]` log would print it a second time. False when
+ * evlog is disabled, the route is excluded, or the plugin is not registered.
+ * @internal
+ */
+export function isRecordedByEvlog(context: { _evlogShouldEmit?: unknown } | undefined): boolean {
+  return context?._evlogShouldEmit === true
+}
+
 /** Request metadata used to decide JSON vs framework error-page rendering. */
 export interface NitroErrorRequestContext {
   pathname: string

packages/evlog/src/nitro/errorHandler.ts

@@ -9,6 +9,7 @@ import {
   buildPlainNitroErrorBody,
   isSensitiveNitroError,
   isExpectedEvlogError,
+  isRecordedByEvlog,
   serializeEvlogErrorResponse,
   markH3ErrorHandled,
   shouldSerializeNitroErrorAsJson,
@@ -56,7 +57,7 @@ export default defineNitroErrorHandler(async (error, event, ctx) => {
 
   // Nitro v2 always passes `ctx`, but a missing context (e.g. the handler
   // invoked directly) must degrade to a flushed response, not a crash.
-  if (!suppressOverlay && !isExpectedEvlogError(evlogError) && ctx?.defaultHandler) {
+  if (!suppressOverlay && !isExpectedEvlogError(evlogError) && !isRecordedByEvlog(event.context) && ctx?.defaultHandler) {
     await ctx.defaultHandler(error, event, { silent: false })
   }
 

packages/evlog/test/nitro-v3/errorHandler.test.ts

@@ -281,6 +281,26 @@ describe('nitro-v3 errorHandler', () => {
 
       expect(defaultHandlerMock).toHaveBeenCalledWith(evlogError, mockEvent, { silent: false })
     })
+
+    it('skips Nitro default logging for any error the evlog plugin records', async () => {
+      vi.stubEnv('NODE_ENV', 'production')
+      const event = { ...mockEvent, req: { ...mockEvent.req, context: { _evlogShouldEmit: true } } }
+
+      await invokeErrorHandler(new TypeError('Cannot read properties of undefined'), event)
+      await invokeErrorHandler(Object.assign(new Error('Upstream unavailable'), { statusCode: 503, fatal: true }), event)
+
+      expect(defaultHandlerMock).not.toHaveBeenCalled()
+    })
+
+    it('keeps Nitro default logging when the route is excluded from evlog', async () => {
+      vi.stubEnv('NODE_ENV', 'production')
+      const event = { ...mockEvent, req: { ...mockEvent.req, context: { _evlogShouldEmit: false } } }
+      const error = new TypeError('Cannot read properties of undefined')
+
+      await invokeErrorHandler(error, event)
+
+      expect(defaultHandlerMock).toHaveBeenCalledWith(error, event, { silent: false })
+    })
   })
 
   describe('HTML page delegation (#390)', () => {

packages/evlog/test/nitro/errorHandler.test.ts

@@ -334,6 +334,26 @@ describe('errorHandler', () => {
 
       expect(defaultHandlerMock).toHaveBeenCalledWith(evlogError, mockEvent, { silent: false })
     })
+
+    it('skips Nitro default logging for any error the evlog plugin records', async () => {
+      vi.stubEnv('NODE_ENV', 'production')
+      const event = { ...mockEvent, context: { _evlogShouldEmit: true } } as typeof mockEvent
+
+      await testErrorHandler(new TypeError('Cannot read properties of undefined'), event, { defaultHandler: defaultHandlerMock })
+      await testErrorHandler(Object.assign(new Error('Upstream unavailable'), { statusCode: 503, fatal: true }), event, { defaultHandler: defaultHandlerMock })
+
+      expect(defaultHandlerMock).not.toHaveBeenCalled()
+    })
+
+    it('keeps Nitro default logging when the route is excluded from evlog', async () => {
+      vi.stubEnv('NODE_ENV', 'production')
+      const event = { ...mockEvent, context: { _evlogShouldEmit: false } } as typeof mockEvent
+      const error = new TypeError('Cannot read properties of undefined')
+
+      await testErrorHandler(error, event, { defaultHandler: defaultHandlerMock })
+
+      expect(defaultHandlerMock).toHaveBeenCalledWith(error, event, { silent: false })
+    })
   })
 
   describe('HTML page delegation (#390)', () => {