fix: infer correct hook handler

package.json

@@ -14,10 +14,11 @@
     "coverage:ci": "c8 --reporter=lcov tap --coverage-report=html --no-browser --no-check-coverage",
     "coverage:ci-check-coverage": "c8 check-coverage --branches 100 --functions 100 --lines 100 --statements 100",
     "lint": "npm run lint:standard && npm run lint:typescript && npm run lint:markdown",
-    "lint:fix": "standard --fix",
+    "lint:fix": "standard --fix && npm run lint:typescript:fix",
     "lint:markdown": "markdownlint-cli2",
     "lint:standard": "standard | snazzy",
     "lint:typescript": "eslint -c types/.eslintrc.json types/**/*.d.ts test/types/**/*.test-d.ts",
+    "lint:typescript:fix": "npm run lint:typescript -- --fix",
     "prepublishOnly": "cross-env PREPUBLISH=true tap --no-check-coverage test/build/**.test.js && npm run test:validator:integrity",
     "test": "npm run lint && npm run unit && npm run test:typescript",
     "test:ci": "npm run unit -- --cov --coverage-report=lcovonly && npm run test:typescript",

test/types/hooks.test-d.ts

@@ -392,3 +392,16 @@ server.addHook('preClose', function (done) {
 server.addHook('preClose', async function () {
   expectType<FastifyInstance>(this)
 })
+
+expectError(server.addHook('onClose', async function (instance, done) {}))
+expectError(server.addHook('onError', async function (request, reply, error, done) {}))
+expectError(server.addHook('onReady', async function (done) {}))
+expectError(server.addHook('onRequest', async function (request, reply, done) {}))
+expectError(server.addHook('onRequestAbort', async function (request, done) {}))
+expectError(server.addHook('onResponse', async function (request, reply, done) {}))
+expectError(server.addHook('onSend', async function (request, reply, payload, done) {}))
+expectError(server.addHook('onTimeout', async function (request, reply, done) {}))
+expectError(server.addHook('preClose', async function (done) {}))
+expectError(server.addHook('preHandler', async function (request, reply, done) {}))
+expectError(server.addHook('preSerialization', async function (request, reply, payload, done) {}))
+expectError(server.addHook('preValidation', async function (request, reply, done) {}))

types/hooks.d.ts

@@ -190,7 +190,7 @@ interface DoneFuncWithErrOrRes {
  *  Note: the hook is NOT called if the payload is a string, a Buffer, a stream or null.
  */
 export interface preSerializationHookHandler<
-  PreSerializationPayload,
+  PreSerializationPayload = unknown,
   RawServer extends RawServerBase = RawServerDefault,
   RawRequest extends RawRequestDefaultExpression<RawServer> = RawRequestDefaultExpression<RawServer>,
   RawReply extends RawReplyDefaultExpression<RawServer> = RawReplyDefaultExpression<RawServer>,
@@ -210,7 +210,7 @@ export interface preSerializationHookHandler<
 }
 
 export interface preSerializationAsyncHookHandler<
-  PreSerializationPayload,
+  PreSerializationPayload = unknown,
   RawServer extends RawServerBase = RawServerDefault,
   RawRequest extends RawRequestDefaultExpression<RawServer> = RawRequestDefaultExpression<RawServer>,
   RawReply extends RawReplyDefaultExpression<RawServer> = RawReplyDefaultExpression<RawServer>,
@@ -233,7 +233,7 @@ export interface preSerializationAsyncHookHandler<
  * Note: If you change the payload, you may only change it to a string, a Buffer, a stream, or null.
  */
 export interface onSendHookHandler<
-  OnSendPayload,
+  OnSendPayload = unknown,
   RawServer extends RawServerBase = RawServerDefault,
   RawRequest extends RawRequestDefaultExpression<RawServer> = RawRequestDefaultExpression<RawServer>,
   RawReply extends RawReplyDefaultExpression<RawServer> = RawReplyDefaultExpression<RawServer>,
@@ -253,7 +253,7 @@ export interface onSendHookHandler<
 }
 
 export interface onSendAsyncHookHandler<
-  OnSendPayload,
+  OnSendPayload = unknown,
   RawServer extends RawServerBase = RawServerDefault,
   RawRequest extends RawRequestDefaultExpression<RawServer> = RawRequestDefaultExpression<RawServer>,
   RawReply extends RawReplyDefaultExpression<RawServer> = RawReplyDefaultExpression<RawServer>,
@@ -432,6 +432,66 @@ export interface onRequestAbortAsyncHookHandler<
   ): Promise<unknown>;
 }
 
+export type LifecycleHook = 'onRequest'
+| 'preParsing'
+| 'preValidation'
+| 'preHandler'
+| 'preSerialization'
+| 'onSend'
+| 'onResponse'
+| 'onRequest'
+| 'onError'
+| 'onTimeout'
+| 'onRequestAbort'
+
+export type LifecycleHookLookup<K extends LifecycleHook> = K extends 'onRequest'
+  ? onRequestHookHandler
+  : K extends 'preParsing'
+    ? preParsingHookHandler
+    : K extends 'preValidation'
+      ? preValidationHookHandler
+      : K extends 'preHandler'
+        ? preHandlerHookHandler
+        : K extends 'preSerialization'
+          ? preSerializationHookHandler
+          : K extends 'onSend'
+            ? onSendHookHandler
+            : K extends 'onResponse'
+              ? onResponseHookHandler
+              : K extends 'onRequest'
+                ? onRequestHookHandler
+                : K extends 'onError'
+                  ? onErrorHookHandler
+                  : K extends 'onTimeout'
+                    ? onTimeoutHookHandler
+                    : K extends 'onRequestAbort'
+                      ? onRequestAbortHookHandler
+                      : never
+
+export type LifecycleHookAsyncLookup<K extends LifecycleHook> = K extends 'onRequest'
+  ? onRequestAsyncHookHandler
+  : K extends 'preParsing'
+    ? preParsingAsyncHookHandler
+    : K extends 'preValidation'
+      ? preValidationAsyncHookHandler
+      : K extends 'preHandler'
+        ? preHandlerAsyncHookHandler
+        : K extends 'preSerialization'
+          ? preSerializationAsyncHookHandler
+          : K extends 'onSend'
+            ? onSendAsyncHookHandler
+            : K extends 'onResponse'
+              ? onResponseAsyncHookHandler
+              : K extends 'onRequest'
+                ? onRequestAsyncHookHandler
+                : K extends 'onError'
+                  ? onErrorAsyncHookHandler
+                  : K extends 'onTimeout'
+                    ? onTimeoutAsyncHookHandler
+                    : K extends 'onRequestAbort'
+                      ? onRequestAbortAsyncHookHandler
+                      : never
+
 // Application Hooks
 
 /**
@@ -555,3 +615,41 @@ export interface preCloseAsyncHookHandler<
     this: FastifyInstance<RawServer, RawRequest, RawReply, Logger, TypeProvider>,
   ): Promise<unknown>;
 }
+
+export type ApplicationHook = 'onRoute'
+| 'onRegister'
+| 'onReady'
+| 'onClose'
+| 'preClose'
+
+export type ApplicationHookLookup<K extends ApplicationHook> = K extends 'onRegister'
+  ? onRegisterHookHandler
+  : K extends 'onReady'
+    ? onReadyHookHandler
+    : K extends 'onClose'
+      ? onCloseHookHandler
+      : K extends 'preClose'
+        ? preCloseHookHandler
+        : never
+
+export type ApplicationHookAsyncLookup<K extends ApplicationHook> = K extends 'onRegister'
+  ? onRegisterHookHandler
+  : K extends 'onReady'
+    ? onReadyAsyncHookHandler
+    : K extends 'onClose'
+      ? onCloseAsyncHookHandler
+      : K extends 'preClose'
+        ? preCloseAsyncHookHandler
+        : never
+
+export type HookLookup <K extends ApplicationHook | LifecycleHook> = K extends ApplicationHook
+  ? ApplicationHookLookup<K>
+  : K extends LifecycleHook
+    ? LifecycleHookLookup<K>
+    : never
+
+export type HookAsyncLookup <K extends ApplicationHook | LifecycleHook> = K extends ApplicationHook
+  ? ApplicationHookAsyncLookup<K>
+  : K extends LifecycleHook
+    ? LifecycleHookAsyncLookup<K>
+    : never