Feat/preflight add logLevel option to silence CORS preflight logs

[gulbaki]

This PR introduces an optional logLevel field to FastifyCorsOptions, letting users override the Fastify logger level for the internal OPTIONS * pre-flight route.

• Adds logLevel to default options and TypeScript typings
• Applies level when registering the pre-flight route
• New unit test verifies OPTIONS logs are suppressed, GET logs remain
• README/types comments updated accordingly

fixes: #320

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[jean-michelet]

I’m not a user of logLevel, but based on the Fastify docs about it, it looks like logLevel, when passed in plugin options, applies to the entire plugin.

In your implementation, however, it only affects the OPTIONS route used for preflight requests.

Given that, a more appropriate name for this option might be preflightLogLevel or optionsRouteLogLevel.

[climba03003]

I’m not a user of logLevel, but based on the Fastify docs about it, it looks like logLevel, when passed in plugin options, applies to the entire plugin.

logLevel only works when the plugin is encapsulated. So, in this plugin the logLevel is ignored by the core and need to apply manually.

[climba03003]

The change below should be enough and there is no need on types change.
The core types already include the logLevel for you.

diff --git a/index.js b/index.js
index 94c1dd2..7ec92a2 100644
--- a/index.js
+++ b/index.js
@@ -46,6 +46,7 @@ function fastifyCors (fastify, opts, next) {
   fastify.decorateRequest('corsPreflightEnabled', false)

   let hideOptionsRoute = true
+  let logLevel
   if (typeof opts === 'function') {
     handleCorsOptionsDelegator(opts, fastify, { hook: defaultOptions.hook }, next)
   } else if (opts.delegator) {
@@ -53,6 +54,7 @@ function fastifyCors (fastify, opts, next) {
     handleCorsOptionsDelegator(delegator, fastify, options, next)
   } else {
     if (opts.hideOptionsRoute !== undefined) hideOptionsRoute = opts.hideOptionsRoute
+    if (opts.logLevel !== undefined) logLevel = opts.logLevel
     const corsOptions = normalizeCorsOptions(opts)
     validateHook(corsOptions.hook, next)
     if (hookWithPayload.indexOf(corsOptions.hook) !== -1) {
@@ -72,7 +74,7 @@ function fastifyCors (fastify, opts, next) {
   // remove most headers (such as the Authentication header).
   //
   // This route simply enables fastify to accept preflight requests.
-  fastify.options('*', { schema: { hide: hideOptionsRoute } }, (req, reply) => {
+  fastify.options('*', { schema: { hide: hideOptionsRoute }, logLevel }, (req, reply) => {
     if (!req.corsPreflightEnabled) {
       // Do not handle preflight requests if the origin option disabled CORS
       reply.callNotFound()

[gulbaki]

@climba03003
I think, if I put the if condition there as you said this code will not work
await app.register(cors, { delegator: () => ({ origin: '*' }), logLevel: 'silent' })

[climba03003]

@climba03003 I think, if I put the if condition there as you said this code will not work await app.register(cors, { delegator: () => ({ origin: '*' }), logLevel: 'silent' })

Same argument apply to hideOptionsRoute, just move those outside the else block.
I am also thinking should we allows, or even deprecate the function feature and use option only.

function delegator() {}
delegator.logLevel = 'info'
delegator.hideOptionsRoute = true

fastify.register(CORS, (instance) => delegator)

[gulbaki]

@climba03003 I think, if I put the if condition there as you said this code will not work await app.register(cors, { delegator: () => ({ origin: '*' }), logLevel: 'silent' })

Same argument apply to hideOptionsRoute, just move those outside the else block. I am also thinking should we allows, or even deprecate the function feature and use option only.

function delegator() {}
delegator.logLevel = 'info'
delegator.hideOptionsRoute = true

fastify.register(CORS, (instance) => delegator)

I have refactored the code as you suggested (logLevel, hideOptionsRoute). I also added tests that cover delegator usage for both.
However, regarding the part:
I am also thinking should we allow, or even deprecate the function feature and use option only.
If there's anything I should do about this, please let me know . I’d be happy to take care of it.

[mcollina]

lgtm

[climba03003]

Should be the last change before land.