perf: cache layout access check (#414)

index.js

@@ -645,13 +645,23 @@ async function fastifyView (fastify, opts) {
   }
 
   function hasAccessToLayoutFile (fileName, ext) {
+    const layoutKey = `layout-${fileName}-${ext}`
+    let result = fastify[viewCache].get(layoutKey)
+
+    if (typeof result === 'boolean') {
+      return result
+    }
+
     try {
       accessSync(join(templatesDir, getPage(fileName, ext)))
-
-      return true
+      result = true
     } catch (e) {
-      return false
+      result = false
     }
+
+    fastify[viewCache].set(layoutKey, result)
+
+    return result
   }
 }
 

test/test-handlebars.js

@@ -331,7 +331,7 @@ test('fastify.view with handlebars engine with layout option on render', t => {
 })
 
 test('fastify.view with handlebars engine with invalid layout option on render should throw', t => {
-  t.plan(3)
+  t.plan(5)
 
   const fastify = Fastify()
   const handlebars = require('handlebars')
@@ -349,6 +349,11 @@ test('fastify.view with handlebars engine with invalid layout option on render s
       t.ok(err instanceof Error)
       t.equal(err.message, 'unable to access template "./templates/invalid-layout.hbs"')
     })
+    // repeated for test coverage of layout access check lru
+    fastify.view('./templates/index-for-layout.hbs', data, { layout: './templates/invalid-layout.hbs' }, (err, compiled) => {
+      t.ok(err instanceof Error)
+      t.equal(err.message, 'unable to access template "./templates/invalid-layout.hbs"')
+    })
   })
 })