From 9992fca8814cb56588e694c72ea050e9875095c1 Mon Sep 17 00:00:00 2001
From: Bradley Meck Farias <bradley.meck@gmail.com>
Date: Sat, 11 Nov 2023 14:31:57 -0600
Subject: [PATCH] optimize enums with a single value

---
 benchmark/bench.js | 24 ++++++++++++++++++++++++
 index.js           | 29 +++++++++++++++++++++++++++++
 test/enum.test.js  | 17 +++++++++++++++++
 3 files changed, 70 insertions(+)

diff --git a/benchmark/bench.js b/benchmark/bench.js
index 12726184..bde02873 100644
--- a/benchmark/bench.js
+++ b/benchmark/bench.js
@@ -40,6 +40,30 @@ for (let i = 0; i < SHORT_ARRAY_SIZE; i++) {
 }
 
 const benchmarks = [
+  {
+    name: 'single enum string',
+    schema: {
+      type: 'string',
+      enum: ['hello world']
+    },
+    input: 'hello world'
+  },
+  {
+    name: 'const string',
+    schema: {
+      type: 'string',
+      const: 'hello world'
+    },
+    input: 'hello world'
+  },
+  {
+    name: 'const number',
+    schema: {
+      type: 'number',
+      const: 123
+    },
+    input: 123
+  },
   {
     name: 'short string',
     schema: {
diff --git a/index.js b/index.js
index 5958c934..e6d502a9 100644
--- a/index.js
+++ b/index.js
@@ -847,6 +847,33 @@ function buildConstSerializer (location, input) {
   return code
 }
 
+function buildSingleEnumSerializer (location, input) {
+  const schema = location.schema
+  const type = schema.type
+
+  const hasNullType = Array.isArray(type) && type.includes('null')
+
+  let code = ''
+
+  if (hasNullType) {
+    code += `
+      if (${input} === null) {
+        json += 'null'
+      } else {
+    `
+  }
+
+  code += `json += '${JSON.stringify(schema.enum[0]).replace(SINGLE_TICK, "\\'")}'`
+
+  if (hasNullType) {
+    code += `
+      }
+    `
+  }
+
+  return code
+}
+
 function buildValue (context, location, input) {
   let schema = location.schema
 
@@ -933,6 +960,8 @@ function buildValue (context, location, input) {
 
   if (schema.const !== undefined) {
     code += buildConstSerializer(location, input)
+  } else if (schema.enum && Array.isArray(schema.enum) && schema.enum.length === 1) {
+    code += buildSingleEnumSerializer(location, input)
   } else if (Array.isArray(type)) {
     code += buildMultiTypeSerializer(context, location, input)
   } else {
diff --git a/test/enum.test.js b/test/enum.test.js
index ab861686..1b543b92 100644
--- a/test/enum.test.js
+++ b/test/enum.test.js
@@ -3,6 +3,23 @@
 const test = require('tap').test
 const build = require('..')
 
+test('use enum with 1 value', (t) => {
+  t.plan(1)
+  const stringify = build({
+    title: 'Example Schema',
+    type: 'object',
+    properties: {
+      status: {
+        type: 'string',
+        enum: ['ok']
+      }
+    }
+  })
+
+  const obj = { status: 'ok' }
+  t.equal('{"status":"ok"}', stringify(obj))
+})
+
 test('use enum without type', (t) => {
   t.plan(1)
   const stringify = build({