add trunc as rounding method (#583)

Author: Uzlopak

README.md

@@ -548,7 +548,7 @@ By default the library will handle automatically [BigInt](https://developer.mozi
 <a name="integer"></a>
 #### Integers
 The `type: integer` property will be truncated if a floating point is provided.
-You can customize this behaviour with the `rounding` option that will accept [`round`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round), [`ceil`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/ceil) or [`floor`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor):
+You can customize this behaviour with the `rounding` option that will accept [`round`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round), [`ceil`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/ceil), [`floor`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor) or [`trunc`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/trunc). Default is `trunc`:
 
 ```js
 const stringify = fastJson(schema, { rounding: 'ceil' })

index.js

@@ -14,6 +14,14 @@ const Location = require('./lib/location')
 
 let largeArraySize = 2e4
 let largeArrayMechanism = 'default'
+
+const validRoundingMethods = [
+  'floor',
+  'ceil',
+  'round',
+  'trunc'
+]
+
 const validLargeArrayMechanisms = [
   'default',
   'json-stringify'
@@ -93,7 +101,7 @@ function build (schema, options) {
   }
 
   if (options.rounding) {
-    if (!['floor', 'ceil', 'round'].includes(options.rounding)) {
+    if (!validRoundingMethods.includes(options.rounding)) {
       throw new Error(`Unsupported integer rounding method ${options.rounding}`)
     }
   }

lib/serializer.js

@@ -15,6 +15,7 @@ module.exports = class Serializer {
       case 'round':
         this.parseInteger = Math.round
         break
+      case 'trunc':
       default:
         this.parseInteger = Math.trunc
         break

test/integer.test.js

@@ -45,6 +45,14 @@ test('render a float as an integer', (t) => {
     { input: 42, output: '42' },
     { input: 1.99999, output: '1' },
     { input: -45.05, output: '-45' },
+    { input: Math.PI, output: '3', rounding: 'trunc' },
+    { input: 5.0, output: '5', rounding: 'trunc' },
+    { input: null, output: '0', rounding: 'trunc' },
+    { input: 0, output: '0', rounding: 'trunc' },
+    { input: 0.0, output: '0', rounding: 'trunc' },
+    { input: 42, output: '42', rounding: 'trunc' },
+    { input: 1.99999, output: '1', rounding: 'trunc' },
+    { input: -45.05, output: '-45', rounding: 'trunc' },
     { input: 0.95, output: '1', rounding: 'ceil' },
     { input: 0.2, output: '1', rounding: 'ceil' },
     { input: 45.95, output: '45', rounding: 'floor' },

types/index.d.ts

@@ -158,8 +158,10 @@ declare namespace build {
     ajv?: AjvOptions
     /**
      * Optionally configure how the integer will be rounded
+     * 
+     * @default 'trunc'
      */
-    rounding?: 'ceil' | 'floor' | 'round'
+    rounding?: 'ceil' | 'floor' | 'round' | 'trunc'
     /**
      * @deprecated 
      * Enable debug mode. Please use `mode: "debug"` instead

types/index.test-d.ts

@@ -13,6 +13,12 @@ const schema2: Schema = {
 build(schema1)(25)
 build(schema2)(-5)
 
+build(schema2, { rounding: 'ceil' })
+build(schema2, { rounding: 'floor' })
+build(schema2, { rounding: 'round' })
+build(schema2, { rounding: 'trunc' })
+expectError(build(schema2, { rounding: 'invalid' }))
+
 // String schema
 const schema3: Schema = {
     type: 'string'