add float truncation (#278)

* add float truncation

* reduce string concatenation

* add rounding option

* add types

Author: Eomm

README.md

@@ -40,6 +40,7 @@ fast-json-stringify obj x 13,537,123 ops/sec ±0.19% (95 runs sampled)
  - <a href="#anyof">`AnyOf`</a>
  - <a href="#ref">`Reuse - $ref`</a>
  - <a href="#long">`Long integers`</a>
+ - <a href="#integer">`Integers`</a>
  - <a href="#nullable">`Nullable`</a>
 - <a href="#security">`Security Notice`</a>
 - <a href="#acknowledgements">`Acknowledgements`</a>
@@ -533,6 +534,16 @@ const obj = {
 console.log(stringify(obj)) // '{"id":18446744073709551615}'
 ```
 
+<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):
+
+```js
+const stringify = fastJson(schema, { rounding: 'ceil' })
+```
+
+
 <a name="nullable"></a>
 #### Nullable
 

index.d.ts

@@ -145,6 +145,10 @@ declare namespace build {
      * Configure Ajv, which is used to evaluate conditional schemas and combined (anyOf) schemas
      */
     ajv?: AjvOptions
+    /**
+     * Optionally configure how the integer will be rounded
+     */
+    rounding?: 'ceil' | 'floor' | 'round'
   }
 }
 

index.js

@@ -54,6 +54,15 @@ function build (schema, options) {
     }
   }
 
+  var intParseFunctionName = 'trunc'
+  if (options.rounding) {
+    if (['floor', 'ceil', 'round'].includes(options.rounding)) {
+      intParseFunctionName = options.rounding
+    } else {
+      throw new Error(`Unsupported integer rounding method ${options.rounding}`)
+    }
+  }
+
   /* eslint no-new-func: "off" */
   let code = `
     'use strict'
@@ -69,23 +78,16 @@ function build (schema, options) {
     ${$asTime.toString()}
     ${$asNumber.toString()}
     ${$asNumberNullable.toString()}
+    ${$asInteger.toString()}
     ${$asIntegerNullable.toString()}
     ${$asNull.toString()}
     ${$asBoolean.toString()}
     ${$asBooleanNullable.toString()}
-  `
 
-  // only handle longs if the module is used
-  if (isLong) {
-    code += `
-      var isLong = ${isLong.toString()}
-      ${$asInteger.toString()}
-    `
-  } else {
-    code += `
-      var $asInteger = $asNumber
+    var isLong = ${isLong ? isLong.toString() : false}
+
+    function parseInteger(int) { return Math.${intParseFunctionName}(int) }
     `
-  }
 
   let location = {
     schema,
@@ -226,7 +228,8 @@ const stringSerializerMap = {
 }
 
 function getStringSerializer (format) {
-  return stringSerializerMap[format] || '$asString'
+  return stringSerializerMap[format] ||
+  '$asString'
 }
 
 function $pad2Zeros (num) {
@@ -243,8 +246,12 @@ function $asInteger (i) {
     return i.toString()
   } else if (typeof i === 'bigint') {
     return i.toString()
-  } else {
+  } else if (Number.isInteger(i)) {
     return $asNumber(i)
+  } else {
+    // if the output is NaN the type is coerced to int 0
+    /* eslint no-undef: "off" */
+    return $asNumber(parseInteger(i) || 0)
   }
 }
 

test/integer.test.js

@@ -23,6 +23,51 @@ test('render an integer as JSON', (t) => {
   t.ok(validate(JSON.parse(output)), 'valid schema')
 })
 
+test('render a float as an integer', (t) => {
+  t.plan(2)
+  try {
+    build({
+      title: 'float as integer',
+      type: 'integer'
+    }, { rounding: 'foobar' })
+  } catch (error) {
+    t.ok(error)
+    t.equals(error.message, 'Unsupported integer rounding method foobar')
+  }
+})
+
+test('render a float as an integer', (t) => {
+  const cases = [
+    { input: Math.PI, output: '3' },
+    { input: 5.0, output: '5' },
+    { input: 1.99999, output: '1' },
+    { input: -45.05, output: '-45' },
+    { input: 0.95, output: '1', rounding: 'ceil' },
+    { input: 0.2, output: '1', rounding: 'ceil' },
+    { input: 45.95, output: '45', rounding: 'floor' },
+    { input: -45.05, output: '-46', rounding: 'floor' },
+    { input: 45.44, output: '45', rounding: 'round' },
+    { input: 45.95, output: '46', rounding: 'round' }
+  ]
+
+  t.plan(cases.length * 2)
+  cases.forEach(checkInteger)
+
+  function checkInteger ({ input, output, rounding }) {
+    const schema = {
+      title: 'float as integer',
+      type: 'integer'
+    }
+
+    const validate = validator(schema)
+    const stringify = build(schema, { rounding })
+    const str = stringify(input)
+
+    t.equal(str, output)
+    t.ok(validate(JSON.parse(str)), 'valid schema')
+  }
+})
+
 test('render an object with an integer as JSON', (t) => {
   t.plan(2)
 

test/types/test.ts

@@ -66,6 +66,7 @@ const schema9: Schema = {
 
 build(schema8)({})
 build(schema9)({ foo: 'bar' })
+build(schema9, { rounding: 'floor' })({ foo: 'bar' })
 
 // Reference schemas
 const schema10: Schema = {