feat: inline validators in standalone output

Author: RelevantShannon

README.md

@@ -128,6 +128,7 @@ const stringify = fastJson(mySchema, {
 - `schema`: external schemas references by $ref property. [More details](#ref)
 - `ajv`: [ajv v8 instance's settings](https://ajv.js.org/options.html) for those properties that require `ajv`. [More details](#anyof)
 - `rounding`: setup how the `integer` types will be rounded when not integers. [More details](#integer)
+- `inlineValidators`: when using standalone mode, embed Ajv-generated validator functions in the output instead of compiling schemas at runtime. [More details](#standalone)
 - `largeArrayMechanism`: set the mechanism that should be used to handle large
 (by default `20000` or more items) arrays. [More details](#largearrays)
 - `compileValidators`: when `true`, the `ajv` validators used by `anyOf`, `oneOf` and
@@ -728,13 +729,21 @@ const code = fastJson({
       type: 'string'
     }
   }
-}, { mode: 'standalone' })
+}, { mode: 'standalone', inlineValidators: true })
 
 fs.writeFileSync('stringify.js', code)
 const stringify = require('stringify.js')
 console.log(stringify({ firstName: 'Foo', surname: 'bar' })) // '{"firstName":"Foo"}'
 ```
 
+Set `inlineValidators` to `true` to include the Ajv-generated functions used by
+`anyOf`, `oneOf`, and `if/then/else` in the same output file. This avoids
+rebuilding an Ajv instance and compiling their schemas at runtime. The
+generated module still requires `fast-json-stringify` for its serializer and
+may require Ajv runtime helpers used by the generated validation code. Custom
+Ajv formats used by these schemas must support Ajv's standalone code
+generation.
+
 <a name="acknowledgments"></a>
 ## Acknowledgments
 

index.js

@@ -256,7 +256,10 @@ function build (schema, options) {
   }
 
   const serializer = new Serializer(options)
-  const validator = new Validator(options.ajv)
+  const validator = new Validator(
+    options.ajv,
+    options.mode === 'standalone' && options.inlineValidators
+  )
 
   for (const schemaId of context.validatorSchemasIds) {
     const schema = context.refResolver.getSchema(schemaId)

lib/standalone.js

@@ -3,9 +3,28 @@
 function buildStandaloneCode (contextFunc, context, serializer, validator) {
   let ajvDependencyCode = ''
   if (context.validatorSchemasIds.size > 0) {
-    ajvDependencyCode += 'const Validator = require(\'fast-json-stringify/lib/validator\')\n'
-    ajvDependencyCode += `const validatorState = ${JSON.stringify(validator.getState())}\n`
-    ajvDependencyCode += 'const validator = Validator.restoreFromState(validatorState)\n'
+    if (context.options.inlineValidators) {
+      const standaloneCode = require('ajv/dist/standalone').default
+      const schemaRefs = Object.fromEntries(
+        [...context.validatorSchemaRefs].map(schemaRef => [schemaRef, schemaRef])
+      )
+
+      ajvDependencyCode += `const validator = (() => {
+        const validators = {}
+        const exports = validators
+        ${standaloneCode(validator.ajv, schemaRefs)}
+        return {
+          validate (schemaRef, data) {
+            const validate = validators[schemaRef]
+            return validate(data)
+          }
+        }
+      })()\n`
+    } else {
+      ajvDependencyCode += 'const Validator = require(\'fast-json-stringify/lib/validator\')\n'
+      ajvDependencyCode += `const validatorState = ${JSON.stringify(validator.getState())}\n`
+      ajvDependencyCode += 'const validator = Validator.restoreFromState(validatorState)\n'
+    }
   } else {
     ajvDependencyCode += 'const validator = null\n'
   }

lib/validator.js

@@ -1,14 +1,20 @@
 'use strict'
 
 const Ajv = require('ajv')
+const { _ } = Ajv
 const fastUri = require('fast-uri')
 const ajvFormats = require('ajv-formats')
 const clone = require('rfdc')({ proto: true })
 
 class Validator {
-  constructor (ajvOptions) {
+  constructor (ajvOptions, inlineValidators) {
+    const codeOptions = inlineValidators
+      ? { code: { ...ajvOptions?.code, source: true, esm: false } }
+      : {}
+
     this.ajv = new Ajv({
       ...ajvOptions,
+      ...codeOptions,
       strictSchema: false,
       validateSchema: false,
       allowUnionTypes: true,
@@ -21,8 +27,9 @@ class Validator {
       keyword: 'fjs_type',
       type: 'object',
       errors: false,
-      validate: (_type, data) => {
-        return data && typeof data.toJSON === 'function'
+      code (context) {
+        const { data } = context
+        context.fail(_`!${data} || typeof ${data}.toJSON !== "function"`)
       }
     })
 

test/standalone-mode.test.js

@@ -39,13 +39,13 @@ test('activate standalone mode', async (t) => {
 })
 
 test('test ajv schema', async (t) => {
-  t.plan(3)
+  t.plan(4)
 
   after(async () => {
     await fs.promises.rm(destination, { force: true })
   })
 
-  const code = build({ mode: 'standalone' }, {
+  const code = build({ mode: 'standalone', inlineValidators: false }, {
     type: 'object',
     properties: {
     },
@@ -94,6 +94,7 @@ test('test ajv schema', async (t) => {
   })
   t.assert.ok(typeof code === 'string')
   t.assert.equal(code.indexOf('ajv') > 0, true)
+  t.assert.match(code, /fast-json-stringify\/lib\/validator/)
 
   const destination = path.resolve(tmpDir, 'standalone2.js')
 
@@ -217,3 +218,109 @@ test('no need to keep external schemas once compiled - with oneOf validator', as
   t.assert.equal(stringify({ oneOfSchema: { baz: 5 } }), '{"oneOfSchema":{"baz":5}}')
   t.assert.equal(stringify({ oneOfSchema: { bar: 'foo' } }), '{"oneOfSchema":{"bar":"foo"}}')
 })
+
+test('inline validators with if/then/else', async (t) => {
+  t.plan(6)
+
+  after(async () => {
+    await fs.promises.rm(destination, { force: true })
+  })
+
+  const ajvOptions = {
+    code: { source: false, esm: true, lines: true }
+  }
+  const code = fjs({
+    type: 'object',
+    properties: {},
+    if: {
+      type: 'object',
+      properties: {
+        kind: { const: 'foo' }
+      },
+      required: ['kind']
+    },
+    then: {
+      properties: {
+        kind: { type: 'string' },
+        foo: { type: 'string' }
+      }
+    },
+    else: {
+      properties: {
+        kind: { type: 'string' },
+        bar: { type: 'integer' }
+      }
+    }
+  }, {
+    mode: 'standalone',
+    inlineValidators: true,
+    ajv: ajvOptions
+  })
+
+  t.assert.ok(typeof code === 'string')
+  t.assert.doesNotMatch(code, /fast-json-stringify\/lib\/validator/)
+  t.assert.match(code, /function validate\d/)
+  t.assert.deepEqual(ajvOptions, {
+    code: { source: false, esm: true, lines: true }
+  })
+
+  const destination = path.resolve(tmpDir, 'standalone-inline-if.js')
+
+  await fs.promises.writeFile(destination, code)
+  const stringify = require(destination)
+
+  t.assert.equal(stringify({ kind: 'foo', foo: 'FOO', bar: 42 }), '{"kind":"foo","foo":"FOO"}')
+  t.assert.equal(stringify({ kind: 'bar', foo: 'FOO', bar: 42 }), '{"kind":"bar","bar":42}')
+})
+
+test('inline validators with external oneOf refs and toJSON values', async (t) => {
+  t.plan(4)
+
+  after(async () => {
+    await fs.promises.rm(destination, { force: true })
+  })
+
+  const code = fjs({
+    type: 'object',
+    properties: {
+      value: {
+        oneOf: [
+          { $ref: 'values#/definitions/timestamp' },
+          { $ref: 'values#/definitions/count' }
+        ]
+      }
+    }
+  }, {
+    mode: 'standalone',
+    inlineValidators: true,
+    schema: {
+      values: {
+        definitions: {
+          timestamp: { type: 'string', format: 'date-time' },
+          count: { type: 'integer' }
+        }
+      }
+    }
+  })
+
+  t.assert.doesNotMatch(code, /fast-json-stringify\/lib\/validator/)
+
+  const destination = path.resolve(tmpDir, 'standalone-inline-oneOf.js')
+
+  await fs.promises.writeFile(destination, code)
+  const stringify = require(destination)
+
+  t.assert.equal(
+    stringify({ value: new Date('2020-01-02T03:04:05.000Z') }),
+    '{"value":"2020-01-02T03:04:05.000Z"}'
+  )
+  t.assert.equal(stringify({ value: 42 }), '{"value":42}')
+  t.assert.throws(() => stringify({ value: true }), /does not match schema definition/)
+})
+
+test('does not emit unused inline validators', (t) => {
+  const code = build({ mode: 'standalone', inlineValidators: true })
+
+  t.assert.doesNotMatch(code, /function validate\d/)
+  t.assert.match(code, /const validator = null/)
+})

types/index.d.ts

@@ -166,6 +166,12 @@ declare namespace build {
      * Running mode of fast-json-stringify
      */
     mode?: 'debug' | 'standalone'
+    /**
+     * Embed Ajv-generated validators in standalone output instead of compiling schemas at runtime
+     *
+     * @default false
+     */
+    inlineValidators?: boolean
     /**
      * Large arrays are defined as arrays containing, by default, `20000`
      * elements or more. That value can be adjusted via the option parameter

types/index.tst.ts

@@ -31,6 +31,10 @@ expect(build).type.not.toBeCallableWith({
   type: 'number'
 }, { rounding: 'invalid' })
 
+build({} as Schema, { inlineValidators: true })
+build({} as Schema, { inlineValidators: false })
+expect(build).type.not.toBeCallableWith({} as Schema, { inlineValidators: 'true' })
+
 // String schema
 build({
   type: 'string'