Adds option to disable union type de-duplication for performance reasons

README.md

@@ -86,6 +86,7 @@ See [server demo](example) and [browser demo](https://github.com/bcherny/json-sc
 | bannerComment | string | `"/* tslint:disable */\n/**\n* This file was automatically generated by json-schema-to-typescript.\n* DO NOT MODIFY IT BY HAND. Instead, modify the source JSONSchema file,\n* and run json-schema-to-typescript to regenerate this file.\n*/"` | Disclaimer comment prepended to the top of each generated file |
 | cwd | string | `process.cwd()` | Root directory for resolving [`$ref`](https://tools.ietf.org/id/draft-pbryan-zyp-json-ref-03.html)s |
 | declareExternallyReferenced | boolean | `true` | Declare external schemas referenced via `$ref`? |
+| disableUnionDeduplication | boolean | `false` | Performance optimization to disable union type de-duplication. |
 | enableConstEnums | boolean | `true` | Prepend enums with [`const`](https://www.typescriptlang.org/docs/handbook/enums.html#computed-and-constant-members)? |
 | format | boolean | `true` | Format code? Set this to `false` to improve performance. |
 | ignoreMinAndMaxItems | boolean | `false` | Ignore maxItems and minItems for `array` types, preventing tuples being generated. |

src/index.ts

@@ -64,6 +64,10 @@ export interface Options {
    * [$RefParser](https://github.com/BigstickCarpet/json-schema-ref-parser) Options, used when resolving `$ref`s
    */
   $refOptions: $RefOptions
+  /**
+   * Performance optimization to disable union type de-duplication.
+   */
+  disableUnionDeduplication: boolean
 }
 
 export const DEFAULT_OPTIONS: Options = {
@@ -90,7 +94,8 @@ export const DEFAULT_OPTIONS: Options = {
     useTabs: false
   },
   unreachableDefinitions: false,
-  unknownAny: true
+  unknownAny: true,
+  disableUnionDeduplication: false,
 }
 
 export function compileFromFile(filename: string, options: Partial<Options> = DEFAULT_OPTIONS): Promise<string> {
@@ -157,7 +162,7 @@ export async function compile(schema: JSONSchema4, name: string, options: Partia
   const parsed = parse(normalized, _options)
   log('blue', 'parser', time(), '✅ Result:', parsed)
 
-  const optimized = optimize(parsed)
+  const optimized = optimize(parsed, _options)
   if (process.env.VERBOSE) {
     if (isDeepStrictEqual(parsed, optimized)) {
       log('cyan', 'optimizer', time(), '✅ No change')

src/optimizer.ts

@@ -1,9 +1,10 @@
 import stringify = require('json-stringify-safe')
 import {uniqBy} from 'lodash'
 import {AST, T_ANY, T_UNKNOWN} from './types/AST'
+import {Options} from './'
 import {log} from './utils'
 
-export function optimize(ast: AST, processed = new Set<AST>()): AST {
+export function optimize(ast: AST, options: Options, processed = new Set<AST>()): AST {
   log('cyan', 'optimizer', ast, processed.has(ast) ? '(FROM CACHE)' : '')
 
   if (processed.has(ast)) {
@@ -15,7 +16,7 @@ export function optimize(ast: AST, processed = new Set<AST>()): AST {
   switch (ast.type) {
     case 'INTERFACE':
       return Object.assign(ast, {
-        params: ast.params.map(_ => Object.assign(_, {ast: optimize(_.ast, processed)}))
+        params: ast.params.map(_ => Object.assign(_, {ast: optimize(_.ast, options, processed)}))
       })
     case 'INTERSECTION':
     case 'UNION':
@@ -31,23 +32,25 @@ export function optimize(ast: AST, processed = new Set<AST>()): AST {
         return T_UNKNOWN
       }
 
-      // [A, B, B] -> [A, B]
-      const shouldTakeStandaloneNameIntoAccount = ast.params.filter(_ => _.standaloneName).length > 1
-      const params = uniqBy(
-        ast.params,
-        _ => `
-          ${_.type}-
-          ${shouldTakeStandaloneNameIntoAccount ? _.standaloneName : ''}-
-          ${stringify((_ as any).params)}
-        `
-      )
-      if (params.length !== ast.params.length) {
-        log('cyan', 'optimizer', '[A, B, B] -> [A, B]', ast)
-        ast.params = params
+      if (!options.disableUnionDeduplication) {
+        // [A, B, B] -> [A, B]
+        const shouldTakeStandaloneNameIntoAccount = ast.params.filter(_ => _.standaloneName).length > 1
+        const params = uniqBy(
+          ast.params,
+          _ => `
+            ${_.type}-
+            ${shouldTakeStandaloneNameIntoAccount ? _.standaloneName : ''}-
+            ${stringify((_ as any).params)}
+          `
+        )
+        if (params.length !== ast.params.length) {
+          log('cyan', 'optimizer', '[A, B, B] -> [A, B]', ast)
+          ast.params = params
+        }
       }
 
       return Object.assign(ast, {
-        params: ast.params.map(_ => optimize(_, processed))
+        params: ast.params.map(_ => optimize(_, options, processed))
       })
     default:
       return ast