Add ability to make default enums from json enums with option

Just a fork and apply changes of bcherny#262 from @cdietschrun

README.md

@@ -88,6 +88,7 @@ See [server demo](example) and [browser demo](https://github.com/bcherny/json-sc
 | 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`? |
 | enableConstEnums | boolean | `true` | Prepend enums with [`const`](https://www.typescriptlang.org/docs/handbook/enums.html#computed-and-constant-members)? |
+| enableStringEnums | boolean | `false` | Create enums from JSON enums with eponymous keys |
 | 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. |
 | maxItems | number | `20` | Maximum number of unioned tuples to emit when representing bounded-size array types, before falling back to emitting unbounded arrays. Increase this to improve precision of emitted types, decrease it to improve performance, or set it to `-1` to ignore `maxItems`.

src/cli.ts

@@ -171,6 +171,8 @@ Boolean values can be set to false using the 'no-' prefix.
       Declare external schemas referenced via '$ref'?
   --enableConstEnums
       Prepend enums with 'const'?
+  --enableStringEnums
+      Create enums from JSON enums instead of union types
   --format
       Format code? Set this to false to improve performance.
   --maxItems

src/index.ts

@@ -43,6 +43,10 @@ export interface Options {
    * Prepend enums with [`const`](https://www.typescriptlang.org/docs/handbook/enums.html#computed-and-constant-members)?
    */
   enableConstEnums: boolean
+  /**
+   * Generate string enums instead of string union types?
+   */
+  enableStringEnums: boolean
   /**
    * Format code? Set this to `false` to improve performance.
    */
@@ -90,6 +94,7 @@ export const DEFAULT_OPTIONS: Options = {
   cwd: process.cwd(),
   declareExternallyReferenced: true,
   enableConstEnums: true,
+  enableStringEnums: false,
   format: true,
   ignoreMinAndMaxItems: false,
   maxItems: 20,

src/parser.ts

@@ -294,6 +294,20 @@ function parseNonLiteral(
         type: 'UNION',
       }
     case 'UNNAMED_ENUM':
+      if (options.enableStringEnums && schema.type === 'string') {
+        return {
+          comment: schema.description,
+          deprecated: schema.deprecated,
+          keyName,
+          standaloneName: standaloneName(schema, keyName, usedNames)!,
+          params: schema.enum!.map(_ => ({
+            ast: parseLiteral(_, undefined),
+            keyName: _ as string,
+          })),
+          type: 'ENUM',
+        }
+      }
+
       return {
         comment: schema.description,
         deprecated: schema.deprecated,

test/__snapshots__/test/test.ts.md

@@ -1081,6 +1081,28 @@ Generated by [AVA](https://avajs.dev).
     }␊
     `
 
+## enumString.js
+
+> Expected output to match snapshot for e2e test: enumString.js
+
+    `/* eslint-disable */␊
+    /**␊
+     * This file was automatically generated by json-schema-to-typescript.␊
+     * DO NOT MODIFY IT BY HAND. Instead, modify the source JSONSchema file,␊
+     * and run json-schema-to-typescript to regenerate this file.␊
+     */␊
+    ␊
+    export interface EnumStringTest {␊
+      stringEnum: StringEnum;␊
+    }␊
+    ␊
+    export const enum StringEnum {␊
+      a = "a",␊
+      b = "b",␊
+      c = "c"␊
+    }␊
+    `
+
 ## extends.1a.js
 
 > Expected output to match snapshot for e2e test: extends.1a.js

test/e2e/enumString.ts

@@ -0,0 +1,16 @@
+export const input = {
+  title: 'enumStringTest',
+  type: 'object',
+  properties: {
+    stringEnum: {
+      type: 'string',
+      enum: ['a', 'b', 'c']
+    }
+  },
+  required: ['stringEnum'],
+  additionalProperties: false
+}
+
+export const options = {
+  enableStringEnums: true
+}