import code

.circleci/config.yml

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+version: 2
+
+defaults: &defaults
+  working_directory: ~/repo
+  docker:
+    - image: circleci/node:12.10.0
+
+jobs:
+  test:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          keys:
+            - v1-dependencies-{{ checksum "package.json" }}
+            - v1-dependencies-
+      - run: yarn
+      - run:
+          name: Run tests
+          command: yarn test
+      - save_cache:
+          paths:
+            - node_modules
+          key: v1-dependencies-{{ checksum "package.json" }}
+      - persist_to_workspace:
+          root: ~/repo
+          paths: .
+
+  deploy:
+    <<: *defaults
+    steps:
+      - attach_workspace:
+          at: ~/repo
+      - run:
+          name: Set registry URL
+          command: npm set registry https://packagecloud.io/thomasaribart/json-typescript/npm/
+      - run:
+          name: Authenticate with registry
+          command: echo "//packagecloud.io/thomasaribart/json-typescript/npm/:_authToken=$NPM_TOKEN" > ~/repo/.npmrc
+      - run:
+          name: Publish package
+          command: npm publish
+
+workflows:
+  version: 2
+  test-deploy:
+    jobs:
+      - test
+      - deploy:
+          requires:
+            - test

.gitignore

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+node_modules

LICENSE

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+MIT License
+
+Copyright (c) 2020 Thomas Aribart
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# json-typescript
+Infer types from your JSON schemas

babel.config.js

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+module.exports = {
+  presets: [
+    ["@babel/preset-env", { targets: { node: "current" } }],
+    "@babel/preset-typescript",
+  ],
+};

package.json

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+{
+  "name": "json-schema-to-ts",
+  "version": "0.1.0",
+  "description": "Infer typescript types from your JSON schemas!",
+  "main": "index.ts",
+  "scripts": {
+    "test": "jest"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.10.4",
+    "@babel/preset-env": "^7.10.4",
+    "@babel/preset-typescript": "^7.10.4",
+    "@types/jest": "^26.0.4",
+    "ajv": "^6.12.3",
+    "babel-jest": "^26.1.0",
+    "jest": "^26.1.0",
+    "typescript": "^3.9.6"
+  },
+  "author": "Thomas Aribart",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/ThomasAribart/json-schema-to-ts.git"
+  },
+  "keywords": [
+    "json",
+    "schema",
+    "typescript",
+    "type",
+    "ts"
+  ],
+  "bugs": {
+    "url": "https://github.com/ThomasAribart/json-schema-to-ts/issues"
+  },
+  "homepage": "https://github.com/ThomasAribart/json-schema-to-ts#readme"
+}

src/array.ts

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+import { FromWriteableSchema } from "./index";
+import { Schema } from "./schema";
+import { Head, Tail, Prepend, ConcatReversed, ShortenReversed } from "./utils";
+
+export type FromArraySchema<S> = "type" extends keyof S
+  ? S["type"] extends "array"
+    ? "items" extends keyof S
+      ? S["items"] extends Schema
+        ? FromWriteableSchema<S["items"]>[]
+        : RecurseOnTupleSchema<
+            S["items"],
+            "additionalItems" extends keyof S ? S["additionalItems"] : true
+          >
+      : any[]
+    : never
+  : never;
+
+type RecurseOnTupleSchema<S, A, R extends any[] = []> = {
+  stop: A extends false
+    ? ShortenReversed<R>
+    : ShortenReversed<R> | ConcatReversed<R, [...any[]]>;
+  continue: S extends any[]
+    ? Head<S> extends Schema
+      ? RecurseOnTupleSchema<
+          Tail<S>,
+          A,
+          Prepend<FromWriteableSchema<Head<S>>, R>
+        >
+      : never
+    : never;
+}[S extends [any, ...any[]] ? "continue" : "stop"];

src/const.ts

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+import { FromWriteableSchema } from "./index";
+
+export type FromConstSchema<S> = "const" extends keyof S
+  ? "type" extends keyof S
+    ? S["const"] & FromWriteableSchema<Omit<S, "const" | "enum">>
+    : S["const"]
+  : never;

src/enum.ts

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+import { FromWriteableSchema } from "./index";
+import { Head, Tail } from "./utils";
+
+export type FromEnumSchema<S> = "enum" extends keyof S
+  ? "type" extends keyof S
+    ? RecurseOnEnumSchema<S["enum"], FromWriteableSchema<Omit<S, "enum">>>
+    : RecurseOnEnumSchema<S["enum"]>
+  : never;
+
+type RecurseOnEnumSchema<S, T = any, R = never> = {
+  stop: R;
+  continue: S extends any[]
+    ? Head<S> extends T
+      ? RecurseOnEnumSchema<Tail<S>, T, R | Head<S>>
+      : RecurseOnEnumSchema<Tail<S>, T, R>
+    : never;
+}[S extends [any, ...any[]] ? "continue" : "stop"];

src/index.ts

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+import { FromObjectSchema } from "./object";
+import { FromArraySchema } from "./array";
+import { FromConstSchema } from "./const";
+import { FromEnumSchema } from "./enum";
+import { Writeable } from "./utils";
+
+export type FromSchema<S> = FromReadonlySchema<S>;
+
+type FromReadonlySchema<S> = FromWriteableSchema<Writeable<S>>;
+
+export type FromWriteableSchema<S> = {
+  any: any;
+  never: never;
+  null: null;
+  boolean: boolean;
+  string: string;
+  number: number;
+  object: FromObjectSchema<S>;
+  array: FromArraySchema<S>;
+  const: FromConstSchema<S>;
+  enum: FromEnumSchema<S>;
+}[InferSchemaType<S>];
+
+type InferSchemaType<S> = S extends true | string
+  ? "any"
+  : S extends false
+  ? "never"
+  : "const" extends keyof S
+  ? "const"
+  : "enum" extends keyof S
+  ? "enum"
+  : "type" extends keyof S
+  ? S["type"] extends "null"
+    ? "null"
+    : S["type"] extends "boolean"
+    ? "boolean"
+    : S["type"] extends "integer" | "number"
+    ? "number"
+    : S["type"] extends "string"
+    ? "string"
+    : S["type"] extends "object"
+    ? "object"
+    : S["type"] extends "array"
+    ? "array"
+    : never
+  : never;

src/object.ts

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+import { FromWriteableSchema } from "./index";
+import { ObjectSchema, Schema } from "./schema";
+import { Merge } from "./utils";
+
+export type FromObjectSchema<S> = S extends ObjectSchema
+  ? "properties" extends keyof S
+    ? number extends keyof S["required"]
+      ? Merge<
+          {
+            [key in Exclude<
+              keyof S["properties"],
+              S["required"][number]
+            >]?: S["properties"][key] extends Schema
+              ? FromWriteableSchema<S["properties"][key]>
+              : never;
+          },
+          {
+            [key in S["required"][number]]: FromWriteableSchema<
+              S["properties"][key]
+            >;
+          }
+        >
+      : {
+          [key in keyof S["properties"]]?: S["properties"][key] extends Schema
+            ? FromWriteableSchema<S["properties"][key]>
+            : never;
+        }
+    : object
+  : never;

src/schema.ts

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+import { Merge } from "./utils";
+
+type CommonProps = {
+  title?: string;
+  description?: string;
+  default?: any;
+  deprecated?: boolean;
+  readOnly?: boolean;
+  writeOnly?: boolean;
+  examples?: any[];
+};
+
+type MakeSchema<SpecificProps = {}> = Merge<CommonProps, SpecificProps>;
+
+export type NullSchema = MakeSchema<{
+  type: "null";
+}>;
+
+export type BooleanSchema = MakeSchema<{
+  type: "boolean";
+}>;
+
+export type StringSchema = MakeSchema<{
+  type: "string";
+  maxLength?: number;
+  minLength?: number;
+  pattern?: string;
+}>;
+
+export type IntegerSchema = MakeSchema<{
+  type: "integer";
+  multipleOf?: number;
+  maximum?: number;
+  exclusiveMaximum?: number;
+  minimum?: number;
+  exclusiveMinimum?: number;
+}>;
+
+export type NumberSchema = MakeSchema<{
+  type: "number";
+  multipleOf?: number;
+  maximum?: number;
+  exclusiveMaximum?: number;
+  minimum?: number;
+  exclusiveMinimum?: number;
+}>;
+
+export type ObjectSchema = MakeSchema<{
+  type: "object";
+  properties?: { [propertyName: string]: Schema };
+  required?: any[];
+  dependentRequired?: { [property: string]: string[] };
+  maxProperties?: number;
+  minProperties?: number;
+}>;
+
+export type ArraySchema = MakeSchema<{
+  type: "array";
+  items?: Schema | any[];
+  maxItems?: number;
+  minItems?: number;
+  uniqueItems?: boolean;
+  additionalItems?: boolean;
+}>;
+
+export type ConstSchema = MakeSchema<{
+  type?:
+    | "null"
+    | "boolean"
+    | "string"
+    | "integer"
+    | "number"
+    | "object"
+    | "array";
+  const: any;
+}>;
+
+export type EnumSchema = MakeSchema<{
+  type?:
+    | "null"
+    | "boolean"
+    | "string"
+    | "integer"
+    | "number"
+    | "object"
+    | "array";
+  enum: any[];
+}>;
+
+export type Schema =
+  | boolean
+  | string
+  | NullSchema
+  | BooleanSchema
+  | StringSchema
+  | IntegerSchema
+  | NumberSchema
+  | ObjectSchema
+  | ArraySchema
+  | ConstSchema
+  | EnumSchema;