openapi-typescript/src/transform/schema.ts

Generate TypeScript types from Swagger OpenAPI specs

import { GlobalContext } from "../types";
import {
  comment,
  nodeType,
  transformRef,
  tsArrayOf,
  tsIntersectionOf,
  tsPartial,
  tsReadonly,
  tsTupleOf,
  tsUnionOf,
} from "../utils";

interface TransformSchemaObjOptions extends GlobalContext {
  required: Set<string>;
}

function hasDefaultValue(node: any): boolean {
  if (node.hasOwnProperty("default")) return true;
  // if (node.hasOwnProperty("$ref")) return true; // TODO: resolve remote $refs?
  return false;
}

/** Take object keys and convert to TypeScript interface */
export function transformSchemaObjMap(obj: Record<string, any>, options: TransformSchemaObjOptions): string {
  let output = "";

  for (const k of Object.keys(obj)) {
    const v = obj[k];
    // 1. JSDoc comment (goes above property)
    if (v.description) output += comment(v.description);

    // 2. name (with “?” if optional property)
    const readonly = tsReadonly(options.immutableTypes);
    const required =
      options.required.has(k) || (options.defaultNonNullable && hasDefaultValue(v.schema || v)) ? "" : "?";
    output += `${readonly}"${k}"${required}: `;

    // 3. transform
    output += transformSchemaObj(v.schema || v, options);

    // 4. close
    output += `;\n`;
  }

  return output.replace(/\n+$/, "\n"); // replace repeat line endings with only one
}

/** transform anyOf */
export function transformAnyOf(anyOf: any, options: TransformSchemaObjOptions): string {
  return tsIntersectionOf(anyOf.map((s: any) => tsPartial(transformSchemaObj(s, options))));
}

/** transform oneOf */
export function transformOneOf(oneOf: any, options: TransformSchemaObjOptions): string {
  return tsUnionOf(oneOf.map((value: any) => transformSchemaObj(value, options)));
}

/** Convert schema object to TypeScript */
export function transformSchemaObj(node: any, options: TransformSchemaObjOptions): string {
  const readonly = tsReadonly(options.immutableTypes);

  let output = "";

  // open nullable
  if (node.nullable) {
    output += "(";
  }

  // pass in formatter, if specified
  const overriddenType = options.formatter && options.formatter(node);
  if (overriddenType) {
    output += overriddenType;
  } else {
    // transform core type
    switch (nodeType(node)) {
      case "ref": {
        output += transformRef(node.$ref);
        break;
      }
      case "string":
      case "number":
      case "boolean": {
        output += nodeType(node) || "any";
        break;
      }
      case "enum": {
        const items: Array<string | number | boolean> = [];
        (node.enum as unknown[]).forEach((item) => {
          if (typeof item === "string") items.push(`'${item.replace(/'/g, "\\'")}'`);
          else if (typeof item === "number" || typeof item === "boolean") items.push(item);
          else if (item === null && !node.nullable) items.push("null");
        });
        output += tsUnionOf(items);
        break;
      }
      case "object": {
        const isAnyOfOrOneOfOrAllOf = "anyOf" in node || "oneOf" in node || "allOf" in node;

        // if empty object, then return generic map type
        if (
          !isAnyOfOrOneOfOrAllOf &&
          (!node.properties || !Object.keys(node.properties).length) &&
          !node.additionalProperties
        ) {
          output += `{ ${readonly}[key: string]: any }`;
          break;
        }

        let properties = transformSchemaObjMap(node.properties || {}, {
          ...options,
          required: new Set(node.required || []),
        });

        // if additional properties, add an intersection with a generic map type
        let additionalProperties: string | undefined;
        if (
          node.additionalProperties ||
          (node.additionalProperties === undefined && options.additionalProperties && options.version === 3)
        ) {
          if ((node.additionalProperties ?? true) === true || Object.keys(node.additionalProperties).length === 0) {
            additionalProperties = `{ ${readonly}[key: string]: any }`;
          } else if (typeof node.additionalProperties === "object") {
            const oneOf: any[] | undefined = (node.additionalProperties as any).oneOf || undefined; // TypeScript does a really bad job at inference here, so we enforce a type
            const anyOf: any[] | undefined = (node.additionalProperties as any).anyOf || undefined; // "
            if (oneOf) {
              additionalProperties = `{ ${readonly}[key: string]: ${transformOneOf(oneOf, options)}; }`;
            } else if (anyOf) {
              additionalProperties = `{ ${readonly}[key: string]: ${transformAnyOf(anyOf, options)}; }`;
            } else {
              additionalProperties = `{ ${readonly}[key: string]: ${
                transformSchemaObj(node.additionalProperties, options) || "any"
              }; }`;
            }
          }
        }

        output += tsIntersectionOf([
          // append allOf/anyOf/oneOf first
          ...(node.allOf ? (node.allOf as any[]).map((node) => transformSchemaObj(node, options)) : []),
          ...(node.anyOf ? [transformAnyOf(node.anyOf, options)] : []),
          ...(node.oneOf ? [transformOneOf(node.oneOf, options)] : []),
          ...(properties ? [`{\n${properties}\n}`] : []), // then properties (line breaks are important!)
          ...(additionalProperties ? [additionalProperties] : []), // then additional properties
        ]);

        break;
      }

      case "array": {
        if (Array.isArray(node.items)) {
          output += `${readonly}${tsTupleOf(node.items.map((node: any) => transformSchemaObj(node, options)))}`;
        } else {
          output += `${readonly}${tsArrayOf(node.items ? transformSchemaObj(node.items as any, options) : "any")}`;
        }
        break;
      }
    }
  }

  // close nullable
  if (node.nullable) {
    output += ") | null";
  }

  return output;
}