feat: generate types for extern declarations

docs/docs/07-examples/10-using-javascript.md

@@ -1,56 +1,58 @@
 ---
-title: Using JavaScript
+title: Using JavaScript/TypeScript
 id: using-javascript
-keywords: [Wing example]
+keywords: [example, javascript, extern, typescript, js, ts]
 ---
 
-Calling a Javascript function from Wing requires two steps. 
+Calling a Javascript function from Wing requires two steps.
 
-First, export the function from Javascript.
-
-This examples exports `isValidUrl` from a file named`url_utils.js`:
+1. Create a .js file that exports some functions
 
 ```js
-exports.isValidUrl = function(url) {
-  try {
-    new URL(url);
-    return true;
-  } catch {
-    return false;
-  }
+// util.js
+
+exports.isValidUrl = function (url) {
+  return URL.canParse(url);
 };
 ```
 
-### Preflight function
-
-To call this in preflight code, define the function as an `extern` in a class.
-
-**Note:** Extern functions must be `static.` 
+In preflight, this file must be a CommonJS module written in Javascript. Inflight, it may be CJS/ESM and either JavaScript or TypeScript.
 
-If you want to use the function outside of the class, be sure to declare it as `pub`.
+2. Use the `extern` keyword in a class to expose the function to Wing. Note that this must be `static`. It may also be `inflight`
 
-```ts 
-class JsExample {  
-  // preflight static 
-  pub extern "./url_utils.js" static isValidUrl(url: str): bool;
+```ts
+class JsExample {
+  pub extern "./util.js" static isValidUrl(url: str): bool;
 }
 
 assert(JsExample.isValidUrl("http://www.google.com"));
 assert(!JsExample.isValidUrl("X?Y"));
 ```
 
-### Inflight
+### Type-safe `extern`
 
-To call the function inflight, add the `inflight` modifier. 
+Running `wing compile` will generate a corresponding `.d.ts` file for each `extern`. This file can be imported into the extern file itself to ensure the extern is type-safe. Either your IDE or a separate usage of the TypeScript compiler can provide type-checking.
 
 ```ts
-class JsExample {  
-  // inflight static method
-  extern "./url_utils.js" static inflight  isValidUrl(url: str): bool;
-}
+// util.ts
+import type extern from "./util.extern";
 
-test "main" {
-  assert(JsExample.isValidUrl("http://www.google.com"));
-  assert(!JsExample.isValidUrl("X?Y"));
-}
+export const isValidUrl: extern["isValidUrl"] = (url) => {
+  // url is known to be a string and that we must return a boolean
+  return URL.canParse(url);
+};
 ```
+
+The .d.ts file can also be used in JavaScript via JSDoc comments and can even be applied at a module export level.
+
+```js
+// util.js
+/** @type {import("./util.extern").default} */
+module.exports = {
+  isValidUrl: (url) => {
+    return URL.canParse(url);
+  },
+};
+```
+
+Coming Soon: The ability to use resources inside an `inflight extern`. See [this issue](https://github.com/winglang/wing/issues/76) for more information.

examples/tests/sdk_tests/function/logging.extern.d.ts

@@ -0,0 +1,3 @@
+export default interface extern {
+  logging: () => Promise<void>,
+}

examples/tests/sdk_tests/service/http-server.extern.d.ts

@@ -0,0 +1,10 @@
+export default interface extern {
+  createServer: (body: string) => Promise<IHttpServer$Inflight>,
+}
+export interface Address {
+  readonly port: number;
+}
+export interface IHttpServer$Inflight {
+  readonly address: () => Promise<Address>;
+  readonly close: () => Promise<void>;
+}

examples/tests/sdk_tests/util/util.extern.d.ts

@@ -0,0 +1,3 @@
+export default interface extern {
+  platform: () => Promise<string>,
+}

examples/tests/sdk_tests/util/uuidv4-helper.extern.d.ts

@@ -0,0 +1,3 @@
+export default interface extern {
+  validateUUIDv4: (uuidv4: string) => Promise<boolean>,
+}

examples/tests/sdk_tests/util/uuidv4.test.w

@@ -1,11 +1,6 @@
 bring util;
 
-class JSHelper { 
-  extern "./uuidv4-helper.js" pub static validateUUIDv4(uuidv4: str): bool;
-}
-
-let data = util.uuidv4();
-assert(JSHelper.validateUUIDv4(data) == true);
+let preflightData = util.uuidv4();
 
 class JSHelperInflight {
   extern "./uuidv4-helper.js" pub static inflight validateUUIDv4(uuidv4: str): bool;
@@ -14,4 +9,5 @@ class JSHelperInflight {
 test "inflight uuidv4" {
   let data = util.uuidv4();
   assert(JSHelperInflight.validateUUIDv4(data) == true);
+  assert(JSHelperInflight.validateUUIDv4(preflightData) == true);
 }

examples/tests/valid/capture_tokens.test.w

@@ -4,7 +4,7 @@ class MyResource {
   api: cloud.Api;
   url: str;
 
-  extern "./url_utils.js" pub static inflight isValidUrl(url: str): bool;
+  extern "./url_utils.ts" pub static inflight isValidUrl(url: str): bool;
 
   new() {
     this.api = new cloud.Api();

examples/tests/valid/dynamo.extern.d.ts

@@ -0,0 +1,4 @@
+export default interface extern {
+  _getItem: (tableName: string, key: Readonly<any>) => Promise<Readonly<any>>,
+  _putItem: (tableName: string, item: Readonly<any>) => Promise<void>,
+}

examples/tests/valid/dynamo.test.w

@@ -54,7 +54,8 @@ class DynamoTable {
     }
   }
 
-  extern "./dynamo.js" static inflight _putItem(tableName: str, item: Json): void;
+  extern "./dynamo.ts" static inflight _getItem(tableName: str, key: Json): Json;
+  extern "./dynamo.ts" static inflight _putItem(tableName: str, item: Json): void;
 
   pub inflight putItem(item: Map<Attribute>) {
     let json = this._itemToJson(item);

examples/tests/valid/dynamo.js → examples/tests/valid/dynamo.ts

@@ -1,8 +1,13 @@
-const { DynamoDBClient, PutItemCommand, GetItemCommand } = require("@aws-sdk/client-dynamodb");
+import type extern from "./dynamo.extern";
+import {
+  DynamoDBClient,
+  PutItemCommand,
+  GetItemCommand,
+} from "@aws-sdk/client-dynamodb";
 
 const client = new DynamoDBClient({});
 
-export async function _putItem(tableName, item) {
+export const _putItem: extern["_putItem"] = async (tableName, item) => {
   const command = new PutItemCommand({
     TableName: tableName,
     Item: item,
@@ -11,15 +16,15 @@ export async function _putItem(tableName, item) {
   const response = await client.send(command);
   console.log(response);
   return;
-}
+};
 
-export async function _getItem(tableName, key) {
+export const _getItem: extern["_getItem"] = async (tableName, key) => {
   const command = new GetItemCommand({
     TableName: tableName,
-    Key: key
+    Key: key,
   });
 
   const response = await client.send(command);
   console.log(response);
   return response;
-}
+};

examples/tests/valid/dynamo_awscdk.test.w

@@ -60,13 +60,13 @@ class DynamoTable {
     }
   }
 
-  extern "./dynamo.js" static inflight _putItem(tableName: str, item: Json): void;
+  extern "./dynamo.ts" static inflight _putItem(tableName: str, item: Json): void;
   pub inflight putItem(item: Map<Attribute>) {
     let json = this._itemToJson(item);
     DynamoTable._putItem(this.tableName, json);
   }
 
-  extern "./dynamo.js" static inflight _getItem(tableName: str, key: Json): Json;
+  extern "./dynamo.ts" static inflight _getItem(tableName: str, key: Json): Json;
   pub inflight getItem(key: Map<Attribute>): Json {
     let json = this._itemToJson(key);
     return DynamoTable._getItem(this.tableName, json);

examples/tests/valid/extern_implementation.test.w

@@ -6,6 +6,7 @@ class Foo {
   extern "./external_js.js" static inflight getUuid(): str;
   extern "./external_js.js" static inflight getData(): str;
   extern "./external_js.js" pub static inflight print(msg: str): void;
+  extern "./external_js.js" pub static preflightBucket(bucket: cloud.Bucket, id: str): Json;
 
   pub inflight call() {
     assert(Foo.regexInflight("[a-z]+-\\d+", "abc-123"));
@@ -20,6 +21,9 @@ assert(Foo.getGreeting("Wingding") == "Hello, Wingding!");
 
 let f = new Foo();
 
+let bucket = new cloud.Bucket() as "my-bucket";
+let result = Foo.preflightBucket(bucket, "my-bucket");
+
 test "call" {
   f.call();
 }