[WIP] [Breaking] Drop Flow type support in favor of TypeScript

Author: jack-guy

.babelrc

@@ -4,7 +4,7 @@
             "@babel/preset-env",
             {
                 "targets": {
-                    "node": "10"
+                    "node": "22"
                 }
             }
         ],

__tests__/genType.test.js

@@ -0,0 +1,29 @@
+import { getResourceTypeReference, getNewKeyTypeFromBatchKeySetType, getLoaderTypeKey } from '../src/genType';
+
+it('getResourceTypeReference converts a resource path to a valid reference', () => {
+    expect(getResourceTypeReference(null, ['foo', 'bar', 'baz'])).toBe(
+        "ResourcesType['foo']['bar']['baz']",
+    );
+});
+
+it('getNewKeyTypeFromBatchKeySetType returns a newKey type with a valid value', () => {
+    expect(
+        getNewKeyTypeFromBatchKeySetType(
+            'bKey',
+            "ResourcesType['foo']['bar']['baz']",
+        ),
+    ).toBe(`Parameters<ResourcesType['foo']['bar']['baz']['bKey']['has']>[0]`);
+});
+
+it('getLoaderTypeKey forces a nullable batchKey to be strictly non-nullable', () => {
+    expect(
+        getLoaderTypeKey(
+            {
+                isBatchResource: true,
+                newKey: 'test_id',
+                batchKey: 'test_ids',
+            },
+            ['a', 'b'],
+        ),
+    ).toBe(`Exclude<Parameters<ResourcesType['a']['b']>[0], 'test_ids'> & { test_id: NonNullable<Parameters<ResourcesType['a']['b']>[0]['test_ids']>[0] }`);
+});

__tests__/genTypeFlow.test.js

@@ -9,14 +9,16 @@ import { getConfig } from '../src/config';
 
 const BABEL_CONFIG = {
     presets: [
-        '@babel/preset-flow',
+        '@babel/preset-typescript',
         [
             '@babel/preset-env',
             {
                 modules: 'commonjs',
             },
         ],
     ],
+    // Babel needs this dummy file name to determine it's a TypeScript file
+    filename: 'file.ts',
 };
 
 const RUNTIME_HELPERS = path.resolve(__dirname, '..', 'src', 'runtimeHelpers.ts');
@@ -45,7 +47,7 @@ expect.extend({
 async function createDataLoaders(config, cb) {
     await tmp.withFile(
         async ({ path }) => {
-            const loadersCode = await babel.transformAsync(codegen(config, RUNTIME_HELPERS), BABEL_CONFIG);
+            const loadersCode = await babel.transformAsync(await codegen(config, RUNTIME_HELPERS), BABEL_CONFIG);
             fs.writeFileSync(path, 'const regeneratorRuntime = require("regenerator-runtime");');
             fs.appendFileSync(path, loadersCode.code);
             // Import the generated code into memory :scream:
@@ -1608,3 +1610,49 @@ test('batch endpoint with propertyBatchKey with reorderResultsByKey handles resp
         ]);
     });
 });
+
+test('embeds resource types', async () => {
+    // For the sake of coverage we pass in these test comments which will get interpolated in the generated code
+    // but otherwise we don't need to test them.
+    const config = {
+        resources: {
+            foo: {
+                isBatchResource: false,
+                docsLink: 'example.com/docs/foo',
+            },
+        },
+        typings: {
+            embedResourcesType: {
+                imports: '// test foo',
+                ResourcesType: '// test bar',
+            },
+        }
+    };
+
+    const resources = {
+        foo: jest
+            .fn()
+            .mockReturnValueOnce(
+                Promise.resolve({
+                    message: 'knock knock',
+                    message_suffix: '!',
+                }),
+            )
+            .mockReturnValueOnce(
+                Promise.resolve({
+                    message: "who's there",
+                    message_suffix: '?',
+                }),
+            ),
+    };
+
+    await createDataLoaders(config, async (getLoaders) => {
+        const loaders = getLoaders(resources);
+
+        const results = await loaders.foo.loadMany([{ bar_id: 1 }, { bar_id: 2 }]);
+        expect(results).toEqual([
+            { message: 'knock knock', message_suffix: '!' },
+            { message: "who's there", message_suffix: '?' },
+        ]);
+    });
+});

__tests__/implementation.test.js

@@ -2,10 +2,10 @@ module.exports = {
     collectCoverage: true,
     coverageThreshold: {
         global: {
-            branches: 89,
-            functions: 92,
-            lines: 95,
-            statements: 94,
+            branches: 100,
+            functions: 100,
+            lines: 100,
+            statements: 100,
         },
     },
     coveragePathIgnorePatterns: ['<rootDir>/src/config.ts', '<rootDir>/__tests__/test-tmp-files'],

jest.config.js

@@ -16,7 +16,7 @@
   },
   "license": "MIT",
   "scripts": {
-    "test": "jest",
+    "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js",
     "build": "babel --verbose --extensions '.ts' src -d lib",
     "prepublishOnly": "make build",
     "typecheck": "tsc --project tsconfig.json"
@@ -25,34 +25,33 @@
     "dataloader-codegen": "./lib/index.js"
   },
   "devDependencies": {
-    "@babel/cli": "^7.6.3",
-    "@babel/core": "^7.6.4",
-    "@babel/preset-flow": "^7.0.0",
-    "@babel/preset-typescript": "^7.6.0",
-    "@types/jest": "^25.1.2",
+    "@babel/cli": "^7.27.2",
+    "@babel/core": "^7.27.4",
+    "@babel/preset-flow": "^7.27.1",
+    "@babel/preset-typescript": "^7.27.1",
+    "@types/jest": "^29.5.14",
     "@types/js-yaml": "^3.12.1",
-    "@types/lodash": "^4.14.144",
-    "@types/node": "^12.7.12",
+    "@types/lodash": "^4.17.17",
+    "@types/node": "^24.0.1",
     "@types/object-hash": "^1.3.0",
-    "@types/prettier": "^1.18.3",
     "@types/yargs": "^13.0.3",
     "flow-bin": "^0.121.0",
     "flowgen": "^1.10.0",
-    "jest": "^25.1.0",
+    "jest": "^29.7.0",
     "regenerator-runtime": "^0.13.3",
     "tmp-promise": "^2.0.2",
-    "typescript": "^3.7.0-beta"
+    "typescript": "^5.8.3"
   },
   "dependencies": {
-    "@babel/preset-env": "^7.6.3",
+    "@babel/preset-env": "^7.27.2",
     "aggregate-error": "^3.0.1",
     "ajv": "^6.11.0",
     "dataloader": "^2.0.0",
     "ensure-error": "^2.0.0",
     "js-yaml": "^3.13.1",
-    "lodash": "^4.17.15",
+    "lodash": "^4.17.17",
     "object-hash": "^2.0.0",
-    "prettier": "^1.19.1",
+    "prettier": "^3.5.3",
     "yargs": "^14.2.0"
   },
   "files": [

package.json

@@ -1,7 +1,7 @@
 import _ from 'lodash';
 import prettier from 'prettier';
 import { GlobalConfig, getResourcePaths } from './config';
-import { getLoaderType, getLoadersTypeMap, getResourceTypings } from './genTypeFlow';
+import { getLoaderType, getLoadersTypeMap, getResourceTypings } from './genType';
 import getLoaderImplementation from './implementation';
 
 function getLoaders(config: object, paths: Array<Array<string>>, current: Array<string>) {
@@ -46,8 +46,6 @@ export default function codegen(
     const { printResourceTypeImports, printResourcesType } = getResourceTypings(config);
 
     const output = `
-        // @flow strict-local
-
         /**
          * !!! THIS FILE IS AUTO-GENERATED. CHANGES MAY BE OVERWRITTEN !!!
          */
@@ -82,21 +80,22 @@ export default function codegen(
          * ===============================
          */
 
-        // https://github.com/facebook/flow/issues/7709#issuecomment-530501257
-        type ExtractArg = <Arg, Ret>([Arg => Ret]) => Arg;
-        type ExtractPromisedReturnValue<A> = <R>((...A) => Promise<R>) => R;
+        type PromisedReturnType<F extends (...args: any) => Promise<any>> =
+            F extends (...args: any) => Promise<infer R> ? R : never;
+
+        type Values<T> = T[keyof T];
 
-        export type DataLoaderCodegenOptions = {|
+        export type DataLoaderCodegenOptions = {
             errorHandler?: (
-                resourcePath: $ReadOnlyArray<string>,
-                // $FlowFixMe: We don't know what type the resource might throw, so we have to type error to "any" :(
+                resourcePath: ReadonlyArray<string>,
+                // We don't know what type the resource might throw, so we have to type error to "any" :(
                 error: any,
             ) => Promise<Error>,
-            resourceMiddleware?: {|
-                before?: <T>(resourcePath: $ReadOnlyArray<string>, resourceArgs: T) => Promise<T>,
-                after?: <T>(resourcePath: $ReadOnlyArray<string>, response: T) => Promise<T>,
-            |};
-        |};
+            resourceMiddleware?: {
+                before?: <T>(resourcePath: ReadonlyArray<string>, resourceArgs: T) => Promise<T>,
+                after?: <T>(resourcePath: ReadonlyArray<string>, response: T) => Promise<T>,
+            };
+        };
 
         /**
          * ===============================
@@ -117,5 +116,5 @@ export default function codegen(
         }
     `;
 
-    return prettier.format(output, { parser: 'babel' });
+    return prettier.format(output, { parser: 'babel-ts' });
 }