feat: expose programmatic api (#2)

README.md

@@ -73,6 +73,26 @@ npx esbuild-jest [...optional-jest-arguments]
 
 You can pass any Jest arguments just like you're running Jest itself.
 
+### Advanced Usage
+
+You can also use the CLI programmatically – especially useful if you are wrapping it in a custom script:
+
+```js
+import { build } from 'esbuild-jest-cli';
+import myPlugin from './my-esbuild-plugin.js';
+
+await build({
+  esbuild: {
+    outdir: 'dist',
+    sourcemap: true,
+    plugins: [myPlugin()],
+  },
+  package: {
+    name: 'custom-name',
+  },
+});
+```
+
 Configuration
 -------------
 
@@ -103,6 +123,19 @@ In the `esbuild` section, you can override any `esbuild` option except for a few
 Any other valid [esbuild configuration options](https://esbuild.github.io/api/#options) are supported as expected.
 
 In `package` section, you can override fields in the generated `package.json`, such as `name`, `scripts`, etc.
+It is also possible to pass a function to modify its contents, e.g.:
+
+```js
+module.exports = {
+  esbuild: {
+    // ...
+  },
+  package: (p) => ({
+    ...p,
+    customField: 'customValue',
+  }),
+};
+```
 
 Troubleshooting
 ---------------

build.mjs

@@ -1,10 +1,13 @@
 #!/usr/bin/env node
 
+import { cosmiconfig } from 'cosmiconfig';
 import { build } from './index.mjs';
 
 try {
-  await build();
+  const explorer = cosmiconfig('esbuild-jest');
+  const esbuildJestBaseConfig = await explorer.search();
+  await build(esbuildJestBaseConfig.config);
 } catch (e) {
-  console.error(`${e}`);
+  console.error(`${e.stack || e}`);
   process.exit(1);
 }

index.mjs

@@ -1,4 +1,4 @@
-import { cosmiconfig } from 'cosmiconfig';
+import merge from 'lodash.merge';
 import { build as esbuild } from 'esbuild';
 
 import esbuildJest from './plugin.mjs';
@@ -7,13 +7,10 @@ import {convertPathToImport} from "./utils/resolve-module.mjs";
 import {importViaChain} from "./utils/resolve-via-chain.mjs";
 import {JEST_DEPENDENCIES} from "./utils/jestDependencies.mjs";
 
-const explorer = cosmiconfig('esbuild-jest');
-
-export async function build() {
+export async function build(esbuildJestConfig = {}) {
   const rootDir = process.cwd();
 
-  const esbuildJestBaseConfig = await explorer.search(rootDir);
-  const esbuildBaseConfig = esbuildJestBaseConfig ? esbuildJestBaseConfig.config.esbuild : {};
+  const esbuildBaseConfig = { ...esbuildJestConfig.esbuild };
   const externalModules = [
     ...JEST_DEPENDENCIES,
     ...(esbuildBaseConfig.external || []),
@@ -68,11 +65,19 @@ export async function build() {
         globalConfig,
         projectConfig,
         tests: tests.map(t => t.path),
-        package: esbuildJestBaseConfig && esbuildJestBaseConfig.config.package,
+        package: wrapPackageMiddleware(esbuildJestConfig.package),
       }),
       ...(esbuildBaseConfig.plugins || []),
     ],
   });
 
   return buildResult;
 }
+
+function wrapPackageMiddleware(config) {
+  return typeof config === 'function' ? config : createPackageMerger(config)
+}
+
+function createPackageMerger(override) {
+  return (pkg) => merge(pkg, override)
+}

package.json

@@ -28,6 +28,7 @@
   "homepage": "https://github.com/wix-incubator/esbuild-jest-cli#readme",
   "dependencies": {
     "cosmiconfig": "^8.1.3",
+    "lodash.merge": "^4.6.2",
     "esbuild": "^0.17.4",
     "import-from": "^4.0.0",
     "resolve-from": "^5.0.0"