From 7a98a2903cee0ecf28869d9178b6ba76d681e9e9 Mon Sep 17 00:00:00 2001
From: Peter <petermoldovia@yahoo.ca>
Date: Mon, 10 Apr 2023 23:22:16 +0200
Subject: [PATCH] Allow Jest to run TypeScript tests

---
 .babelrc.js | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 .babelrc.js

diff --git a/.babelrc.js b/.babelrc.js
new file mode 100644
index 000000000..e78347082
--- /dev/null
+++ b/.babelrc.js
@@ -0,0 +1,31 @@
+module.exports = (api) => {
+	// Source: https://www.wisdomgeek.com/development/web-development/how-to-setup-jest-typescript-babel-webpack-project/
+	// Testing if babel is being run in test mode
+	const isTest = api.env('test');
+	/**
+	 * Cache the returned value forever and don't call this function again. This is the default behavior but since we
+	 * are reading the env value above, we need to explicitly set it after we are done doing that, else we get a
+	 * caching was left unconfigured error.
+	 */
+	api.cache(true);
+	return {
+		plugins: ['@babel/plugin-transform-runtime'],
+		presets: [
+			// Enabling Babel to understand TypeScript
+			'@babel/preset-typescript',
+			[
+				// Allows smart transpilation according to target environments
+				'@babel/preset-env',
+				{
+					/**
+					 * Specifying what module type should the output be in.
+					 * For test cases, we transpile all the way down to commonjs since jest does not understand TypeScript.
+					 * For all other cases, we don't transform since we want Webpack to do that in order for it to do
+					 * dead code elimination (tree shaking) and intelligently select what all to add to the bundle.
+					 */
+					modules: isTest ? 'commonjs' : false,
+				},
+			],
+		],
+	};
+};