feat: add FASTIFY_AUTOLOAD_TYPESCRIPT environment variable (#327)

README.md

@@ -292,6 +292,18 @@ Autoload can be customised using the following options:
   // { country: 'be', language: 'nl' }
   ```
 
+## Override Typescript detection per Environment variable
+
+It is possible to override the automatic detection of a typescript capable runtime per `FASTIFY_AUTOLOAD_TYPESCRIPT` environment variable. If set to a truthy value Autoload will load `.ts` files, expecting that node has a typescript capable loader.
+
+This is useful for cases, where you want to use Autoload for loading typescript files but detecting the typescript loader fails, because for example you are using a custom loader.
+
+You can use it like this:
+
+```sh
+FASTIFY_AUTOLOAD_TYPESCRIPT=1 node --loader=my-custom-loader index.ts
+```
+
 ## Plugin Configuration
 
 Each plugin can be individually configured using the following module properties:

index.js

@@ -5,6 +5,7 @@ const url = require('node:url')
 const { readdir } = require('node:fs').promises
 const pkgUp = require('pkg-up')
 
+const isFastifyAutoloadTypescriptOverride = !!process.env.FASTIFY_AUTOLOAD_TYPESCRIPT
 const isTsNode = (Symbol.for('ts-node.register.instance') in process) || !!process.env.TS_NODE_DEV
 const isBabelNode = (process?.execArgv || []).concat(process?.argv || []).some((arg) => arg.indexOf('babel-node') >= 0)
 
@@ -16,7 +17,8 @@ const isSWCNode = typeof process.env._ === 'string' && process.env._.includes('.
 const isTsm = process._preload_modules && process._preload_modules.includes('tsm')
 const isEsbuildRegister = process._preload_modules && process._preload_modules.includes('esbuild-register')
 const isTsx = process._preload_modules && process._preload_modules.toString().includes('tsx')
-const typescriptSupport = isTsNode || isVitestEnvironment || isBabelNode || isJestEnvironment || isSWCRegister || isSWCNodeRegister || isSWCNode || isTsm || isTsx || isEsbuildRegister
+const typescriptSupport = isFastifyAutoloadTypescriptOverride || isTsNode || isVitestEnvironment || isBabelNode || isJestEnvironment || isSWCRegister || isSWCNodeRegister || isSWCNode || isTsm || isTsx || isEsbuildRegister
+
 const forceESMEnvironment = isVitestEnvironment || false
 const routeParamPattern = /\/_/ig
 const routeMixedParamPattern = /__/g