TS_NODE_OPTIONS

This will remap all `TS_NODE_` environment to
`NODE_` environment variables for the child process
being spawned.

Fixes #471

README.md

@@ -42,6 +42,11 @@ ts-node -p '"Hello, world!"'
 
 # Pipe scripts to execute with TypeScript.
 echo "console.log('Hello, world!')" | ts-node
+
+# Passing NODE_OPTIONS to the underlying process using TS_NODE_OPTIONS.
+# All `TS_NODE_*` environment variables will be passed as `NODE_*` environment
+# variables to your code.
+TS_NODE_ENV="--inspect-brk" ts-node
 ```
 
 ![TypeScript REPL](https://github.com/TypeStrong/ts-node/raw/master/screenshot.png)

src/bin.ts

@@ -36,6 +36,17 @@ v8flags(function (err, v8flags) {
     '--expose-http2'
   ])
 
+  const env: { [key: string]: string | undefined } = {}
+
+  for (const key of Object.keys(process.env)) {
+    const val = process.env[key]
+    if (key.substring(0, 8) === 'TS_NODE_') {
+      env[key.substring(3)] = val
+    } else {
+      env[key] = val
+    }
+  }
+
   for (let i = 0; i < argv.length; i++) {
     const arg = argv[i]
     const flag = arg.split('=', 1)[0]
@@ -62,6 +73,7 @@ v8flags(function (err, v8flags) {
       //
       // See: https://nodejs.org/api/child_process.html#child_process_options_detached
       detached: true,
+      env,
       stdio: 'inherit'
     }
   )