Fix: Only create @babel/node IPC channel when needed

packages/babel-node/src/babel-node.js

@@ -84,8 +84,12 @@ getV8Flags(async function (err, v8Flags) {
       throw err;
     }
 
+    // passthrough IPC only if babel-node itself has an IPC channel
+    const shouldPassthroughIPC = process.send !== undefined;
     const proc = child_process.spawn(process.argv[0], args, {
-      stdio: ["inherit", "inherit", "inherit", "ipc"],
+      stdio: shouldPassthroughIPC
+        ? ["inherit", "inherit", "inherit", "ipc"]
+        : "inherit",
     });
     proc.on("exit", function (code, signal) {
       process.on("exit", function () {
@@ -96,7 +100,9 @@ getV8Flags(async function (err, v8Flags) {
         }
       });
     });
-    proc.on("message", message => process.send && process.send(message));
+    if (shouldPassthroughIPC) {
+      proc.on("message", message => process.send(message));
+    }
     process.on("SIGINT", () => proc.kill("SIGINT"));
   }
 });

packages/babel-node/test/fixtures.js

@@ -44,7 +44,7 @@ const saveInFiles = function (files) {
   });
 };
 
-const assertTest = function (stdout, stderr, opts) {
+const assertTest = function (stdout, stderr, ipcMessage, opts) {
   const expectStderr = opts.stderr.trim();
   stderr = stderr.trim();
 
@@ -72,6 +72,10 @@ const assertTest = function (stdout, stderr, opts) {
     throw new Error("stdout:\n" + stdout);
   }
 
+  if (opts.ipc) {
+    expect(ipcMessage).toEqual(opts.ipcMessage);
+  }
+
   if (opts.outFiles) {
     const actualFiles = readDir(path.join(tmpLoc));
 
@@ -101,10 +105,16 @@ const buildTest = function (testName, opts) {
     args.push("--config-file", "../config.json");
     args = args.concat(opts.args);
 
-    const spawn = child.spawn(process.execPath, args);
+    const spawnOpts = {};
+    if (opts.ipc) {
+      spawnOpts.stdio = ["pipe", "pipe", "pipe", "ipc"];
+    }
+
+    const spawn = child.spawn(process.execPath, args, spawnOpts);
 
     let stderr = "";
     let stdout = "";
+    let ipcMessage;
 
     spawn.stderr.on("data", function (chunk) {
       stderr += chunk;
@@ -114,11 +124,17 @@ const buildTest = function (testName, opts) {
       stdout += chunk;
     });
 
+    if (opts.ipc) {
+      spawn.on("message", function (message) {
+        ipcMessage = message;
+      });
+    }
+
     spawn.on("close", function () {
       let err;
 
       try {
-        assertTest(stdout, stderr, opts);
+        assertTest(stdout, stderr, ipcMessage, opts);
       } catch (e) {
         err = e;
       }

packages/babel-node/test/fixtures/cli/subprocess-send/in-files/payload.js → packages/babel-node/test/fixtures/cli/subprocess-ipc/in-files/payload.js

@@ -1,2 +1,2 @@
 process.send({ hello: "world" });
-console.log("sent");
+console.log("ipc enabled");

packages/babel-node/test/fixtures/cli/subprocess-ipc/options.json

@@ -0,0 +1,6 @@
+{
+  "args": ["payload.js"],
+  "ipcMessage": { "hello": "world" },
+  "ipc": true,
+  "stdout": "ipc enabled"
+}

packages/babel-node/test/fixtures/cli/subprocess-no-ipc/in-files/payload.js

@@ -0,0 +1,3 @@
+if (process.send == null) {
+    console.log("ipc disabled");
+}

packages/babel-node/test/fixtures/cli/subprocess-send/options.json → packages/babel-node/test/fixtures/cli/subprocess-no-ipc/options.json

@@ -1,4 +1,4 @@
 {
   "args": ["payload.js"],
-  "stdout": "sent"
+  "stdout": "ipc disabled"
 }