Warn about async calls in parse()

Cherry-picked from tj#1917.

lib/command.js

@@ -12,6 +12,8 @@ const { suggestSimilar } = require('./suggestSimilar');
 
 // @ts-check
 
+const PRODUCTION = process.env.NODE_ENV === 'production';
+
 class Command extends EventEmitter {
   /**
    * Initialize a new `Command`.
@@ -906,7 +908,11 @@ Expecting one of '${allowedValues.join("', '")}'`);
 
   parse(argv, parseOptions) {
     const userArgs = this._prepareUserArgs(argv, parseOptions);
-    this._parseCommand([], userArgs);
+    const result = this._parseCommand([], userArgs);
+    if (!PRODUCTION && isThenable(result)) {
+      console.warn(`.parse() is incompatible with async hooks and actions.
+Use .parseAsync() instead.`);
+    }
 
     return this;
   }
@@ -1188,8 +1194,7 @@ Expecting one of '${allowedValues.join("', '")}'`);
    */
 
   _chainOrCall(promise, fn) {
-    // thenable
-    if (promise && promise.then && typeof promise.then === 'function') {
+    if (isThenable(promise)) {
       // already have a promise, chain callback
       return promise.then(() => fn());
     }
@@ -2193,4 +2198,14 @@ function getCommandAndParents(startCommand) {
   return result;
 }
 
+/**
+ * @param {*} value
+ * @returns {boolean}
+ * @api private
+ */
+
+function isThenable(value) {
+  return typeof value?.then === 'function';
+}
+
 exports.Command = Command;