In the section on Node applications, please warn users about the name of the output file

[gilramir]

I wasted some time debugging a strange issue, and finally realized that the Gren compiler changes the javascript application based on whether the output file has a ".js" extension or not.

E.g., I compiled the "cat" project in the example-projects, repo, like this:

gren make --output=app.js Main
node app.js

It compiled, but nothing happened when I ran it.

Then I compiled it without the .js extension:

gren make --output=app Main
node app

And it worked as expected.
A diff of app to app.js shows:

--- app 2026-03-27 07:42:57.157644252 -0500
+++ app.js      2026-03-27 07:42:16.131507826 -0500
@@ -1,6 +1,3 @@
-#!/usr/bin/env node
-
-try {
 (function(scope){
 'use strict';

@@ -4458,10 +4455,4 @@
 };
 var $gren_lang$core$Json$Decode$succeed = _Json_succeed;
 var $author$project$Main$main = $gren_lang$node$Node$defineSimpleProgram($author$project$Main$init);
-_Platform_export({'Main':{'init':$author$project$Main$main($gren_lang$core$Json$Decode$succeed({  }))}});}(this.module ? this.module.exports : this));
-this.Gren.Main.init({});
-}
-catch (e)
-{
-console.error(e);
-}
+_Platform_export({'Main':{'init':$author$project$Main$main($gren_lang$core$Json$Decode$succeed({  }))}});}(this.module ? this.module.exports : this));

But also, I wonder, is this behavior necessary, considering that the project has been declared to be platform=node and type=application?

[robinheghan]

Thanks for reporting this. I agree, it can be a bit confusing.

We're sort of following Elm's lead here, as it will generate different code based on whether you output to a .js or .html file.

When you leave off the .js suffix, it will generate code that's meant to be executed directly. Adding .js makes it possible to import the code using require(./app.js) from a different JS file. This capability is important.

1. gren-make-static is only compatible with applications that don't have the suffix, due to limitations in how Node.js SAE works.
2. Is necessary when you want to register ports. Executing app.js won't start the application, as you're expected to do that yourself.

So we still need different ways of compiling an application, but I guess the better way to go about this would be to add a cli flag in the future, as the .js suffix detection can be confusing.