Changes the opt-out character from _ to #

[dlmr]

The change

This change is needed since we might have collisions with internal modules in Node otherwise, as seen here.

An example where this is a problem is in browserify-zlib that has the following code:

var Transform = require('_stream_transform');

Roc will in some instances process this code through its resolver and the following branch will be true.

// request = _stream_transform
if (request.charAt(0) === '_') {
   // stream_transform
   return request.substring(1);
}

This means that the code will now try to require stream_transform instead of the correct _stream_transform. This will then result in an error since this module does not exist.

ModuleNotFoundError: Module not found: Error: Cannot resolve module 'stream_transform' in /project/node_modules/browserify-zlib/src

This change means that opting out now is done in the following way.

-import React from '_react';
-var React = require('_react');
+import React from '#react';
+var React = require('#react');

Question

Is the # a good character to use for opt-out? Is there a better alternative that we can use?

[lizell]

Great fix!

I'm not very into what characters to use or not in the require realm, so # works for me.

[andreasrs]

👍
Looks good.

Like @lizell I do not really have any strong opinions on what character is best for this. I don't know how safe # is. Do you think multiple characters could be considered for this opt-out? It should be rarely used, and the most important thing is that it never collides.

[dlmr]

When selecting the character for the opt-out we want to make sure it does not match the following.

1. A normal path.
2. A npm module.
3. An internal Node module.

We unfortunately missed that the third point could contain underscore, hence this bug.

So given this conditions we need to use something that is:

1. Not a path, that is an absolute or relative path in either Windows or Unix. Begins with either ., / or a drive character in Windows like C.
2. A non valid starting character for a module name, the code used to validate it can be seen here. Basically it means that it should not start with a . or a _ and it needs to be "URL-friendly" (encodeURIComponent should not change the input).
3. Internal modules might start with _.

This leaves us with some alternatives and the only other requirement that we are after is that it is easy to type and remember. Alternatives include characters like %, &, =, : and >.

[lizell]

So maybe :? It has a local touch to it if you ask me. ;)

[lizell]

If the character choice is the only thing holding this PR back, I'm happy with any! ;)

[bjarneo]

I vote for fish. >==#>

If that's a no go, I vote for #.

[dlmr]

The only problem I have with : is that it might be easy to miss since it does not take as much "space".

require(':react');

require('#react');

With that logic however we do not need to use only a single character but could go for multiple ones like :: or maybe a 🐟 … 😄