Add a `strict` option for path resolution about rollup-plugin-includepaths

[matthieusieben]

As a workaround, I wrote my own extension. I post it here so that you understand the logic I meant:

        {
            resolveId (file, origin) {
                if (file.charAt(0) === '/') {
                    return file
                } else if (file.charAt(0) === '.') {
                    const basePath = path.dirname(origin)
                    return fileExists(path.join(basePath, file))
                        || fileExists(path.join(basePath, file + '.js'))
                } else {
                    return fileExists(path.join(__dirname, 'src', file))
                        || fileExists(path.join(__dirname, 'src', file + '.js'))
                        || fileExists(path.join(__dirname, 'src', file, 'index.js'))
                }
                function fileExists (file) {
                    try {
                        let stat = fs.statSync(file);
                        return stat.isFile() && file || null;
                    } catch (e) {
                        return null;
                    }
                }
            }
        }

my options for includepaths would be as follows

includepaths({
  external: [],
  paths: [ 'src' ],
  relativeStrict: true,
  extensions: [ '.js', '.json', '.html' ]
}),

[darlanalves]

I've been thinking about this issue and it seems a bit complicated to cover all cases.

What if you have both cases in the same project? e.g a file called events.js in the root folder (src) and another file trying to use the builtin events module. If both use the same import name ('events'), is impossible to determine which is which.

If you prepend the file with a slash ('/events') that would in turn shadow imports with an absolute path if the logic changes.
If you only resolve files starting with ./ or ../, you have to "hardcode" the entire path to "events.js" somehow.

Correct me if I'm wrong, but this confusion is caused by a "sloppiness" in the way Node.JS resolves the file paths.
ES6 module syntax should always include the file extension in the module path ("events.js"). I'm not sure if that resolves all cases, but I think in your case you should use the file extension to differentiate between a file import ('events.js') and a builtin module import ('events'), rather than changing the resolution logic.

What do you think?