Is it possible to create custom resolver in webpack?

I have my own convention when require modules. E.g. require("./components/SettingsPanel"); should be resolved to require("./components/SettingsPanel/SettingsPanel.js");

Is there any way to create such resolver?

Yes, it's possible. To avoid ambiguity and for easier implementation, we'll use a prefix hash symbol as marker of your convention:

require("#./components/SettingsPanel");

Then add this to your configuration file (of course, you can refactor it later):

var webpack = require('webpack');
var path = require('path');

var MyConventionResolver = {
  apply: function(resolver) {
    resolver.plugin('module', function(request, callback) {
      if (request.request[0] === '#') {
        var req = request.request.substr(1);
        var obj = {
          path: request.path,
          request: req + '/' + path.basename(req) + '.js',
          query: request.query,
          directory: request.directory
        };
        this.doResolve(['file'], obj, callback);
      }
      else {
        callback();
      }
    });
  }
};


module.exports = {
    resolve: {
      plugins: [
        MyConventionResolver
      ]
    }
    // ...
};

Created an updated example to work with Webpack v4. Purposely did not use ES6 syntax for backwards compatibility. You can make it a class if you wish.

You can read more about resolver examples at https://github.com/webpack/enhanced-resolve.

Thanks Ricardo for supplying the original answer.

var webpack = require('webpack');
var path = require('path');

function MyConventionResolver (source, target) {
    this.source = source || 'resolve';
    this.target = target || 'resolve';
}

MyConventionResolver.prototype.apply = function(resolver) {
    var target = resolver.ensureHook(this.target);
    resolver.getHook(this.source).tapAsync('MyConventionResolver', function(request, resolveContext, callback) {
        if (request.request[0] === '#') {
            var req = request.request.substr(1);
            var obj = Object.assign({}, request, {
                request: req + '/' + path.basename(req) + '.js',
            });
            return resolver.doResolve(target, obj, null, resolveContext, callback);
        }
        callback();
    });
}


// In your Webpack Config
module.exports = {
    ...
    resolve: {
        plugins: [new MyConventionResolver()]
    }
};