directives.js

// Define core directive code + attributes and store that as a module value
angular.module('com.namespace.directives').value('MyDirectiveCore', MyDirectiveCore);

function MyDirectiveCore($compile) {
  this.restrict = 'A';
  this.priority = 10;
  this.link = postLink;

  return this;
  
  function postLink(scope, element, attrs) {
    // Use $compile, scope, element, ... whatever
  }
}

// Define directive to be used in HTML, injecting core definition from previous module
angular.module('com.namespace.directives').directive('myDirective', ['$compile', 'MyDirectiveCore', factory]);

function factory($compile, MyDirectiveCore) {

    return new MyDirectiveCore($compile);
}