knex/src/schema/columnbuilder.js

import { extend, each, toArray } from 'lodash'

// The chainable interface off the original "column" method.
export default function ColumnBuilder(client, tableBuilder, type, args) {
  this.client = client;
  this._method = 'add';
  this._single = {};
  this._modifiers = {};
  this._statements = [];
  this._type = columnAlias[type] || type;
  this._args = args;
  this._tableBuilder = tableBuilder;

  // If we're altering the table, extend the object
  // with the available "alter" methods.
  if (tableBuilder._method === 'alter') {
    extend(this, AlterMethods);
  }
}

// All of the modifier methods that can be used to modify the current query.
const modifiers = [
  'default', 'defaultsTo', 'defaultTo', 'unsigned',
  'nullable', 'first', 'after', 'comment', 'collate'
];

// Aliases for convenience.
const aliasMethod = {
  default:    'defaultTo',
  defaultsTo: 'defaultTo',
};

// If we call any of the modifiers (index or otherwise) on the chainable, we pretend
// as though we're calling `table.method(column)` directly.
each(modifiers, function(method) {
  const key = aliasMethod[method] || method
  ColumnBuilder.prototype[method] = function() {
    this._modifiers[key] = toArray(arguments);
    return this;
  };
});

ColumnBuilder.prototype.notNull =
ColumnBuilder.prototype.notNullable = function notNullable() {
  return this.nullable(false)
}

each(['index', 'primary', 'unique'], function(method) {
  ColumnBuilder.prototype[method] = function() {
    if (this._type.toLowerCase().indexOf('increments') === -1) {
      this._tableBuilder[method].apply(this._tableBuilder,
        [this._args[0]].concat(toArray(arguments)));
    }
    return this;
  };
});

// Specify that the current column "references" a column,
// which may be tableName.column or just "column"
ColumnBuilder.prototype.references = function(value) {
  return this._tableBuilder.foreign.call(this._tableBuilder, this._args[0], undefined, this)
    ._columnBuilder(this)
    .references(value);
};

const AlterMethods = {};

// Specify that the column is to be dropped. This takes precedence
// over all other rules for the column.
AlterMethods.drop = function() {
  this._single.drop = true;

  return this;
};

// Specify the "type" that we're looking to set the
// Knex takes no responsibility for any data-loss that may
// occur when changing data types.
AlterMethods.alterType = function(type) {
  this._statements.push({
    grouping: 'alterType',
    value: type
  });

  return this;
};

// Set column method to alter (default is add).
AlterMethods.alter = function() {
  this._method = 'alter';

  return this;
};

// Alias a few methods for clarity when processing.
const columnAlias = {
  'float'  : 'floating',
  'enum'   : 'enu',
  'boolean': 'bool',
  'string' : 'varchar',
  'bigint' : 'bigInteger'
};