@a-la/import

@a-la/import

@a-la/import is a a set of rules for alamode to transpile the import statement into a require call in Node.js.

À La Mode is a RegExp-based transpiler which works faster than AST-based transpilers such as @babel, has fewer dependencies, and occupies less disk space.

yarn add -E @a-la/import

Table Of Contents

• Table Of Contents
• API
  • ALaImport Sequence
  • Options
• Output Example
• Lines Preservation
  • Named Imports
  • Named & Default
• Checklist
• TODO
• Copyright

API

The ALaImport is the default export and an array containing a sequence of rules for Replaceable.

import ALaImport from '@a-la/import'

ALaImport Sequence

The rule set exported as an array by ALaImport has multiple regexes and replacer functions to match all possible cases. The replacer functions expect to see the matchers property on the context, which is set by alamode to access cut out strings. The transform can be run using @a-la/context which is a lightweight version of alamode which mimics its stream functionality.

/* yarn example/ */
import ALaContext from '@a-la/context'
import ALaImport from '@a-la/import'

const STRING = `import aLaMode from 'alamode'
import ALaImport from "@a-la/import"
import App from 'koa'
import test from './test'
`

;(async () => {
  const context = new ALaContext()
  const { result } = await context.stream(ALaImport, STRING)
  console.log(result)
})()

let aLaMode = require('alamode'); if (aLaMode && aLaMode.__esModule) aLaMode = aLaMode.default;
let ALaImport = require("@a-la/import"); if (ALaImport && ALaImport.__esModule) ALaImport = ALaImport.default;
let App = require('koa'); if (App && App.__esModule) App = App.default;
const test = require('./test');

Options

The transform accepts a number of options via the .alamoderc.

• replacement option is used to substitute the name or path of an imported module.

  {
    "env": {
      "test-build": {
        "import": {
          "replacement": {
            "from": "^((../)+)src",
            "to": "$1build"
          }
        }
      }
    }
  }
  

• esCheck option is used to always enforce the if (mod.__esModule) check -- by default, this is switched off for local imports, but is added when requiring external packages to make it compatible with Babel and TypeScript.

  {
    "env": {
      "test-build": {
        "import": {
          "esCheck": "always",
        }
      }
    }
  }
  

Output Example

The set of rules changes import to require statements. When importing a default module, a check will be made to see if it was transpiled with Babel which is indicated by the presence of the __esModule property, and if it was, then the default property is reassinged to the variable.

import aLaMode from 'alamode'
import scopeALaMode from "@a-la/import"

import { methodA, methodB } from 'alamode'
import { methodC, methodD as aliasD } from 'alamode'
import defaultALaMode, {
  methodE, methodF,
} from 'alamode'

import def, * as tests from './tests'

let aLaMode = require('alamode'); if (aLaMode && aLaMode.__esModule) aLaMode = aLaMode.default;
let scopeALaMode = require("@a-la/import"); if (scopeALaMode && scopeALaMode.__esModule) scopeALaMode = scopeALaMode.default;

const { methodA, methodB } = require('alamode');
const { methodC, methodD: aliasD } = require('alamode');
let defaultALaMode = require('alamode'); const {
  methodE, methodF,
} = defaultALaMode; if (defaultALaMode && defaultALaMode.__esModule) defaultALaMode = defaultALaMode.default;

const tests = def = require('./tests');

Lines Preservation

The transform will attempt to preserve lines as they are for easier generation of source maps by alamode. In future, this might change.

Named Imports

The named imports are only changed to replace as into :, otherwise the destructuring syntax is the same as for imports themselves.

import { test, test2,
  test3 as alias3 }
from 'package'

const { test, test2,
  test3: alias3 }
= require('package');

Named & Default

When there is a default import along with named once, the line numbers will be respected.

import def, {
  test, test2,
  test3 as alias3,
  test4
    as
  alias4,
}
  from
  'package'

let def = require('package'); const {
  test, test2,
  test3: alias3,
  test4
    :
  alias4,
}
  =
  def; if (def && def.__esModule) def = def.default;

Checklist

• import defaultExport from "module-name"
• import * as name from "module-name";
• import { export } from "module-name";
• import { export as alias } from "module-name";
• import { export1 , export2 } from "module-name";
• import { export1 , export2 as alias2 , [...] } from "module-name";
• import defaultExport, { export [ , [...] ] } from "module-name";
• import defaultExport, * as name from "module-name";
• import "module-name";
• var promise = import(module-name);

TODO

• Add an option to ignore the __esModule check for specified packages.
• Better from 'package' handling when matchers' logic is updated in the restream.

Copyright

(c) À La Mode 2018

Changelog

1.7.0

• [feature] Do not add the __esModule check to modules imported locally.

20 September 2018