codemods

A collection of transforms for use with facebook/jscodeshift.

• 🌩 Installation
• 🕹 Usage
• ⚙️ Contributing
• 📝 API
  • use-string-literal-props
  • add-react-import
  • import-from-root
  • remove-react-prop-types
  • remove-react-default-props
  • sort-jsx-props
  • sort-object-props
  • use-named-exports
  • use-named-imports
• ❓ Quick Intro To Making A Codemod
• 🙋🏾‍♀️ Getting Help

🌩 Installation

git clone https://github.com/JamieMason/codemods.git
cd codemods
yarn install

🕹 Usage

# yarn
yarn name-of-the-transform <path-to-file>

# npm
npm run name-of-the-transform -- <path-to-file>

# jscodeshift
jscodeshift -t ./transforms/name-of-the-transform.js <path-to-file>

⚙️ Contributing

Transforms can be created at ./transforms/<transform-name>.js and tested by adding example input files at ./test/fixtures/<transform-name>/<scenario-name>.input.js with the corresponding expected output alongside it at ./test/fixtures/<transform-name>/<scenario-name>.output.js.

All fixtures are discovered and tested when running yarn test.

📝 API

use-string-literal-props

Convert JSX props which are expressions for a string literal, into just a string literal.

/* INPUT */
const SomeComponent = () => (
  <AnotherComponent
    foo={'string'}
    label={`template with 0 substitutions`}
    whatever={`template with ${1} substitution`}
  />
);

/* OUTPUT */
const SomeComponent = () => (
  <AnotherComponent
    foo="string"
    label="template with 0 substitutions"
    whatever={`template with ${1} substitution`}
  />
);

add-react-import

Import React if it is missing from a file which uses JSX.

/* INPUT */
export const Component = () => <div />

/* OUTPUT */
import React from "react";
export const Component = () => <div />

import-from-root

Rewrite deep imports to import from a packages' root index.

Set the Environment Variable IMPORT_FROM_ROOT to apply this transform only to packages whose name starts with that string: IMPORT_FROM_ROOT=some-package yarn import-from-root <path-to-file>

/* INPUT */
import { foo } from "some-package/foo/bar/baz";

/* OUTPUT */
import { foo } from "some-package";

remove-react-prop-types

Remove use of React PropTypes.

/* INPUT */
import React from 'react'
import PropTypes from 'prop-types'

export const Greet = ({ name }) => <span>Hi {name}</span>
Greet.propTypes = { name: PropTypes.string }
/* OUTPUT */
import React from 'react'

export const Greet = ({ name }) => <span>Hi {name}</span>

remove-react-default-props

Remove use of React defaultProps.

/* INPUT */
import React from 'react'

export const Greet = ({ name }) => <span>Hi {name}</span>
Greet.defaultProps = { name: 'Stranger' }
/* OUTPUT */
import React from 'react'

export const Greet = ({ name }) => <span>Hi {name}</span>

sort-jsx-props

Sort props of JSX Components alphabetically.

/* INPUT */
<Music zootWoman={true} rickJames={true} zapp={true} />

/* OUTPUT */
<Music rickJames={true} zapp={true} zootWoman={true} />

sort-object-props

Sort members of Object Literals alphabetically.

/* INPUT */
const players = { messi: true, bergkamp: true, ginola: true };

/* OUTPUT */
const players = { bergkamp: true, ginola: true, messi: true };

use-named-exports

Naively convert a default export to a named export using the name of the file, which may clash with other variable names in the file. This codemod would need following up on with ESLint and some manual fixes.

/* INPUT */
// ~/Dev/repo/src/apps/health/server.js
export default mount("/health", app);

/* OUTPUT */
// ~/Dev/repo/src/apps/health/server.js
export const server = mount("/health", app);

use-named-imports

Naively convert a default import to a named import using the original name, which may not match what the module is actually exporting. This codemod would need following up on with ESLint and some manual fixes.

/* INPUT */
import masthead from "@sky-uk/koa-masthead";

/* OUTPUT */
import { masthead } from "@sky-uk/koa-masthead";

❓ Quick Intro To Making A Codemod

1. Open ASTExplorer with the Parser set to esprima and Transform set to jscodeshift.
2. Paste some Source in the Top-Left Panel which you want to Transform.
3. Edit your Codemod in the Bottom-Left Panel.

There will be 4 Panels:

Panel	Purpose
Top-Left	Source you want to transform
Top-Right	The AST of your Source
Bottom-Left	Your Codemod Script
Bottom-Right	The Result of applying your Codemod to your Source

The docs for jscodeshift aren't enough and you will need to refer to ast-type definitions to know what is available. Using VariableDeclaration as an example, you can find all variable declarations using the PascalCase j.VariableDeclaration

j(file.source).find(j.VariableDeclaration);

and create new variable declarations using the camelCase j.variableDeclarator.

j.variableDeclaration("const", [
  j.variableDeclarator(j.identifier(fileName), exportedValue)
]);

The VariableDeclaration definition shows what fields it takes, which are the arguments the j.variableDeclarator function takes, which are an Identifier (a variable with a name but no value), or a VariableDeclarator (a variable with a name as well as a value assigned).

If we look up the definition of VariableDeclarator we see it takes two arguments called id and init. The id is an identifier j.identifier('varName') and init is a value to initialise the variable with, which should be the AST of whatever value you want to assign. For a simple literal value, that would be j.literal('hello').

Putting that all together you have a Hello World Codemod of:

export default (file, api) => {
  const j = api.jscodeshift;

  // Have a look in the console at what APIs are available
  console.log({
    jscodeshiftAPI: j,
    fileAPI: j(file.source)
  });

  return j(file.source)
    .find(j.Program)
    .forEach(path => {
      // Unwrap the AST node from this wrapper
      const emptyFile = path.value;

      // add a comment
      const singleLineComment = j.commentLine(" Hello World");
      const varName = j.identifier("hello");
      emptyFile.comments = [singleLineComment];

      // add a const
      const literalString = j.literal("world");
      const nameValuePair = j.variableDeclarator(varName, literalString);
      const constVarStatement = j.variableDeclaration("const", [nameValuePair]);
      emptyFile.body = [constVarStatement];
    })
    .toSource();
};

Good luck!

🙋🏾‍♀️ Getting Help

• Get help with issues by creating a Bug Report.
• Discuss ideas by opening a Feature Request.