(refactor/types): re-write src/index.js in TypeScript

- make heavy use of the multiple iterations on types in others' PRs,
  my own iterations on that, and then @types/react-signature-canvas
  - credit where credit is due!

- refactor init logic a bit to get around `| null` everywhere
  - kinda hacky but better than ifs or ! (non-nullable) everywhere
- use ! for canvas.getContext('2d') calls for same reason
  - c.f. microsoft/TypeScript#19229

- refactor naming everywhere to src/index.tsx

- configure tsconfig -- no need for allowJs anymore, but jsx needs to
  be set as TS is actually reading it now
- configure jest -- ts-jest needed to read TSX files

(deps): add DT typings for prop-types, react, and signature_pad
(deps): add a declaration file for trim-canvas as it doesn't have
types built-in yet (TODO for me!)
  - use typings/ to hold external declarations

example/src/index.js

@@ -1,7 +1,7 @@
 import React, { Component } from 'react'
 import ReactDOM from 'react-dom'
 
-import SignaturePad from '../../src/index.js'
+import SignaturePad from '../../src/index.tsx'
 
 import styles from './styles.module.css'
 

jest.config.js

@@ -9,7 +9,8 @@ module.exports = {
   ],
   transform: {
     // support babel-jest. TSDX defaults to just ts-jest. see https://github.com/jaredpalmer/tsdx/pull/486
-    '\\.js$': 'babel-jest'
+    '\\.js$': 'babel-jest',
+    '\\.tsx$': 'ts-jest'
   },
   // support JS + JSX. TSDX defaults to just TS + TSX. see https://github.com/jaredpalmer/tsdx/pull/486
   testMatch: ['**/?(*.)+(spec|test).[jt]s?(x)'],

package.json

@@ -55,6 +55,7 @@
     "react-dom": "0.14 - 17"
   },
   "dependencies": {
+    "@types/signature_pad": "^2.3.0",
     "signature_pad": "^2.3.2",
     "trim-canvas": "^0.1.0"
   },
@@ -63,6 +64,8 @@
     "@wojtekmaj/enzyme-adapter-react-17": "^0.6.6",
     "@babel/core": "^7.8.4",
     "@babel/preset-react": "^7.8.3",
+    "@types/prop-types": "^15.7.3",
+    "@types/react": "^16.9.19",
     "babel-eslint": "^10.0.2",
     "canvas": "^2.9.0",
     "enzyme": "^3.10.0",

src/index.js → src/index.tsx

@@ -3,7 +3,12 @@ import React, { Component } from 'react'
 import SignaturePad from 'signature_pad'
 import trimCanvas from 'trim-canvas'
 
-export class SignatureCanvas extends Component {
+export interface ReactSignatureCanvasProps extends SignaturePad.SignaturePadOptions {
+  canvasProps?: React.CanvasHTMLAttributes<HTMLCanvasElement>,
+  clearOnResize?: boolean
+}
+
+export class SignatureCanvas extends Component<ReactSignatureCanvasProps> {
   static propTypes = {
     // signature_pad's props
     velocityFilterWeight: PropTypes.number,
@@ -24,7 +29,15 @@ export class SignatureCanvas extends Component {
     clearOnResize: true
   }
 
-  _sigPad = null
+  // this is some hack-ish init and casting to avoid `| null` everywhere :/
+  _sigPad: SignaturePad = {} as SignaturePad
+  _canvas: HTMLCanvasElement = {} as HTMLCanvasElement
+
+  private readonly setRef = (ref: HTMLCanvasElement | null) => {
+    if (ref) {
+      this._canvas = ref
+    }
+  }
 
   _excludeOurProps = () => {
     const { canvasProps, clearOnResize, ...sigPadProps } = this.props
@@ -47,23 +60,23 @@ export class SignatureCanvas extends Component {
   }
 
   // return the canvas ref for operations like toDataURL
-  getCanvas = () => {
+  getCanvas = (): HTMLCanvasElement => {
     return this._canvas
   }
 
   // return a trimmed copy of the canvas
-  getTrimmedCanvas = () => {
+  getTrimmedCanvas = (): HTMLCanvasElement => {
     // copy the canvas
     const copy = document.createElement('canvas')
     copy.width = this._canvas.width
     copy.height = this._canvas.height
-    copy.getContext('2d').drawImage(this._canvas, 0, 0)
+    copy.getContext('2d')!.drawImage(this._canvas, 0, 0)
     // then trim it
     return trimCanvas(copy)
   }
 
   // return the internal SignaturePad reference
-  getSignaturePad = () => {
+  getSignaturePad = (): SignaturePad => {
     return this._sigPad
   }
 
@@ -94,48 +107,48 @@ export class SignatureCanvas extends Component {
     if (!height) {
       canvas.height = canvas.offsetHeight * ratio
     }
-    canvas.getContext('2d').scale(ratio, ratio)
+    canvas.getContext('2d')!.scale(ratio, ratio)
     this.clear()
   }
 
   render () {
     const { canvasProps } = this.props
-    return <canvas ref={(ref) => { this._canvas = ref }} {...canvasProps} />
+    return <canvas ref={this.setRef} {...canvasProps} />
   }
 
   // all wrapper functions below render
   //
-  on = () => {
+  on: SignaturePad['on'] = () => {
     window.addEventListener('resize', this._checkClearOnResize)
     return this._sigPad.on()
   }
 
-  off = () => {
+  off: SignaturePad['off'] = () => {
     window.removeEventListener('resize', this._checkClearOnResize)
     return this._sigPad.off()
   }
 
-  clear = () => {
+  clear: SignaturePad['clear'] = () => {
     return this._sigPad.clear()
   }
 
-  isEmpty = () => {
+  isEmpty: SignaturePad['isEmpty'] = () => {
     return this._sigPad.isEmpty()
   }
 
-  fromDataURL = (dataURL, options) => {
+  fromDataURL: SignaturePad['fromDataURL'] = (dataURL, options) => {
     return this._sigPad.fromDataURL(dataURL, options)
   }
 
-  toDataURL = (type, encoderOptions) => {
+  toDataURL: SignaturePad['toDataURL'] = (type, encoderOptions) => {
     return this._sigPad.toDataURL(type, encoderOptions)
   }
 
-  fromData = (pointGroups) => {
+  fromData: SignaturePad['fromData'] = (pointGroups) => {
     return this._sigPad.fromData(pointGroups)
   }
 
-  toData = () => {
+  toData: SignaturePad['toData'] = () => {
     return this._sigPad.toData()
   }
 }

test/index.spec.js

@@ -2,7 +2,7 @@ import { jest, describe, it, test, expect } from 'jest-without-globals'
 import { mount } from 'enzyme'
 import React from 'react'
 
-import SignatureCanvas from '../src/index.js'
+import SignatureCanvas from '../src/index.tsx'
 import { propsF, dotF } from './fixtures.js'
 
 test('mounts canvas and instance properly', () => {

tsconfig.json

@@ -1,5 +1,5 @@
 {
-  "include": ["src", "types"],
+  "include": ["src", "typings"],
   "compilerOptions": {
     "module": "esnext",
     "lib": ["dom", "esnext"],
@@ -18,6 +18,6 @@
       "*": ["src/*", "node_modules/*"]
     },
     "esModuleInterop": true,
-    "allowJs": true
+    "jsx": "react"
   }
 }

typings/trim-canvas.d.ts

@@ -0,0 +1,3 @@
+declare module 'trim-canvas' {
+  export default function trimCanvas (canvas: HTMLCanvasElement): HTMLCanvasElement
+}