chore(gatsby): convert gatsby-link to typescript

packages/gatsby-link/.babelrc

@@ -1 +1,8 @@
-{}
+{
+  "presets": [["babel-preset-gatsby-package"]],
+  "overrides": [
+    {
+      "presets": [["babel-preset-gatsby-package", { "browser": true }]]
+    }
+  ]
+}

packages/gatsby-link/index.d.ts

@@ -1,6 +1,17 @@
 import * as React from "react"
 import { NavigateFn, LinkProps } from "@reach/router" // These come from `@types/reach__router`
 
+declare global {
+  /* eslint-disable @typescript-eslint/interface-name-prefix */
+  interface Window {
+    ___push: (to: string) => void
+    ___replace: (to: string) => void
+    ___navigate: (to: string, options?: NavigateOptions<{}>) => void
+    ___loader: { enqueue: (arg0: string) => {}, hovering: (arg0: string) => {} }
+  }
+  /* eslint-disable @typescript-eslint/interface-name-prefix */
+}
+
 // eslint-disable-next-line @typescript-eslint/naming-convention
 export interface GatsbyLinkProps<TState> extends LinkProps<TState> {
   /** A class to apply when this Link is active */

packages/gatsby-link/src/__tests__/index.js → packages/gatsby-link/src/__tests__/index.tsx

@@ -8,49 +8,81 @@ import {
   createMemorySource,
   createHistory,
   LocationProvider,
+  NavigateOptions,
 } from "@reach/router"
 import { Link, navigate, withPrefix, withAssetPrefix } from "../"
 
+type IntersectionObserverType = jest.Mock<
+  {
+    observe: (ref: Record<string, unknown>) => void
+    unobserve: (ref: Record<string, unknown>) => void
+    disconnect: () => void
+    trigger: (ref: Record<string, unknown>) => void
+  },
+  [cb: any]
+>
+
+interface ICustomNodeJsGlobal extends NodeJS.Global {
+  __BASE_PATH__: string | undefined
+  __PATH_PREFIX__: string | undefined
+  ___navigate: (
+    to: string,
+    options?: NavigateOptions<Record<string, unknown>>
+  ) => void
+  ___loader: {
+    enqueue: (arg0: string) => Record<string, unknown>
+    hovering?: (arg0: string) => Record<string, unknown>
+  }
+  IntersectionObserver: IntersectionObserverType
+}
+
+declare const global: ICustomNodeJsGlobal
+
 beforeEach(() => {
   global.__BASE_PATH__ = ``
   global.__PATH_PREFIX__ = ``
 })
 
 afterEach(cleanup)
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
+const getWithPrefix = (pathPrefix = ``) => {
+  global.__BASE_PATH__ = pathPrefix
+  return withPrefix
+}
+
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 const getInstance = (props, pathPrefix = ``) => {
   getWithPrefix()(pathPrefix)
   return <Link {...props} />
 }
 
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 const getNavigate = () => {
   global.___navigate = jest.fn()
   return navigate
 }
 
-const getWithPrefix = (pathPrefix = ``) => {
-  global.__BASE_PATH__ = pathPrefix
-  return withPrefix
-}
-
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 const getWithAssetPrefix = (prefix = ``) => {
   global.__PATH_PREFIX__ = prefix
   return withAssetPrefix
 }
 
-const setup = ({ sourcePath = `/`, linkProps, pathPrefix = `` } = {}) => {
+// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
+const setup = ({ sourcePath = `/`, pathPrefix = ``, linkProps = {} } = {}) => {
   const intersectionInstances = new WeakMap()
   // mock intersectionObserver
   global.IntersectionObserver = jest.fn(cb => {
     const instance = {
-      observe: ref => {
+      observe: (ref: Record<string, unknown>): void => {
         intersectionInstances.set(ref, instance)
       },
-      unobserve: ref => {
+      unobserve: (ref: Record<string, unknown>): void => {
         intersectionInstances.delete(ref)
       },
-      disconnect: () => {},
-      trigger: ref => {
+      disconnect: (): void => {},
+      trigger: (ref: Record<string, unknown>): void => {
         cb([
           {
             target: ref,
@@ -62,19 +94,20 @@ const setup = ({ sourcePath = `/`, linkProps, pathPrefix = `` } = {}) => {
 
     return instance
   })
+
   global.__BASE_PATH__ = pathPrefix
   const source = createMemorySource(sourcePath)
   const history = createHistory(source)
 
   const utils = render(
     <LocationProvider history={history}>
       <Link
+        {...linkProps}
         to="/"
         className="link"
         style={{ color: `black` }}
         activeClassName="is-active"
         activeStyle={{ textDecoration: `underline` }}
-        {...linkProps}
       >
         link
       </Link>
@@ -386,7 +419,7 @@ describe(`ref forwarding`, () => {
   })
 
   it(`handles a RefObject (React >=16.4)`, () => {
-    const ref = React.createRef(null)
+    const ref = React.createRef()
     setup({ linkProps: { ref } })
 
     expect(ref.current).toEqual(expect.any(HTMLElement))

packages/gatsby-link/src/__tests__/is-local-link.js → packages/gatsby-link/src/__tests__/is-local-link.ts

@@ -8,16 +8,24 @@ describe(`isLocalLink`, () => {
     expect(isLocalLink(`https://www.gatsbyjs.com`)).toBe(false)
   })
   it(`returns undefined if input is undefined or not a string`, () => {
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore purposefully wrong
     expect(isLocalLink(undefined)).toBeUndefined()
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore purposefully wrong
     expect(isLocalLink(-1)).toBeUndefined()
   })
   // TODO(v5): Unskip Tests
   it.skip(`throws TypeError if input is undefined`, () => {
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore error case
     expect(() => isLocalLink(undefined)).toThrowError(
       `Expected a \`string\`, got \`undefined\``
     )
   })
   it.skip(`throws TypeError if input is not a string`, () => {
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore error case
     expect(() => isLocalLink(-1)).toThrowError(
       `Expected a \`string\`, got \`number\``
     )

packages/gatsby-link/src/__tests__/rewrite-link-path.js → packages/gatsby-link/src/__tests__/rewrite-link-path.ts

@@ -1,11 +1,23 @@
-import { rewriteLinkPath } from "../rewrite-link-path"
+import type { TrailingSlash } from "gatsby-page-utils"
+
+import { rewriteLinkPath, type rewriteLinkPathType } from "../rewrite-link-path"
+
+interface ICustomNodeJsGlobal extends NodeJS.Global {
+  __TRAILING_SLASH__: TrailingSlash | undefined | string
+  __PATH_PREFIX__: string | undefined
+}
+
+declare const global: ICustomNodeJsGlobal
 
 beforeEach(() => {
   global.__TRAILING_SLASH__ = ``
   global.__PATH_PREFIX__ = undefined
 })
 
-const getRewriteLinkPath = (option = `legacy`, pathPrefix = undefined) => {
+const getRewriteLinkPath = (
+  option: string = `legacy`,
+  pathPrefix: string | undefined = undefined
+): rewriteLinkPathType => {
   global.__TRAILING_SLASH__ = option
   global.__PATH_PREFIX__ = pathPrefix
   return rewriteLinkPath