perf(gatsby/babel): Optimize hook destructuring

packages/babel-preset-gatsby/.babelrc

@@ -1,3 +1,9 @@
 {
-  "presets": [["babel-preset-gatsby-package"]]
+  "presets": [["babel-preset-gatsby-package"]],
+  "overrides": [
+    {
+      "test": ["**/*.ts", "**/*.tsx"],
+      "plugins": [["@babel/plugin-transform-typescript", { "isTSX": true }]]
+    }
+  ]
 }

packages/babel-preset-gatsby/README.md

@@ -15,6 +15,7 @@ For more information on how to customize the Babel configuration of your Gatsby
 - [`babel-plugin-transform-react-remove-prop-types`](https://github.com/oliviertassinari/babel-plugin-transform-react-remove-prop-types)
 - [`@babel/plugin-proposal-nullish-coalescing-operator`](https://babeljs.io/docs/en/babel-plugin-proposal-nullish-coalescing-operator)
 - [`@babel/plugin-proposal-optional-chaining`](https://babeljs.io/docs/en/babel-plugin-proposal-optional-chaining)
+- [`babel-plugin-optimize-hook-destructuring`](https://www.github.com/gatsbyjs/gatsby/packages/babel-plugin-optimize-hook-destructring)
 
 ## Usage
 

packages/babel-preset-gatsby/src/__tests__/__snapshots__/index.js.snap

@@ -3,6 +3,12 @@
 exports[`babel-preset-gatsby should specify proper presets and plugins when stage is build-html 1`] = `
 Object {
   "plugins": Array [
+    Array [
+      "<PROJECT_ROOT>/packages/babel-preset-gatsby/src/optimize-hook-destructuring.ts",
+      Object {
+        "lib": true,
+      },
+    ],
     Array [
       "<PROJECT_ROOT>/node_modules/@babel/plugin-proposal-class-properties/lib/index.js",
       Object {
@@ -66,6 +72,12 @@ Object {
 exports[`babel-preset-gatsby should specify proper presets and plugins when stage is build-javascript 1`] = `
 Object {
   "plugins": Array [
+    Array [
+      "<PROJECT_ROOT>/packages/babel-preset-gatsby/src/optimize-hook-destructuring.ts",
+      Object {
+        "lib": true,
+      },
+    ],
     Array [
       "<PROJECT_ROOT>/node_modules/@babel/plugin-proposal-class-properties/lib/index.js",
       Object {
@@ -133,6 +145,12 @@ Object {
 exports[`babel-preset-gatsby should specify proper presets and plugins when stage is build-stage 1`] = `
 Object {
   "plugins": Array [
+    Array [
+      "<PROJECT_ROOT>/packages/babel-preset-gatsby/src/optimize-hook-destructuring.ts",
+      Object {
+        "lib": true,
+      },
+    ],
     Array [
       "<PROJECT_ROOT>/node_modules/@babel/plugin-proposal-class-properties/lib/index.js",
       Object {
@@ -194,6 +212,12 @@ Object {
 exports[`babel-preset-gatsby should specify proper presets and plugins when stage is develop 1`] = `
 Object {
   "plugins": Array [
+    Array [
+      "<PROJECT_ROOT>/packages/babel-preset-gatsby/src/optimize-hook-destructuring.ts",
+      Object {
+        "lib": true,
+      },
+    ],
     Array [
       "<PROJECT_ROOT>/node_modules/@babel/plugin-proposal-class-properties/lib/index.js",
       Object {

packages/babel-preset-gatsby/src/__tests__/optimize-hook-destructuring.js

@@ -0,0 +1,39 @@
+import { transform } from "@babel/core"
+import preset from "babel-preset-gatsby"
+import plugin from "../optimize-hook-destructuring"
+
+const trim = s => s.join(`\n`).trim().replace(/^\s+/gm, ``)
+
+const babel = code =>
+  transform(code, {
+    filename: `noop.js`,
+    presets: [preset],
+    plugins: [plugin],
+    babelrc: false,
+    configFile: false,
+    sourceType: `module`,
+    compact: true,
+    caller: {
+      name: `tests`,
+      supportsStaticESM: true,
+    },
+  }).code
+
+describe(`optimize-hook-destructuring`, () => {
+  it(`should transform Array-destructured hook return values use object destructuring`, () => {
+    const output = babel(
+      trim`
+      import { useState } from 'react';
+      const [count, setCount] = useState(0);
+    `
+    )
+
+    expect(output).toMatch(trim`
+    \"use strict\";var _react=require(\"react\");const{0:count,1:setCount}=(0,_react.useState)(0);
+    `)
+
+    expect(output).toMatchInlineSnapshot(
+      `"\\"use strict\\";var _react=require(\\"react\\");const{0:count,1:setCount}=(0,_react.useState)(0);"`
+    )
+  })
+})

packages/babel-preset-gatsby/src/index.js

@@ -70,6 +70,12 @@ module.exports = function preset(_, options = {}) {
       ],
     ],
     plugins: [
+      [
+        resolve(`./optimize-hook-destructuring`),
+        {
+          lib: true,
+        },
+      ],
       [
         resolve(`@babel/plugin-proposal-class-properties`),
         {

packages/babel-preset-gatsby/src/optimize-hook-destructuring.ts

@@ -0,0 +1,71 @@
+import { NodePath, PluginObj, Visitor } from "@babel/core"
+import * as BabelTypes from "@babel/types"
+import { Program } from "@babel/types"
+
+// matches any hook-like (the default)
+const isHook = /^use[A-Z]/
+
+// matches only built-in hooks provided by React et al
+const isBuiltInHook = /^use(Callback|Context|DebugValue|Effect|ImperativeHandle|LayoutEffect|Memo|Reducer|Ref|State)$/
+
+interface IState {
+  opts?: {
+    onlyBuiltIns?: boolean
+    lib?: boolean
+  }
+}
+
+export default function ({
+  types: t,
+}: {
+  types: typeof BabelTypes
+}): PluginObj<Program> {
+  const visitor: Visitor = {
+    CallExpression(path, state: IState): void {
+      const onlyBuiltIns = state.opts?.onlyBuiltIns || false
+
+      // if specified, options.lib is a list of libraries that provide hook functions
+      const libs =
+        state.opts?.lib === true ? [`react`, `preact/hooks`] : [state.opts!.lib]
+
+      // skip function calls that are not the init of a variable declaration:
+      if (!t.isVariableDeclarator(path.parent)) return
+
+      // skip function calls where the return value is not Array-destructured:
+      if (!t.isArrayPattern(path.parent.id)) return
+
+      // name of the (hook) function being called:
+      const hookName = (path.node.callee as BabelTypes.Identifier).name
+
+      if (libs) {
+        const binding = path.scope.getBinding(hookName)
+        // not an import
+        if (!binding || binding.kind !== `module`) return
+
+        const specifier = (binding.path.parent as BabelTypes.ImportDeclaration)
+          .source.value
+        // not a match
+        if (!libs.some(lib => lib === specifier)) return
+      }
+
+      // only match function calls with names that look like a hook
+      if (!(onlyBuiltIns ? isBuiltInHook : isHook).test(hookName)) return
+
+      path.parent.id = t.objectPattern(
+        path.parent.id.elements.map((element, i) =>
+          t.objectProperty(t.numericLiteral(i), element!)
+        )
+      )
+    },
+  }
+
+  return {
+    name: `optimize-hook-destructuring`,
+    visitor: {
+      // this is a workaround to run before preset-env destroys destructured assignments
+      Program<Program>(path: NodePath<Program>, state: any): void {
+        path.traverse(visitor, state)
+      },
+    },
+  }
+}

packages/gatsby-dev-cli/src/__tests__/watch.js

@@ -183,6 +183,7 @@ describe(`watching`, () => {
 })
 
 const monoRepoPackages = [
+  `babel-plugin-optimize-hook-destructuring`,
   `babel-plugin-remove-graphql-queries`,
   `babel-preset-gatsby`,
   `babel-preset-gatsby-package`,