feat(query-on-demand): loading indicator

packages/gatsby/cache-dir/app.js

@@ -7,6 +7,7 @@ import socketIo from "./socketIo"
 import emitter from "./emitter"
 import { apiRunner, apiRunnerAsync } from "./api-runner-browser"
 import { setLoader, publicLoader } from "./loader"
+import { Indicator } from "./loading-indicator/indicator"
 import DevLoader from "./dev-loader"
 import syncRequires from "$virtual/sync-requires"
 // Generated during bootstrap
@@ -122,6 +123,30 @@ apiRunnerAsync(`onClientEntry`).then(() => {
     ReactDOM.render
   )[0]
 
+  let dismissLoadingIndicator
+  if (
+    process.env.GATSBY_EXPERIMENTAL_QUERY_ON_DEMAND &&
+    process.env.GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR === `true`
+  ) {
+    let indicatorMountElement
+
+    const showIndicatorTimeout = setTimeout(() => {
+      indicatorMountElement = document.createElement(
+        `first-render-loading-indicator`
+      )
+      document.body.append(indicatorMountElement)
+      ReactDOM.render(<Indicator />, indicatorMountElement)
+    }, 1000)
+
+    dismissLoadingIndicator = () => {
+      clearTimeout(showIndicatorTimeout)
+      if (indicatorMountElement) {
+        ReactDOM.unmountComponentAtNode(indicatorMountElement)
+        indicatorMountElement.remove()
+      }
+    }
+  }
+
   Promise.all([
     loader.loadPage(`/dev-404-page/`),
     loader.loadPage(`/404.html`),
@@ -130,6 +155,10 @@ apiRunnerAsync(`onClientEntry`).then(() => {
     const preferDefault = m => (m && m.default) || m
     const Root = preferDefault(require(`./root`))
     domReady(() => {
+      if (dismissLoadingIndicator) {
+        dismissLoadingIndicator()
+      }
+
       renderer(<Root />, rootElement, () => {
         apiRunner(`onInitialClientRender`)
       })

packages/gatsby/cache-dir/debug-log.js

@@ -0,0 +1,13 @@
+// inspired by https://github.com/GoogleChrome/workbox/blob/3d02230f0e977eb1dc86c48f16ea4bcefdae12af/packages/workbox-core/src/_private/logger.ts
+
+const styles = [
+  `background: rebeccapurple`,
+  `border-radius: 0.5em`,
+  `color: white`,
+  `font-weight: bold`,
+  `padding: 2px 0.5em`,
+].join(`;`)
+
+export function debugLog(...args) {
+  console.debug(`%cgatsby`, styles, ...args)
+}

packages/gatsby/cache-dir/loading-indicator/index.js

@@ -0,0 +1,31 @@
+import React from "react"
+
+import emitter from "../emitter"
+import { Indicator } from "./indicator"
+
+// no hooks because we support react versions without hooks support
+export class LoadingIndicatorEventHandler extends React.Component {
+  state = { visible: false }
+
+  show = () => {
+    this.setState({ visible: true })
+  }
+
+  hide = () => {
+    this.setState({ visible: false })
+  }
+
+  componentDidMount() {
+    emitter.on(`onDelayedLoadPageResources`, this.show)
+    emitter.on(`onRouteUpdate`, this.hide)
+  }
+
+  componentWillUnmount() {
+    emitter.off(`onDelayedLoadPageResources`, this.show)
+    emitter.off(`onRouteUpdate`, this.hide)
+  }
+
+  render() {
+    return <Indicator visible={this.state.visible} />
+  }
+}

packages/gatsby/cache-dir/loading-indicator/indicator.js

@@ -0,0 +1,64 @@
+import React from "react"
+import Portal from "./portal"
+import Style from "./style"
+import { isLoadingIndicatorEnabled } from "$virtual/loading-indicator"
+import { debugLog } from "../debug-log"
+
+if (typeof window === `undefined`) {
+  throw new Error(
+    `Loading indicator should never be imported in code that doesn't target only browsers`
+  )
+}
+
+if (module.hot) {
+  module.hot.accept(`$virtual/loading-indicator`, () => {
+    // isLoadingIndicatorEnabled is imported with ES import so no need
+    // for dedicated handling as HMR just replace it in that case
+  })
+}
+
+// HMR can rerun this, so check if it was set before
+// we also set it on window and not just in module scope because of HMR resetting
+// module scope
+if (typeof window.___gatsbyDidShowLoadingIndicatorBefore === `undefined`) {
+  window.___gatsbyDidShowLoadingIndicatorBefore = false
+}
+
+export function Indicator({ visible = true }) {
+  if (!isLoadingIndicatorEnabled()) {
+    return null
+  }
+
+  if (!window.___gatsbyDidShowLoadingIndicatorBefore) {
+    // not ideal to this in render function, but that's just console info
+    debugLog(
+      `A loading indicator is displayed in-browser whenever content is being requested upon navigation (Query On Demand).\n\nYou can disable the loading indicator for your current session by visiting ${window.location.origin}/___loading-indicator/disable`
+    )
+    window.___gatsbyDidShowLoadingIndicatorBefore = true
+  }
+
+  return (
+    <Portal>
+      <Style />
+      <div
+        data-gatsby-loading-indicator="root"
+        data-gatsby-loading-indicator-visible={visible}
+        aria-live="assertive"
+      >
+        <div data-gatsby-loading-indicator="spinner" aria-hidden="true">
+          <svg
+            xmlns="http://www.w3.org/2000/svg"
+            viewBox="0 0 24 24"
+            fill="currentColor"
+          >
+            <path d="M0 0h24v24H0z" fill="none" />
+            <path d="M12 6v3l4-4-4-4v3c-4.42 0-8 3.58-8 8 0 1.57.46 3.03 1.24 4.26L6.7 14.8c-.45-.83-.7-1.79-.7-2.8 0-3.31 2.69-6 6-6zm6.76 1.74L17.3 9.2c.44.84.7 1.79.7 2.8 0 3.31-2.69 6-6 6v-3l-4 4 4 4v-3c4.42 0 8-3.58 8-8 0-1.57-.46-3.03-1.24-4.26z" />
+          </svg>
+        </div>
+        <div data-gatsby-loading-indicator="text">
+          {visible ? `Preparing requested page` : ``}
+        </div>
+      </div>
+    </Portal>
+  )
+}

packages/gatsby/cache-dir/loading-indicator/portal.js

@@ -0,0 +1,43 @@
+import * as React from "react"
+import { createPortal } from "react-dom"
+
+// this is `fast-refresh-overlay/portal` ported to class component
+// because we don't have guarantee that query on demand users will use
+// react version that supports hooks
+// TO-DO: consolidate both portals into single shared component (need testing)
+class ShadowPortal extends React.Component {
+  mountNode = React.createRef(null)
+  portalNode = React.createRef(null)
+  shadowNode = React.createRef(null)
+  state = {
+    createdElement: false,
+  }
+
+  componentDidMount() {
+    const ownerDocument = this.mountNode.current.ownerDocument
+    this.portalNode.current = ownerDocument.createElement(`gatsby-portal`)
+    this.shadowNode.current = this.portalNode.current.attachShadow({
+      mode: `open`,
+    })
+    ownerDocument.body.appendChild(this.portalNode.current)
+    this.setState({ createdElement: true })
+  }
+
+  componentWillUnmount() {
+    if (this.portalNode.current && this.portalNode.current.ownerDocument) {
+      this.portalNode.current.ownerDocument.body.removeChild(
+        this.portalNode.current
+      )
+    }
+  }
+
+  render() {
+    return this.shadowNode.current ? (
+      createPortal(this.props.children, this.shadowNode.current)
+    ) : (
+      <span ref={this.mountNode} />
+    )
+  }
+}
+
+export default ShadowPortal

packages/gatsby/cache-dir/loading-indicator/style.js

@@ -0,0 +1,115 @@
+import React from "react"
+
+function css(strings, ...keys) {
+  const lastIndex = strings.length - 1
+  return (
+    strings.slice(0, lastIndex).reduce((p, s, i) => p + s + keys[i], ``) +
+    strings[lastIndex]
+  )
+}
+
+const Style = () => (
+  <style
+    dangerouslySetInnerHTML={{
+      __html: css`
+        :host {
+          --purple-60: #663399;
+          --gatsby: var(--purple-60);
+          --purple-40: #b17acc;
+          --purple-20: #f1defa;
+          --dimmedWhite: rgba(255, 255, 255, 0.8);
+          --white: #ffffff;
+          --black: #000000;
+          --grey-90: #232129;
+          --radii: 4px;
+          --z-index-normal: 5;
+          --z-index-elevated: 10;
+          --shadow: 0px 2px 4px rgba(46, 41, 51, 0.08),
+            0px 4px 8px rgba(71, 63, 79, 0.16);
+        }
+
+        [data-gatsby-loading-indicator="root"] {
+          font: 14px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
+            Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji",
+            "Segoe UI Symbol" !important;
+          background: var(--white);
+          color: var(--grey-90);
+          position: fixed;
+          bottom: 1.5em;
+          left: 1.5em;
+          box-shadow: var(--shadow);
+          border-radius: var(--radii);
+          z-index: var(--z-index-elevated);
+          border-left: 0.25em solid var(--purple-40);
+          display: flex;
+          align-items: center;
+          justify-content: space-between;
+          flex-wrap: nowrap;
+          padding: 0.75em 1.15em;
+          min-width: 196px;
+        }
+
+        [data-gatsby-loading-indicator-visible="false"] {
+          opacity: 0;
+          visibility: hidden;
+          will-change: opacity, transform;
+          transform: translateY(45px);
+          transition: all 0.3s ease-in-out;
+        }
+
+        [data-gatsby-loading-indicator-visible="true"] {
+          opacity: 1;
+          visibility: visible;
+          transform: translateY(0px);
+          transition: all 0.3s ease-in-out;
+        }
+
+        [data-gatsby-loading-indicator="spinner"] {
+          animation: spin 1s linear infinite;
+          height: 18px;
+          width: 18px;
+          color: var(--gatsby);
+        }
+
+        [data-gatsby-loading-indicator="text"] {
+          margin-left: 0.75em;
+          line-height: 18px;
+        }
+
+        @keyframes spin {
+          0% {
+            transform: rotate(0);
+          }
+          100% {
+            transform: rotate(360deg);
+          }
+        }
+
+        @media (prefers-reduced-motion: reduce) {
+          [data-gatsby-loading-indicator="spinner"] {
+            animation: none;
+          }
+          [data-gatsby-loading-indicator-visible="false"] {
+            transition: none;
+          }
+
+          [data-gatsby-loading-indicator-visible="true"] {
+            transition: none;
+          }
+        }
+
+        @media (prefers-color-scheme: dark) {
+          [data-gatsby-loading-indicator="root"] {
+            background: var(--grey-90);
+            color: var(--white);
+          }
+          [data-gatsby-loading-indicator="spinner"] {
+            color: var(--purple-20);
+          }
+        }
+      `,
+    }}
+  />
+)
+
+export default Style

packages/gatsby/cache-dir/navigation.js

@@ -43,6 +43,12 @@ const onPreRouteUpdate = (location, prevLocation) => {
 const onRouteUpdate = (location, prevLocation) => {
   if (!maybeRedirect(location.pathname)) {
     apiRunner(`onRouteUpdate`, { location, prevLocation })
+    if (
+      process.env.GATSBY_EXPERIMENTAL_QUERY_ON_DEMAND &&
+      process.env.GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR === `true`
+    ) {
+      emitter.emit(`onRouteUpdate`, { location, prevLocation })
+    }
   }
 }
 

packages/gatsby/cache-dir/root.js

@@ -14,6 +14,7 @@ import EnsureResources from "./ensure-resources"
 import FastRefreshOverlay from "./fast-refresh-overlay"
 
 import { reportError, clearError } from "./error-overlay-handler"
+import { LoadingIndicatorEventHandler } from "./loading-indicator"
 
 // TODO: Remove entire block when we make fast-refresh the default
 // In fast-refresh, this logic is all moved into the `error-overlay-handler`
@@ -147,5 +148,9 @@ const ConditionalFastRefreshOverlay = ({ children }) => {
 export default () => (
   <ConditionalFastRefreshOverlay>
     <StaticQueryStore>{WrappedRoot}</StaticQueryStore>
+    {process.env.GATSBY_EXPERIMENTAL_QUERY_ON_DEMAND &&
+      process.env.GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR === `true` && (
+        <LoadingIndicatorEventHandler />
+      )}
   </ConditionalFastRefreshOverlay>
 )

packages/gatsby/src/services/initialize.ts

@@ -227,6 +227,18 @@ export async function initialize({
 
   process.env.GATSBY_HOT_LOADER = getReactHotLoaderStrategy()
 
+  // TODO: figure out proper way of disabling loading indicator
+  // for now GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR=false gatsby develop
+  // will work, but we don't want to force users into using env vars
+  if (
+    process.env.GATSBY_EXPERIMENTAL_QUERY_ON_DEMAND &&
+    !process.env.GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR
+  ) {
+    // if query on demand is enabled and GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR was not set at all
+    // enable loading indicator
+    process.env.GATSBY_QUERY_ON_DEMAND_LOADING_INDICATOR = `true`
+  }
+
   // theme gatsby configs can be functions or objects
   if (config && config.__experimentalThemes) {
     reporter.warn(