From c8db78fad43294413b950c49205adcf3dbb6dd1e Mon Sep 17 00:00:00 2001
From: Michal Piechowiak <misiek.piechowiak@gmail.com>
Date: Tue, 11 May 2021 17:41:22 +0200
Subject: [PATCH] fix(gatsby-plugin-mdx): enable hmr when importing mdx
 (#31288)

* save MDXContent to different file

* tmp: skip mdx loader unit tests

* test(e2e-mdx): upgrade cypress, setup running dev

* test(e2e-mdx): add hmr test case

* only apply hmr workaround to develop stage

* don't save mdx component to fs, use webpack tricks with query params

* wait for hmr in mdx/develop

* drop passthrough fs location

* revert unneeded change

* more reverts

* revert devtool debugging change

* adjust unit tests

* add more e2e test - editing prop in markdown, editing component imported by mdx
---
 e2e-tests/mdx/cypress-dev.json                |   6 +
 e2e-tests/mdx/cypress.json                    |   5 +-
 e2e-tests/mdx/cypress/integration/hmr.js      |  71 ++
 e2e-tests/mdx/package.json                    |  21 +-
 e2e-tests/mdx/scripts/history.js              |  25 +
 e2e-tests/mdx/scripts/reset.js                |  21 +
 e2e-tests/mdx/scripts/update.js               | 103 +++
 .../mdx/src/components/hmr-component-edit.js  |   7 +
 e2e-tests/mdx/src/components/hmr-prop-edit.js |   7 +
 e2e-tests/mdx/src/pages/hmr.mdx               |   8 +
 .../gatsby/create-webpack-config.js           |   1 +
 .../__snapshots__/mdx-loader.test.js.snap     | 722 ++++++++++++++++--
 .../gatsby-plugin-mdx/loaders/mdx-loader.js   |  23 +
 .../loaders/mdx-loader.test.js                | 115 ++-
 packages/gatsby-plugin-mdx/utils/gen-mdx.js   |   8 +-
 packages/gatsby/src/utils/webpack.config.js   |  41 +-
 16 files changed, 1057 insertions(+), 127 deletions(-)
 create mode 100644 e2e-tests/mdx/cypress-dev.json
 create mode 100644 e2e-tests/mdx/cypress/integration/hmr.js
 create mode 100644 e2e-tests/mdx/scripts/history.js
 create mode 100644 e2e-tests/mdx/scripts/reset.js
 create mode 100644 e2e-tests/mdx/scripts/update.js
 create mode 100644 e2e-tests/mdx/src/components/hmr-component-edit.js
 create mode 100644 e2e-tests/mdx/src/components/hmr-prop-edit.js
 create mode 100644 e2e-tests/mdx/src/pages/hmr.mdx

diff --git a/e2e-tests/mdx/cypress-dev.json b/e2e-tests/mdx/cypress-dev.json
new file mode 100644
index 0000000000000..89024688f2bea
--- /dev/null
+++ b/e2e-tests/mdx/cypress-dev.json
@@ -0,0 +1,6 @@
+{
+  "baseUrl": "http://localhost:8000",
+  "env": {
+    "GATSBY_COMMAND": "develop"
+  }
+}
diff --git a/e2e-tests/mdx/cypress.json b/e2e-tests/mdx/cypress.json
index db2ba6ad5f8d9..42fda02830191 100644
--- a/e2e-tests/mdx/cypress.json
+++ b/e2e-tests/mdx/cypress.json
@@ -1,3 +1,6 @@
 {
-  "baseUrl": "http://localhost:9000"
+  "baseUrl": "http://localhost:9000",
+  "env": {
+    "GATSBY_COMMAND": "build"
+  }
 }
diff --git a/e2e-tests/mdx/cypress/integration/hmr.js b/e2e-tests/mdx/cypress/integration/hmr.js
new file mode 100644
index 0000000000000..353184fc9ce44
--- /dev/null
+++ b/e2e-tests/mdx/cypress/integration/hmr.js
@@ -0,0 +1,71 @@
+if (Cypress.env("GATSBY_COMMAND") === `develop`) {
+  before(() => {
+    cy.exec(`npm run reset`)
+  })
+
+  after(() => {
+    cy.exec(`npm run reset`)
+  })
+
+  it(`Can hot-reload markdown content`, () => {
+    cy.visit(`/hmr`, {
+      onBeforeLoad: win => {
+        cy.spy(win.console, "log").as(`hmrConsoleLog`)
+      },
+    }).waitForRouteChange()
+    cy.get(`h2`).invoke(`text`).should(`eq`, `Lorem`)
+
+    cy.exec(
+      `npm run update -- --file src/pages/hmr.mdx --exact --replacements "Lorem:Ipsum"`
+    )
+
+    cy.get(`@hmrConsoleLog`).should(`be.calledWithMatch`, `App is up to date`)
+    cy.wait(1000)
+
+    cy.get(`h2`).invoke(`text`).should(`eq`, `Ipsum`)
+  })
+
+  it(`Can hot-reload react content (i.e. change prop in mdx content)`, () => {
+    cy.visit(`/hmr`, {
+      onBeforeLoad: win => {
+        cy.spy(win.console, "log").as(`hmrConsoleLog`)
+      },
+    }).waitForRouteChange()
+    cy.get(`[data-testid="test-prop-edit"]`)
+      .invoke(`text`)
+      .should(`eq`, `prop-before`)
+
+    cy.exec(
+      `npm run update -- --file src/pages/hmr.mdx --exact --replacements "prop-before:prop-after"`
+    )
+
+    cy.get(`@hmrConsoleLog`).should(`be.calledWithMatch`, `App is up to date`)
+    cy.wait(1000)
+
+    cy.get(`[data-testid="test-prop-edit"]`)
+      .invoke(`text`)
+      .should(`eq`, `prop-after`)
+  })
+
+  it(`Can hot-reload imported js components`, () => {
+    cy.visit(`/hmr`, {
+      onBeforeLoad: win => {
+        cy.spy(win.console, "log").as(`hmrConsoleLog`)
+      },
+    }).waitForRouteChange()
+    cy.get(`[data-testid="test-imported-edit"]`)
+      .invoke(`text`)
+      .should(`eq`, `component-before`)
+
+    cy.exec(
+      `npm run update -- --file src/components/hmr-component-edit.js --exact --replacements "component-before:component-after"`
+    )
+
+    cy.get(`@hmrConsoleLog`).should(`be.calledWithMatch`, `App is up to date`)
+    cy.wait(1000)
+
+    cy.get(`[data-testid="test-imported-edit"]`)
+      .invoke(`text`)
+      .should(`eq`, `component-after`)
+  })
+}
diff --git a/e2e-tests/mdx/package.json b/e2e-tests/mdx/package.json
index fde0c84ad8827..5e103c197b723 100644
--- a/e2e-tests/mdx/package.json
+++ b/e2e-tests/mdx/package.json
@@ -5,7 +5,7 @@
   "dependencies": {
     "@mdx-js/mdx": "^1.6.6",
     "@mdx-js/react": "^1.6.6",
-    "cypress": "^3.1.0",
+    "cypress": "^7.2.0",
     "fs-extra": "^8.1.0",
     "gatsby": "^3.0.0",
     "gatsby-plugin-mdx": "^2.0.0",
@@ -19,14 +19,21 @@
   ],
   "license": "MIT",
   "scripts": {
-    "build": "gatsby build",
-    "develop": "gatsby develop",
+    "build": "cross-env CYPRESS_SUPPORT=y gatsby build",
+    "develop": "cross-env CYPRESS_SUPPORT=y gatsby develop",
     "format": "prettier --write '**/*.js'",
-    "test": "cross-env CYPRESS_SUPPORT=y npm run build && npm run start-server-and-test",
-    "start-server-and-test": "start-server-and-test serve http://localhost:9000 cy:run",
+    "test:build": "cross-env CYPRESS_SUPPORT=y npm run build && npm run start-server-and-test:build",
+    "test:develop": "npm run start-server-and-test:develop || (npm run reset && exit 1)",
+    "test": "npm run test:build && npm run test:develop",
+    "start-server-and-test:develop": "start-server-and-test develop http://localhost:8000 cy:run:develop",
+    "start-server-and-test:build": "start-server-and-test serve http://localhost:9000 cy:run:build",
     "serve": "gatsby serve",
-    "cy:open": "cypress open",
-    "cy:run": "node ../../scripts/cypress-run-with-conditional-record-flag.js --browser chrome"
+    "cy:open:develop": "cypress open --config-file cypress-dev.json",
+    "cy:open:build": "cypress open",
+    "cy:run:build": "node ../../scripts/cypress-run-with-conditional-record-flag.js --browser chrome --group production",
+    "cy:run:develop": "node ../../scripts/cypress-run-with-conditional-record-flag.js --browser chrome --config-file cypress-dev.json --group development",
+    "reset": "node scripts/reset.js",
+    "update": "node scripts/update.js"
   },
   "devDependencies": {
     "cross-env": "^5.2.0",
diff --git a/e2e-tests/mdx/scripts/history.js b/e2e-tests/mdx/scripts/history.js
new file mode 100644
index 0000000000000..2b6996deffe35
--- /dev/null
+++ b/e2e-tests/mdx/scripts/history.js
@@ -0,0 +1,25 @@
+const fs = require(`fs-extra`)
+
+const HISTORY_FILE = `__history__.json`
+
+exports.__HISTORY_FILE__ = HISTORY_FILE
+
+exports.getHistory = async (file = HISTORY_FILE) => {
+  try {
+    const contents = await fs
+      .readFile(file, `utf8`)
+      .then(contents => JSON.parse(contents))
+
+    return new Map(contents)
+  } catch (e) {
+    return new Map()
+  }
+}
+
+exports.writeHistory = async (contents, file = HISTORY_FILE) => {
+  try {
+    await fs.writeFile(file, JSON.stringify([...contents]), `utf8`)
+  } catch (e) {
+    console.error(e)
+  }
+}
diff --git a/e2e-tests/mdx/scripts/reset.js b/e2e-tests/mdx/scripts/reset.js
new file mode 100644
index 0000000000000..9aabb5ed7bb82
--- /dev/null
+++ b/e2e-tests/mdx/scripts/reset.js
@@ -0,0 +1,21 @@
+const fs = require(`fs-extra`)
+const path = require(`path`)
+
+const { __HISTORY_FILE__, getHistory } = require(`./history`)
+
+async function reset() {
+  const history = await getHistory()
+
+  await Promise.all(
+    Array.from(history).map(([filePath, value]) => {
+      if (typeof value === `string`) {
+        return fs.writeFile(path.resolve(filePath), value, `utf8`)
+      }
+      return fs.remove(path.resolve(filePath))
+    })
+  )
+
+  await fs.remove(__HISTORY_FILE__)
+}
+
+reset()
diff --git a/e2e-tests/mdx/scripts/update.js b/e2e-tests/mdx/scripts/update.js
new file mode 100644
index 0000000000000..094fc0c111ee0
--- /dev/null
+++ b/e2e-tests/mdx/scripts/update.js
@@ -0,0 +1,103 @@
+const fs = require(`fs-extra`)
+const path = require(`path`)
+const yargs = require(`yargs`)
+
+const { getHistory, writeHistory } = require(`./history`)
+
+const args = yargs
+  .option(`file`, {
+    demand: true,
+    type: `string`,
+  })
+  .option(`replacements`, {
+    default: [],
+    type: `array`,
+  })
+  .option(`exact`, {
+    default: false,
+    type: `boolean`,
+  })
+  .option(`delete`, {
+    default: false,
+    type: `boolean`,
+  })
+  .option(`fileContent`, {
+    default: JSON.stringify(
+      `
+    import * as React from 'react';
+    
+    import Layout from '../components/layout';
+    
+    export default function SomeComponent() {
+      return (
+        <Layout>
+          <h1 data-testid="message">Hello %REPLACEMENT%</h1>
+        </Layout>
+      )
+    }
+    `
+    ).trim(),
+    type: `string`,
+  })
+  .option(`fileSource`, {
+    type: `string`,
+  })
+  .option(`restore`, {
+    default: false,
+    type: `boolean`,
+  }).argv
+
+async function update() {
+  const history = await getHistory()
+
+  const { file: fileArg, replacements, restore } = args
+  const filePath = path.resolve(fileArg)
+  if (restore) {
+    const original = history.get(filePath)
+    if (original) {
+      await fs.writeFile(filePath, original, `utf-8`)
+    } else if (original === false) {
+      await fs.remove(filePath)
+    } else {
+      console.log(`Didn't make changes to "${fileArg}". Nothing to restore.`)
+    }
+    history.delete(filePath)
+    return
+  }
+  let exists = true
+  if (!fs.existsSync(filePath)) {
+    exists = false
+    let fileContent
+    if (args.fileSource) {
+      fileContent = await fs.readFile(args.fileSource, `utf8`)
+    } else if (args.fileContent) {
+      fileContent = JSON.parse(args.fileContent).replace(/\+n/g, `\n`)
+    }
+    await fs.writeFile(filePath, fileContent, `utf8`)
+  }
+  const file = await fs.readFile(filePath, `utf8`)
+
+  if (!history.has(filePath)) {
+    history.set(filePath, exists ? file : false)
+  }
+
+  if (args.delete) {
+    if (exists) {
+      await fs.remove(filePath)
+    }
+  } else {
+    const contents = replacements.reduce((replaced, pair) => {
+      const [key, value] = pair.split(`:`)
+      return replaced.replace(
+        args.exact ? key : new RegExp(`%${key}%`, `g`),
+        value
+      )
+    }, file)
+
+    await fs.writeFile(filePath, contents, `utf8`)
+  }
+
+  await writeHistory(history)
+}
+
+update()
diff --git a/e2e-tests/mdx/src/components/hmr-component-edit.js b/e2e-tests/mdx/src/components/hmr-component-edit.js
new file mode 100644
index 0000000000000..c7a70d646a637
--- /dev/null
+++ b/e2e-tests/mdx/src/components/hmr-component-edit.js
@@ -0,0 +1,7 @@
+import React from "react"
+
+const HMRImportEditComponent = () => (
+  <div data-testid="test-imported-edit">component-before</div>
+)
+
+export default HMRImportEditComponent
diff --git a/e2e-tests/mdx/src/components/hmr-prop-edit.js b/e2e-tests/mdx/src/components/hmr-prop-edit.js
new file mode 100644
index 0000000000000..b67dd3de30a35
--- /dev/null
+++ b/e2e-tests/mdx/src/components/hmr-prop-edit.js
@@ -0,0 +1,7 @@
+import React from "react"
+
+const HMRPropEditComponent = ({ test }) => (
+  <div data-testid="test-prop-edit">{test}</div>
+)
+
+export default HMRPropEditComponent
diff --git a/e2e-tests/mdx/src/pages/hmr.mdx b/e2e-tests/mdx/src/pages/hmr.mdx
new file mode 100644
index 0000000000000..294f97e970378
--- /dev/null
+++ b/e2e-tests/mdx/src/pages/hmr.mdx
@@ -0,0 +1,8 @@
+import HMRImportEditComponent from "../components/hmr-component-edit"
+import HMRPropEditComponent from "../components/hmr-prop-edit"
+
+## Lorem
+
+<HMRImportEditComponent />
+
+<HMRPropEditComponent test="prop-before" />
diff --git a/packages/gatsby-plugin-mdx/gatsby/create-webpack-config.js b/packages/gatsby-plugin-mdx/gatsby/create-webpack-config.js
index fa441f8d38168..e08f154c58e70 100644
--- a/packages/gatsby-plugin-mdx/gatsby/create-webpack-config.js
+++ b/packages/gatsby-plugin-mdx/gatsby/create-webpack-config.js
@@ -76,6 +76,7 @@ module.exports = (
               options: {
                 cache: cache,
                 actions: actions,
+                isolateMDXComponent: stage === `develop`,
                 ...other,
                 pluginOptions: options,
               },
diff --git a/packages/gatsby-plugin-mdx/loaders/__snapshots__/mdx-loader.test.js.snap b/packages/gatsby-plugin-mdx/loaders/__snapshots__/mdx-loader.test.js.snap
index 772d412259508..a3640f04edc8d 100644
--- a/packages/gatsby-plugin-mdx/loaders/__snapshots__/mdx-loader.test.js.snap
+++ b/packages/gatsby-plugin-mdx/loaders/__snapshots__/mdx-loader.test.js.snap
@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`mdx-loader snapshot [lessBabel=true] with body 1`] = `
+exports[`mdx-loader snapshot with body 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -29,7 +29,7 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with frontmatter 1`] = `
+exports[`mdx-loader snapshot with frontmatter 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -62,7 +62,77 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with frontmatter-layout 1`] = `
+exports[`mdx-loader snapshot with frontmatter-isDevelopStage 1`] = `
+import MDXContent from "/frontmatter-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/frontmatter-isDevelopStage?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-isDevelopStage 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+const layoutProps = {};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/frontmatter-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/frontmatter-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-isDevelopStage-lessBabel 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+const layoutProps = {};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -97,22 +167,92 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with frontmatter-layout-namedExports 1`] = `
+exports[`mdx-loader snapshot with frontmatter-layout-isDevelopStage 1`] = `
+import MDXContent from "/frontmatter-layout-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/frontmatter-layout-isDevelopStage?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout-isDevelopStage 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+const layoutProps = {};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/frontmatter-layout-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/frontmatter-layout-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout-isDevelopStage-lessBabel 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+const layoutProps = {};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout-lessBabel 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
-export const meta = {
-  author: "chris",
-};
 export const _frontmatter = {
   one: "two",
   three: 4,
   array: [1, 2, 3],
 };
 const layoutProps = {
-  meta,
   _frontmatter,
 };
 
@@ -136,7 +276,7 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with frontmatter-namedExports 1`] = `
+exports[`mdx-loader snapshot with frontmatter-layout-namedExports 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -154,7 +294,9 @@ const layoutProps = {
   meta,
   _frontmatter,
 };
-const MDXLayout = "wrapper";
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
 export default function MDXContent({ components, ...props }) {
   return (
     <MDXLayout
@@ -173,15 +315,26 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with layout 1`] = `
+exports[`mdx-loader snapshot with frontmatter-layout-namedExports-isDevelopStage 1`] = `
+import MDXContent from "/frontmatter-layout-namedExports-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/frontmatter-layout-namedExports-isDevelopStage?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout-namedExports-isDevelopStage 2`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
-export const _frontmatter = {};
+export const meta = {
+  author: "chris",
+};
 const layoutProps = {
-  _frontmatter,
+  meta,
 };
 
 const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
@@ -204,7 +357,16 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with layout-namedExports 1`] = `
+exports[`mdx-loader snapshot with frontmatter-layout-namedExports-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/frontmatter-layout-namedExports-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/frontmatter-layout-namedExports-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-layout-namedExports-isDevelopStage-lessBabel 2`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -213,10 +375,8 @@ import { mdx } from "@mdx-js/react";
 export const meta = {
   author: "chris",
 };
-export const _frontmatter = {};
 const layoutProps = {
   meta,
-  _frontmatter,
 };
 
 const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
@@ -239,7 +399,7 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot [lessBabel=true] with namedExports 1`] = `
+exports[`mdx-loader snapshot with frontmatter-layout-namedExports-lessBabel 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -248,12 +408,18 @@ import { mdx } from "@mdx-js/react";
 export const meta = {
   author: "chris",
 };
-export const _frontmatter = {};
+export const _frontmatter = {
+  one: "two",
+  three: 4,
+  array: [1, 2, 3],
+};
 const layoutProps = {
   meta,
   _frontmatter,
 };
-const MDXLayout = "wrapper";
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
 export default function MDXContent({ components, ...props }) {
   return (
     <MDXLayout
@@ -272,13 +438,17 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with body 1`] = `
+exports[`mdx-loader snapshot with frontmatter-lessBabel 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
-export const _frontmatter = {};
+export const _frontmatter = {
+  one: "two",
+  three: 4,
+  array: [1, 2, 3],
+};
 const layoutProps = {
   _frontmatter,
 };
@@ -301,18 +471,22 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with frontmatter 1`] = `
+exports[`mdx-loader snapshot with frontmatter-namedExports 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
+export const meta = {
+  author: "chris",
+};
 export const _frontmatter = {
   one: "two",
   three: 4,
   array: [1, 2, 3],
 };
 const layoutProps = {
+  meta,
   _frontmatter,
 };
 const MDXLayout = "wrapper";
@@ -334,23 +508,28 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with frontmatter-layout 1`] = `
+exports[`mdx-loader snapshot with frontmatter-namedExports-isDevelopStage 1`] = `
+import MDXContent from "/frontmatter-namedExports-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/frontmatter-namedExports-isDevelopStage?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-namedExports-isDevelopStage 2`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
-export const _frontmatter = {
-  one: "two",
-  three: 4,
-  array: [1, 2, 3],
+export const meta = {
+  author: "chris",
 };
 const layoutProps = {
-  _frontmatter,
+  meta,
 };
-
-const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
-
+const MDXLayout = "wrapper";
 export default function MDXContent({ components, ...props }) {
   return (
     <MDXLayout
@@ -369,7 +548,16 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with frontmatter-layout-namedExports 1`] = `
+exports[`mdx-loader snapshot with frontmatter-namedExports-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/frontmatter-namedExports-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/frontmatter-namedExports-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = { one: "two", three: 4, array: [1, 2, 3] };
+
+`;
+
+exports[`mdx-loader snapshot with frontmatter-namedExports-isDevelopStage-lessBabel 2`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -378,18 +566,10 @@ import { mdx } from "@mdx-js/react";
 export const meta = {
   author: "chris",
 };
-export const _frontmatter = {
-  one: "two",
-  three: 4,
-  array: [1, 2, 3],
-};
 const layoutProps = {
   meta,
-  _frontmatter,
 };
-
-const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
-
+const MDXLayout = "wrapper";
 export default function MDXContent({ components, ...props }) {
   return (
     <MDXLayout
@@ -408,7 +588,7 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with frontmatter-namedExports 1`] = `
+exports[`mdx-loader snapshot with frontmatter-namedExports-lessBabel 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
@@ -445,19 +625,58 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with layout 1`] = `
+exports[`mdx-loader snapshot with isDevelopStage 1`] = `
+import MDXContent from "/isDevelopStage?type=component";
+export default MDXContent;
+export * from "/isDevelopStage?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with isDevelopStage 2`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
+const layoutProps = {};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/isDevelopStage-lessBabel?type=component";
+
 export const _frontmatter = {};
-const layoutProps = {
-  _frontmatter,
-};
 
-const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+`;
+
+exports[`mdx-loader snapshot with isDevelopStage-lessBabel 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
 
+const layoutProps = {};
+const MDXLayout = "wrapper";
 export default function MDXContent({ components, ...props }) {
   return (
     <MDXLayout
@@ -476,18 +695,14 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with layout-namedExports 1`] = `
+exports[`mdx-loader snapshot with layout 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
 /* @jsx mdx */
 
-export const meta = {
-  author: "chris",
-};
 export const _frontmatter = {};
 const layoutProps = {
-  meta,
   _frontmatter,
 };
 
@@ -511,7 +726,408 @@ MDXContent.isMDXComponent = true;
 
 `;
 
-exports[`mdx-loader snapshot with namedExports 1`] = `
+exports[`mdx-loader snapshot with layout-isDevelopStage 1`] = `
+import MDXContent from "/layout-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/layout-isDevelopStage?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with layout-isDevelopStage 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+const layoutProps = {};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with layout-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/layout-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/layout-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with layout-isDevelopStage-lessBabel 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+const layoutProps = {};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with layout-lessBabel 1`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const _frontmatter = {};
+const layoutProps = {
+  _frontmatter,
+};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with layout-namedExports 1`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+export const _frontmatter = {};
+const layoutProps = {
+  meta,
+  _frontmatter,
+};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with layout-namedExports-isDevelopStage 1`] = `
+import MDXContent from "/layout-namedExports-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/layout-namedExports-isDevelopStage?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with layout-namedExports-isDevelopStage 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+const layoutProps = {
+  meta,
+};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with layout-namedExports-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/layout-namedExports-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/layout-namedExports-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with layout-namedExports-isDevelopStage-lessBabel 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+const layoutProps = {
+  meta,
+};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with layout-namedExports-lessBabel 1`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+export const _frontmatter = {};
+const layoutProps = {
+  meta,
+  _frontmatter,
+};
+
+const MDXLayout = ({ children, ...props }) => <div>{children}</div>;
+
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with lessBabel 1`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const _frontmatter = {};
+const layoutProps = {
+  _frontmatter,
+};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with namedExports 1`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+export const _frontmatter = {};
+const layoutProps = {
+  meta,
+  _frontmatter,
+};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with namedExports-isDevelopStage 1`] = `
+import MDXContent from "/namedExports-isDevelopStage?type=component";
+export default MDXContent;
+export * from "/namedExports-isDevelopStage?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with namedExports-isDevelopStage 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+const layoutProps = {
+  meta,
+};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with namedExports-isDevelopStage-lessBabel 1`] = `
+import MDXContent from "/namedExports-isDevelopStage-lessBabel?type=component";
+export default MDXContent;
+export * from "/namedExports-isDevelopStage-lessBabel?type=component";
+
+export const _frontmatter = {};
+
+`;
+
+exports[`mdx-loader snapshot with namedExports-isDevelopStage-lessBabel 2`] = `
+import * as React from "react";
+/* @jsx mdx */
+import { mdx } from "@mdx-js/react";
+/* @jsx mdx */
+
+export const meta = {
+  author: "chris",
+};
+const layoutProps = {
+  meta,
+};
+const MDXLayout = "wrapper";
+export default function MDXContent({ components, ...props }) {
+  return (
+    <MDXLayout
+      {...layoutProps}
+      {...props}
+      components={components}
+      mdxType="MDXLayout"
+    >
+      <h1>{\`Some title\`}</h1>
+      <p>{\`a bit of a paragraph\`}</p>
+      <p>{\`some content\`}</p>
+    </MDXLayout>
+  );
+}
+MDXContent.isMDXComponent = true;
+
+`;
+
+exports[`mdx-loader snapshot with namedExports-lessBabel 1`] = `
 import * as React from "react";
 /* @jsx mdx */
 import { mdx } from "@mdx-js/react";
diff --git a/packages/gatsby-plugin-mdx/loaders/mdx-loader.js b/packages/gatsby-plugin-mdx/loaders/mdx-loader.js
index 9d9b9fb85b201..fdd574914b074 100644
--- a/packages/gatsby-plugin-mdx/loaders/mdx-loader.js
+++ b/packages/gatsby-plugin-mdx/loaders/mdx-loader.js
@@ -1,6 +1,7 @@
 const _ = require(`lodash`)
 const { getOptions } = require(`loader-utils`)
 const grayMatter = require(`gray-matter`)
+const path = require(`path`)
 const unified = require(`unified`)
 const babel = require(`@babel/core`)
 const { createRequireFromPath, slash } = require(`gatsby-core-utils`)
@@ -95,7 +96,9 @@ const hasDefaultExport = (str, options) => {
 
 module.exports = async function mdxLoader(content) {
   const callback = this.async()
+
   const {
+    isolateMDXComponent,
     getNode: rawGetNode,
     getNodes,
     getNodesByType,
@@ -106,6 +109,25 @@ module.exports = async function mdxLoader(content) {
     ...helpers
   } = getOptions(this)
 
+  const resourceQuery = this.resourceQuery || ``
+  if (isolateMDXComponent && !resourceQuery.includes(`type=component`)) {
+    const { data } = grayMatter(content)
+
+    const requestPath = `/${path.relative(
+      this.rootContext,
+      this.resourcePath
+    )}?type=component`
+
+    return callback(
+      null,
+      `import MDXContent from "${requestPath}";
+export default MDXContent;
+export * from "${requestPath}"
+
+export const _frontmatter = ${JSON.stringify(data)};`
+    )
+  }
+
   const options = withDefaultOptions(pluginOptions)
 
   let fileNode = getNodes().find(
@@ -214,6 +236,7 @@ ${contentWithoutFrontmatter}`
     reporter,
     cache,
     pathPrefix,
+    isolateMDXComponent,
   })
 
   try {
diff --git a/packages/gatsby-plugin-mdx/loaders/mdx-loader.test.js b/packages/gatsby-plugin-mdx/loaders/mdx-loader.test.js
index 9fcfda0f782d3..f6f72ee98ec48 100644
--- a/packages/gatsby-plugin-mdx/loaders/mdx-loader.test.js
+++ b/packages/gatsby-plugin-mdx/loaders/mdx-loader.test.js
@@ -34,16 +34,18 @@ some content`,
       input.namedExports ? code.namedExports : ``,
       code.body,
     ].join(`\n\n`),
+    isDevelopStage: input.isDevelopStage,
+    lessBabel: input.lessBabel,
   }
 }
 
 // generate a table of all possible combinations of genMDXfile input
-const fixtures = new BaseN([true, false], 3)
+const fixtures = new BaseN([true, false], 5)
   .toArray()
-  .map(([frontmatter, layout, namedExports]) =>
-    genMDXFile({ frontmatter, layout, namedExports })
+  .map(([frontmatter, layout, namedExports, isDevelopStage, lessBabel]) =>
+    genMDXFile({ frontmatter, layout, namedExports, isDevelopStage, lessBabel })
   )
-  .map(({ name, content }) => [
+  .map(({ name, content, isDevelopStage, lessBabel }) => [
     name,
     {
       internal: { type: `File` },
@@ -51,6 +53,8 @@ const fixtures = new BaseN([true, false], 3)
       absolutePath: `/fake/${name}`,
     },
     content,
+    isDevelopStage,
+    lessBabel,
   ])
 
 describe(`mdx-loader`, () => {
@@ -64,71 +68,56 @@ describe(`mdx-loader`, () => {
   })
   test.each(fixtures)(
     `snapshot with %s`,
-    async (filename, fakeGatsbyNode, content) => {
-      const loader = mdxLoader.bind({
-        async() {
-          return (err, result) => {
-            expect(err).toBeNull()
-            expect(result).toMatchSnapshot()
-          }
-        },
-        query: {
-          getNodes(_type) {
-            return fixtures.map(([, node]) => node)
-          },
-          getNodesByType(_type) {
-            return fixtures.map(([, node]) => node)
-          },
-          pluginOptions: {
-            lessBabel: false, // default
+    async (filename, fakeGatsbyNode, content, isDevelopStage, lessBabel) => {
+      let err
+      let result
+
+      const createLoader = (opts = {}) =>
+        mdxLoader.bind({
+          async() {
+            return (_err, _result) => {
+              err = _err
+              result = _result
+            }
           },
-          cache: {
-            get() {
-              return false
+          query: {
+            getNodes(_type) {
+              return fixtures.map(([, node]) => node)
             },
-            set() {
-              return
+            getNodesByType(_type) {
+              return fixtures.map(([, node]) => node)
             },
-          },
-        },
-        resourcePath: fakeGatsbyNode.absolutePath,
-      })
-      await loader(content)
-    }
-  )
-
-  test.each(fixtures)(
-    `snapshot [lessBabel=true] with %s`,
-    async (filename, fakeGatsbyNode, content) => {
-      const loader = mdxLoader.bind({
-        async() {
-          return (err, result) => {
-            expect(err).toBeNull()
-            expect(result).toMatchSnapshot()
-          }
-        },
-        query: {
-          getNodes(_type) {
-            return fixtures.map(([, node]) => node)
-          },
-          getNodesByType(_type) {
-            return fixtures.map(([, node]) => node)
-          },
-          pluginOptions: {
-            lessBabel: true,
-          },
-          cache: {
-            get() {
-              return false
+            pluginOptions: {
+              lessBabel,
             },
-            set() {
-              return
+            cache: {
+              get() {
+                return false
+              },
+              set() {
+                return
+              },
             },
+            isolateMDXComponent: isDevelopStage,
           },
-        },
-        resourcePath: fakeGatsbyNode.absolutePath,
-      })
-      await loader(content)
+          resourcePath: fakeGatsbyNode.absolutePath,
+          resourceQuery: fakeGatsbyNode.absolutePath,
+          rootContext: `/fake/`,
+          ...opts,
+        })
+
+      await createLoader()(content)
+      expect(err).toBeNull()
+      expect(result).toMatchSnapshot()
+      err = result = undefined
+
+      if (isDevelopStage) {
+        await createLoader({
+          resourceQuery: `${fakeGatsbyNode.absolutePath}?type=component`,
+        })(content)
+        expect(err).toBeNull()
+        expect(result).toMatchSnapshot()
+      }
     }
   )
 })
diff --git a/packages/gatsby-plugin-mdx/utils/gen-mdx.js b/packages/gatsby-plugin-mdx/utils/gen-mdx.js
index a991745f032a1..38ed9459eadc0 100644
--- a/packages/gatsby-plugin-mdx/utils/gen-mdx.js
+++ b/packages/gatsby-plugin-mdx/utils/gen-mdx.js
@@ -51,13 +51,14 @@ async function genMDX(
     reporter,
     cache,
     pathPrefix,
+    isolateMDXComponent,
     ...helpers
   },
   { forceDisableCache = false } = {}
 ) {
   const pathPrefixCacheStr = pathPrefix || ``
   const payloadCacheKey = node =>
-    `gatsby-plugin-mdx-entire-payload-${node.internal.contentDigest}-${pathPrefixCacheStr}`
+    `gatsby-plugin-mdx-entire-payload-${node.internal.contentDigest}-${pathPrefixCacheStr}-${isolateMDXComponent}`
 
   if (!forceDisableCache) {
     const cachedPayload = await cache.get(payloadCacheKey(node))
@@ -89,7 +90,10 @@ async function genMDX(
   // pull classic style frontmatter off the raw MDX body
   debug(`processing classic frontmatter`)
   const { data, content: frontMatterCodeResult } = grayMatter(node.rawBody)
-  const content = `${frontMatterCodeResult}
+
+  const content = isolateMDXComponent
+    ? frontMatterCodeResult
+    : `${frontMatterCodeResult}
 
 export const _frontmatter = ${JSON.stringify(data)}`
 
diff --git a/packages/gatsby/src/utils/webpack.config.js b/packages/gatsby/src/utils/webpack.config.js
index 538442bd46b0d..034c2aeea5bd3 100644
--- a/packages/gatsby/src/utils/webpack.config.js
+++ b/packages/gatsby/src/utils/webpack.config.js
@@ -38,6 +38,7 @@ module.exports = async (
   port,
   { parentSpan } = {}
 ) => {
+  let fastRefreshPlugin
   const modulesThatUseGatsby = await getGatsbyDependents()
   const directoryPath = withBasePath(directory)
 
@@ -219,7 +220,7 @@ module.exports = async (
       case `develop`: {
         configPlugins = configPlugins
           .concat([
-            plugins.fastRefresh({ modulesThatUseGatsby }),
+            (fastRefreshPlugin = plugins.fastRefresh({ modulesThatUseGatsby })),
             new ForceCssHMRForEdgeCases(),
             plugins.hotModuleReplacement(),
             plugins.noEmitOnErrors(),
@@ -810,5 +811,43 @@ module.exports = async (
     parentSpan,
   })
 
+  if (fastRefreshPlugin) {
+    // Fast refresh plugin has `include` option that determines
+    // wether HMR code gets injected. We need to make sure all custom loaders
+    // (like .ts or .mdx) that use our babel-loader will be taken into account
+    // when deciding which modules get fast-refresh HMR addition.
+    const fastRefreshIncludes = []
+    const babelLoaderLoc = require.resolve(`./babel-loader`)
+    for (const rule of getConfig().module.rules) {
+      if (!rule.use) {
+        continue
+      }
+
+      const hasBabelLoader = (Array.isArray(rule.use)
+        ? rule.use
+        : [rule.use]
+      ).some(loaderConfig => loaderConfig.loader === babelLoaderLoc)
+
+      if (hasBabelLoader) {
+        fastRefreshIncludes.push(rule.test)
+      }
+    }
+
+    // start with default include of fast refresh plugin
+    const includeRegex = /\.([jt]sx?|flow)$/i
+    includeRegex.test = modulePath => {
+      // drop query param from request (i.e. ?type=component for mdx-loader)
+      // so loader rule test work well
+      const queryParamStartIndex = modulePath.indexOf(`?`)
+      if (queryParamStartIndex !== -1) {
+        modulePath = modulePath.substr(0, queryParamStartIndex)
+      }
+
+      return fastRefreshIncludes.some(re => re.test(modulePath))
+    }
+
+    fastRefreshPlugin.options.include = includeRegex
+  }
+
   return getConfig()
 }