From 34df27a3bd278f49a9b81cdb59146a79e8841669 Mon Sep 17 00:00:00 2001
From: Lennart <lekoarts@gmail.com>
Date: Tue, 13 Sep 2022 07:54:09 +0200
Subject: [PATCH] fix(gatsby-plugin-mdx): Add React import when not defined
 (#36595)

---
 .../src/__tests__/gatsby-layout-loader.ts     | 12 ++++---
 .../src/gatsby-layout-loader.ts               | 32 ++++++++++++++++++-
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/packages/gatsby-plugin-mdx/src/__tests__/gatsby-layout-loader.ts b/packages/gatsby-plugin-mdx/src/__tests__/gatsby-layout-loader.ts
index 546051f09e684..a80a348a07cce 100644
--- a/packages/gatsby-plugin-mdx/src/__tests__/gatsby-layout-loader.ts
+++ b/packages/gatsby-plugin-mdx/src/__tests__/gatsby-layout-loader.ts
@@ -71,7 +71,8 @@ describe(`webpack loader: loads and injects Gatsby layout component`, () => {
 
   it(`MDX without layout`, async () => {
     await expect(parseMDX(exampleMDX)).resolves.toMatchInlineSnapshot(`
-            "import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
+            "import React from \\"react\\";
+            import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
             import {Fragment as _Fragment, jsx as _jsx, jsxs as _jsxs} from \\"react/jsx-runtime\\";
             function MDXContent(props = {}) {
               const {wrapper: MDXLayout} = props.components || ({});
@@ -109,7 +110,8 @@ describe(`webpack loader: loads and injects Gatsby layout component`, () => {
         `import TemplateComponent from "./some-path"\n\n${exampleMDX}\n\nexport default TemplateComponent`
       )
     ).resolves.toMatchInlineSnapshot(`
-            "import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
+            "import React from \\"react\\";
+            import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
             import {Fragment as _Fragment, jsx as _jsx, jsxs as _jsxs} from \\"react/jsx-runtime\\";
             import TemplateComponent from \\"./some-path\\";
             const MDXLayout = TemplateComponent;
@@ -146,7 +148,8 @@ describe(`webpack loader: loads and injects Gatsby layout component`, () => {
     await expect(
       parseMDX(`${exampleMDX}\n\nexport {default} from "./some-path"`)
     ).resolves.toMatchInlineSnapshot(`
-            "import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
+            "import React from \\"react\\";
+            import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
             import {Fragment as _Fragment, jsx as _jsx, jsxs as _jsxs} from \\"react/jsx-runtime\\";
             import MDXLayout from \\"./some-path\\";
             function MDXContent(props = {}) {
@@ -182,7 +185,8 @@ describe(`webpack loader: loads and injects Gatsby layout component`, () => {
     await expect(
       parseMDX(`${exampleMDX}\n\nexport {Layout as default} from "./some-path"`)
     ).resolves.toMatchInlineSnapshot(`
-            "import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
+            "import React from \\"react\\";
+            import GATSBY_COMPILED_MDX from \\"/mocked-layout.ts?contentFilePath=/mocked-content.mdx\\";
             import {Fragment as _Fragment, jsx as _jsx, jsxs as _jsxs} from \\"react/jsx-runtime\\";
             import {Layout as MDXLayout} from \\"./some-path\\";
             function MDXContent(props = {}) {
diff --git a/packages/gatsby-plugin-mdx/src/gatsby-layout-loader.ts b/packages/gatsby-plugin-mdx/src/gatsby-layout-loader.ts
index a85733eb584b4..2f58b39bbaaa6 100644
--- a/packages/gatsby-plugin-mdx/src/gatsby-layout-loader.ts
+++ b/packages/gatsby-plugin-mdx/src/gatsby-layout-loader.ts
@@ -47,6 +47,7 @@ const gatsbyLayoutLoader: LoaderDefinition = async function (
   this.addDependency(path.resolve(mdxPath))
 
   const acorn = await cachedImport<typeof import("acorn")>(`acorn`)
+  // @ts-ignore - We typecast below
   const { default: jsx } = await cachedImport(`acorn-jsx`)
   const { generate } = await cachedImport<typeof import("astring")>(`astring`)
   const { buildJsx } = await cachedImport<
@@ -98,6 +99,8 @@ const gatsbyLayoutLoader: LoaderDefinition = async function (
       },
     })
 
+    let hasClassicReactImport = false
+
     /**
      * Replace default export with wrapper function that injects compiled MDX as children
      * Input:
@@ -107,6 +110,13 @@ const gatsbyLayoutLoader: LoaderDefinition = async function (
      **/
     const newBody: Array<any> = []
     AST.body.forEach(child => {
+      if (
+        child.type === `ImportDeclaration` &&
+        child.source.value === `react`
+      ) {
+        hasClassicReactImport = true
+      }
+
       if (child.type !== `ExportDefaultDeclaration`) {
         newBody.push(child)
         return
@@ -137,7 +147,7 @@ const gatsbyLayoutLoader: LoaderDefinition = async function (
             type: `Identifier`,
             name: `GatsbyMDXWrapper`,
           },
-          expression: true,
+          expression: false,
           generator: false,
           async: false,
           params: [
@@ -207,6 +217,26 @@ const gatsbyLayoutLoader: LoaderDefinition = async function (
         },
       } as unknown as ExportDefaultDeclaration)
     })
+
+    if (!hasClassicReactImport) {
+      newBody.unshift({
+        type: `ImportDeclaration`,
+        specifiers: [
+          {
+            type: `ImportDefaultSpecifier`,
+            local: {
+              type: `Identifier`,
+              name: `React`,
+            },
+          },
+        ],
+        source: {
+          type: `Literal`,
+          value: `react`,
+        },
+      })
+    }
+
     AST.body = newBody
 
     buildJsx(AST)