refactor: remove sub-eslintrc, fix more lint errors (#7530)

packages/docusaurus-mdx-loader/src/remark/toc/__tests__/__fixtures__/no-heading-with-toc-export.md

@@ -0,0 +1,9 @@
+foo
+
+`bar`
+
+```js
+baz
+```
+
+export const toc = 1;

packages/docusaurus-mdx-loader/src/remark/toc/__tests__/__snapshots__/index.test.ts.snap

@@ -1,5 +1,18 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`toc remark plugin does not overwrite TOC var if no TOC 1`] = `
+"foo
+
+\`bar\`
+
+\`\`\`js
+baz
+\`\`\`
+
+export const toc = 1;
+"
+`;
+
 exports[`toc remark plugin escapes inline code 1`] = `
 "export const toc = [
 	{

packages/docusaurus-mdx-loader/src/remark/toc/__tests__/index.test.ts

@@ -30,6 +30,14 @@ describe('toc remark plugin', () => {
     expect(result).toMatchSnapshot();
   });
 
+  // A very implicit API: we allow users to hand-write the toc variable. It will
+  // get overwritten in most cases, but until we find a better way, better keep
+  // supporting this
+  it('does not overwrite TOC var if no TOC', async () => {
+    const result = await processFixture('no-heading-with-toc-export');
+    expect(result).toMatchSnapshot();
+  });
+
   it('works on non text phrasing content', async () => {
     const result = await processFixture('non-text-content');
     expect(result).toMatchSnapshot();

packages/docusaurus-mdx-loader/src/remark/toc/index.ts

@@ -89,8 +89,10 @@ export default function plugin(): Transformer {
     const {children} = root as Parent<Literal>;
     const targetIndex = getOrCreateExistingTargetIndex(children);
 
-    children[targetIndex]!.value = `export const ${name} = ${stringifyObject(
-      headings,
-    )};`;
+    if (headings.length) {
+      children[targetIndex]!.value = `export const ${name} = ${stringifyObject(
+        headings,
+      )};`;
+    }
   };
 }