fix(v2): hide mobile collapsible doc toc if no headings

[slorber]

Motivation

When a page has no heading (empty toc), we should not display the mobile collapsible toc button because it does not reveal any TOC.

Problem can be seen on:

• https://docusaurus.io/docs/create-doc
• https://docs.temporal.io/docs/glossary

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

preview

Related PRs

#4273

[netlify]

✔️ [V2]

🔨 Explore the source changes: b634af1

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/60efe3b5907db8000853bb53

😎 Browse the preview: https://deploy-preview-5172--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	61
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-5172--docusaurus-2.netlify.app/

[github-actions]

Size Change: -484 B (0%)

Total Size: 850 kB

Filename	Size	Change
website/build/docs-tests/index.html	20.3 kB	-242 B (-1%)
website/build/docs-tests/standalone/index.html	18.8 kB	-242 B (-1%)

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	58.8 kB
website/build/assets/css/styles.********.css	89 kB
website/build/assets/js/main.********.js	459 kB
website/build/blog/2017/12/14/introducing-docusaurus/index.html	62.4 kB
website/build/blog/index.html	26.3 kB
website/build/docs/index.html	40.2 kB
website/build/docs/installation/index.html	47.9 kB
website/build/index.html	27.3 kB

_{compressed-size-action}

[slorber]

@lex111 @sw-yx was wondering

Is it fine to have some pages not having that component? Could user be confused about why some pages have the mobile TOC and not others?

For consistency, should we keep displaying the collapsible and display something like "Empty table of contents" when uncollapsing?

[lex111]

Of course, it's perfectly all right, why not? The user will probably realize that if there is no collapsible element, then there is no TOC for that page.

[slorber]

ok let's keep it that way then ;)

[swyxio]

sorry @slorber didn't see this message til now - i personally would have voted the opposite way, when there is no TOC, dont show the component. not a big deal but thats my preference, if its useless dont show it

[slorber]

@sw-yx it's what I did with this PR, just upgrade/reswizzle and the empty toc on glossary page should be gone

[swyxio]

oh! awesome