@gsejourne

Describe the bug

Setting an outputDir of docs/... fails consistently with the following error:
`outputDir: docs/business/accounts/business-wallet/Topups, docPath: ./docs

Loading of api failed for "[...]/docusaurus-home/bucket/business/accounts/business-wallet/business-wallet-app/topups.yaml"

[ERROR] TypeError: Cannot read properties of undefined (reading 'replace')
at groupByTags ([...]/docusaurus-home/node_modules/docusaurus-plugin-openapi-docs/lib/sidebars/index.js:86:38)
at generateSidebarSlice ([...]/docusaurus-home/node_modules/docusaurus-plugin-openapi-docs/lib/sidebars/index.js:224:24)
at generateApiDocs ([...]/docusaurus-home/node_modules/docusaurus-plugin-openapi-docs/lib/index.js:107:53)
at async [...]/docusaurus-home/node_modules/docusaurus-plugin-openapi-docs/lib/index.js:503:15
[INFO] Docusaurus version: 3.8.1
Node version: v22.14.0`

However, if I change the API config section to use ./docs/... instead, it works fine.
This may be related to the fact that my docusaurus project is configured with baseUrl: '/', and not `baseUrl: '/docs'.

Expected behavior

Given the online doc example for the outputPath gives a string of docs/... the build should work fine instead of throwing this .replace error.
It actually shouldn't matter whether the outputPath starts with ./ or not.

Current behavior

The build stops with the error reported above.

Possible solution

This is where it fails:

const basePath = docPath ? outputDir.split(docPath!)[1].replace(/^\/+/g, "") : outputDir.slice(outputDir.indexOf("/", 1)).replace(/^\/+/g, "");
See https://github.com/PaloAltoNetworks/docusaurus-openapi-docs/blob/main/packages/docusaurus-plugin-openapi-docs/src/sidebars/index.ts#L128

The issue is that [outputDir.split(docPath)[1]] will be undefined if [docPath] doesn't contain the exact string from docPath: in my case, it's set to ./docs -- which IS NOT something I set, but probably (wrongly) assumed given I'm using basePath / for my project.

Steps to reproduce

1. Configure docusaurus project with basePath: '/'
2. Add an API in the config section with outputPath: 'docs/....`
3. Run the gen-api-docs all command to see it fail.
4. Change the api config to use outputPath: './docs/...'
5. Run the gen-api-docs all command again to see it succeed.

Context

As described above:

• Using a docusaurus project with basePath: '/'
• Adding API docs as usual fails.

Your Environment

• Version used: Docusaurus 3.8.1 -- docusaurus-plugin-openapi-docs@^4.5.1
• Environment name and version (e.g. node v22.14.0):
• Operating System and version (desktop or mobile): OS X Sequoia 15.6.1