feat(core): add support for array of global prefixes

[malkovitc]

PR Checklist

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

• Bugfix
• Feature

What is the current behavior?

Issue Number: #16095

setGlobalPrefix() only accepts a single string prefix. Users who need to expose the same API under multiple base paths (e.g., for different deployment environments) previously used regex-style prefixes like (prefixOne|prefixTwo), which are no longer supported by path-to-regexp v8 in NestJS v11.

What is the new behavior?

setGlobalPrefix() now accepts either a string or an array of strings:

// Single prefix (existing behavior)
app.setGlobalPrefix('api');

// Multiple prefixes (new)
app.setGlobalPrefix(['api', 'v1']);
// Routes will be registered under both /api/... and /v1/...

This provides a migration path for users who previously relied on regex-style prefixes.

Changes:

• Updated INestApplication.setGlobalPrefix() interface to accept string | string[]
• Added getGlobalPrefixes() method to ApplicationConfig to retrieve all prefixes
• Updated RoutePathFactory to generate paths for each prefix in the array
• Updated RouteInfoPathExtractor to generate middleware paths for all prefixes
• Added unit tests for the new functionality

Does this PR introduce a breaking change?

• Yes
• No

The change is backward compatible - existing code using a single string prefix will continue to work.

[coveralls]

Pull Request Test Coverage Report for Build 052bf0c4-da67-43b3-ba46-c7a94794509b

Details

• 19 of 21 (90.48%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 89.671%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/core/middleware/route-info-path-extractor.ts	9	11	81.82%

Totals
Change from base Build e3800a39-758b-42fd-9609-068501388108:	-0.01%
Covered Lines:	7423
Relevant Lines:	8278

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💛 - Coveralls

[kamilmysliwiec]

This will break packages like @nestjs/swagger IIRC

[malkovitc]

@kamilmysliwiec Thanks for the review!

I analyzed the @nestjs/swagger compatibility:

Current behavior with this PR:

1. getGlobalPrefix() still returns string (the first element of the array) - no breaking change
2. RoutePathFactory.create() accepts both string and string[] and handles both correctly
3. Added new getGlobalPrefixes() method for packages that want to support multiple prefixes

Swagger analysis:

Swagger uses getGlobalPrefix(app) which calls applicationConfig.getGlobalPrefix(). With this PR:

• If user sets single prefix: app.setGlobalPrefix('api') → swagger works exactly as before
• If user sets array: app.setGlobalPrefix(['api', 'v1']) → swagger sees 'api' (first element) and generates docs for that prefix only

This is a functional limitation, not a breaking change - swagger will continue to work, but won't automatically know about additional prefixes.

Proposed path forward:

1. This PR maintains full backward compatibility
2. @nestjs/swagger can later be updated to use getGlobalPrefixes() to generate documentation for all prefixes
3. Users who need multiple prefixes can use them now; swagger support can be added incrementally

Would this approach work? Or would you prefer a different solution?