Remove trailing slash from OpenAPI server URLs when pathBase is empty

[Copilot]

Remove trailing slash from OpenAPI server URLs when pathBase is empty

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Remove trailing slash from server URLs with empty pathBase per OpenAPI spec

Description

UriHelper.BuildAbsolute() appends a trailing slash when both pathBase and path are empty. This causes generated OpenAPI documents to contain https://example.com/ instead of https://example.com, diverging from OpenAPI 3.1.0 specification examples.

Changes:

• Modified GetOpenApiServers() to strip trailing slash when pathBase.HasValue is false
• Preserves trailing slash when pathBase explicitly contains "/" to maintain intentional path structure
• Updated test expectations and snapshot tests to reflect correct behavior

Before:

{
  "servers": [
    { "url": "https://example.com/" }
  ]
}

After:

{
  "servers": [
    { "url": "https://example.com" }
  ]
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[OpenAPI] Trailing slash in servers.url when generating OpenAPI spec</issue_title>
<issue_description>### Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When generating an OpenAPI document in ASP.NET Core, the servers section ends up with a URL that includes a trailing /. This comes from GetOpenApiServers method, which relies on UriHelper.BuildAbsolute(). That helper always appends a trailing slash.

According to the OpenAPI 3.1.0 specification (section 4.8.5.2), the server URLs in the examples is shown without a trailing slash. Because of the current behavior, the generated document doesn’t align with the expected format.

The issue shows up immediately after adding AddOpenApi() with no extra configuration: the generated document contains https://example.com/ instead of https://example.com

Expected Behavior

servers.url should be generated without a trailing slash, matching the example from the specification.

Steps To Reproduce

Steps:

1. Create a ASP.NET Core project (minimal api / web api).
2. Register OpenAPI using AddOpenApi().
3. Open the generated document.
4. The servers section shows a URL ending with /.

Exceptions (if any)

No response

.NET Version

10.0.100

Anything else?

Microsoft.AspNetCore.OpenApi 10
Visual Studio Insiders 2026 11206.111
OpenAPI v3.1.0, ServerObject - https://spec.openapis.org/oas/v3.1.0.html#server-object</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [OpenAPI] Trailing slash in servers.url when generating OpenAPI spec #64702

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