Fix numeric suffix added to interface method names in ByTag mode

[Copilot]

Description:

When multipleInterfaces: ByTag is set, method names were receiving unnecessary global numeric suffixes (e.g., InfoGET2Async, InfoGET3Async) even though the names were unique within their respective interfaces. Uniqueness should be enforced per-interface, not across the entire spec.

Root cause: generator.GenerateFile() auto-populates NSwag OperationId values with globally unique names (e.g., infoGET, infoGET2, infoGET3). Since the interface generator was constructed after this call, CheckForDuplicateOperationIds() found no duplicates and kept the MultipleClientsFromOperationIdOperationNameGenerator, which used these globally-suffixed names verbatim.

A secondary bug: interfaceName was null! for the 2nd+ operations in each tag group, breaking per-interface deduplication via IdentifierUtils.Counted.

Changes

• RefitGenerator – Construct the interface generator before GenerateFile() so CheckForDuplicateOperationIds() sees original null OperationIds and correctly switches to MultipleClientsFromFirstTagAndPathSegmentsOperationNameGenerator
• RefitMultipleInterfaceByTagGenerator – Fix null! interfaceName for 2nd+ operations per group so IdentifierUtils.Counted deduplicates correctly at the interface level
• RefitInterfaceGenerator – Add IdentifierUtils.Counted deduplication to guard against path-segment collisions within a single interface (e.g., two operations at different paths sharing the same last segment and HTTP method)
• IdentifierUtils.Sanitize – Guard against empty string input that previously threw InvalidOperationException
• OperationNameGenerator.SupportsMultipleClients – Delegate to defaultGenerator instead of throwing NotImplementedException, required now that the generator is set before GenerateFile() is called

Example OpenAPI Specifications:

openapi: '3.0.0'
info:
  title: Test API
  version: '1.0'
paths:
  /api/manage/info:
    get:
      tags: [Manage]
      responses: { '200': { description: ok } }
    post:
      tags: [Manage]
      responses: { '200': { description: ok } }
  /api/account/info:
    get:
      tags: [Account]
      responses: { '200': { description: ok } }
  /api/user/info:
    get:
      tags: [User]
      responses: { '200': { description: ok } }

Example generated Refit interface

Before (buggy — IAccountApi and IUserApi got global suffixes):

public partial interface IManageApi
{
    [Get("/api/manage/info")]
    Task InfoGET();
    [Post("/api/manage/info")]
    Task InfoPOST();
}
public partial interface IAccountApi
{
    [Get("/api/account/info")]
    Task InfoGET2();   // unnecessary suffix
}
public partial interface IUserApi
{
    [Get("/api/user/info")]
    Task InfoGET3();   // unnecessary suffix
}

After (fixed — names are unique per-interface):

public partial interface IManageApi
{
    [Get("/api/manage/info")]
    Task InfoGet();
    [Post("/api/manage/info")]
    Task InfoPost();
}
public partial interface IAccountApi
{
    [Get("/api/account/info")]
    Task Info();
}
public partial interface IUserApi
{
    [Get("/api/user/info")]
    Task Info();
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• collector.exceptionless.io
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/441dc2a7085145ae89517c0309aa5f71 get --global ls credential.usern/usr/bin/md5sum (dns block)
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/8fbc23b60083492b9b8f25ae4fe344f5 de8d07a4bb684a0d3e608ac7172/Project.csproj --global ndor/bin/bash user.email (dns block)
  • Triggering command: /usr/bin/dotnet dotnet /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests.dll --maximum-parallel-tests 1 /var/lib/dpkg/info/libheif-plugin-aomdec:amd64.list /var/lib/dpkg/info/landscape-common.list /var/lib/dpkg/info/libksba8:amd64.list /var/lib/dpkg/info/libsubid4:amd64.list /var/lib/dpkg/info/libldap2:amd64.list /var/lib/dpkg/info/base-passwd.list /var/lib/dpkg/info/libvulkan1:amd64.list /var/lib/dpkg/info/sysstat.list --no�� se/net10.0/123d477f0c5c4f7a85b590cfcc679888/Project.csproj (dns block)
• config.exceptionless.io
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/441dc2a7085145ae89517c0309aa5f71 get --global ls credential.usern/usr/bin/md5sum (dns block)
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/8fbc23b60083492b9b8f25ae4fe344f5 de8d07a4bb684a0d3e608ac7172/Project.csproj --global ndor/bin/bash user.email (dns block)
  • Triggering command: /usr/bin/dotnet dotnet /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests.dll /var/lib/dpkg/info/libsensors-config.list /var/lib/dpkg/info/ruby-webrick.list /var/lib/dpkg/info/mysql-client-8.0.list /var/lib/dpkg/info/pastebinit.list /var/lib/dpkg/info/libllvm16t64:amd64.list /var/lib/dpkg/info/php-pear.list /var/lib/dpkg/info/libmecab2:amd64.list /var/lib/dpkg/info/libice6:amd64.list /var/lib/dpkg/info/tmux.list /var/lib/dpkg/info/mysql-common.list --no�� se/net10.0/1ee87/usr/share/dotnet/dotnet (dns block)
• developers.intellihr.io
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/441dc2a7085145ae89517c0309aa5f71 get --global ls credential.usern/usr/bin/md5sum (dns block)
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/8fbc23b60083492b9b8f25ae4fe344f5 de8d07a4bb684a0d3e608ac7172/Project.csproj --global ndor/bin/bash user.email (dns block)
  • Triggering command: /usr/bin/dotnet dotnet /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests.dll /var/lib/dpkg/info/libsensors-config.list /var/lib/dpkg/info/ruby-webrick.list /var/lib/dpkg/info/mysql-client-8.0.list /var/lib/dpkg/info/pastebinit.list /var/lib/dpkg/info/libllvm16t64:amd64.list /var/lib/dpkg/info/php-pear.list /var/lib/dpkg/info/libmecab2:amd64.list /var/lib/dpkg/info/libice6:amd64.list /var/lib/dpkg/info/tmux.list /var/lib/dpkg/info/mysql-common.list --no�� se/net10.0/1ee87/usr/share/dotnet/dotnet (dns block)
• heartbeat.exceptionless.io
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/441dc2a7085145ae89517c0309aa5f71 get --global ls credential.usern/usr/bin/md5sum (dns block)
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/8fbc23b60083492b9b8f25ae4fe344f5 de8d07a4bb684a0d3e608ac7172/Project.csproj --global ndor/bin/bash user.email (dns block)
  • Triggering command: /usr/bin/dotnet dotnet /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests.dll --maximum-parallel-tests 1 /var/lib/dpkg/info/libheif-plugin-aomdec:amd64.list /var/lib/dpkg/info/landscape-common.list /var/lib/dpkg/info/libksba8:amd64.list /var/lib/dpkg/info/libsubid4:amd64.list /var/lib/dpkg/info/libldap2:amd64.list /var/lib/dpkg/info/base-passwd.list /var/lib/dpkg/info/libvulkan1:amd64.list /var/lib/dpkg/info/sysstat.list --no�� se/net10.0/123d477f0c5c4f7a85b590cfcc679888/Project.csproj (dns block)
• petstore.swagger.io
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/441dc2a7085145ae89517c0309aa5f71 get --global ls credential.usern/usr/bin/md5sum (dns block)
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/8fbc23b60083492b9b8f25ae4fe344f5 de8d07a4bb684a0d3e608ac7172/Project.csproj --global ndor/bin/bash user.email (dns block)
  • Triggering command: /usr/bin/dotnet dotnet /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests.dll /var/lib/dpkg/info/libsensors-config.list /var/lib/dpkg/info/ruby-webrick.list /var/lib/dpkg/info/mysql-client-8.0.list /var/lib/dpkg/info/pastebinit.list /var/lib/dpkg/info/libllvm16t64:amd64.list /var/lib/dpkg/info/php-pear.list /var/lib/dpkg/info/libmecab2:amd64.list /var/lib/dpkg/info/libice6:amd64.list /var/lib/dpkg/info/tmux.list /var/lib/dpkg/info/mysql-common.list --no�� se/net10.0/1ee87/usr/share/dotnet/dotnet (dns block)
• petstore3.swagger.io
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/441dc2a7085145ae89517c0309aa5f71 get --global ls credential.usern/usr/bin/md5sum (dns block)
  • Triggering command: /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests --server dotnettestcli --dotnet-test-pipe /tmp/8fbc23b60083492b9b8f25ae4fe344f5 de8d07a4bb684a0d3e608ac7172/Project.csproj --global ndor/bin/bash user.email (dns block)
  • Triggering command: /usr/bin/dotnet dotnet /home/REDACTED/work/refitter/refitter/src/Refitter.Tests/bin/Release/net10.0/Refitter.Tests.dll /var/lib/dpkg/info/libsensors-config.list /var/lib/dpkg/info/ruby-webrick.list /var/lib/dpkg/info/mysql-client-8.0.list /var/lib/dpkg/info/pastebinit.list /var/lib/dpkg/info/libllvm16t64:amd64.list /var/lib/dpkg/info/php-pear.list /var/lib/dpkg/info/libmecab2:amd64.list /var/lib/dpkg/info/libice6:amd64.list /var/lib/dpkg/info/tmux.list /var/lib/dpkg/info/mysql-common.list --no�� se/net10.0/1ee87/usr/share/dotnet/dotnet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Code Generator adds numeric suffix to Interface method name when not needed</issue_title>
<issue_description>Describe the bug
When the flag "multipleInterfaces" is set to "ByTag", the method names are still being renamed to have numerical suffixes even though the names are unique within the Interface (e.g. InfoGET3Async).

The check for method name uniqueness should be performed at the interface level, and not at the OpenAPI specification level.

    public partial interface IManageApi
    {
        [Headers("Accept: text/plain, application/json, text/json")]
        [Post("/api/manage/2fa")]
        Task<IApiResponse> _2faAsync([Body] TwoFactorRequest? body = default, CancellationToken cancellationToken = default);

        [Headers("Accept: text/plain, application/json, text/json")]
        [Get("/api/manage/info")]
        Task<IApiResponse> InfoGET3Async(CancellationToken cancellationToken = default);

        [Headers("Accept: text/plain, application/json, text/json")]
        [Post("/api/manage/info")]
        Task<IApiResponse> InfoPOSTAsync([Body] InfoRequest? body = default, [Header("confirmEmail")] string? confirmEmail = default, CancellationToken cancellationToken = default);
    }

Support Key: 7l7irxz

OpenAPI Specifications
n/a

</issue_description>

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

@christianhelle Thanks for taking the time to report this @dammitjanet

For the best code generation experience, I think that specifying the operationId at the OpenAPI specification level is best. Code generators, like mine, would try to do best guess attempts on how to name methods for each operation and one of the ways this is done is by looking at things like the verbs, path segments, and tags

You can maybe experiment with the --operation-name-generator CLI tool argument to try out different naming styles. Possible values for --operation-name-generator are documented here. The operation name generator options are taken directly from NSwag, the tool I use to parse the OpenAPI spec and generate models</comment_new>
<comment_new>@christianhelle
We could look into implementing some sort of "last line of defense" that checks if the generated method name will compile and if not, make a naive attempt to replace invalid characters with "something else". Something like this would never be perfect but it could save someone like @dammitjanet time and avoid changing the OpenAPI spec itself to get the generated code to work</comment_new>
<comment_new>@christianhelle
I thought this was fixed 2 years ago. I'll investigate this myself later and see what I can do. For now I'll assign CoPilot to the issue and hopefully it can point what could be wrong</comment_new>

• Fixes Code Generator adds numeric suffix to Interface method name when not needed #361

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.64%. Comparing base (bbdab25) to head (5697bed).
⚠️ Report is 40 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #914      +/-   ##
==========================================
+ Coverage   93.26%   93.64%   +0.38%     
==========================================
  Files          23       23              
  Lines        2063     1433     -630     
==========================================
- Hits         1924     1342     -582     
+ Misses         39       38       -1     
+ Partials      100       53      -47     

Flag	Coverage Δ
unittests	93.64% <100.00%> (+0.38%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

Fixes method-name numeric suffixing when generating multiple Refit interfaces in MultipleInterfaces.ByTag mode by ensuring operation-name uniqueness is evaluated per interface (not globally across the spec) and by hardening identifier generation.

Changes:

• Construct the interface generator before NSwag DTO generation so operation-name generator selection happens before NSwag auto-populates globally-unique OperationIds.
• Fix per-tag interface name tracking so per-interface deduplication (IdentifierUtils.Counted) works across all operations in a tag group.
• Add additional identifier guards/deduplication (IdentifierUtils.Sanitize empty input guard; per-interface operation-name dedup in RefitInterfaceGenerator) and add a regression test.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Refitter.Tests/Examples/MultipleInterfacesByTagsWithSamePathSegmentTests.cs	New regression test for ByTag cross-interface suffixing
src/Refitter.Core/RefitMultipleInterfaceByTagGenerator.cs	Fixes interfaceName being null! for subsequent ops in a tag group
src/Refitter.Core/RefitInterfaceGenerator.cs	Adds per-interface operation-name deduplication using IdentifierUtils.Counted
src/Refitter.Core/RefitGenerator.cs	Moves interface generator creation before GenerateFile() to avoid NSwag global OperationId suffixing side effects
src/Refitter.Core/OperationNameGenerator.cs	Implements SupportsMultipleClients by delegating to the wrapped generator
src/Refitter.Core/IdentifierUtils.cs	Prevents Sanitize() from throwing on empty input

Comments suppressed due to low confidence (1)

src/Refitter.Core/RefitMultipleInterfaceByTagGenerator.cs:69

• In ByTag mode, dynamic querystring parameter helper types are named from the operation name only (e.g., "InfoQueryParams"). Now that method names are intentionally allowed to repeat across different interfaces, two interfaces can easily produce the same type name when UseDynamicQuerystringParameters is enabled (>=2 query params), causing a compile-time duplicate type error. Consider including the interface name (or group key) in the generated dynamicQuerystringParameterType to keep these helper type names unique across all generated interfaces.

                var operationName = GetOperationName(interfaceName, op.PathItem.Key, operations.Key, operation);
                var dynamicQuerystringParameterType = operationName + "QueryParams";
                var operationModel = generator.CreateOperationModel(operation);

---

You can also share your feedback on Copilot code review. Take the survey.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud