Fix ArgumentException in OpenApiCSharpCodeGenerator.Sanitize method #1163

Copilot · 2025-05-19T21:29:08Z

Issue Description

When generating C# code from OpenAPI specifications, users were experiencing a System.ArgumentException with the message "String cannot be of zero length. Parameter name: oldValue". This occurred in the Sanitize method of the OpenApiCSharpCodeGenerator class.

Root Cause

The issue was in the Sanitize method where it was using null as the replacement value in the String.Replace() method:

private static string Sanitize(string code) =>
    code.Replace("using System.Net.Mime;", null);

In C#, passing null as the replacement value to String.Replace() can cause the "String cannot be of zero length" exception.

Solution

The fix was to change the null value to an empty string:

private static string Sanitize(string code) =>
    code.Replace("using System.Net.Mime;", "");

This ensures that the String.Replace() method works as expected and removes the "using System.Net.Mime;" statement from the generated code without throwing an exception.

Testing

A unit test was added to verify that the Sanitize method correctly removes the "using System.Net.Mime;" statement from the generated code.

Fixes #1157.

Warning

Firewall rules blocked me from connecting to one or more addresses

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

crl3.digicert.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
crl4.digicert.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
ocsp.digicert.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
- Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
petstore.swagger.io
- Triggering command: /usr/lib/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/apiclientcodegen/apiclientcodegen/src/Core/ApiClientCodeGen.Core.Tests/bin/Debug/net8.0/ApiClientCodeGen.Core.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/apiclientcodegen/apiclientcodegen/src/Core/ApiClientCodeGen.Core.Tests/bin/Debug/net8.0/ApiClientCodeGen.Core.Tests.deps.json /home/REDACTED/work/apiclientcodegen/apiclientcodegen/src/Core/ApiClientCodeGen.Core.Tests/bin/Debug/net8.0/testhost.dll --port 39373 --endpoint 127.0.0.1:039373 --role client --parentprocessid 3545 --telemetryoptedin false (dns block)
s.symcb.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
s.symcd.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
ts-crl.ws.symantec.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
ts-ocsp.ws.symantec.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (dns block)
www.microsoft.com
- Triggering command: dotnet build src/Core/ApiClientCodeGen.Core/ApiClientCodeGen.Core.csproj (dns block)
- Triggering command: dotnet test src/Core/ApiClientCodeGen.Core.Tests/ApiClientCodeGen.Core.Tests.csproj --filter FullyQualifiedName~Rapicgen.Core.Generators.OpenApi (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 my firewall allow list

💡 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.

Co-authored-by: christianhelle <710400+christianhelle@users.noreply.github.com>

Copilot

Pull Request Overview

This PR fixes an ArgumentException in the Sanitize method by switching from a null replacement to an empty string and adds a unit test to verify removal of the using System.Net.Mime; line.

Change String.Replace to use "" instead of null
Add a test to confirm the Sanitize method strips the mime using statement

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Core/ApiClientCodeGen.Core/Generators/OpenApi/OpenApiCSharpCodeGenerator.cs	Replace `null` with `""` in `Sanitize` to prevent exception
src/Core/ApiClientCodeGen.Core.Tests/Generators/OpenApi/OpenApiCSharpCodeGeneratorSanitizeTests.cs	Introduce a unit test for the `Sanitize` method

Comments suppressed due to low confidence (1)

src/Core/ApiClientCodeGen.Core.Tests/Generators/OpenApi/OpenApiCSharpCodeGeneratorSanitizeTests.cs:9

Add a test case where the input code does not contain using System.Net.Mime; to ensure Sanitize returns the original string unchanged.

[Fact]

src/Core/ApiClientCodeGen.Core/Generators/OpenApi/OpenApiCSharpCodeGenerator.cs

netpirates · 2025-06-08T14:41:44Z

Hi, I took the latest update and try to generate client from openAPIspec. still I see same error in VS2022.
String cannot be of zero length.
Parameter name: oldValue
Severity Code Description Project File Line Suppression State
Error (active) String cannot be of zero length.
Parameter name: oldValue WebApplication1 WebApplication1\WebApplication1\APIClient 1

Severity Code Description Project File Line Suppression State
Error (active) OpenApiCSharpCodeGenerator WebApplication1 WebApplication1\WebApplication1\APIClient 1

If i try the same in VS2019 i get below error
6/8/2025 10:55:12 AM: System.ArgumentException: String cannot be of zero length.
Parameter name: oldValue
at System.String.ReplaceInternal(String oldValue, String newValue)
at System.String.Replace(String oldValue, String newValue)
at Rapicgen.Core.Generators.OpenApi.OpenApiCSharpCodeGenerator.GenerateCode(IProgressReporter pGenerateProgress) in D:\a\apiclientcodegen\apiclientcodegen\src\Core\ApiClientCodeGen.Core\Generators\OpenApi\OpenApiCSharpCodeGenerator.cs:line 84
at Rapicgen.CustomTool.SingleFileCodeGenerator.Generate(String wszInputFilePath, String bstrInputFileContents, String wszDefaultNamespace, IntPtr[] rgbOutputFileContents, UInt32& pcbOutput, IVsGeneratorProgress pGenerateProgress)
6/8/2025 10:55:12 AM: System.ArgumentException: String cannot be of zero length.
Parameter name: oldValue
at System.String.ReplaceInternal(String oldValue, String newValue)
at System.String.Replace(String oldValue, String newValue)
at Rapicgen.Core.Generators.OpenApi.OpenApiCSharpCodeGenerator.GenerateCode(IProgressReporter pGenerateProgress) in D:\a\apiclientcodegen\apiclientcodegen\src\Core\ApiClientCodeGen.Core\Generators\OpenApi\OpenApiCSharpCodeGenerator.cs:line 84
at Rapicgen.CustomTool.SingleFileCodeGenerator.Generate(String wszInputFilePath, String bstrInputFileContents, String wszDefaultNamespace, IntPtr[] rgbOutputFileContents, UInt32& pcbOutput, IVsGeneratorProgress pGenerateProgress)
6/8/2025 10:55:13 AM: Unable to generate code

…pCodeGenerator.cs Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

coderabbitai · 2025-06-10T22:31:08Z

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… ensure extension is not null before processing

sonarqubecloud · 2025-06-10T22:52:44Z

Quality Gate failed

Failed conditions
25.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

Initial plan for issue

ba84962

Copilot AI assigned Copilot and christianhelle May 19, 2025

Copilot started work on behalf of christianhelle May 19, 2025 21:29 View session

Fix ArgumentException in OpenApiCSharpCodeGenerator.Sanitize method

e7b274d

Co-authored-by: christianhelle <710400+christianhelle@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Argument null exception~~ Fix ArgumentException in OpenApiCSharpCodeGenerator.Sanitize method May 19, 2025

Copilot AI requested a review from christianhelle May 19, 2025 21:34

Copilot finished work on behalf of christianhelle May 19, 2025 21:35

christianhelle requested a review from Copilot May 22, 2025 07:44

Copilot AI reviewed May 22, 2025

View reviewed changes

src/Core/ApiClientCodeGen.Core/Generators/OpenApi/OpenApiCSharpCodeGenerator.cs Outdated Show resolved Hide resolved

Update src/Core/ApiClientCodeGen.Core/Generators/OpenApi/OpenApiCShar…

b4614dd

…pCodeGenerator.cs Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Refactor configuration file handling in OpenApiCSharpCodeGenerator to…

8dae3c2

… ensure extension is not null before processing

christianhelle marked this pull request as ready for review June 11, 2025 14:15

christianhelle mentioned this pull request Jun 11, 2025

Argument null exception #1157

Closed

christianhelle merged commit f632dfc into master Jun 11, 2025
39 of 46 checks passed

christianhelle deleted the copilot/fix-1157 branch June 11, 2025 19:25

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Fix ArgumentException in OpenApiCSharpCodeGenerator.Sanitize method #1163

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