RicoSuter/NSwag · error · CommandLineException

Runtime: " + Runtime + "\n" + stackTrace

Error message

Runtime: " + Runtime + "\n" + stackTrace

What it means

NSwagDocument.StartCommandLineProcessAsync launches an external process (e.g. a second NSwag/dotnet process for a different runtime) and throws CommandLineException when the process exits with an error, attaching the Runtime and its stack trace. If stderr contains 'The system cannot find the file specified', a hint about installing .NET Core / dotnet on PATH is appended.

Solutions

1. Install the .NET Core SDK/runtime matching the document's Runtime setting and ensure 'dotnet' is on PATH ('dotnet --version').
2. Change the document's 'runtime' property to a runtime available on the machine (e.g. WinX64 or Net80).
3. Read the attached stack trace / inner message to find the actual process failure (e.g. missing commands DLL) and fix that underlying issue.

Example fix

// before (nswag.json)
"runtime": "NetCore21"
// after
"runtime": "Net80" // or install the .NET Core 2.1 runtime

var dotnet = RunAndCapture("dotnet", "--version"); // fail early if dotnet is missing
if (string.IsNullOrWhiteSpace(dotnet))
    throw new InvalidOperationException("'dotnet' is not on PATH; install the required .NET runtime.");

try { var output = await document.StartCommandLineProcessAsync(process, arguments); }
catch (CommandLineException ex)
{ log.Error($"NSwag subprocess failed (runtime {document.Runtime}): {ex.Message} \n{ex.StackTrace}"); throw; }

When it happens

Trigger: The spawned process (dotnet/hosts run for a document targeting a different Runtime) fails or is missing: non-zero exit, 'dotnet' not on PATH, or the target runtime/host executable cannot be found.

Common situations: Documents with runtime NetCore21/NetCore50 etc. executed on a machine where that .NET Core runtime or 'dotnet' CLI is not installed; PATH problems in CI or services; Windows 'cannot find the file specified' because dotnet.exe is absent.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

• Project outputs could not be located in
• Unable to retrieve project metadata. Ensure it's an…
• Unknown error
• The specified runtime in the document
• The ouput of is a 32-bit application and requires…

AI-assisted analysis of RicoSuter/NSwag@63daf8fcc3 (2026-09-14). Data as JSON: /api/errors/03b156c9a0a2249f. Report an issue: GitHub.

Appendix: source

Thrown at src/NSwag.Commands/NSwagDocument.cs:221

                if (stackTraceStart < 0)
                {
                    stackTraceStart = error.IndexOf("   at ", StringComparison.Ordinal);
                }

                var message = stackTraceStart > 0 ? error.Substring(0, stackTraceStart) : error;
                var stackTrace = stackTraceStart > 0 ? error.Substring(stackTraceStart) : "";

                if (message.Contains("Could not load type"))
                {
                    message += "Try running the document in another runtime, e.g. /runtime:NetCore20";
                }

                if (message.Contains("The system cannot find the file specified"))
                {
                    message += "Check if .NET Core is installed and 'dotnet' is globally available.";
                }

                throw new CommandLineException(message, "Runtime: " + Runtime + "\n" + stackTrace);
            }

            return output;
        }

        private string GetDocumentDirectory()
        {
            var absoluteDocumentPath = PathUtilities.MakeAbsolutePath(Path, Directory.GetCurrentDirectory());
            return System.IO.Path.GetDirectoryName(absoluteDocumentPath);
        }

#pragma warning disable CA1822
        private string GetArgumentsPrefix()
#pragma warning restore CA1822
        {
#if NET462

            var runtime = Runtime != Runtime.Default ? Runtime : RuntimeUtilities.CurrentRuntime;

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