RicoSuter/NSwag · error · Error

Unknown error

Error message

Unknown error

What it means

nswag.js runs 'dotnet --info' (spawnSync) to detect the installed .NET Core version before launching the NSwag command host. If the spawn itself failed it rethrows that error; if dotnet ran but exited non-zero with an empty stderr, the script throws new Error("Unknown error"). This means the .NET runtime probe failed without a diagnostic message.

Solutions

1. Run 'dotnet --info' manually in the same shell to see the real failure and fix the .NET SDK installation (reinstall from https://dotnet.microsoft.com).
2. Ensure the dotnet executable is on PATH and functional for the user running nswag.
3. In CI, use a setup step (e.g. actions/setup-dotnet) to install a supported .NET Core SDK before running nswag.
4. Check for a global.json pinning an SDK version that is not installed, and remove or correct it.
5. Upgrade the @nswag/npm package so its supportedCoreVersions list matches your installed .NET version, avoiding the related 'not supported' exit path.

// Before invoking nswag CLI, probe dotnet yourself
const { spawnSync } = require('child_process');
const r = spawnSync('dotnet', ['--info'], { encoding: 'utf8' });
if (r.error || r.status !== 0) {
  console.error('dotnet CLI is broken or missing; install the .NET SDK first');
  process.exit(1);
}

function isDotnetAvailable() {
  const r = require('child_process').spawnSync('dotnet', ['--info'], { encoding: 'utf8' });
  return !r.error && r.status === 0;
}

try {
  execSync('npx nswag run nswag.json');
} catch (err) {
  if (String(err.message).includes('Unknown error')) {
    console.error('nswag failed to probe dotnet; verify "dotnet --info" works manually');
  }
  process.exit(1);
}

When it happens

Trigger: Running the nswag npm CLI on a machine where 'dotnet --info' exits non-zero (broken or partially uninstalled .NET SDK, corrupted installation, permission issues), where stderr is empty so no better message can be surfaced.

Common situations: CI containers without the .NET SDK installed or with only the runtime; dotnet on PATH but a broken multi-level-lookup/globaljson setup; antivirus or permissions killing dotnet; incompatible SDK version left after an upgrade; PATH pointing to a shim that fails.

Related errors

• Project outputs could not be located in
• Unable to retrieve project metadata. Ensure it's an…
• Runtime: " + Runtime + "\n" + stackTrace
• 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/80b32d207154563a. Report an issue: GitHub.

Appendix: source

Thrown at src/NSwag.Npm/bin/nswag.js:96

else if (runtimeIndices.length === 1) {
    args.splice(runtimeIndices[0], 1);
}

if (runtimeValue) {
    if (runtimeValue.toLowerCase() === "netcore") {

        // detect latest installed NetCore Version
        console.log("Trying to detect latest installed NetCore Version.");
        var infoCmd = "dotnet";
        var infoArgs = ["--version"];

        try {
            var result = c.spawnSync(infoCmd, infoArgs, { encoding: 'utf8' });
            if (result.error) {
                throw result.error;
            }
            if (result.status !== 0) {
                throw new Error(result.stderr ? result.stderr.toString() : "Unknown error");
            }
            var coreVersion = result.stdout.trim();
            const version = supportedCoreVersions.find(v => coreVersion.startsWith(v.ver));
            if (!version) {
                console.error("Error: Detected .NET Core version '" + coreVersion + "' is not supported.");
                process.exit(1);
            }
            console.log("Using supported .NET Core version: " + version.dir);
            runtimeValue = version.dir;
        } catch (error) {
            console.error("Error: Could not detect .NET Core version.");
            console.debug(error);
            process.exit(1);
        }
    }

    if (!runtimeValue.toLowerCase().startsWith("win")) {
        const isSupported = supportedCoreVersions.some(v => v.dir.toLowerCase() === runtimeValue.toLowerCase());

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