OpenAPITools/openapi-generator · error · RuntimeException

Empty method name (operationId) not allowed

Error message

Empty method name (operationId) not allowed

What it means

XojoClientCodegen.toOperationId (line 429) camelize+sanitizeName's the operationId and then refuses an empty result. This happens when the spec's operationId (or the derived name) consists entirely of characters that sanitizeName strips, leaving nothing to build a Xojo method name from. The check is defensive — normal specs never hit it — but a RuntimeException is thrown because generation cannot continue without a method name.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/XojoClientCodegen.java:429

            if (sec.isApiKey) sec.name = toVarName(sec.name);
        }

        return securities;
    }

    @Override
    public GeneratorLanguage generatorLanguage() {
        return GeneratorLanguage.XOJO;
    }

    @Override
    public String toOperationId(String operationId) {
        operationId = camelize(sanitizeName(operationId));

        // Throw exception if method name is empty.
        // This should not happen but keep the check just in case
        if (StringUtils.isEmpty(operationId)) {
            throw new RuntimeException("Empty method name (operationId) not allowed");
        }

        // method name cannot use reserved keyword, e.g. return
        if (isReservedWord(operationId)) {
            String newOperationId = camelize(("Call_" + operationId));
            LOGGER.warn("{} (reserved word) cannot be used as method name. Renamed to {}", operationId, newOperationId);
            return newOperationId;
        }

        // operationId starts with a number
        if (operationId.matches("^\\d.*")) {
            LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER));
            operationId = camelize(sanitizeName("Call_" + operationId));
        }

        return operationId;
    }

View on GitHub (pinned to fcec517be3)

Solutions

  1. Open the spec and give every operation (paths -> verbs) a non-empty operationId containing at least one letter or digit (e.g. 'getUser').
  2. If operationIds look fine, check for operationIds made only of punctuation/whitespace or duplicated special characters after sanitization.
  3. Validate the spec with a linter (Swagger Editor / spectral) before generation to catch malformed identifiers.

Example fix

# before (openapi.yaml)
paths:
  /users:
    get:
      operationId: "###"

# after
paths:
  /users:
    get:
      operationId: getUser
Defensive patterns

Strategy: validation

Validate before calling

// Node: reject operations whose operationId sanitizes to empty before generating
const spec = require('./openapi.json');
for (const [path, item] of Object.entries(spec.paths ?? {}))
  for (const [verb, op] of Object.entries(item))
    if (/^(get|put|post|delete|options|head|patch|trace)$/.test(verb)) {
      const id = (op.operationId ?? '').replace(/[^a-zA-Z0-9]/g, '');
      if (id.length === 0) throw new Error(`${verb.toUpperCase()} ${path}: empty/invalid operationId`);
    }

Try / catch

catch (RuntimeException e) {
    // message names the offending operation path — fix the spec and regenerate
    if (e.getMessage().contains("Empty method name (operationId) not allowed")) {
        throw new SpecError("An operationId sanitized to empty; add a valid operationId to every operation", e);
    }
    throw e;
}

Prevention

When it happens

Trigger: An OpenAPI operation with operationId: "###" or "///" (only special characters), or a missing operationId on a path whose auto-derived name sanitizes to empty. Only the Xojo generator path shown throws here, but any spec with such an operation is the root cause.

Common situations: Hand-edited specs where operationId was deleted instead of renamed; codegen'd specs from tools that emit symbol-only identifiers; specs with non-ASCII operationIds that sanitization strips to nothing.

Related errors

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/231063999aa4eaf4. Report an issue: GitHub.