OpenAPITools/openapi-generator · error · UnsupportedOperationException

{collectionFormat} (collection format) not supported

Error message

{collectionFormat} (collection format) not supported

What it means

Error "{collectionFormat} (collection format) not supported" thrown in OpenAPITools/openapi-generator.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellHttpClientCodegen.java:1151

            return word.substring(0, 1).toLowerCase(Locale.ROOT) + word.substring(1);
        }
    }

    private String mapCollectionFormat(String collectionFormat) {
        switch (collectionFormat) {
            case "csv":
                return "CommaSeparated";
            case "tsv":
                return "TabSeparated";
            case "ssv":
            case "space":
                return "SpaceSeparated";
            case "pipes":
                return "PipeSeparated";
            case "multi":
                return "MultiParamArray";
            default:
                throw new UnsupportedOperationException(collectionFormat + " (collection format) not supported");
        }
    }

    private String getMimeDataType(String mimeType) {
        if (StringUtils.isBlank(mimeType)) {
            return MIME_NO_CONTENT;
        }
        if (knownMimeDataTypes.containsKey(mimeType)) {
            return knownMimeDataTypes.get(mimeType);
        }
        String shortenedName = mimeType.replaceFirst("application/", "");
        return "Mime" + toTypeName("", shortenedName);
    }

    private static String generateNextName(String name) {
        Pattern pattern = Pattern.compile("\\d+\\z");
        Matcher matcher = pattern.matcher(name);
        if (matcher.find()) {

View on GitHub (pinned to fcec517be3)

Solutions

1. Use a supported collection format for array query parameters (e.g. csv) in the spec.

When it happens

Trigger: Thrown when a parameter in the spec uses a collectionFormat that the Haskell http-client generator does not support. Change the parameter's collectionFormat to a supported one.

Common situations: See trigger scenarios.

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/d938172024db1655. Report an issue: GitHub.