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/HaskellServantCodegen.java:648

        return op;
    }

    private String makeQueryListType(String type, String collectionFormat) {
        type = type.substring(1, type.length() - 1);
        switch (collectionFormat) {
            case "csv":
                return "(QueryList 'CommaSeparated (" + type + "))";
            case "tsv":
                return "(QueryList 'TabSeparated (" + type + "))";
            case "space":
            case "ssv":
                return "(QueryList 'SpaceSeparated (" + type + "))";
            case "pipes":
                return "(QueryList 'PipeSeparated (" + type + "))";
            case "multi":
                return "(QueryList 'MultiParamArray (" + type + "))";
            default:
                throw new UnsupportedOperationException(collectionFormat + " (collection format) not supported");
        }
    }

    // Remove characters from a string that do not belong in a model classname
    private String fixModelChars(String string) {
        return string.replace(".", "").replace("-", "");
    }

    // Override fromModel to create the appropriate model namings
    @Override
    public CodegenModel fromModel(String name, Schema mod) {
        CodegenModel model = super.fromModel(name, mod);

        setGenerateToSchema(model);

        // Clean up the class name to remove invalid characters
        model.classname = fixModelChars(model.classname);
        if (typeMapping.containsValue(model.classname)) {

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 Servant 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/52ca6d4537afb558. Report an issue: GitHub.