grpc-ecosystem/grpc-gateway · error

the provided default value

Error message

the provided default value %q does not match provider type %q, or is not properly quoted with escaped quotations

What it means

Validation error from validateDefaultValueTypeAndFormat for string-typed header parameters: the default value is not a properly quoted JSON string (isQuotedString failed) — it may be unquoted, single-quoted, or contain unescaped quotes. The offending inputs are the default value and its declared type from the openapiv2 options.

Solutions

1. Wrap the default value in escaped double quotes, e.g. "\"value\"".
2. Escape any inner double quotes in the value.

When it happens

Trigger: Thrown at protoc-gen-openapiv2/internal/genopenapi/template.go:2758 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grpc-ecosystem/grpc-gateway@a58a4436a3 (2026-09-02). Data as JSON: /api/errors/51bef5e98e432137. Report an issue: GitHub.

Appendix: source

Thrown at protoc-gen-openapiv2/internal/genopenapi/template.go:2758

			"int16",
			"int32",
			"int64",
			"":
			return nil
		default:
			return fmt.Errorf("the provided format %q is not a valid extension of the type %q", format, headerType)
		}
	case "boolean":
		return nil
	}
	return fmt.Errorf("the provided header type %q is not supported", headerType)
}

func validateDefaultValueTypeAndFormat(headerType string, defaultValue string, format string) error {
	switch headerType {
	case "string":
		if !isQuotedString(defaultValue) {
			return fmt.Errorf("the provided default value %q does not match provider type %q, or is not properly quoted with escaped quotations", defaultValue, headerType)
		}
		switch format {
		case "date-time":
			unquoteTime := strings.Trim(defaultValue, `"`)
			if _, err := time.Parse(time.RFC3339, unquoteTime); err != nil {
				return fmt.Errorf("the provided default value %q is not a valid RFC3339 date-time string", defaultValue)
			}
		case "date":
			const layoutRFC3339Date = "2006-01-02"
			unquoteDate := strings.Trim(defaultValue, `"`)
			if _, err := time.Parse(layoutRFC3339Date, unquoteDate); err != nil {
				return fmt.Errorf("the provided default value %q is not a valid RFC3339 date-time string", defaultValue)
			}
		}
	case "number":
		if err := isJSONNumber(defaultValue, headerType); err != nil {
			return err
		}

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