OpenAPITools/openapi-generator · error · RuntimeException

Error parsing version expression '{requestedVersion}' as a v

Error message

Error parsing version expression '{requestedVersion}' as a version constraint

What it means

Thrown inside JavaHelidonCommonCodegen's VersionConstraint helper when the requested Helidon version string is neither a plain unsigned integer (that path is error 129) nor parseable by the Aether/Maven version scheme as a version constraint. The generator supports exact versions ('4.1.0') and Maven ranges ('[3.0.0,4.0.0)'), and anything else — suffixes, partial semver, junk — fails here with this wrapper RuntimeException.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaHelidonCommonCodegen.java:878

        private VersionConstraint constraint(VersionScheme versionScheme, String requestedVersion) {
            try {
                int asSingleNumber = Integer.parseUnsignedInt(requestedVersion);
                try {
                    return versionScheme.parseVersionConstraint(String.format(Locale.getDefault(),
                            "[%s,%d-alpha)",
                            requestedVersion,
                            asSingleNumber + 1));
                } catch (InvalidVersionSpecificationException ex) {
                    throw new RuntimeException("Error preparing constraint for version expression '"
                            + requestedVersion
                            + "' treated as major version " + asSingleNumber,
                            ex);
                }
            } catch (NumberFormatException nfe) {
                try {
                    return versionScheme.parseVersionConstraint(requestedVersion);
                } catch (InvalidVersionSpecificationException ex) {
                    throw new RuntimeException("Error parsing version expression '"
                            + requestedVersion
                            + "' as a version constraint",
                            ex);
                }
            }
        }

        /**
         * Retrieves the list of supported versions from the web site or, failing that, local preferences or, failing that,
         * hard-coded versions.
         *
         * @return list of supported versions
         * @throws IOException in case of error accessing the web site and reading the local file
         */
        private List<String> versions() throws IOException, BackingStoreException {

            HttpClient httpClient = HttpClient.newBuilder()
                    .connectTimeout(CONNECTION_TIMEOUT)

View on GitHub (pinned to fcec517be3)

Solutions

Use an exact released version: helidonVersion=4.1.0
Or a well-formed Maven range: helidonVersion="[4.0.0,5.0.0)" — note brackets/parentheses and both bounds
Remove prefixes like 'v' and any build-metadata decorations; '4.1.0-SNAPSHOT' alone is fine
Echo the interpolated value in CI before generation to catch empty/mangled variable substitution

Example fix

# before
openapi-generator-cli generate -g java-helidon-server -i api.yaml \
  --additional-properties helidonVersion=4.x

# after
openapi-generator-cli generate -g java-helidon-server -i api.yaml \
  --additional-properties helidonVersion=4.1.0

Defensive patterns

Strategy: validation

Validate before calling

String v = String.valueOf(opts.get("helidonVersion"));
boolean exact = v.matches("\d+(\.\d+)*(-[A-Za-z0-9.]+)?");
boolean range = v.startsWith("[") || v.startsWith("(");
if (!exact && !range) {
    throw new IllegalArgumentException("helidonVersion '" + v + "' is neither an exact version nor a Maven range like [3.0.0,4.0.0)");
}

Try / catch

try {
    generator.generate();
} catch (RuntimeException e) {
    if (e.getMessage() != null && e.getMessage().contains("version expression")) {
        throw new IllegalArgumentException("Bad helidonVersion: " + opts.get("helidonVersion"), e);
    }
    throw e;
}

Prevention

Reject 'v'-prefixed and wildcard ('4.x', 'latest') version strings at config load time
Echo interpolated CI variables into the build log before generation to spot mangled values
Reuse the same version-format helper everywhere versions enter your pipeline

When it happens

Trigger: Passing --additional-properties helidonVersion=4.x, helidonVersion=v4.1.0, helidonVersion="4.1.0-SNAPSHOT (build 42)", helidonVersion=latest, or a truncated range like "[3.0.0," to -g java-helidon-server / -g java-helidon-client. Any input Aether's parseVersionConstraint rejects after the numeric shortcut also failed.

Common situations: Developers used to semver tooling pass '4.x' or 'v4.1.0' style selectors that Maven ranges do not understand. CI pipelines interpolating environment variables into helidonVersion can inject empty or decorated strings ('4.1.0-rc{BUILD}').

Related errors

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/b610ff0c098e9548. Report an issue: GitHub.