HMCL-dev/HMCL · error · IllegalArgumentException

Theme condition field has no accepted values:

Error message

Theme condition field has no accepted values: 

What it means

When building a ThemeCondition from a requirements map, every condition field must accept at least one value. If a field's value set is empty the condition can never match, so the constructor rejects it eagerly with IllegalArgumentException.

Solutions

1. Add at least one accepted value to the condition field, e.g. "os" -> Set.of("windows", "linux").
2. Remove the empty condition field from the requirements map entirely if the condition is unnecessary.
3. Validate the map before constructing: skip or reject entries whose value set is empty.
4. If values are computed at runtime, fall back to a known-good default value set when the computed set is empty.

Example fix

// before
Map<String, Set<String>> req = new LinkedHashMap<>();
req.put("os", new LinkedHashSet<>()); // empty -> throws
ThemeCondition c = new ThemeCondition(req);
// after
Map<String, Set<String>> req = new LinkedHashMap<>();
if (!osValues.isEmpty()) {
    req.put("os", osValues);
}
ThemeCondition c = new ThemeCondition(req);

for (Map.Entry<String, Set<String>> e : requirements.entrySet()) {
    if (e.getKey().trim().isEmpty() || e.getValue().isEmpty())
        throw new IllegalArgumentException("Invalid condition entry: " + e.getKey());
}

try {
    ThemeCondition c = new ThemeCondition(requirements);
} catch (IllegalArgumentException e) {
    LOG.warning("Dropping unsatisfiable condition: " + e.getMessage());
}

When it happens

Trigger: Calling the ThemeCondition constructor (or the programmatic builder path, e.g. ThemeCondition.of / fromJson feeding it) with a map such as Map.of("os", Set.of()) — a key present with an empty value set.

Common situations: Building conditions programmatically after filtering values (a filter removed everything); deserializing JSON where a condition array was empty upstream; refactors that initialize a LinkedHashSet but never populate it.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Empty theme condition value for
• Theme condition array is empty:
• Theme condition array must contain strings:
• Theme condition key is blank
• Theme condition value must be a string or string array:

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/c33f9a076b7b6fdc. Report an issue: GitHub.

Appendix: source

Thrown at HMCL/src/main/java/org/jackhuang/hmcl/theme/ThemeCondition.java:69

    /// Condition key for the current UI language.
    static final String KEY_LANGUAGE = "language";

    /// Supported operating system condition values.
    private static final Set<String> SUPPORTED_OS_VALUES = Set.of("windows", "macos", "linux", "freebsd", "unknown");

    /// Creates a condition from normalized accepted values.
    ///
    /// @param requirements normalized accepted values keyed by condition name
    public ThemeCondition {
        Objects.requireNonNull(requirements);

        LinkedHashMap<String, Set<String>> copy = new LinkedHashMap<>();
        for (Map.Entry<String, Set<String>> entry : requirements.entrySet()) {
            String key = normalizeKey(entry.getKey());
            Set<String> values = entry.getValue();
            if (values.isEmpty()) {
                throw new IllegalArgumentException("Theme condition field has no accepted values: " + key);
            }

            LinkedHashSet<String> valueCopy = new LinkedHashSet<>();
            for (String value : values) {
                valueCopy.add(normalizeValue(key, value));
            }
            copy.put(key, Collections.unmodifiableSet(valueCopy));
        }
        requirements = Collections.unmodifiableMap(copy);
    }

    /// Parses a theme condition from a JSON object.
    ///
    /// @param object the condition object
    /// @return the parsed condition
    /// @throws JsonParseException if the condition contains malformed values
    public static ThemeCondition fromJson(JsonObject object) throws JsonParseException {
        Objects.requireNonNull(object);

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