HMCL-dev/HMCL · error · JsonParseException

Empty theme condition value for

Error message

Empty theme condition value for 

What it means

ThemeCondition.normalizeValue trims each condition value and rejects ones that are empty after trimming. A blank value can never match anything, so fromJson fails with this JsonParseException naming the condition key.

Solutions

1. Replace the empty string with a real value, e.g. "os": ["windows"].
2. Remove the empty entry from the array (or delete the condition key if no values remain).
3. Filter blank strings out of condition values before building the ThemeCondition.
4. Catch JsonParseException and point the user at the offending key in their theme file.

Example fix

// before (theme.json)
// "os": ["windows", ""]
// after
"os": ["windows"]

boolean ok = values.stream().allMatch(v -> v != null && !v.trim().isEmpty());

static boolean hasNoBlankValues(java.util.Collection<String> values) {
    return values.stream().allMatch(v -> v != null && !v.trim().isEmpty());
}

try {
    ThemeCondition c = ThemeCondition.fromJson(element);
} catch (JsonParseException e) {
    LOG.warning("Blank condition value: " + e.getMessage());
}

When it happens

Trigger: A theme JSON condition value that is "" or " ", e.g. {"os": ["windows", " "]} or {"language": ""}, passed through ThemeCondition.fromJson (or the ThemeCondition constructor path).

Common situations: Hand-edited theme files with leftover empty strings after deleting a value; editors saving placeholder quotes; generators emitting empty strings when a variable is unset.

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

• Theme condition array is empty:
• Theme condition array must contain strings:
• Theme condition value must be a string or string array:
• Theme condition key is blank
• Unsupported brightness condition value:

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/1bb1e6c55e83fb46. Report an issue: GitHub.

Appendix: source

Thrown at HMCL/src/main/java/org/jackhuang/hmcl/theme/ThemeCondition.java:172

    /// Normalizes and validates a condition key.
    private static String normalizeKey(String key) {
        Objects.requireNonNull(key);

        String normalized = key.trim();
        if (normalized.isEmpty()) {
            throw new JsonParseException("Theme condition key is blank");
        }
        return normalized;
    }

    /// Normalizes and validates one condition value.
    private static String normalizeValue(String key, String value) {
        Objects.requireNonNull(key);
        Objects.requireNonNull(value);

        String trimmed = value.trim();
        if (trimmed.isEmpty()) {
            throw new JsonParseException("Empty theme condition value for " + key);
        }
        String normalized = trimmed.toLowerCase(Locale.ROOT);

        return switch (key) {
            case KEY_BRIGHTNESS -> switch (normalized) {
                    case "light", "dark" -> normalized;
                    default -> throw new JsonParseException("Unsupported brightness condition value: " + value);
                };
            case KEY_OS -> normalizeOperatingSystemValue(normalized, value);
            case KEY_LANGUAGE -> normalized;
            default -> trimmed;
        };
    }

    /// Normalizes an operating system condition value.
    private static String normalizeOperatingSystemValue(String normalized, String original) {
        String value = switch (normalized) {
            case "win", "windows" -> "windows";

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