What causes "Theme-pack author must be an object or a string" in HMCL-dev/HMCL?

Change the manifest's "author" value to a plain string, e.g. {"author": "Alice"}.

HMCL-dev/HMCL · error · JsonParseException

Theme-pack author must be an object or a string

Error message

Theme-pack author must be an object or a string

What it means

Thrown by ThemePackAuthor.fromJson when a theme-pack manifest's author field is neither a JSON object nor a string. The library accepts either a plain string author or an object with a localized 'name' field; anything else (number, boolean, array, null) is rejected so malformed manifests fail loudly at load time instead of producing a broken author record.

Solutions

Change the manifest's "author" value to a plain string, e.g. {"author": "Alice"}.
Or use the object form with a "name" field: {"author": {"name": "Alice"}} (name may be a LocalizedText object).
Remove arrays/numbers/booleans; multiple authors or extra metadata are not supported in this field.
Re-export the theme pack with ThemePackExporter so the manifest is generated correctly.

Example fix

// before (theme.json)
{"author": ["Alice", "Bob"]}
// after
{"author": "Alice"}
// or
{"author": {"name": "Alice"}}

Defensive patterns

Strategy: type-guard

Validate before calling

boolean validAuthor(JsonElement e) {
    return e instanceof JsonObject || (e != null && e.isJsonPrimitive() && e.getAsJsonPrimitive().isString());
}

Type guard

if (!(json instanceof JsonObject) && !(json instanceof JsonPrimitive p && p.isString())) throw new IllegalArgumentException("author must be object or string");

Try / catch

try { ThemePackAuthor a = ThemePackAuthor.fromJson(json); } catch (JsonParseException e) { log.warn("Invalid author element: " + json); }

Prevention

Always author manifests as {"author": "Name"} or {"author": {"name": ...}}
Validate manifests with a JSON schema before distributing packs
Never encode multiple authors as an array

When it happens

Trigger: Parsing a theme.json/manifest whose "author" key is set to a JSON number, boolean, array, or null while deserializing via ThemePackAuthor.fromJson / ThemePackManifest.fromJson.

Common situations: Hand-edited theme-pack manifests, third-party tools generating manifests with numeric author IDs, or pack authors writing {"author": ["a","b"]} to express multiple authors instead of one string or one object.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/7010d660009be2a4. Report an issue: GitHub.

Appendix: source

Thrown at HMCL/src/main/java/org/jackhuang/hmcl/theme/ThemePackAuthor.java:97

    /// Parses author metadata from a JSON object or a plain string.
    ///
    /// @param json the author metadata JSON
    /// @return the parsed author metadata, or `null` when `json` is `null`
    /// @throws JsonParseException if `json` is neither an object nor a string author name
    public static @Nullable ThemePackAuthor fromJson(@Nullable JsonElement json) throws JsonParseException {
        if (json == null || json instanceof JsonNull)
            return null;

        if (json instanceof JsonPrimitive primitive && primitive.isString()) {
            try {
                return new ThemePackAuthor(LocalizedText.plain(primitive.getAsString()));
            } catch (IllegalArgumentException e) {
                throw new JsonParseException(e);
            }
        }

        if (!(json instanceof JsonObject jsonObject)) {
            throw new JsonParseException("Theme-pack author must be an object or a string");
        }

        JsonElement nameJson = jsonObject.get("name");
        if (nameJson == null) {
            throw new JsonParseException("Missing author name: " + json);
        }

        LocalizedText name = LocalizedText.fromJson(nameJson);
        if (name == null) {
            throw new JsonParseException("The author name is null");
        }

        try {
            return new ThemePackAuthor(name);
        } catch (IllegalArgumentException e) {
            throw new JsonParseException(e);
        }
    }

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