HMCL-dev/HMCL · error · JsonParseException

MinecraftInstanceConfiguration missing `type`

Error message

MinecraftInstanceConfiguration missing `type`

What it means

ModpackConfiguration.validate() also requires the top-level `type` field to identify the configuration kind (e.g. "minecraftInstance"). It throws JsonParseException("MinecraftInstanceConfiguration missing `type`") when type is null after JSON deserialization, so the modpack's format cannot be determined.

Solutions

1. Add "type": "minecraftInstance" to the top level of modpack.json.
2. Re-export the modpack with the official packaging tool so all required fields are written.
3. Check the key spelling/casing is exactly `type`.
4. Validate the full modpack.json against the current modpack schema before distribution.

Example fix

// before (modpack.json)
// { "manifest": { "name": "MyPack" } }
// after
// { "type": "minecraftInstance", "manifest": { "name": "MyPack" } }

try {
    ModpackConfiguration cfg = GSON.fromJson(json, ModpackConfiguration.class);
    cfg.validate();
} catch (JsonParseException e) {
    // modpack.json missing type — reject or regenerate the pack
}

try {
    config.validate();
} catch (JsonParseException e) {
    if (e.getMessage().contains("missing `type`")) {
        // add "type": "minecraftInstance" or re-export the pack
    }
}

When it happens

Trigger: Calling validate() on a ModpackConfiguration parsed from modpack.json without the `type` key, or with type explicitly set to null.

Common situations: Hand-written modpack.json omitting the type discriminator; upgrading from an older modpack format that lacked type; copy-pasting only the manifest section into a new file; key renamed/case-mismatched.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• MinecraftInstanceConfiguration missing `manifest`
• ServerModpackManifest.fileApi cannot be blank
• ServerModpackManifest.files cannot be null
• FileInformation missing `path`.
• FileInformation missing file hash code.

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/624b4ed1d7d92832. Report an issue: GitHub.

Appendix: source

Thrown at HMCLCore/src/main/java/org/jackhuang/hmcl/modpack/ModpackConfiguration.java:94

    public ModpackConfiguration<T> setOverrides(List<FileInformation> overrides) {
        return new ModpackConfiguration<>(manifest, type, name, version, overrides);
    }

    public ModpackConfiguration<T> setVersion(String version) {
        return new ModpackConfiguration<>(manifest, type, name, version, overrides);
    }

    public List<FileInformation> getOverrides() {
        return Collections.unmodifiableList(overrides);
    }

    @Override
    public void validate() throws JsonParseException {
        if (manifest == null)
            throw new JsonParseException("MinecraftInstanceConfiguration missing `manifest`");
        if (type == null)
            throw new JsonParseException("MinecraftInstanceConfiguration missing `type`");
    }

    @Immutable
    public static class FileInformation implements Validation {
        private final String path; // relative
        private final String hash;
        private final String downloadURL;

        public FileInformation() {
            this(null, null);
        }

        public FileInformation(String path, String hash) {
            this(path, hash, null);
        }

        public FileInformation(String path, String hash, String downloadURL) {
            this.path = path;

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