MoonFeatureGate

MoonFeatureGate is a MoonBit-native feature flag and gradual rollout toolkit. It evaluates flags locally, explains why a value was chosen, and keeps the core runtime independent from a hosted control plane.

This repository is prepared for the 2026 MoonBit open-source ecosystem competition. The project focuses on reusable engineering infrastructure: targeting rules, stable percentage rollout, typed flag values, CLI validation, examples, tests, and a clear path toward OpenFeature-style providers.

Project Summary

MoonFeatureGate provides a compact local runtime for feature management in MoonBit projects. It is useful for libraries, demos, WASM applications, and small services that need auditable rollout decisions without depending on a remote feature-flag platform.

Core capabilities in 0.1.0:

• typed flag values for bool, string, int, and double values
• local bool evaluation with default, disabled, static, rollout, and target match explanations
• deterministic 0..9999 rollout buckets over flag_key:targeting_key
• a compact text configuration DSL
• a runnable CLI demo
• black-box and white-box MoonBit tests
• CI verification for formatting, checks, tests, and demo execution

Quick Start

Run the verification set from the repository root:

moon info
moon fmt --check
moon check --warn-list +73
moon test
moon run cmd/moonfeaturegate

Expected demo output:

MoonFeatureGate demo
flag=new_checkout
user=user-42
value=true
reason=rollout_match

Core API

test {
  let provider = @moonfeaturegate.empty_provider().with_bool_rollout(
    "new_checkout",
    true,
    percentage=2500,
  )
  let ctx = @moonfeaturegate.context("user-42").with_attr(
    "plan",
    @moonfeaturegate.string_value("beta"),
  )
  let detail = @moonfeaturegate.evaluate_bool(
    provider,
    "new_checkout",
    ctx,
    default=false,
  )
  inspect(detail.flag_key, content="new_checkout")
}

Configuration DSL

Each non-empty line defines one flag. Lines starting with # are comments.

flag new_checkout bool true rollout 2500
flag beta_banner bool true target plan beta

Supported 0.1.0 forms:

• flag <key> bool <true|false>
• flag <key> bool <true|false> rollout <0..10000>
• flag <key> bool <true|false> target <attribute> <string-value>

Repository Layout

• MoonFeatureGate.mbt, provider.mbt, rollout.mbt, parser.mbt: core library implementation
• *_test.mbt: library test coverage
• cmd/moonfeaturegate: runnable CLI demo
• examples/flags.mfg: sample configuration file
• docs/design.md: design notes and extension direction
• docs/acceptance-checklist.md: competition closeout checklist
• docs/closeout.md: final submission notes

Competition Notes

• This is an original MoonBit project, not a direct port of a single upstream library.
• The design is informed by mature feature-flag systems and the vendor-neutral OpenFeature idea, while the first release intentionally keeps a compact local API.
• The repository is public, licensed under Apache-2.0, and prepared for Mooncakes publication.
• Planned extensions include JSON/TOML providers, an OpenFeature-like provider boundary, metrics hooks, remote config polling, and a small web preview.

Links

• GitHub: https://github.com/wccerty/MoonFeatureGate
• GitLink: https://gitlink.org.cn/Wccerty/MoonFeatureGate
• Mooncakes: https://mooncakes.io/docs/wccerty/moonfeaturegate

中文简介

MoonFeatureGate 是一个 MoonBit 原生的特性开关与灰度发布工具库。它支持本地规则评估、用户定向、 稳定百分比分桶、命中原因解释和 CLI 校验，适合用于 MoonBit 项目的功能灰度、实验开关和配置策略管理。

项目面向 MoonBit 开源生态建设，重点补齐工程基础设施方向中的“可测试、可审查、可复用”的本地特性管理能力。