MoonTemplate

MoonTemplate is a MoonBit-native text template engine for generating HTML, emails, configuration files, prompts, and code snippets from simple declarative templates.

Why This Project

MoonTemplate targets the common “generate structured text from data” problem in the MoonBit ecosystem:

static page generators
CLI report generation
config and manifest synthesis
email and notification rendering
code scaffolding and boilerplate generation

The implementation is intentionally small, readable, and reviewable, but it already covers the core engineering surface expected from an OSC2026 acceptance repository: public source, reproducible checks, real tests, CI, a CLI entry point, API snapshots, and source-attribution documentation.

Feature Set

Variable interpolation: {{ name }}
Filter pipelines: {{ name | trim | uppercase }}
Built-in filters: trim, uppercase, lowercase, escape_html, escape_json, slugify
Custom filters via Engine::register_filter
Conditional rendering with if / else
Loop rendering with {% for item in list %}
Native CLI for file-based or inline rendering
Public API snapshot tracked in src/moontemplate/pkg.generated.mbti

Template Syntax

Hello, {{ user | trim }}!

{% if is_admin %}
Role: ADMIN
{% else %}
Role: USER
{% endif %}

Members:
{% for member in users %}
- {{ member | trim }}
{% endfor %}

Loop variables are read from comma-separated strings in the input context. Empty items are ignored.

More syntax examples live in docs/syntax.md.

Quick Start

Add the library

moon add Project2026-creator/moontemplate

Render from MoonBit

import "Project2026-creator/moontemplate/src/moontemplate" @moontemplate

let template =
  #|Hello, {{ user | trim }}!
  #|{% if admin %}Welcome back, admin.{% else %}Welcome back.{% endif %}

let engine = @moontemplate.Engine::new(template).unwrap()
let ctx = Map([], capacity=2)
ctx.set("user", " MoonBit ")
ctx.set("admin", "true")

let output = engine.render(ctx)
println(output)

Register a custom filter

import "Project2026-creator/moontemplate/src/moontemplate" @moontemplate

let engine = @moontemplate.Engine::new("{{ name | suffix }}").unwrap()
engine.register_filter("suffix", fn(value) { value + "!" })

Safe output helpers

Use escape_html when interpolating untrusted text into HTML, escape_json when producing a JSON string value, and slugify when deriving a stable ASCII-oriented identifier:

<h1 id="{{ title | slugify }}">{{ title | escape_html }}</h1>
{{ payload | escape_json }}

The tracked examples/secure-output.txt file demonstrates the HTML use case end to end.

CLI Usage

The CLI package targets native, so it needs a system C compiler when you run it locally.

moon run src/cli --target native -- --file examples/welcome.txt --var name=MoonBit
moon run src/cli --target native -- --template "Hello {{ name | uppercase }}" --var name=moonbit
moon run src/cli --target native -- --file examples/secure-output.txt --var "title=MoonBit & Templates" --var "body=<strong>safe</strong>"

The first command reads the tracked example file examples/welcome.txt, so it can be copied and run immediately after cloning.

Supported options:

--file <path> or positional file path
--template <inline-template>
--var key=value (repeatable)
--help

--file and --template are mutually exclusive. A missing file, malformed variable assignment, parser error, or unknown option is reported as a CLI error.

For a larger, repeatable native workload, run scripts/benchmark.ps1 on Windows or scripts/benchmark.sh on Linux/macOS. The same 10-iteration benchmark runs in both CI workflows and reports total and average milliseconds in the job log; it is an end-to-end CLI baseline, not a hardware independent performance promise.

Quality Gates

CI installs the current stable MoonBit toolchain from the official installer. The repository is checked with the current toolchain available at validation time; this validation used moonc 0.10.4, which is newer than the 0.10.3 version mentioned in the organizer feedback.

Local verification:

moon fmt --check
moon info
moon build
moon check --deny-warn
moon test --deny-warn
moon check --target native --deny-warn
moon test --target native --deny-warn

The native commands require a C compiler (build-essential on the CI runner).

Repository acceptance helpers:

Repository Links

GitHub: https://github.com/Project2026-creator/MoonTemplate
GitLink: https://gitlink.org.cn/Hero001/moontemplate
Mooncakes package name: Project2026-creator/moontemplate

License

MoonTemplate is released under the Apache 2.0 License. See LICENSE.