swsml-derive-0.2.1 has been yanked.

swsml

SWE Serial << 19 * 99 >> — 1999

In memory of the Chinese victims of the NATO bombing of the Chinese Embassy in Yugoslavia on 7 May 1999.
谨以此编号纪念 1999 年 5 月 7 日（贝尔格莱德时间）北约轰炸中国驻南斯拉夫联盟大使馆中遇难的三位中国记者：邵云环、许杏虎、朱颖。

SML — SNOWARE Markup Language for Rust: a declarative data/configuration format, an alternative to JSON and YAML. Features: optional quotes, fragments, contracts (schema layer with enums, defaults and composition), include directive, environment-variable inlining, zero dependencies (optional serde).

English below ｜中文在上方，English 在下方

包名是 swsml 而非 sml-rs——后者已被无关项目占用（Smart Message Language 智能电表协议解析器）。 lib 名仍为 sml，因此 use sml::{...} 不受影响。

The crate is named swsml because sml-rs was taken by an unrelated project (a smart-meter protocol parser). The lib name is still sml, so use sml::{...} is unaffected.

中文

SML（SNOWARE Markup Language）的 Rust 实现：声明式数据/配置格式，JSON/YAML 的替代品。

Logo：黑花括号 {} 表示语法骨架（块的边界），蓝色雪花 ❄ 表示精确的取值点。

安装

[dependencies]
swsml = "0.1"

# 需要 serde 互操作时：
# swsml = { version = "0.1", features = ["serde"] }

# 不需要 derive 宏时可关闭默认 feature，回到完全零依赖：
# swsml = { version = "0.1", default-features = false }

快速开始

use sml::{parse, to_sml};

let v = parse("name: John\nage: 27")?;
assert_eq!(v.get("name").and_then(|x| x.as_str()), Some("John"));
assert_eq!(v.get("age"), Some(&sml::Value::Int(27)));

// 序列化回 SML（可 round-trip）
println!("{}", to_sml(&v));

语法一览

@version v1

# 引号可选：裸词即字符串
firstName: John
age: 27

# 块冒号可省：address { } 等价于 address: { }
address {
    streetAddress: "21 2nd Street"   # 含空格才需要引号
    state: NY                         # 裸词
}

# 数组：逗号可选
phoneNumbers: [ { type: home } { type: office } ]

# 片段：定义 + 以「值」形式引用
@base { region: cn-north-1 }
region: &base

# 环境变量内联
apiKey: $env.RESEND_API_KEY

# 词中 @ 无需转义（仅词首的 @ 才是片段标记）
contact {
    to: a@b.c
    from: "sal <sal@mail.swebase.cn>"
}

注释

SML 支持五种注释，单行三种、多行两种：

# 单行注释（到行尾）

-- 另一种单行注释（到行尾）

// C 风格单行注释（到行尾）

/* 多行注释
   可跨行
   块内也可使用 */

_* 另一种多行注释
   以 *_ 结束 *_

server {
    port: 8080 -- 行内注释
    /* 多行注释也能出现在块或数组里 */
    hosts: [ a -- 主 b # 备 ]
}

注意：--、//、/*、_* 仅在组合出现时才是注释；单个 -、/、_ 仍按普通字符处理（如 a/b/c、my-word、foo_bar）。

特性

特性	说明
引号可选	裸词即字符串（`state: NY`）
块冒号可省	`address { }` ≡ `address: { }`
数组分隔灵活	`[ a b c ]`、每行一个、逗号可选
片段	`@name { }` 定义，`&name` 以值形式引用并展开
契约	可选 schema 层：字段类型、枚举、默认值、区间、组合
include 指令	拆分配置，可嵌套、可在块内注入字段
版本声明	`@version v1`，便于将来演进不破坏旧文档
环境变量内联	`$env.VAR`
类型自识别	`true/false/null` / 数字 / 字符串
注释	单行 `#`、`--` 与 `//`；多行 `/* /` 与 `_ *_`

数据类型

SML 是纯数据格式，值模型与 JSON 同构，共 7 种：

pub enum Value {
    Null,
    Bool(bool),
    Int(i64),
    Float(f64),
    Str(String),
    Array(Vec<Value>),
    Object(BTreeMap<String, Value>),
}

顶层支持三种形态（与 to_sml 输出对称）：键值块、{ ... } 对象块、[ ... ] 数组。

// 对象数组（如「历史记录」这类列表数据）
let v = parse("[ { ts: \"2026-01-01\" to: \"a@b.c\" } ]")?;

顶层标量（如单独的 42）不可往返——SML 顶层需为容器。

契约（Contract）

SML 本身无类型系统。契约是可选的 schema 层，为块提供结构体约束、枚举、默认值、取值区间。

use sml::parse;

let text = r#"
@contract Server {
    host: str                              # 必填（默认 required）
    port: int default 5432                 # 缺失时填充
    tls: bool default false
    tags: [str] optional                   # 可选，元素须为字符串
    status: enum [ active standby retired ]
    weight: num min 0 max 100
}
db {
    @is Server
    host: db1.internal
    status: active
    weight: 80
}
"#;
let v = parse(text)?;
// port / tls 由 default 填充
assert_eq!(v.get("db.port"), Some(&sml::Value::Int(5432)));

@contract Name { } 定义契约（不进解析结果）；@is Name 在块内应用
应用时填充 default，并校验必填、类型、枚举、数值区间、数组元素类型
校验发生在解析期，违反即返回错误（而非留到应用侧）
契约须在 @is 之前定义（顺序依赖）
不使用契约时行为完全不变 —— 向后兼容

类型：str / int / num / bool / any / [T] / enum [ ... ] 修饰符：required（默认）/ optional / default <值> / min <数> / max <数>

组合（而非继承）

契约之间不共享字段定义，而是「字段的类型是另一个契约」——直接写契约名，可多层嵌套：

@contract Address {
    city: str
    country: str default CN
}
@contract Server {
    host: str
    address: Address        # 组合：该字段的值须符合 Address 契约
}
db {
    @is Server
    host: db1.internal
    address { city: Beijing }   # country 缺 -> 自动填 CN
}

嵌套块会递归校验并回填默认值；被引用契约可在之后定义。

严格模式（默认严格）

未声明字段默认被拒绝（能立即发现 prot 这类拼写错误）。确需放宽须显式写 loose：

@contract Metrics loose {   # 允许额外字段
    latency: num min 0
}

loose 只放宽「未声明字段」，已声明字段照样校验。

include 指令

# app.sml
app: resender
database {
    include "conf.d/db.sml"   # 在块内注入一组字段
    pool: 16
}

let v = sml::parse_file("app.sml")?;

相对路径按被包含文件自身所在目录解析（同 C 预处理器）
语义是文本内联而非对象合并，因此可出现在块内部
循环引用、文件缺失均返回错误，不静默跳过；嵌套上限 32 层

parse() 是纯函数（不做 IO），include 由 parse_file() / resolve_includes() 处理，因此在无文件系统的环境（WASM / 沙箱）中仍可安全嵌入 parse()。

版本声明

use sml::{parse_versioned, Version};

let (v, ver) = parse_versioned("@version v1\nname: John")?;
assert_eq!(ver, Version::V1);

未声明时默认按当前版本处理，既有文档不受影响
声明了不支持的版本会报错，而非静默按错误语法解析
version 是保留字，不可作为片段名

serde 支持（可选）

启用 serde feature 后，Value 实现 Serialize/Deserialize，可与任意 serde 后端互操作：

let v = parse("name: John\nage: 27")?;
let json = serde_json::to_string(&v)?;          // {"name":"John","age":27}
let back: sml::Value = serde_json::from_str(&json)?;

采用手写实现而非 #[derive]，以保证数据形状自然： Value::Int(27) 序列化为 27，而非 derive 会产生的 {"Int":27}。

serde 桥：任意 serde 类型一键反序列化

serde feature 还提供 sml::serde::{from_str, from_value, to_value, to_string}，任何 #[derive(serde::Deserialize / Serialize)] 类型都能像 toml-rs 一样直接与 SML 互转（枚举沿用 __type 约定，也兼容 { VariantName: ... } 外部标签）：

use serde::Deserialize;

#[derive(Deserialize)]
struct Server { host: String, port: u16 }

let s: Server = sml::serde::from_str("host: web.example\nport: 8080\n").unwrap();
let text = sml::serde::to_string(&s).unwrap();

Value 也因此可与 toml/serde_json 双向互通：

let v: sml::Value = sml::parse("host: web.example\nport: 8080\n").unwrap();
let toml_text = toml::to_string(&v).unwrap();            // SML -> TOML
let back: sml::Value = toml::from_str(&toml_text).unwrap(); // TOML -> SML

不启用该 feature 时，本 crate 为零依赖。

自然序列化宏（derive，默认开启）

derive feature（默认开启）提供 #[derive(SmlSerialize, SmlDeserialize)]，把自定义结构体/枚举「自然地」映射为 SML，无需引入 serde：

use sml::{SmlDeserialize, SmlSerialize};

#[derive(SmlSerialize, SmlDeserialize, Debug)]
struct Server {
    host: String,
    #[sml(default)]
    port: i32,
    #[sml(rename = "tls-enabled")]
    tls_enabled: bool,
    #[sml(skip)]
    secret: String,
}

#[derive(SmlSerialize, SmlDeserialize, Debug)]
enum Status {
    Active,
    #[sml(rename = "stand-by")]
    StandBy,
}

let s = Server {
    host: "web.example".into(),
    port: 8080,
    tls_enabled: true,
    secret: "hunter2".into(),
};
let text = s.to_sml();   // host: web.example / port: 8080 / tls-enabled: true
let back = Server::from_sml(&text)?;   // secret 由 skip 重置为 Default

// 也支持 toml-rs 风格的顶层函数（derive 默认开启时可用）：
let text = sml::to_string(&s);
let back: Server = sml::from_str(&text)?;

映射规则（形状与 to_sml 输出对称）：

结构体 → 块：字段名即键；Option 字段为 None 时省略
枚举单元变体 → 裸词（status: Active）
枚举带数据变体 → 带 __type 的块（{ __type: Circle _value: 3 }）
单元结构体 → 裸词；newtype → 透明；tuple 结构体 → 数组

属性： #[sml(rename = "...")] 改名、#[sml(skip)] 跳过（反序列化时重置为 Default）、 #[sml(default)] 缺失时用 Default、#[sml(flatten)] 并入子块，容器级 #[sml(rename_all = "kebab-case")] 批量改名。泛型结构体/枚举也支持（自动补充 T: SmlSerialize 等约束）。

运行示例

cargo run --example include_demo
cargo run --example include_demo --features serde   # 额外打印 JSON
cargo run --example derive_demo                     # derive 宏「自然」序列化

多语言实现

语言	位置
Soup / Lua	`../lua/`（`lib/sml.soup`）
Rust	本目录
C	`../c/sml.h`
JavaScript	`../js/sml.mjs`

License

MulanPSL-2.0

English

Rust implementation of SML — SNOWARE Markup Language: a declarative data/configuration format, an alternative to JSON and YAML.

Installation

[dependencies]
swsml = "0.1"

# With serde interop:
# swsml = { version = "0.1", features = ["serde"] }

Quick start

use sml::{parse, to_sml};

let v = parse("name: John\nage: 27")?;
assert_eq!(v.get("name").and_then(|x| x.as_str()), Some("John"));
assert_eq!(v.get("age"), Some(&sml::Value::Int(27)));

// Serialize back to SML (round-trip safe)
println!("{}", to_sml(&v));

Syntax at a glance

@version v1

# Quotes optional: bare words are strings
firstName: John
age: 27

# Block colon optional
address {
    streetAddress: "21 2nd Street"
    state: NY
}

# Arrays: commas optional
phoneNumbers: [ { type: home } { type: office } ]

# Fragment: defined then referenced as a *value*
@base { region: cn-north-1 }
region: &base

# Environment variable inlining
apiKey: $env.RESEND_API_KEY

# `@` inside a word needs no escaping (only a leading `@` is a fragment marker)
contact {
    to: a@b.c
    from: "sal <sal@mail.swebase.cn>"
}

Comments

SML supports five comment styles: three single-line and two multi-line:

# single-line comment (to end of line)

-- another single-line comment (to end of line)

// C-style single-line comment (to end of line)

/* multi-line comment
   spanning lines
   also usable inside blocks */

_* another multi-line comment
   ended by *_ *_

server {
    port: 8080 -- inline comment
    /* multi-line comments also work inside blocks / arrays */
    hosts: [ a -- primary b # backup ]
}

Note: --, //, /*, _* are only comments as combinations; a lone -, /, or _ is still an ordinary character (e.g. a/b/c, my-word, foo_bar).

Features

Feature	Description
Optional quotes	Bare words are strings (`state: NY`)
Optional block colon	`address { }` ≡ `address: { }`
Flexible array separators	`[ a b c ]`, one per line, commas optional
Fragments	`@name { }` defines, `&name` references as a value
Contracts	Optional schema layer: types, enums, defaults, ranges, composition
`include` directive	Split config files; nestable, injectable inside blocks
Version declaration	`@version v1` for forward-compatible evolution
Env var inlining	`$env.VAR`
Type inference	`true/false/null` / numbers / strings
Comments	single-line `#`, `--` and `//`; multi-line `/* /` and `_ *_`

Data types

SML is a pure data format; its value model is isomorphic to JSON with 7 variants:

pub enum Value {
    Null,
    Bool(bool),
    Int(i64),
    Float(f64),
    Str(String),
    Array(Vec<Value>),
    Object(BTreeMap<String, Value>),
}

Three top-level forms are supported (symmetric with to_sml output): key-value blocks, { ... } object blocks, and [ ... ] arrays.

let v = parse("[ { ts: \"2026-01-01\" to: \"a@b.c\" } ]")?;

A top-level scalar (e.g. a lone 42) cannot round-trip — the top level must be a container.

Contracts

SML has no type system of its own. Contracts are an optional schema layer providing struct-like constraints, enums, defaults and numeric ranges.

use sml::parse;

let text = r#"
@contract Server {
    host: str                              # required (default)
    port: int default 5432                 # filled when missing
    tls: bool default false
    tags: [str] optional                   # optional, items must be strings
    status: enum [ active standby retired ]
    weight: num min 0 max 100
}
db {
    @is Server
    host: db1.internal
    status: active
    weight: 80
}
"#;
let v = parse(text)?;
// port / tls come from `default`
assert_eq!(v.get("db.port"), Some(&sml::Value::Int(5432)));

@contract Name { } defines a contract (not included in the parse result); @is Name applies it inside a block
Applying one fills defaults and validates required fields, types, enums, numeric ranges and array item types
Validation happens at parse time — violations return errors immediately
A contract must be defined before the @is that uses it
Without contracts, behaviour is unchanged — fully backward compatible

Types: str / int / num / bool / any / [T] / enum [ ... ] Modifiers: required (default) / optional / default <value> / min <n> / max <n>

Composition (not inheritance)

Contracts do not share field definitions; instead, a field's type can be another contract. Just write the contract name — nesting works to any depth:

@contract Address {
    city: str
    country: str default CN
}
@contract Server {
    host: str
    address: Address        # the value must satisfy the Address contract
}
db {
    @is Server
    host: db1.internal
    address { city: Beijing }   # country missing -> filled with CN
}

Nested blocks are validated recursively and defaults are filled. A referenced contract may be defined later.

Strict mode (strict by default)

Fields not declared in the contract are rejected by default (this catches typos like prot). To allow extras, write loose explicitly:

@contract Metrics loose {   # allow undeclared fields
    latency: num min 0
}

loose only relaxes undeclared fields; declared ones are still validated.

The `include` directive

# app.sml
app: resender
database {
    include "conf.d/db.sml"   # injects a set of fields into this block
    pool: 16
}

let v = sml::parse_file("app.sml")?;

Relative paths resolve against the including file's own directory (like the C preprocessor)
Semantics are text inlining, not object merging, so it works inside blocks
Cycles and missing files return errors (never silently skipped); depth limit 32

parse() is a pure function (no I/O); include is handled by parse_file() / resolve_includes(). This makes parse() safe to embed in environments without a filesystem (WASM / sandboxes).

Version declaration

use sml::{parse_versioned, Version};

let (v, ver) = parse_versioned("@version v1\nname: John")?;
assert_eq!(ver, Version::V1);

Undeclared documents use the current version — existing documents are unaffected
An unsupported declared version errors instead of parsing with wrong grammar
version is a reserved word and cannot be a fragment name

Serde support (optional)

With the serde feature, Value implements Serialize/Deserialize and interoperates with any serde backend:

let v = parse("name: John\nage: 27")?;
let json = serde_json::to_string(&v)?;          // {"name":"John","age":27}
let back: sml::Value = serde_json::from_str(&json)?;

This uses a hand-written implementation rather than #[derive] to keep the data shape natural: Value::Int(27) serializes to 27, not {"Int":27}.

Serde bridge: one-shot deserialization for any serde type

The serde feature also provides sml::serde::{from_str, from_value, to_value, to_string}. Any #[derive(serde::Deserialize / Serialize)] type can go back and forth with SML just like toml-rs (enums use the __type convention and also accept { VariantName: ... } external tags):

use serde::Deserialize;

#[derive(Deserialize)]
struct Server { host: String, port: u16 }

let s: Server = sml::serde::from_str("host: web.example\nport: 8080\n").unwrap();
let text = sml::serde::to_string(&s).unwrap();

Value interoperates bidirectionally with toml / serde_json as well:

let v: sml::Value = sml::parse("host: web.example\nport: 8080\n").unwrap();
let toml_text = toml::to_string(&v).unwrap();              // SML -> TOML
let back: sml::Value = toml::from_str(&toml_text).unwrap(); // TOML -> SML

Without this feature the crate is dependency-free.

Natural derive macros (default on)

The derive feature (enabled by default) provides #[derive(SmlSerialize, SmlDeserialize)] to map your own structs/enums to SML "naturally", without pulling in serde:

use sml::{SmlDeserialize, SmlSerialize};

#[derive(SmlSerialize, SmlDeserialize, Debug)]
struct Server {
    host: String,
    #[sml(default)]
    port: i32,
    #[sml(rename = "tls-enabled")]
    tls_enabled: bool,
    #[sml(skip)]
    secret: String,
}

#[derive(SmlSerialize, SmlDeserialize, Debug)]
enum Status {
    Active,
    #[sml(rename = "stand-by")]
    StandBy,
}

let s = Server { host: "web.example".into(), port: 8080, tls_enabled: true, secret: "x".into() };
let text = s.to_sml();             // host: web.example / port: 8080 / tls-enabled: true
let back = Server::from_sml(&text)?;   // `secret` is reset to Default (skip)

// toml-rs style top-level functions are also provided (with the default `derive` feature):
let text = sml::to_string(&s);
let back: Server = sml::from_str(&text)?;

Mapping rules (symmetric with to_sml output):

struct → block: field names are the keys; Option fields are omitted when None
enum unit variants → bare words (status: Active)
enum variants with data → __type block ({ __type: Circle _value: 3 })
unit struct → bare word; newtype → transparent; tuple struct → array

Attributes: #[sml(rename = "...")], #[sml(skip)], #[sml(default)], #[sml(flatten)], and container-level #[sml(rename_all = "kebab-case")]. Generic types are supported (bounds such as T: SmlSerialize are added automatically).

Examples

cargo run --example include_demo
cargo run --example include_demo --features serde   # also prints JSON
cargo run --example derive_demo                     # derive macros

Other language implementations

Language	Location
Soup / Lua	`../lua/` (`lib/sml.soup`)
Rust	this directory
C	`../c/sml.h`
JavaScript	`../js/sml.mjs`

License

MulanPSL-2.0

swsml-derive 0.2.1

swsml

中文

安装

快速开始

语法一览

注释

特性

数据类型

契约（Contract）

组合（而非继承）

严格模式（默认严格）

include 指令

版本声明

serde 支持（可选）

serde 桥：任意 serde 类型一键反序列化

自然序列化宏（derive，默认开启）

运行示例

多语言实现

License

English

Installation

Quick start

Syntax at a glance

Comments

Features

Data types

Contracts

Composition (not inheritance)

Strict mode (strict by default)

The include directive

Version declaration

Serde support (optional)

Serde bridge: one-shot deserialization for any serde type

Natural derive macros (default on)

Examples

Other language implementations

License

The `include` directive