Crate gray_matter

gray_matter is a tool for easily extracting front matter out of a string. It is a fast Rust implementation of the original gray-matter by Jon Schlinkert.

What can gray_matter do?

It can take some string or file like this:

---
title: This is the title
tags:
    - awesome-tag
    - more-awesome-tag
---

# Header

This is my really cool document!

and strip the YAML contained within the delimiters (---), to create a struct like this¹:

MyStruct {
    title: "This is the title",
    tags: ["awesome-tag", "more-awesome-tag"]
}

Why would I use this?

You want to have configurability inside plain text documents, like for example a Markdown document. Pandoc and Hugo are examples of tools that use this kind of configuration, but the sky really is the limit.

What formats are supported?

gray_matter has built in support for YAML, TOML and JSON, but the Engine trait allows for virtually any format you wish to be supported.

Examples

Basic parsing

use gray_matter::Matter;
use gray_matter::engine::YAML;
use serde::Deserialize;

const INPUT: &str = r#"---
title: gray-matter-rs
tags:
  - gray-matter
  - rust
---
Some excerpt
---
Other stuff
"#;

fn main() {
    // Select one parser engine, such as YAML, and parse it
    // into gray_matter's custom data type: `Pod`
    let matter = Matter::<YAML>::new();
    let result = matter.parse(INPUT);

    // You can now inspect the data from gray_matter.
    assert_eq!(result.content, "Some excerpt\n---\nOther stuff");
    assert_eq!(result.excerpt, Some("Some excerpt".to_owned()));
    assert_eq!(result.data.as_ref().unwrap()["title"].as_string(), Ok("gray-matter-rs".to_string()));
    assert_eq!(result.data.as_ref().unwrap()["tags"][0].as_string(), Ok("gray-matter".to_string()));
    assert_eq!(result.data.as_ref().unwrap()["tags"][1].as_string(), Ok("rust".to_string()));

    // The `Pod` data type can be a bit unwieldy, so
    // you can also deserialize it into a custom struct
    #[derive(Deserialize, Debug)]
    struct FrontMatter {
        title: String,
        tags: Vec<String>
    }

    // Deserialize `result` manually:
    let front_matter: FrontMatter = result.data.unwrap().deserialize().unwrap();
    println!("{:?}", front_matter);
    // FrontMatter { title: "gray-matter-rs", tags: ["gray-matter", "rust"] }

    // ...or skip a step, by using `parse_with_struct`.
    let result_with_struct = matter.parse_with_struct::<FrontMatter>(INPUT).unwrap();
    println!("{:?}", result_with_struct.data)
    // FrontMatter { title: "gray-matter-rs", tags: ["gray-matter", "rust"] }
}

---

1. The struct is purely for demonstration. ↩

Modules

• engine
  A module containing the Engine trait, along with gray_matter’s default engines.

Structs

• Matter
  Coupled with an Engine of choice, Matter stores delimiter(s) and handles parsing.
• ParsedEntity
  ParsedEntity stores a parsed result.
• ParsedEntityStruct
  ParsedEntityStruct stores the parsed result with the front matter deserialized into a struct T.

Enums

• Error
• Pod
  A polyglot data type for representing the parsed front matter.