Crate toml_edit

Expand description

`toml_edit`

This crate allows you to parse and modify toml documents, while preserving comments, spaces* and relative order* or items.

It is primarily tailored to the needs of cargo-edit.

Example

use toml_edit::{Document, value};

let toml = r#"
"hello" = 'toml!' # comment
['a'.b]
"#;
let mut doc = toml.parse::<Document>().expect("invalid doc");
assert_eq!(doc.to_string(), toml);
// let's add a new key/value pair inside a.b: c = {d = "hello"}
doc["a"]["b"]["c"]["d"] = value("hello");
// autoformat inline table a.b.c: { d = "hello" }
doc["a"]["b"]["c"].as_inline_table_mut().map(|t| t.fmt());
let expected = r#"
"hello" = 'toml!' # comment
['a'.b]
c = { d = "hello" }
"#;
assert_eq!(doc.to_string(), expected);

Limitations

Things it does not preserve:

Different quotes and spaces around the same table key, e.g.

[ 'a'. b]
[ "a"  .c]
[a.d]

will be represented as (spaces are removed, the first encountered quote type is used)

['a'.b]
['a'.c]
['a'.d]

Children tables before parent table (tables are reordered by default, see test).
Scattered array of tables (tables are reordered by default, see test).

The reason behind the first limitation is that Table does not store its header, allowing us to safely swap two tables (we store a mapping in each table: child key -> child table).

This last two limitations allow us to represent a toml document as a tree-like data structure, which enables easier implementation of editing operations and an easy to use and type-safe API. If you care about the above two cases, you can use Document::to_string_in_original_order() to reconstruct tables in their original order.