CODEWITHSUNDEEP
rustrust-cargo
Mr.Smithyyy
Mr.Smithyyy

Reputation: 1329

Can cargo.toml contain custom properties

I've recently started with Rust and coming from a Node background I'm curious if the cargo.toml file for a project can be extended to include custom properties.

For example, in Node, some packages let you put configuration options in the package.json file (like babel):

{
  "name": "my-package",
  "version": "1.0.0",
  "babel": {
    "presets": [ ... ],
    "plugins": [ ... ],
  }
}

I've looked through the manifest docs but I can't seem to find anything about custom properties.

For example, what if I had a CLI tool and it has a configurable option. Do I have to have the user make a config file just for this option or could I include in the cargo.toml like so:

[package]
name = "my_project"
version = "0.1.0"
edition = "2018"
# custom property
store: ["one", "two", "three"]

[dependencies]

Also, if this is a "sure, as long as you have name and version as required", is it something that should be avoided?

Upvotes: 2

Views: 700

Answers (1)

pretzelhammer
pretzelhammer

Reputation: 15105

The Rust equivalent would be Cargo features. You can define features for a crate like this in the crate's Cargo.toml:

[package]
name = "crate_with_features"
version = "1.0.0"
edition = "2018"

[features]
# default set of features
default = ["has_foo", "has_bar"]

# can use these for conditional compilation
has_foo = []
has_bar = []

And then if you had a lib.rs like this:

[cfg(feature = "has_foo")]
pub fn foo() {
    println!("foo");
}

[cfg(feature = "has_bar")]
pub fn bar() {
    println!("bar");
}

People would be able to select just which features of your crate they want. For example:

[package]
name = "other_project"

[dependencies]
crate_with_features = "1.0.0"

In the default case, crate_with_features would come with both foo and bar functions since the default feature requires both of them, but people could choose to only use one or the other by specifying:

[package]
name = "other_project"

[dependencies.crate_with_features]
version = "1.0.0"
# don't include default feature set
default-features = false
# cherry pick individual features
features = ["has_foo"]

In the above example crate_with_features would only be compiled with the foo function for that project.

The Rust Reference has a page on conditional compilation if you'd like to learn more about that specifically.

Upvotes: 3

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