67 releases
0.18.2 | Oct 4, 2024 |
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0.18.0 | May 24, 2024 |
0.16.7 | Jan 4, 2024 |
0.16.6 | Sep 27, 2023 |
0.3.3 | Mar 26, 2022 |
#72 in Encoding
3,462 downloads per month
Used in 48 crates
(36 directly)
790KB
18K
SLoC
hcl-rs
A rust library for interacting with the Hashicorp Configuration Language (HCL).
Features
- A parser for the HCL syntax specification
- Types for all HCL structures, e.g. body, blocks and attributes
- Supporting macros like
body!
for constructing HCL data structures - Supports the expression and template sub-languages in attribute values
- Support for deserializing and serializing arbitrary types that
implement
serde::Deserialize
orserde::Serialize
- Evaluation of the HCL expression and template sub-languages
Cargo features
perf
: enables parser performance optimizations such as inlining of small strings on the stack. This feature is disabled by default.
Deserialization examples
Deserialize arbitrary HCL according to the HCL JSON Specification:
use serde_json::{json, Value};
let input = r#"
some_attr = {
foo = [1, 2]
bar = true
}
some_block "some_block_label" {
attr = "value"
}
"#;
let expected = json!({
"some_attr": {
"foo": [1, 2],
"bar": true
},
"some_block": {
"some_block_label": {
"attr": "value"
}
}
});
let value: Value = hcl::from_str(input).unwrap();
assert_eq!(value, expected);
If you need to preserve context about the HCL structure, deserialize into
hcl::Body
instead:
use hcl::{Block, Body, Expression};
let input = r#"
some_attr = {
"foo" = [1, 2]
"bar" = true
}
some_block "some_block_label" {
attr = "value"
}
"#;
let expected = Body::builder()
.add_attribute((
"some_attr",
Expression::from_iter([
("foo", Expression::from(vec![1, 2])),
("bar", Expression::Bool(true)),
]),
))
.add_block(
Block::builder("some_block")
.add_label("some_block_label")
.add_attribute(("attr", "value"))
.build(),
)
.build();
let body: Body = hcl::from_str(input).unwrap();
assert_eq!(body, expected);
Serialization examples
An example to serialize some terraform configuration:
use hcl::expr::Traversal;
use hcl::{Block, Body, Variable};
let body = Body::builder()
.add_block(
Block::builder("resource")
.add_label("aws_sns_topic_subscription")
.add_label("my-subscription")
.add_attribute((
"topic_arn",
Traversal::builder(Variable::new("aws_sns_topic").unwrap())
.attr("my-topic")
.attr("arn")
.build(),
))
.add_attribute(("protocol", "sqs"))
.add_attribute((
"endpoint",
Traversal::builder(Variable::new("aws_sqs_queue").unwrap())
.attr("my-queue")
.attr("arn")
.build(),
))
.build(),
)
.build();
let expected = r#"
resource "aws_sns_topic_subscription" "my-subscription" {
topic_arn = aws_sns_topic.my-topic.arn
protocol = "sqs"
endpoint = aws_sqs_queue.my-queue.arn
}
"#.trim_start();
let serialized = hcl::to_string(&body).unwrap();
assert_eq!(serialized, expected);
Also have a look at the other examples provided in the documentation of the
ser
module to learn how you can construct HCL blocks when serializing custom types.
Expression evaluation
The eval
module
documentation contains more
details and examples for expression and template evaluation, but here's a very
short example:
use hcl::Value;
use hcl::eval::{Context, Evaluate};
use hcl::expr::TemplateExpr;
let expr = TemplateExpr::from("Hello ${name}!");
let mut ctx = Context::new();
ctx.declare_var("name", "World");
assert_eq!(expr.evaluate(&ctx).unwrap(), Value::from("Hello World!"));
Macros
This crate provides a couple of macros to ease building HCL data structures. Have a look at their documentation for usage examples.
Contributing
Contributions are welcome! Please read
CONTRIBUTING.md
before creating a PR.
License
The source code of hcl-rs is licensed under either of Apache License, Version 2.0 or MIT license at your option.
Dependencies
~2.2–3MB
~57K SLoC