Terrars is a set of ergonomic tools for building Terraform configs from Rust. This is an alternative to the CDK.

Benefits

• Share definitions with your code (like endpoints, names, ids)
• Type safety - including resource property references
• Fewer layers - just your code and Terraform

Current status: Usable, but may have some rough edges and missing features. Let me know if you encounter issues.

What it is

Terrars is a library with some data structures for describing and serializing Terraform stacks. Stack is the root data type.

Terrars also provides a command, terrars-generate, which generates Rust code for provider-specific types. In the current directory, it creates a module for each provider you specify.

Usage

1. Generate schemas for the providers you want. As an example, andrewbaxter/stripe

   You need to have terraform and rustfmt installed and on your path.

   Run cargo install terrars, then terrars-generate andrewbaxter/stripe 0.0.14 (or whatever the latest version is).

   Copy stripe/ into your project source tree somewhere and add pub mod stripe to the parent module.

2. Develop your code

   Create a Stack and set up provider types and provider:

   rust let mut stack = BuildStack { state_path: PathBuf::from_str("mystack.tfstate").unwrap(), }.build(); let pt = provider_type_stripe(&mut stack); BuildProviderStripe { provider_type: pt, token: STRIPE_TOKEN, }.build(&mut stack);

   Then create resources:

   rust let my_product = BuildProduct { name: "My Product".into(), }.build(&mut stack); let my_price = BuildPrice { ... }.build(&mut stack); my_price.set_product(my_product.id()); ...

   Finally, write the stack out:

   rust fs::write("mystack.tf.json", stack.serialize()?)?;

3. Call terraform on your stack as usual

   Stack also has methods run() and get_output() to call terraform for you. You must have terraform in your path.

Data model

The base library has BuildStack, BuildVariable and BuildOutput structs for creating those three items.

terrars-generate creates provider_type_*(), BuildProvider*, and BuildResource*/BuildData* for you for all resources/datasources in the provider.

In general Build* structs have required fields and a build() method that makes the object usable and registers it with the Stack.

Limitations

• Limited name sanitization

  If a provider field or resource name clashes with a rust keyword or metavalue name things may fail to compile.

• Not all Terraform features have been implemented

  The only ones I'm aware of missing at the moment are resource "provisioning" and for-each/count.

• References for collection types are not implemented

  I don't know if those are generally valid in the first place, outside of for-each/count.

• ignore_changes takes strings rather than an enum

• No variable or output static type checking

  I'd like to add a derive macro for generating variables/outputs automatically from a structure at some point.