leo/docs/rfc/003-imports-stabilization.md

# Leo RFC 003: Imports Stabilization

## Authors

- Max Bruce
- Collin Chin
- Alessandro Coglio
- Eric McCarthy
- Jon Pavlik
- Damir Shamanaev
- Damon Sicore
- Howard Wu

## Status

DRAFT

# Summary

This proposal aims to improve the import management system in Leo programs to
make program environment more reproducible, predictable and compatible. To achieve that
we suggest few changes to Leo CLI and Manifest:

- add a "dependencies" section to Leo Manifest and add a command to pull those dependencies;
- allow custom names for imports to manually resolve name conflicts;
- add "curve" and "proving system" sections to the Manifest;
- add "inlcude" and "exclude" parameters for "proving system" and "curve";

Later this solution can be improved by adding a lock-file which would lock
imported packages based on both their contents and version. 

# Motivation

The current design of imports does not provide any guarantees on what's stored 
in program imports and published with the program to Aleo Package Manager. 
When dependency is "added", it is stored inside imports folder, and it is possible
to manually edit and/or add packages in this folder.

Also, imports are stored under package name which makes it impossible to import
two different packages with the same name. 

Another important detail in the scope of this proposal is that in future Leo
programs will have the ability to be run with different proving systems 
and curves, possibly creating incompatibility between programs written 
for different proving systems or curves. To make a foundation for these features
imports need to be managed with include/exclude lists for allowed (compatible) 
proving systems and curves.

# Design

## Leo Manifest

Dependencies section:

```toml
[dependencies]
name = { author = "author", package = "package", version = "version" }

[dependencies.name]
author = "author"
package = "package"
version = "1.0"
```

## Leo CLI 

To support updated Manifest new command should be added to Leo CLI. 

```bash
# pull imports
leo pull 
```

## Imports Restructurization

One of the goals of proposed changes is to allow importing packages with the
same name but different authors. To resolve name conflict we suggest storing
imports as they are named in Leo Manifest file (Leo.toml).


<!-- The suggested change is soft. It changes only the way imports are organized 
with minimal changes to other parts of the language.

We can consider implementing imports/username-package storage, but imports 
will have to be resolved on a different level in compiler. -->

# Drawbacks

This change might require the update of already published programs on Aleo PM due to
Leo Manifest change. However it is possible to implement it in a backward-compatible
way.

# Effect on Ecosystem

Proposed improvement provides safety inside Leo programs and should not affect
ecosystem except for the tools which use Leo directly (such as Aleo Studio). 

It is possible that some of the proposed features will open new features on Aleo PM. 

# Alternatives

Another approach to the stated cases is to keep everything as we have now but change
the way programs are imported and stored and make names unique. Also, current 
implementation provides some guarantees on import stablitity and consistency.