# 🥣 Blend

[![ci](https://github.com/mimiquate/blend/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/mimiquate/blend/actions?query=branch%3Amain)
[![Hex.pm](https://img.shields.io/hexpm/v/blend.svg)](https://hex.pm/packages/blend)
[![Docs](https://img.shields.io/badge/docs-gray.svg)](https://hexdocs.pm/blend)

Test your package against different versions of its dependencies.

Generates and maintains multiple lockfiles so that you can test your package
against different variations of your dependencies versions.

## Installation

If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `blend` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:blend, "~> 0.3.0", only: :dev}
  ]
end
```

## Usage

### 1. Generate `blend.exs`

```
$ mix blend.init
```

### 2. Define your blends

```elixir
# blend.exs

# Example for testing against 1.x and 2.x of plug_crypto
%{
  plug_crypto_1: [{:plug_crypto, "~> 1.2"}],
  plug_crypto_2: [{:plug_crypto, "~> 2.0"}]
}
```

Edit and set your blends in the auto-generated `blend.exs` file.


### 3. Resolve blends and generate lockfiles

```
$ mix blend.get
```

to resolve your blends and generate new lockfiles with variations of your dependencies under the new `/blend` folder.

```
blend
├── _build
├── deps
├── plug_crypto_1.mix.lock
└── plug_crypto_2.mix.lock

```

### 4. Ignore blend build artifacts

```
# .gitignore

/blend/_build
/blend/deps
```

Add to your `.gitignore` file, before comitting your changes.


### 5. Running in the context of a blend lockfile

#### Option A. Overriding your `mix.lock`.

If you just need a CI job step to run against a blend lockfile, it might be enough to just:

```
$ cp blend/<blend_name>.mix.lock mix.lock
```

Now you can run any task, e.g. run your tests.

```
$ mix test
```

#### Option B. `BLEND` env var configuration

A more permanent configuration for running mix tasks in the context of a blend lockfile with a simple env var
can be acomplished by customizing your `mix.exs` a bit, with the following steps.

##### 1. Create a new file `blend/premix.exs` with the following command:

```
$ mix blend.premix
```

This will generate a `blend/premix.exs` file that needs to be compiled at the top of your `mix.exs` file
so that some mix env vars are properly set based on the `BLEND` env var before running any mix task.

##### 2. Modify your `mix.exs`.

```elixir
# mix.exs

Code.compile_file("blend/premix.exs")         # New

defmodule YourApp.MixProject do
  ...
  def project do
    [
      ...
    ]
    |> Keyword.merge(maybe_lockfile_option()) # New
  end
  ....

  defp maybe_lockfile_option do               # New
    case System.get_env("MIX_LOCKFILE") do    #
      nil -> []                               #
      "" -> []                                #
      lockfile -> [lockfile: lockfile]        #
    end                                       #
  end                                         #
end            
```

##### 3. Enjoy

Now you can run any task, e.g. run your tests, against different lockfiles locally by just executing:

```
$ BLEND=<blend_name> mix test
```

## Commands

```
$ mix blend.init         # Generate blend.exs
$ mix blend.get          # Generate blend lockfiles
$ mix blend.update --all # Update blend lockfiles to latest possible versions
$ mix blend.list         # List blends
$ mix blend.premix       # Generate premix.exs file
```

## License

Copyright 2024 Mimiquate

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.