Write the up configuration

Omni can be added to manage a repository dependencies pretty easily: just create an .omni.yaml file at the root of your repository and define the up configuration for your dependencies.

Let's consider a simple repository with two tools we want to work on. One in Go, and one in Python:

Go tool

/path/to/repo/go/src/gosayhello.go

package main

import (
	"flag"
	"fmt"
)

func main() {
	goodbye := flag.Bool("goodbye", false, "say goodbye instead of hello")
	flag.Parse()

	name := flag.Arg(0)
	if name == "" {
		panic("Who do you wanna greet?")
	}

	greeting := "Hello"
	if *goodbye {
		greeting = "Goodbye"
	}

	fmt.Printf("%s, %s!\n", greeting, name)
}

Python tool

/path/to/repo/python/pysayhello.py

#!/usr/bin/env python

import argparse

parser = argparse.ArgumentParser(description='Say hello in Python')
parser.add_argument('name', help='name to greet')
parser.add_argument('--goodbye', action='store_true')

args = parser.parse_args()

greeting = "Goodbye" if args.goodbye else "Hello"
print("{}, {}!".format(greeting, args.name))

We can first add the relevant dependencies to make sure we have access to the right tools; since we don't have a version preference here, we can also simply make sure we have access to the latest version:

/path/to/repo/.omni.yaml

up:
  - python
  - go

Running omni up will now install those dependencies for us, and omni's dynamic environment will make sure that we can use them right away.

This means that we can now run our commands through python python/pysayhello.py xaf or go run go/src/gosayhello.go xaf even if Python and Go are not accessible anywhere else in our system: we are using omni's dynamic environment, which gives us access to the expected versions of those tools to run our commands.

You might observe a slight delay when running go run go/src/gosayhello.go xaf. This is related to calling go run everytime we run that command. To make things more efficient at call time, we can compile a binary during omni up using a custom operation:

/path/to/repo/.omni.yaml

up:
  - python
  - go
  - custom:
      name: "Compile sayhello go binary"
      met?: |
        bin="go/bin/gosayhello"
        [ -f "$bin" ] && \
          [ -x "$bin" ] && \
          [ "$bin" -nt go/src/gosayhello.go ]
      meet: "go build -o go/bin/gosayhello go/src/gosayhello.go"
      unmeet: "rm go/bin/gosayhello"

Which means that instead of calling go run go/src/gosayhello.go xaf, we can now call go/bin/gosayhello xaf directly. That binary will automatically be updated, if necessary, anytime we run omni up in that repository.