Max Howell mxcl

Dependency Locking with the Swift Package Manager

Introduction

In a vibrant packaging ecosystem, dependencies update continuously with bug-fixes and feature improvements. When working against a collection of dependencies, especially in a team, it is vital to lock the graph and update it so that all team members receive the exact same graph at the same time.

The typical flow for this in dependency management is to create and use a dependency “Lockfile”.

Motivation

One of the core benefits of tea: it's relocatable. tea does not pollute your system environment, everything gets "installed" in a relocatable folder ~/.tea.

tea can also install languages like node and ruby and it's dependency managers, npm and gem, respectively. However, these language dependency managers install packages to global directories like ~/.npm and ~/.gem. Tools from these ecosystems expect to find packages in these locations.

In this RFC, we would love to hear feedback from the community.

	# This is more "Ruby", and I agree that I don't necessarily agree with
	# all the syntax choices. The else condition isn't required as the
	# function returns nil if no other code paths executed. You could argue
	# that, that is a regression waiting to happen though.

	def just_one_kind_of_response? item, controller
	case controller
	when 'actions'
	item.comments.blank? or item.suggestions.blank? or detail.comments.blank?
	when 'thoughts'

	// Trying to write a function that does some select/map magic with easy error handling

	let cities = [[
	"name": "Geneva",
	"population": 184538
	],[
	"name": "Bern",
	"population": 123154
	], [
	"name": "Zurich",

	import Darwin //.C.stdlib

	// updated for Swift 2.0 beta4

	private func merge<T: Comparable>(a: ArraySlice<T>, _ b: ArraySlice<T>, mergeInto acc: ArraySlice<T> = []) -> ArraySlice<T> {
	guard let aF = a.first, bF = b.first else {
	return acc + a + b
	}
	return aF < bF
	? merge(dropFirst(a), b, mergeInto: acc + [aF])