Sam is a Make-like utility which allows to specify tasks like Ruby's Rake do using plain Crystal code. This allows you to reuse existing application code base and/or include tasks from your dependencies.
Add this to your application's
dependencies: sam: github: imdrasil/sam.cr version: 0.3.2
shards install Sam-file will be added to the root of your project (unless you already have one).
Tasks are the main unit in
sam.cr. Task has a name, a list of prerequisites and a list of actions (block of a code).
Sam extends the global context with own DSL. To define a task use
task method which accepts the task name as the 1st argument.
task "name" do end
If you want to define prerequisites, add the array with their names as the 2nd argument:
task "name", ["prereq1", "prereq2"] do end
Sam does no magic with your
sam.cr file - it is just a common
.cr source file which allows you to recompile it with any possible code you want such amount of times you need. Therefore the most obvious way to execute any task is:
$ crystal sam.cr -- name
--here means that
nameis passed as an argument to executed file not
In addition to this you are able to configure your makefile to invoke sam tasks. This allows you to use shorten variant
$ make sam name
This solution still requires
--in some cases - see the following section.
To automatically preconfigure makefile run
$ crystal sam.cr -- generate:makefile
This will modify existing Makefile or create new one. Be careful - this will silent all nonexisting makefile tasks on invocation.
To see a list of all available tasks with their descriptions:
$ crystal sam.cr -- help
To pass arguments to your task just list them after it's name:
> crystal sam.cr -- name john rob ned
They are passed to a task as a 2nd block argument.
task "name" do |_, args| puts args.as(String) end
args here is an instance of
Sam::Args class that contains arguments and named arguments passed to each task. Any argument passed from a console is treated as a
Float64 values also can be specified during task invocation from inside of another one.
Each task has own collection of arguments; only prerequisites shares with target task same
As was mentioned named argument also can be specified by the following ways:
-argument "value with spaces"
argument="value with spaces"
One important restriction with named arguments usage and makefile-style task invocation:
-- should be placed to explicitly specify that specified arguments belongs to compiled program not crystal compiler:
$ make sam name john $ # but $ make same name -- argument=john
More than one task can be specified (even with own arguments) - just separate them by
$ crystal sam.cr -- name john @ surname argument=snow
Sam allow you to invoke tasks within another ones and even passing own args object. To do this just call
#invoke method with task name (and arguments if needed) on task object passed as 1st argument:
task "name" do |t| t.invoke("surname") end task "surname" do puts "Snow" end
If specified task was already invoked before - it will be ignored. To force task invocation - use
Another task could be invoked from current using
invoke method. It has next signatures:
as projects grow amount of defined tasks grow as well. To simplify navigation and increase readability tasks can be grouped in namespaces:
namespace "main" do task "build" do # Build the main program end end namespace "samples" do task "build" do # Build the sample programs end end task "build", %w[main:build samples:build] do end
When task is invoked from other one, provided path will float up through current task namespace and search given task path on each level until top level. Task could have same name as any existing namespace.
task "one" do end namespace "one" do namespace "two" task "test" do |t| t.invoke("one") end end end
In the example above next paths are checked (in given order):
one(as task not namespace)
Sam tasks can be loaded from installed dependencies. To do this helper macro
load_dependencies can be used:
load_dependencies "lib1", "lib2"
This is translated to
Before running tests call
$ crystal examples/sam.cr -- setup