DSL: passing output data between steps

Author: dersam

dsl/step_communication.rb

@@ -0,0 +1,18 @@
+# typed: false
+# frozen_string_literal: true
+
+# How do we pass information between steps?
+# Demonstrate by passing result of a command output to another step
+
+config do
+  cmd(:echo) { display! }
+end
+
+execute do
+  cmd(:ls) { "ls -al" }
+  cmd(:echo) do
+    # TODO: this is a bespoke output object for cmd, is there a generic one we can offer
+    first_line = cmd(:ls).command_output.split("\n").second
+    "echo '#{first_line}'"
+  end
+end

lib/roast/dsl/cog.rb

@@ -4,12 +4,14 @@
 module Roast
   module DSL
     class Cog
+      class CogAlreadyRanError < StandardError; end
+
       class << self
         def on_create
           eigen = self
           proc do |instance_name = Random.uuid, &action|
-            #: self as Roast::DSL::ExecutionContext
-            add_cog_instance(instance_name, eigen.new(action))
+            #: self as Roast::DSL::WorkflowExecutionContext
+            add_cog_instance(instance_name, eigen.new(instance_name, action))
           end
         end
 
@@ -39,23 +41,28 @@ def find_child_config_or_default
         end
       end
 
-      attr_reader :output
+      attr_reader :name, :output
 
-      def initialize(cog_input_proc)
+      def initialize(name, cog_input_proc)
+        @name = name
         @cog_input_proc = cog_input_proc
+        @finished = false
       end
 
-      def input
-        @cog_input_proc.call
-      end
+      def run!(config, cog_execution_context)
+        raise CogAlreadyRanError if ran?
 
-      def run!(config)
         @config = config
-        @output = execute
+        @output = execute(cog_execution_context.instance_exec(&@cog_input_proc))
+        @finished = true
+      end
+
+      def ran?
+        @finished
       end
 
       # Inheriting cog must implement this
-      def execute
+      def execute(input)
         raise NotImplementedError
       end
     end

lib/roast/dsl/cog/store.rb

@@ -7,10 +7,7 @@ class Cog
       class Store
         class CogAlreadyDefinedError < Roast::Error; end
 
-        #: (Symbol) -> Roast::DSL::Cog?
-        def find(id)
-          store[id]
-        end
+        delegate :[], to: :store
 
         #: (Symbol, Roast::DSL::Cog) -> Roast::DSL::Cog
         def insert(id, inst)

lib/roast/dsl/cog_execution_context.rb

@@ -0,0 +1,29 @@
+# typed: true
+# frozen_string_literal: true
+
+module Roast
+  module DSL
+    # Contains the cogs already executed in this run.
+    class CogExecutionContext
+      # Raises if you access a cog in an execution block that hasn't already been run.
+      class IncompleteCogExecutionAccessError < StandardError; end
+
+      def initialize(cogs, bound_names)
+        @cogs = cogs
+        bind_cog_methods(bound_names)
+      end
+
+      private
+
+      def bind_cog_methods(bound_names)
+        bound_names.map do |name|
+          define_singleton_method(name.to_sym, ->(name) do
+            @cogs[name].tap do |cog|
+              raise IncompleteCogExecutionAccessError unless cog.ran?
+            end.output
+          end)
+        end
+      end
+    end
+  end
+end

lib/roast/dsl/cogs/cmd.rb

@@ -7,7 +7,7 @@ module Cogs
       class Cmd < Cog
         class Output
           #: String?
-          attr_reader :output
+          attr_reader :command_output
 
           #: String?
           attr_reader :err
@@ -21,7 +21,7 @@ class Output
           #|  Process::Status? status
           #| ) -> void
           def initialize(output, error, status)
-            @output = output
+            @command_output = output
             @err = error
             @status = status
           end
@@ -37,12 +37,16 @@ def print_all!
           def print_all?
             !!@values[:print_all]
           end
+
+          def display!
+            print_all!
+          end
         end
 
-        #: () -> Output
-        def execute
+        #: (String) -> Output
+        def execute(input)
           result = Output.new(*Roast::Helpers::CmdRunner.capture3(input))
-          puts result.output if @config.print_all?
+          puts result.command_output if @config.print_all?
           result
         end
       end

lib/roast/dsl/executor.rb

@@ -32,7 +32,7 @@ def prepare!(input)
 
         @config_context = ConfigContext.new(@cogs, @config_proc)
         @config_context.prepare!
-        @execution_context = ExecutionContext.new(@cogs, @cog_stack, @execution_proc)
+        @execution_context = WorkflowExecutionContext.new(@cogs, @cog_stack, @execution_proc)
         @execution_context.prepare!
 
         @prepared = true
@@ -44,7 +44,10 @@ def start!
         raise ExecutorAlreadyCompletedError if @completed
 
         @cog_stack.map do |name, cog|
-          cog.run!(@config_context.fetch_merged_config(cog.class, name.to_sym))
+          cog.run!(
+            @config_context.fetch_merged_config(cog.class, name.to_sym),
+            @execution_context.cog_execution_context,
+          )
         end
 
         @completed = true
@@ -63,7 +66,7 @@ def config(&block)
         @config_proc = block
       end
 
-      #: { () [self: ExecutionContext] -> void} -> void
+      #: { () [self: WorkflowExecutionContext] -> void} -> void
       def execute(&block)
         @execution_proc = block
       end

lib/roast/dsl/execution_context.rb renamed to lib/roast/dsl/workflow_execution_context.rb

@@ -3,31 +3,41 @@
 
 module Roast
   module DSL
-    class ExecutionContext
+    class WorkflowExecutionContext
       def initialize(cogs, cog_stack, execution_proc)
         @cogs = cogs
         @cog_stack = cog_stack
         @execution_proc = execution_proc
+        @bound_names = []
       end
 
       def prepare!
         bind_default_cogs
         instance_eval(&@execution_proc)
       end
 
+      def cog_execution_context
+        @cog_execution_context ||= CogExecutionContext.new(@cogs, @bound_names)
+      end
+
       private
 
       def add_cog_instance(name, cog)
         @cogs.insert(name, cog)
         @cog_stack.push([name, cog])
       end
 
+      def output(name)
+        @cogs[name].output
+      end
+
       #: () -> void
       def bind_default_cogs
         bind_cog(Cogs::Cmd, :cmd)
       end
 
       def bind_cog(cog_class, name)
+        @bound_names << name
         instance_eval do
           define_singleton_method(name, &cog_class.on_create)
         end

sorbet/rbi/shims/lib/roast/dsl/execution_context.rbi renamed to sorbet/rbi/shims/lib/roast/dsl/workflow_execution_context.rbi

@@ -3,7 +3,7 @@
 
 module Roast
   module DSL
-    class ExecutionContext
+    class WorkflowExecutionContext
       #: (?Symbol?) {() [self: Roast::DSL::Cogs::Cmd] -> String} -> void
       def cmd(name = nil, &block); end
     end