Be more explicit when capturing and processing output.

Gemfile.lock

@@ -3,7 +3,7 @@ PATH
   specs:
     ruby-terraform (1.8.0.pre.7)
       immutable-struct (~> 2.4)
-      lino (= 3.2.0.pre.7)
+      lino (= 3.2.0.pre.9)
 
 GEM
   remote: https://rubygems.org/
@@ -31,7 +31,7 @@ GEM
     diff-lcs (1.5.1)
     docile (1.4.0)
     drb (2.2.1)
-    excon (0.110.0)
+    excon (0.111.0)
     faker (3.4.1)
       i18n (>= 1.8.11, < 2)
     faraday (2.10.0)
@@ -66,7 +66,7 @@ GEM
     immutable-struct (2.4.1)
     json (2.7.2)
     language_server-protocol (3.17.0.3)
-    lino (3.2.0.pre.7)
+    lino (3.2.0.pre.9)
       childprocess (~> 5.0.0)
       hamster (~> 3.0)
       open4 (~> 1.3)

lib/ruby_terraform/commands/base.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'lino'
+require 'tempfile'
 
 require_relative '../errors'
 
@@ -12,12 +13,12 @@ class Base
       # Constructs an instance of the command.
       #
       def initialize(opts = {})
-        @binary  = opts[:binary]  || RubyTerraform.configuration.binary
-        @logger  = opts[:logger]  || RubyTerraform.configuration.logger
+        @binary = opts[:binary] || RubyTerraform.configuration.binary
+        @logger = opts[:logger] || RubyTerraform.configuration.logger
         @options = opts[:options] || RubyTerraform.configuration.options
-        @stdin   = opts[:stdin]   || RubyTerraform.configuration.stdin
-        @stdout  = opts[:stdout]  || RubyTerraform.configuration.stdout
-        @stderr  = opts[:stderr]  || RubyTerraform.configuration.stderr
+        @stdin = opts[:stdin] || RubyTerraform.configuration.stdin
+        @stdout = opts[:stdout] || RubyTerraform.configuration.stdout
+        @stderr = opts[:stderr] || RubyTerraform.configuration.stderr
       end
 
       # rubocop:enable Metrics/AbcSize
@@ -32,30 +33,24 @@ def initialize(opts = {})
       # @option invocation_options [Hash<String, String>] :environment A map
       #   of environment variables to expose at command invocation time.
       def execute(parameters = {}, invocation_options = {})
+        parameters = resolve_parameters(parameters)
+        invocation_options = resolve_invocation_options(invocation_options)
+
         do_before(parameters)
-        build_and_execute_command(parameters, invocation_options)
+        result = build_and_execute_command(parameters, invocation_options)
         do_after(parameters)
+
+        prepare_result(result, parameters, invocation_options)
       rescue Lino::Errors::ExecutionError
         message = "Failed while running '#{command_name}'."
         logger.error(message)
         raise Errors::ExecutionError, message
       end
 
-      protected
+      private
 
       attr_reader :binary, :logger, :stdin, :stdout, :stderr
 
-      def build_and_execute_command(parameters, invocation_options)
-        command = build_command(parameters, invocation_options)
-
-        logger.debug("Running '#{command}'.")
-        command.execute(
-          stdin:,
-          stdout:,
-          stderr:
-        )
-      end
-
       def command_name
         self.class.to_s.split('::')[-1].downcase
       end
@@ -64,11 +59,7 @@ def do_before(_parameters); end
 
       def do_after(_parameters); end
 
-      private
-
       def build_command(parameters, invocation_options)
-        parameters = resolve_parameters(parameters)
-
         Lino::CommandLineBuilder
           .for_command(@binary)
           .with_environment_variables(invocation_options[:environment] || {})
@@ -80,10 +71,8 @@ def build_command(parameters, invocation_options)
           .build
       end
 
-      def resolve_parameters(parameters)
-        parameter_defaults(parameters)
-          .merge(parameters)
-          .merge(parameter_overrides(parameters))
+      def process_result(result, _parameters, _invocation_options)
+        result
       end
 
       def parameter_defaults(_parameters)
@@ -94,6 +83,10 @@ def parameter_overrides(_parameters)
         {}
       end
 
+      def invocation_option_defaults(_invocation_options)
+        { capture: [], result: :processed }
+      end
+
       def subcommands
         []
       end
@@ -105,6 +98,59 @@ def options
       def arguments(_parameters)
         []
       end
+
+      def build_and_execute_command(parameters, invocation_options)
+        command = build_command(parameters, invocation_options)
+        stdout = resolve_stdout(invocation_options)
+        stderr = resolve_stderr(invocation_options)
+
+        logger.debug("Running '#{command}'.")
+        command.execute(stdin:, stdout:, stderr:)
+
+        process_streams(invocation_options, stdout, stderr)
+      end
+
+      def resolve_parameters(parameters)
+        parameter_defaults(parameters)
+          .merge(parameters)
+          .merge(parameter_overrides(parameters))
+      end
+
+      def resolve_invocation_options(invocation_options)
+        invocation_option_defaults(invocation_options)
+          .merge(invocation_options)
+      end
+
+      def resolve_stdout(invocation_options)
+        invocation_options[:capture].include?(:stdout) ? Tempfile.new : @stdout
+      end
+
+      def resolve_stderr(invocation_options)
+        invocation_options[:capture].include?(:stderr) ? Tempfile.new : @stderr
+      end
+
+      def process_streams(invocation_options, stdout, stderr)
+        cap = invocation_options[:capture]
+
+        return nil if cap == []
+
+        result = {}
+        result = add_contents_to_result(cap, result, :stdout, stdout, :output)
+        add_contents_to_result(cap, result, :stderr, stderr, :error)
+      end
+
+      def add_contents_to_result(capture, result, stream_name, stream, type)
+        return result unless capture.include?(stream_name)
+
+        stream.rewind
+        result.merge({ type => stream.read })
+      end
+
+      def prepare_result(result, parameters, invocation_options)
+        return result if invocation_options[:result] == :raw
+
+        process_result(result, parameters, invocation_options)
+      end
     end
   end
 end

lib/ruby_terraform/commands/output.rb

@@ -42,8 +42,8 @@ class Output < Base
       include RubyTerraform::Options::Global
 
       # @!visibility private
-      def stdout
-        @stdout.respond_to?(:string) ? @stdout : (@stdout = StringIO.new)
+      def invocation_option_defaults(invocation_options)
+        super.merge(capture: [:stdout])
       end
 
       # @!visibility private
@@ -67,9 +67,8 @@ def arguments(parameters)
       end
 
       # @!visibility private
-      def do_after(parameters)
-        result = stdout.string
-        parameters[:name] ? result.chomp : result
+      def process_result(result, parameters, _invocation_options)
+        parameters[:name] ? result[:output].chomp : result[:output]
       end
     end
   end

ruby_terraform.gemspec

@@ -39,7 +39,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 3.1'
 
   spec.add_dependency 'immutable-struct', '~> 2.4'
-  spec.add_dependency 'lino', '3.2.0.pre.7'
+  spec.add_dependency 'lino', '3.2.0.pre.9'
 
   spec.add_development_dependency 'bundler'
   spec.add_development_dependency 'faker'