Add validation to cog configs

lib/roast/dsl/cog/config.rb

@@ -5,6 +5,17 @@ module Roast
   module DSL
     class Cog
       class Config
+        class ConfigError < Roast::Error; end
+
+        class InvalidConfigError < ConfigError; end
+
+        # Validate that the config instance has all required parameters set in an acceptable manner
+        #
+        # Inheriting cog should implement this for its config class if validation is desired.
+        #
+        #: () -> void
+        def validate!; end
+
         #: Hash[Symbol, untyped]
         attr_reader :values
 

lib/roast/dsl/config_manager.rb

@@ -53,6 +53,7 @@ def config_for(cog_class, name = nil)
         end.values.each { |cfg| config = config.merge(cfg) }
         name_scoped_config = fetch_name_scoped_config(cog_class, name) unless name.nil?
         config = config.merge(name_scoped_config) if name_scoped_config
+        config.validate!
         config
       end
 

lib/roast/dsl/system_cogs/map.rb

@@ -8,8 +8,6 @@ class Map < SystemCog
         class Config < Cog::Config
           #: (Integer) -> void
           def parallel(value)
-            raise ArgumentError, "value must be >= 0" if value < 0
-
             # treat 0 as unlimited parallelism
             @values[:parallel] = value > 0 ? value : nil
           end
@@ -24,9 +22,17 @@ def no_parallel!
             @values[:parallel] = 1
           end
 
+          def validate!
+            valid_parallel!
+          end
+
           #: () -> Integer?
-          def max_parallel_tasks
-            @values.fetch(:parallel, 1)
+          def valid_parallel!
+            parallel = @values.fetch(:parallel, 1)
+            return if parallel.nil?
+            raise InvalidConfigError, "'parallel' must be >= 0 if specified" if parallel < 0
+
+            parallel
           end
         end
 
@@ -103,7 +109,8 @@ def create_map_system_cog(params, input_proc)
                 em
               end
 
-              max_parallel_semaphore = Async::Semaphore.new(config.max_parallel_tasks) if config.max_parallel_tasks.present?
+              max_parallel_tasks = config.valid_parallel!
+              max_parallel_semaphore = Async::Semaphore.new(max_parallel_tasks) if max_parallel_tasks.present?
               tasks = input.items.map.with_index do |item, index|
                 if max_parallel_semaphore
                   max_parallel_semaphore.async { create_and_run_execution_manager.call(item, index) }