Add Introspect::Graph#find!

lib/trailblazer/activity/introspect.rb

@@ -8,6 +8,13 @@ module Introspect
 
       # @private This API is still under construction.
       class Graph
+        class NodeNotFound < RuntimeError
+          def initialize(id = nil)
+            return super("Cannot find node with id=#{id.inspect}") if id
+            super("Cannot find node for given block")
+          end
+        end
+
         def initialize(activity)
           @activity = activity
           @schema   = activity.to_h or raise
@@ -22,6 +29,10 @@ def find(id = nil, &block)
           find_with_block(&block)
         end
 
+        def find!(id = nil, &block)
+          find(id, &block) or raise NodeNotFound.new(id)
+        end
+
         def collect(strategy: :circuit)
           @map.keys.each_with_index.collect { |task, i| yield find_with_block { |node| node.task == task }, i }
         end

test/introspect_test.rb

@@ -28,6 +28,28 @@ class IntrospectionTest < Minitest::Spec
       end
     end
 
+    describe "#find!" do
+      let(:node) { graph.find!(:B) }
+      it { expect(node.class).must_equal Activity::Introspect::Graph::Node }
+      it { expect(node[:id]).must_equal :B }
+
+      it "raises exception when {:id} is invalid" do
+        exception = assert_raises Activity::Introspect::Graph::NodeNotFound do
+          graph.find!(:Z)
+        end
+
+        expect(exception.message).must_equal "Cannot find node with id=:Z"
+      end
+
+      it "raises exception when node is not selected via block" do
+        exception = assert_raises Activity::Introspect::Graph::NodeNotFound do
+          graph.find!{ |node| nil }
+        end
+
+        expect(exception.message).must_equal "Cannot find node for given block"
+      end
+    end
+
     describe "#collect" do
       it "provides 1-arg {node}" do
         nodes = graph.collect { |node| node }