Detect and report state cycles precisely (#139)

Author: Fryuni

cucumber-tsflow-specs/features/custom-context-objects.feature

@@ -203,7 +203,7 @@ Feature: Custom context objects
         And the output contains "The state is 'initial value'"
         And the output contains "The state is 'step value'"
 
-    Scenario: Circular dependencies are explicitly communicated to the developer
+    Scenario: Cyclic imports are detected and communicated to the developer
         Given a file named "features/a.feature" with:
             """feature
             Feature: some feature
@@ -276,11 +276,11 @@ Feature: Custom context objects
         Then it fails
         And the error output contains text:
             """
-            Undefined context type at index 0 for StateOne, do you possibly have a circular dependency?
+            Error: Undefined dependency detected in StateOne. You possibly have an import cycle.
+            See https://nodejs.org/api/modules.html#modules_cycles
             """
 
-
-    Scenario: Circular dependencies within the same file are vaguely communicated to the developer
+    Scenario: Cyclic state dependencies are detected and communicated to the developer
         Given a file named "features/a.feature" with:
             """feature
             Feature: some feature
@@ -346,10 +346,10 @@ Feature: Custom context objects
         Then it fails
         And the error output contains text:
             """
-            Undefined context type at index 0 for StepsTwo, do you possibly have a circular dependency?
+            Error: Cyclic dependency detected: StateOne -> StateTwo -> StateOne
             """
 
-    Scenario: In-file circular dependencies are thrown as maximum call stack exceeded errors
+    Scenario: Cyclic single-file state dependencies are detected and communicated to the developer
         Given a file named "features/a.feature" with:
         """feature
         Feature: some feature
@@ -401,4 +401,7 @@ Feature: Custom context objects
         """
         When I run cucumber-js
         Then it fails
-        And the output contains "RangeError: Maximum call stack size exceeded"
+        And the error output contains text:
+            """
+            Error: Cyclic dependency detected: StateOne -> StateTwo -> StateOne
+            """

cucumber-tsflow/src/binding-decorator.ts

@@ -51,6 +51,29 @@ const stepPatternRegistrations = new Map<StepPattern, StepBindingFlags>();
 
 // tslint:disable:no-bitwise
 
+function ensureNoCyclicDependencies(target: any, currentPath: any[] = []) {
+  const dependencies = BindingRegistry.instance.getContextTypesForTarget(target.prototype);
+
+  if (dependencies.length === 0) {
+    return;
+  }
+
+  for (const dependency of dependencies) {
+    if (dependency === undefined) {
+      throw new Error(
+          `Undefined dependency detected in ${target.name}. You possibly have an import cycle.\n`
+          + 'See https://nodejs.org/api/modules.html#modules_cycles'
+      );
+    }
+
+    if (currentPath.includes(dependency)) {
+      throw new Error(`Cyclic dependency detected: ${dependency.name} -> ${target.name} -> ${currentPath.map((t) => t.name).join(' -> ')}`);
+    }
+
+    ensureNoCyclicDependencies(dependency, [...currentPath, target]);
+  }
+}
+
 /**
  * A class decorator that marks the associated class as a CucumberJS binding.
  *
@@ -68,13 +91,7 @@ export function binding(requiredContextTypes?: ContextType[]): TypeDecorator {
       requiredContextTypes
     );
 
-    if (Array.isArray(requiredContextTypes)) {
-      for (const i in requiredContextTypes) {
-        if (typeof requiredContextTypes[i] === 'undefined') {
-          throw new Error(`Undefined context type at index ${i} for ${target.name}, do you possibly have a circular dependency?`);
-        }
-      }
-    }
+    ensureNoCyclicDependencies(target);
 
     const allBindings: StepBinding[] = [
       ...bindingRegistry.getStepBindingsForTarget(target),