Merge pull request #47 from ccremer/if-else

Add IfOrElse predicate

predicate.go

@@ -51,6 +51,21 @@ func If(predicate Predicate, originalStep Step) Step {
 	return wrappedStep
 }
 
+// IfOrElse returns a new step that wraps the given steps and executes its action based on the given Predicate.
+// The name of the step is taken from `trueStep`.
+// The context.Context from the pipeline is passed through the given actions.
+func IfOrElse(predicate Predicate, trueStep Step, falseStep Step) Step {
+	wrappedStep := Step{Name: trueStep.Name}
+	wrappedStep.F = func(ctx context.Context) Result {
+		if predicate(ctx) {
+			return trueStep.F(ctx)
+		} else {
+			return falseStep.F(ctx)
+		}
+	}
+	return wrappedStep
+}
+
 // Bool returns a Predicate that simply returns v when evaluated.
 // Use BoolPtr() over Bool() if the value can change between setting up the pipeline and evaluating the predicate.
 func Bool(v bool) Predicate {

predicate_test.go

@@ -131,6 +131,41 @@ func TestIf(t *testing.T) {
 	}
 }
 
+func TestIfOrElse(t *testing.T) {
+	counter := 0
+	tests := map[string]struct {
+		givenPredicate Predicate
+		expectedCalls  int
+	}{
+		"GivenWrappedStep_WhenPredicateEvalsTrue_ThenRunMainAction": {
+			givenPredicate: truePredicate(&counter),
+			expectedCalls:  2,
+		},
+		"GivenWrappedStep_WhenPredicateEvalsFalse_ThenRunAlternativeAction": {
+			givenPredicate: falsePredicate(&counter),
+			expectedCalls:  -2,
+		},
+	}
+
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			counter = 0
+			trueStep := NewStep("true", func(_ context.Context) Result {
+				counter++
+				return newEmptyResult("true")
+			})
+			falseStep := NewStep("false", func(ctx context.Context) Result {
+				counter--
+				return newEmptyResult("false")
+			})
+			wrapped := IfOrElse(tt.givenPredicate, trueStep, falseStep)
+			result := wrapped.F(nil)
+			require.NoError(t, result.Err())
+			assert.Equal(t, tt.expectedCalls, counter)
+			assert.Equal(t, trueStep.Name, wrapped.Name)
+		})
+	}
+}
 func TestBoolPtr(t *testing.T) {
 	called := false
 	b := false