Log and return zero val objects on CtorArgs

container_test.go

@@ -415,8 +415,14 @@ func TestInvokeFailureUnresolvedDependencies(t *testing.T) {
 	err = c.Invoke(func(p1 *Parent1) {})
 	require.Contains(t, err.Error(), "unable to resolve *dig.Parent1")
 
-	err = c.Invoke(func(p12 *Parent12) {})
-	require.Contains(t, err.Error(), "dependency of type *dig.Parent12 is not registered")
+	var zeroP12 *Parent12
+	err = c.Invoke(func(p12 *Parent12) {
+		zeroP12 = p12
+	})
+	require.NoError(t, err)
+	newZeroP12, ok := reflect.Zero(reflect.TypeOf(zeroP12)).Interface().(*Parent12)
+	require.True(t, ok)
+	assert.Equal(t, zeroP12, newZeroP12)
 }
 
 func TestProvide(t *testing.T) {

internal/graph/graph.go

@@ -23,6 +23,7 @@ package graph
 import (
 	"bytes"
 	"fmt"
+	"log"
 	"reflect"
 
 	"github.com/pkg/errors"
@@ -204,7 +205,8 @@ func (g *Graph) ConstructorArguments(ctype reflect.Type) ([]reflect.Value, error
 			}
 			args[idx] = v
 		} else {
-			return nil, fmt.Errorf("%v dependency of type %v is not registered", ctype, arg)
+			log.Printf("Assigning zero value for arguments in %v. Dependency of type %v is not yet registered", ctype, arg)
+			args[idx] = reflect.Zero(arg)
 		}
 	}
 	return args, nil

internal/graph/graph_test.go

@@ -94,6 +94,20 @@ func TestResolvedArguments(t *testing.T) {
 	assert.Equal(t, reflect.TypeOf(values[1].Interface()).String(), "*graph.Parent12")
 }
 
+func Test_UnprovidedConstructorArguments(t *testing.T) {
+	t.Parallel()
+	g := NewGraph()
+
+	values, err := g.ConstructorArguments(reflect.TypeOf(constructor))
+	require.NoError(t, err)
+
+	assert.Equal(t, reflect.TypeOf(values[0].Interface()).String(), "*graph.Parent1")
+	assert.Equal(t, reflect.TypeOf(values[1].Interface()).String(), "*graph.Parent12")
+
+	assert.Equal(t, values[0], reflect.Zero(reflect.TypeOf(values[0].Interface())))
+	assert.Equal(t, values[1], reflect.Zero(reflect.TypeOf(values[1].Interface())))
+}
+
 func TestGraphString(t *testing.T) {
 	g := NewGraph()
 	p1 := &Parent1{