remove break after input in pipeline

kyaml/kio/kio.go

@@ -75,11 +75,6 @@ type Pipeline struct {
 
 	// Outputs are where the transformed Resource Configuration is written.
 	Outputs []Writer `yaml:"outputs,omitempty"`
-
-	// ContinueIfInputEmpty indicates should pipeline continue when the
-	// the input result is empty. This is useful when we want to run outputs
-	// even the input is empty.
-	ContinueIfInputEmpty bool
 }
 
 // Execute executes each step in the sequence, returning immediately after encountering
@@ -104,10 +99,6 @@ func (p Pipeline) ExecuteWithCallback(callback PipelineExecuteCallbackFunc) erro
 		}
 		result = append(result, nodes...)
 	}
-	if len(result) == 0 && !p.ContinueIfInputEmpty {
-		// no inputs to operate on
-		return nil
-	}
 
 	// apply operations
 	var err error
@@ -117,6 +108,9 @@ func (p Pipeline) ExecuteWithCallback(callback PipelineExecuteCallbackFunc) erro
 			callback(op)
 		}
 		result, err = op.Filter(result)
+		// TODO: This len(result) == 0 should be removed and empty result list should be
+		// handled by outputs. However currently the some writer like LocalPackageReadWriter
+		// will clear the output directory and which will cause unpredictable results
 		if len(result) == 0 || err != nil {
 			return errors.Wrap(err)
 		}

kyaml/kio/kio_test.go

@@ -78,7 +78,7 @@ func TestPipelineWithCallback(t *testing.T) {
 	}
 }
 
-func TestContinueIfInputEmpty(t *testing.T) {
+func TestEmptyInput(t *testing.T) {
 	actual := &bytes.Buffer{}
 	output := ByteWriter{
 		Sort:               true,
@@ -88,8 +88,7 @@ func TestContinueIfInputEmpty(t *testing.T) {
 	output.Writer = actual
 
 	p := Pipeline{
-		Outputs:              []Writer{output},
-		ContinueIfInputEmpty: true,
+		Outputs: []Writer{output},
 	}
 
 	err := p.Execute()
@@ -108,3 +107,45 @@ items: []
 		t.FailNow()
 	}
 }
+
+func TestEmptyInputWithFilter(t *testing.T) {
+	actual := &bytes.Buffer{}
+	output := ByteWriter{
+		Sort:               true,
+		WrappingKind:       ResourceListKind,
+		WrappingAPIVersion: ResourceListAPIVersion,
+	}
+	output.Writer = actual
+
+	filters := []Filter{
+		FilterFunc(func(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
+			nodes = append(nodes, yaml.NewMapRNode(&map[string]string{
+				"foo": "bar",
+			}))
+			return nodes, nil
+		}),
+		FilterFunc(func(nodes []*yaml.RNode) ([]*yaml.RNode, error) { return nodes, nil }),
+	}
+
+	p := Pipeline{
+		Outputs: []Writer{output},
+		Filters: filters,
+	}
+
+	err := p.Execute()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := `
+apiVersion: config.kubernetes.io/v1alpha1
+kind: ResourceList
+items:
+- foo: bar
+`
+
+	if !assert.Equal(t,
+		strings.TrimSpace(expected), strings.TrimSpace(actual.String())) {
+		t.FailNow()
+	}
+}