From 501684a9c61f34187ff2bb00c85e5c98da73d91d Mon Sep 17 00:00:00 2001
From: Donny Xia <donnyxia@google.com>
Date: Thu, 20 Aug 2020 11:54:56 -0700
Subject: [PATCH] remove break after input in pipeline

---
 cmd/config/internal/commands/source.go |  2 +-
 kyaml/kio/kio.go                       | 12 ++-----
 kyaml/kio/kio_test.go                  | 47 ++++++++++++++++++++++++--
 3 files changed, 48 insertions(+), 13 deletions(-)

diff --git a/cmd/config/internal/commands/source.go b/cmd/config/internal/commands/source.go
index d731aa5c8..7873956ce 100644
--- a/cmd/config/internal/commands/source.go
+++ b/cmd/config/internal/commands/source.go
@@ -77,6 +77,6 @@ func (r *SourceRunner) runE(c *cobra.Command, args []string) error {
 		inputs = []kio.Reader{&kio.ByteReader{Reader: c.InOrStdin()}}
 	}
 
-	err := kio.Pipeline{Inputs: inputs, Outputs: outputs, ContinueIfInputEmpty: true}.Execute()
+	err := kio.Pipeline{Inputs: inputs, Outputs: outputs}.Execute()
 	return handleError(c, err)
 }
diff --git a/kyaml/kio/kio.go b/kyaml/kio/kio.go
index c5165ab04..ee53bca40 100644
--- a/kyaml/kio/kio.go
+++ b/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)
 		}
diff --git a/kyaml/kio/kio_test.go b/kyaml/kio/kio_test.go
index ad4cd70bb..9a3a9ea27 100644
--- a/kyaml/kio/kio_test.go
+++ b/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()
+	}
+}