Add checking for duplicate declared resources

Fixes tektoncd#2241

(cherry picked from commit 29966ea)

pkg/apis/pipeline/v1alpha1/pipeline_validation.go

@@ -43,6 +43,13 @@ func (p *Pipeline) Validate(ctx context.Context) *apis.FieldError {
 }
 
 func validateDeclaredResources(ps *PipelineSpec) error {
+	encountered := map[string]struct{}{}
+	for _, r := range ps.Resources {
+		if _, ok := encountered[r.Name]; ok {
+			return fmt.Errorf("resource with name %q appears more than once", r.Name)
+		}
+		encountered[r.Name] = struct{}{}
+	}
 	required := []string{}
 	for _, t := range ps.Tasks {
 		if t.Resources != nil {

pkg/apis/pipeline/v1alpha1/pipeline_validation_test.go

@@ -213,6 +213,15 @@ func TestPipeline_Validate(t *testing.T) {
 				tb.PipelineTaskInputResource("the-resource", "great-resource", tb.From("bar"))),
 		)),
 		failureExpected: true,
+	}, {
+		name: "duplicate resource declaration",
+		p: tb.Pipeline("pipeline", "namespace", tb.PipelineSpec(
+			tb.PipelineDeclaredResource("duplicate-resource", v1alpha1.PipelineResourceTypeGit),
+			tb.PipelineDeclaredResource("duplicate-resource", v1alpha1.PipelineResourceTypeGit),
+			tb.PipelineTask("foo", "foo-task",
+				tb.PipelineTaskInputResource("the-resource", "duplicate-resource")),
+		)),
+		failureExpected: true,
 	}, {
 		name: "output resources missing from declaration",
 		p: tb.Pipeline("pipeline", "namespace", tb.PipelineSpec(

pkg/apis/pipeline/v1beta1/pipeline_validation.go

@@ -42,6 +42,13 @@ func (p *Pipeline) Validate(ctx context.Context) *apis.FieldError {
 }
 
 func validateDeclaredResources(ps *PipelineSpec) error {
+	encountered := map[string]struct{}{}
+	for _, r := range ps.Resources {
+		if _, ok := encountered[r.Name]; ok {
+			return fmt.Errorf("resource with name %q appears more than once", r.Name)
+		}
+		encountered[r.Name] = struct{}{}
+	}
 	required := []string{}
 	for _, t := range ps.Tasks {
 		if t.Resources != nil {

pkg/apis/pipeline/v1beta1/pipeline_validation_test.go

@@ -350,6 +350,28 @@ func TestPipeline_Validate(t *testing.T) {
 			},
 		},
 		failureExpected: true,
+	}, {
+		name: "duplicate resource declaration",
+		p: &v1beta1.Pipeline{
+			ObjectMeta: metav1.ObjectMeta{Name: "pipeline"},
+			Spec: v1beta1.PipelineSpec{
+				Resources: []v1beta1.PipelineDeclaredResource{{
+					Name: "duplicate-resource", Type: v1beta1.PipelineResourceTypeGit,
+				}, {
+					Name: "duplicate-resource", Type: v1beta1.PipelineResourceTypeGit,
+				}},
+				Tasks: []v1beta1.PipelineTask{{
+					Name:    "foo",
+					TaskRef: &v1beta1.TaskRef{Name: "foo-task"},
+					Resources: &v1beta1.PipelineTaskResources{
+						Inputs: []v1beta1.PipelineTaskInputResource{{
+							Name: "the-resource", Resource: "duplicate-resource",
+						}},
+					},
+				}},
+			},
+		},
+		failureExpected: true,
 	}, {
 		name: "output resources missing from declaration",
 		p: &v1beta1.Pipeline{