Define a helper method pkg/controller.FilterRunRef

This will be useful to external Custom Task controllers to filter out
update notifications for Runs of irrelevant types.

pkg/controller/filter.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2020 The Tekton Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package controller provides helper methods for external controllers for
+// Custom Task types.
+package controller
+
+import (
+	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1alpha1"
+)
+
+// FilterRunRef returns a filter that can be passed to a Run Informer, which
+// filters out Runs for apiVersion and kinds that a controller doesn't care
+// about.
+//
+// For example, a controller impl that wants to be notified of updates to Runs
+// which reference a Task with apiVersion "example.dev/v0" and kind "Example":
+//
+//     runinformer.Get(ctx).Informer().AddEventHandler(cache.FilteringResourceEventHandler{
+//       FilterFunc: FilterRunRef("example.dev/v0", "Example"),
+//       Handler:    controller.HandleAll(impl.Enqueue),
+//     })
+func FilterRunRef(apiVersion, kind string) func(interface{}) bool {
+	return func(obj interface{}) bool {
+		r, ok := obj.(*v1alpha1.Run)
+		if !ok {
+			// Somehow got informed of a non-Run object.
+			// Ignore.
+			return false
+		}
+		if r == nil || r.Spec.Ref == nil {
+			// These are invalid, but just in case they get
+			// created somehow, don't panic.
+			return false
+		}
+
+		return r.Spec.Ref.APIVersion == apiVersion && r.Spec.Ref.Kind == v1alpha1.TaskKind(kind)
+	}
+}

pkg/controller/filter_test.go

@@ -0,0 +1,105 @@
+/*
+Copyright 2020 The Tekton Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package controller_test
+
+import (
+	"testing"
+
+	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1alpha1"
+	"github.com/tektoncd/pipeline/pkg/controller"
+)
+
+const (
+	apiVersion = "example.dev/v0"
+	kind       = "Example"
+)
+
+func TestFilterRunRef(t *testing.T) {
+	for _, c := range []struct {
+		desc string
+		in   interface{}
+		want bool
+	}{{
+		desc: "not a Run",
+		in:   struct{}{},
+		want: false,
+	}, {
+		desc: "nil Run",
+		in:   (*v1alpha1.Run)(nil),
+		want: false,
+	}, {
+		desc: "nil ref",
+		in: &v1alpha1.Run{
+			Spec: v1alpha1.RunSpec{
+				Ref: nil,
+			},
+		},
+		want: false,
+	}, {
+		desc: "Run without matching apiVersion",
+		in: &v1alpha1.Run{
+			Spec: v1alpha1.RunSpec{
+				Ref: &v1alpha1.TaskRef{
+					APIVersion: "not-matching",
+					Kind:       kind,
+				},
+			},
+		},
+		want: false,
+	}, {
+		desc: "Run without matching kind",
+		in: &v1alpha1.Run{
+			Spec: v1alpha1.RunSpec{
+				Ref: &v1alpha1.TaskRef{
+					APIVersion: apiVersion,
+					Kind:       "not-matching",
+				},
+			},
+		},
+		want: false,
+	}, {
+		desc: "Run with matching apiVersion and kind",
+		in: &v1alpha1.Run{
+			Spec: v1alpha1.RunSpec{
+				Ref: &v1alpha1.TaskRef{
+					APIVersion: apiVersion,
+					Kind:       kind,
+				},
+			},
+		},
+		want: true,
+	}, {
+		desc: "Run with matching apiVersion and kind and name",
+		in: &v1alpha1.Run{
+			Spec: v1alpha1.RunSpec{
+				Ref: &v1alpha1.TaskRef{
+					APIVersion: apiVersion,
+					Kind:       kind,
+					Name:       "some-name",
+				},
+			},
+		},
+		want: true,
+	}} {
+		t.Run(c.desc, func(t *testing.T) {
+			got := controller.FilterRunRef(apiVersion, kind)(c.in)
+			if got != c.want {
+				t.Fatalf("FilterRunRef(%q, %q) got %t, want %t", apiVersion, kind, got, c.want)
+			}
+		})
+	}
+}