test: extend gomega to use YAML for API types

Some of our API types contain fields that get rendered very poorly by
gomega.format.Object because they contain lots of internal information, for
example CreationTimestamp. As a result, dumping full API object typically gets
truncated.

What we want is a representation that is a) multi-line (in contrast to the
stringer implemented by our types) and b) drops empty fields where it
was defined that this is okay.

The normal YAML representation fits that requirement. We just need to teach
gomega how and when to do that. This cannot be done for each type through a
generated GomegaString method (lots of code, additional dependency in public
API on YAML encoder), but it can be done inside tests by adding a formatting
handler (new gomega feature).

test/e2e/e2e_test.go

@@ -67,6 +67,7 @@ import (
 	_ "k8s.io/kubernetes/test/e2e/framework/debug/init"
 	_ "k8s.io/kubernetes/test/e2e/framework/metrics/init"
 	_ "k8s.io/kubernetes/test/e2e/framework/node/init"
+	_ "k8s.io/kubernetes/test/utils/format"
 )
 
 // handleFlags sets up all flags and parses the command line.

test/e2e_kubeadm/e2e_kubeadm_suite_test.go

@@ -32,6 +32,7 @@ import (
 	_ "k8s.io/kubernetes/test/e2e/framework/debug/init"
 	_ "k8s.io/kubernetes/test/e2e/framework/metrics/init"
 	_ "k8s.io/kubernetes/test/e2e/framework/node/init"
+	_ "k8s.io/kubernetes/test/utils/format"
 )
 
 func TestMain(m *testing.M) {

test/e2e_node/e2e_node_suite_test.go

@@ -57,6 +57,7 @@ import (
 	_ "k8s.io/kubernetes/test/e2e/framework/debug/init"
 	_ "k8s.io/kubernetes/test/e2e/framework/metrics/init"
 	_ "k8s.io/kubernetes/test/e2e/framework/node/init"
+	_ "k8s.io/kubernetes/test/utils/format"
 
 	"github.com/onsi/ginkgo/v2"
 	"github.com/onsi/gomega"

test/utils/format/format.go

@@ -0,0 +1,80 @@
+/*
+Copyright 2022 The Kubernetes 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 format is an extension of Gomega's format package which
+// improves printing of objects that can be serialized well as YAML,
+// like the structs in the Kubernetes API.
+//
+// Just importing it is enough to activate this special YAML support
+// in Gomega.
+package format
+
+import (
+	"reflect"
+	"strings"
+
+	"github.com/onsi/gomega/format"
+
+	"sigs.k8s.io/yaml"
+)
+
+func init() {
+	format.RegisterCustomFormatter(handleYAML)
+}
+
+// Object makes Gomega's [format.Object] available without having to import that
+// package.
+func Object(object interface{}, indentation uint) string {
+	return format.Object(object, indentation)
+}
+
+// handleYAML formats all values as YAML where the result
+// is likely to look better as YAML:
+//   - pointer to struct or struct where all fields
+//     have `json` tags
+//   - slices containing such a value
+//   - maps where the key or value are such a value
+func handleYAML(object interface{}) (string, bool) {
+	value := reflect.ValueOf(object)
+	if !useYAML(value.Type()) {
+		return "", false
+	}
+	y, err := yaml.Marshal(object)
+	if err != nil {
+		return "", false
+	}
+	return "\n" + strings.TrimSpace(string(y)), true
+}
+
+func useYAML(t reflect.Type) bool {
+	switch t.Kind() {
+	case reflect.Pointer, reflect.Slice, reflect.Array:
+		return useYAML(t.Elem())
+	case reflect.Map:
+		return useYAML(t.Key()) || useYAML(t.Elem())
+	case reflect.Struct:
+		// All fields must have a `json` tag.
+		for i := 0; i < t.NumField(); i++ {
+			field := t.Field(i)
+			if _, ok := field.Tag.Lookup("json"); !ok {
+				return false
+			}
+		}
+		return true
+	default:
+		return false
+	}
+}

test/utils/format/format_test.go

@@ -0,0 +1,81 @@
+/*
+Copyright 2022 The Kubernetes 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 format_test
+
+import (
+	"fmt"
+	"regexp"
+	"testing"
+
+	"github.com/onsi/gomega/format"
+	"github.com/stretchr/testify/assert"
+
+	v1 "k8s.io/api/core/v1"
+)
+
+func TestGomegaFormatObject(t *testing.T) {
+	for name, test := range map[string]struct {
+		value       interface{}
+		expected    string
+		indentation uint
+	}{
+		"int":            {value: 1, expected: `<int>: 1`},
+		"string":         {value: "hello world", expected: `<string>: "hello world"`},
+		"struct":         {value: myStruct{a: 1, b: 2}, expected: `<format_test.myStruct>: {a: 1, b: 2}`},
+		"gomegastringer": {value: typeWithGomegaStringer(2), expected: `<format_test.typeWithGomegaStringer>: my stringer 2`},
+		"pod": {value: v1.Pod{}, expected: `<v1.Pod>: 
+    metadata:
+      creationTimestamp: null
+    spec:
+      containers: null
+    status: {}`},
+		"pod-indented": {value: v1.Pod{}, indentation: 1, expected: `    <v1.Pod>: 
+        metadata:
+          creationTimestamp: null
+        spec:
+          containers: null
+        status: {}`},
+		"pod-ptr": {value: &v1.Pod{}, expected: `<*v1.Pod | <hex>>: 
+    metadata:
+      creationTimestamp: null
+    spec:
+      containers: null
+    status: {}`},
+		"pod-hash": {value: map[string]v1.Pod{}, expected: `<map[string]v1.Pod | len:0>: 
+    {}`},
+		"podlist": {value: v1.PodList{}, expected: `<v1.PodList>: 
+    items: null
+    metadata: {}`},
+	} {
+		t.Run(name, func(t *testing.T) {
+			actual := format.Object(test.value, test.indentation)
+			actual = regexp.MustCompile(`\| 0x[a-z0-9]+`).ReplaceAllString(actual, `| <hex>`)
+			assert.Equal(t, test.expected, actual)
+		})
+	}
+
+}
+
+type typeWithGomegaStringer int
+
+func (v typeWithGomegaStringer) GomegaString() string {
+	return fmt.Sprintf("my stringer %d", v)
+}
+
+type myStruct struct {
+	a, b int
+}