Add crd:validation:Schemaless marker

This marker will avoid trying to do any type detection
on any struct field on which it is set. This gives
users a safety valve when they hit an edge case where
type inference does the wrong thing for them.

Signed-off-by: Max Smythe <smythe@google.com>

Author: maxsmythe

.golangci.yml

@@ -1,6 +1,4 @@
 run:
-  modules-download-mode: readonly
-
   # Increase the default deadline from 1m as some module operations can take a
   # while if uncached!
   deadline: 5m

pkg/crd/markers/validation.go

@@ -26,6 +26,10 @@ import (
 	"sigs.k8s.io/controller-tools/pkg/markers"
 )
 
+const (
+	SchemalessName = "kubebuilder:validation:Schemaless"
+)
+
 // ValidationMarkers lists all available markers that affect CRD schema generation,
 // except for the few that don't make sense as type-level markers (see FieldOnlyMarkers).
 // All markers start with `+kubebuilder:validation:`, and continue with their type name.
@@ -82,6 +86,9 @@ var FieldOnlyMarkers = []*definitionWithHelp{
 
 	must(markers.MakeDefinition("kubebuilder:validation:EmbeddedResource", markers.DescribesField, XEmbeddedResource{})).
 		WithHelp(XEmbeddedResource{}.Help()),
+
+	must(markers.MakeDefinition(SchemalessName, markers.DescribesField, Schemaless{})).
+		WithHelp(Schemaless{}.Help()),
 }
 
 // ValidationIshMarkers are field-and-type markers that don't fall under the
@@ -225,6 +232,16 @@ type XPreserveUnknownFields struct{}
 // field, yet it is possible. This can be combined with PreserveUnknownFields.
 type XEmbeddedResource struct{}
 
+// +controllertools:marker:generateHelp:category="CRD validation"
+// Schemaless marks a field as being a schemaless object.
+//
+// Schemaless objects are not introspected, so you must provide
+// any type and validation information yourself. One use for this
+// tag is for embedding fields that hold JSONSchema typed objects.
+// Because this field disables all type checking, it is recommended
+// to be used only as a last resort.
+type Schemaless struct{}
+
 func (m Maximum) ApplyToSchema(schema *apiext.JSONSchemaProps) error {
 	if schema.Type != "integer" {
 		return fmt.Errorf("must apply maximum to an integer")

pkg/crd/markers/zz_generated.markerhelp.go

@@ -23,6 +23,7 @@ import (
 	"strings"
 
 	apiext "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	crdmarkers "sigs.k8s.io/controller-tools/pkg/crd/markers"
 
 	"sigs.k8s.io/controller-tools/pkg/loader"
 	"sigs.k8s.io/controller-tools/pkg/markers"
@@ -378,7 +379,12 @@ func structToSchema(ctx *schemaContext, structType *ast.StructType) *apiext.JSON
 			}
 		}
 
-		propSchema := typeToSchema(ctx.ForInfo(&markers.TypeInfo{}), field.RawField.Type)
+		var propSchema *apiext.JSONSchemaProps
+		if field.Markers.Get(crdmarkers.SchemalessName) != nil {
+			propSchema = &apiext.JSONSchemaProps{}
+		} else {
+			propSchema = typeToSchema(ctx.ForInfo(&markers.TypeInfo{}), field.RawField.Type)
+		}
 		propSchema.Description = field.Doc
 
 		applyMarkers(ctx, field.Markers, propSchema, field.RawField)

pkg/crd/schema.go

@@ -154,14 +154,19 @@ type CronJobSpec struct {
 
 	// This tests that min/max properties work
 	MinMaxProperties MinMaxObject `json:"minMaxProperties,omitempty"`
+
+	// This tests that the schemaless marker works
+	// +kubebuilder:validation:Schemaless
+	Schemaless []byte `json:"schemaless,omitempty"`
 }
 
 // +kubebuilder:validation:Type=object
 // +kubebuilder:pruning:PreserveUnknownFields
 type Preserved struct {
-	ConcreteField string `json:"concreteField"`
-	Rest map[string]interface{} `json:"-"`
+	ConcreteField string                 `json:"concreteField"`
+	Rest          map[string]interface{} `json:"-"`
 }
+
 func (p *Preserved) UnmarshalJSON(data []byte) error {
 	if err := json.Unmarshal(data, &p.Rest); err != nil {
 		return err

pkg/crd/testdata/cronjob_types.go

@@ -5071,6 +5071,8 @@ spec:
               schedule:
                 description: The schedule in Cron format, see https://en.wikipedia.org/wiki/Cron.
                 type: string
+              schemaless:
+                description: This tests that the schemaless marker works
               startingDeadlineSeconds:
                 description: Optional deadline in seconds for starting the job if
                   it misses scheduled time for any reason.  Missed jobs executions

pkg/crd/testdata/testdata.kubebuilder.io_cronjobs.yaml

@@ -107,13 +107,13 @@ fetch_kb_tools
 # setup testing env
 setup_envs
 
-header_text "running golangci-lint"
-
 header_text "generating marker help"
 pushd cmd/controller-gen > /dev/null
   go generate
 popd > /dev/null
 
+header_text "running golangci-lint"
+
 golangci-lint run --disable-all \
     --enable=misspell \
     --enable=golint \