apis/nfd: drop the private template caching fields

Drop the private fields – that were supposed to be used for caching parsed
templates – from the Rule type. Keep the API typedefs cleaner and
simpler. Moreover, the caching was not even used in practice,
effectively complicating code without any benefit: the way the types
are used in nfd-master creates a local copy of Rule type storing the
cached template in the copy, wasting it from any future users.

There are also other possible caveats in caching like we tried to do it.
For example the objects returned by the api lister are supposed to be
treated as read-only - in particular if we would be to modify them there
should at least be proper locking in place as nfd-master potentially
processes the same rule (the same Go object) in parallel for multiple
nodes. If any optimization like this will be pursued it should be done
properly, probably with private type(s) at the consumer's end, not
contaminating the API types.

pkg/apis/nfd/v1alpha1/rule.go

@@ -112,15 +112,12 @@ func (r *Rule) executeLabelsTemplate(in matchedFeatures, out map[string]string)
 		return nil
 	}
 
-	if r.labelsTemplate == nil {
-		t, err := newTemplateHelper(r.LabelsTemplate)
-		if err != nil {
-			return fmt.Errorf("failed to parse LabelsTemplate: %w", err)
-		}
-		r.labelsTemplate = t
+	th, err := newTemplateHelper(r.LabelsTemplate)
+	if err != nil {
+		return fmt.Errorf("failed to parse LabelsTemplate: %w", err)
 	}
 
-	labels, err := r.labelsTemplate.expandMap(in)
+	labels, err := th.expandMap(in)
 	if err != nil {
 		return fmt.Errorf("failed to expand LabelsTemplate: %w", err)
 	}
@@ -134,15 +131,13 @@ func (r *Rule) executeVarsTemplate(in matchedFeatures, out map[string]string) er
 	if r.VarsTemplate == "" {
 		return nil
 	}
-	if r.varsTemplate == nil {
-		t, err := newTemplateHelper(r.VarsTemplate)
-		if err != nil {
-			return err
-		}
-		r.varsTemplate = t
+
+	th, err := newTemplateHelper(r.VarsTemplate)
+	if err != nil {
+		return err
 	}
 
-	vars, err := r.varsTemplate.expandMap(in)
+	vars, err := th.expandMap(in)
 	if err != nil {
 		return err
 	}
@@ -216,22 +211,6 @@ func newTemplateHelper(name string) (*templateHelper, error) {
 	return &templateHelper{template: tmpl}, nil
 }
 
-// DeepCopy is a stub to augment the auto-generated code
-func (h *templateHelper) DeepCopy() *templateHelper {
-	if h == nil {
-		return nil
-	}
-	out := new(templateHelper)
-	h.DeepCopyInto(out)
-	return out
-}
-
-// DeepCopyInto is a stub to augment the auto-generated code
-func (h *templateHelper) DeepCopyInto(out *templateHelper) {
-	// HACK: just re-use the template
-	out.template = h.template
-}
-
 func (h *templateHelper) execute(data interface{}) (string, error) {
 	var tmp bytes.Buffer
 	if err := h.template.Execute(&tmp, data); err != nil {

pkg/apis/nfd/v1alpha1/rule_test.go

@@ -369,17 +369,14 @@ var-2=
 	assert.Equal(t, map[string]string{"foo": "bar"}, m.Labels, "instances should have matched")
 	assert.Empty(t, m.Vars)
 
-	r2.labelsTemplate = nil
 	r2.LabelsTemplate = "foo"
 	_, err = r2.Execute(f)
 	assert.Error(t, err)
 
-	r2.labelsTemplate = nil
 	r2.LabelsTemplate = "{{"
 	_, err = r2.Execute(f)
 	assert.Error(t, err)
 
-	r2.labelsTemplate = nil
 	r2.LabelsTemplate = ""
 	r2.VarsTemplate = "bar=baz"
 	m, err = r2.Execute(f)
@@ -387,12 +384,10 @@ var-2=
 	assert.Empty(t, m.Labels)
 	assert.Equal(t, map[string]string{"bar": "baz"}, m.Vars, "instances should have matched")
 
-	r2.varsTemplate = nil
 	r2.VarsTemplate = "bar"
 	_, err = r2.Execute(f)
 	assert.Error(t, err)
 
-	r2.varsTemplate = nil
 	r2.VarsTemplate = "{{"
 	_, err = r2.Execute(f)
 	assert.Error(t, err)

pkg/apis/nfd/v1alpha1/types.go

@@ -178,10 +178,6 @@ type Rule struct {
 	// MatchAny specifies a list of matchers one of which must match.
 	// +optional
 	MatchAny []MatchAnyElem `json:"matchAny"`
-
-	// private helpers/cache for handling golang templates
-	labelsTemplate *templateHelper `json:"-"`
-	varsTemplate   *templateHelper `json:"-"`
 }
 
 // MatchAnyElem specifies one sub-matcher of MatchAny.

pkg/apis/nfd/v1alpha1/zz_generated.deepcopy.go

@@ -503,14 +503,6 @@ func (in *Rule) DeepCopyInto(out *Rule) {
 			(*in)[i].DeepCopyInto(&(*out)[i])
 		}
 	}
-	if in.labelsTemplate != nil {
-		in, out := &in.labelsTemplate, &out.labelsTemplate
-		*out = (*in).DeepCopy()
-	}
-	if in.varsTemplate != nil {
-		in, out := &in.varsTemplate, &out.varsTemplate
-		*out = (*in).DeepCopy()
-	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new Rule.