support config metadata

pkg/star/feature.go

@@ -39,6 +39,7 @@ const (
 	ResultVariableName   string          = "result"
 	DefaultValueAttrName string          = "default"
 	DescriptionAttrName  string          = "description"
+	MetadataAttrName     string          = "metadata"
 	// TODO: Fully migrate to overrides over rules
 	RulesAttrName     string = "rules"
 	OverridesAttrName string = "overrides"
@@ -54,6 +55,7 @@ var (
 		OverridesAttrName:    {},
 		validatorAttrName:    {},
 		unitTestsAttrName:    {},
+		MetadataAttrName:     {},
 	}
 )
 
@@ -295,6 +297,22 @@ func (fb *featureBuilder) getDescription(featureVal *starlarkstruct.Struct) (str
 	return dsc.GoString(), nil
 }
 
+func (fb *featureBuilder) getMetadata(featureVal *starlarkstruct.Struct) (*structpb.Value, error) {
+	metadataVal, err := featureVal.Attr(MetadataAttrName)
+	if err != nil {
+		return nil, errors.Wrap(err, "metadata attribute")
+	}
+	metadataDict, ok := metadataVal.(*starlark.Dict)
+	if !ok {
+		return nil, fmt.Errorf("metadata must be a dict (got a %s)", metadataVal.Type())
+	}
+	metadataMap, err := translateContext(metadataDict)
+	if err != nil {
+		return nil, errors.Wrap(err, "translate metadata attribute")
+	}
+	return structpb.NewValue(metadataMap)
+}
+
 func (fb *featureBuilder) addOverrides(f *feature.Feature, featureVal *starlarkstruct.Struct) ([]starlark.Value, error) {
 	overridesVal, err := featureVal.Attr(OverridesAttrName)
 	if err != nil {

pkg/star/static/traverse.go

@@ -30,6 +30,7 @@ const (
 	ResultVariableName   string          = "result"
 	DefaultValueAttrName string          = "default"
 	DescriptionAttrName  string          = "description"
+	MetadataAttrName     string          = "metadata"
 	// TODO: Fully migrate to overrides over rules
 	RulesAttrName     string = "rules"
 	OverridesAttrName string = "overrides"
@@ -40,11 +41,13 @@ func defaultNoop(v *build.Expr) error           { return nil }
 func descriptionNoop(v *build.StringExpr) error { return nil }
 func rulesNoop(rules *overridesWrapper) error   { return nil }
 func importsNoop(imports *importsWrapper) error { return nil }
+func metadataNoop(ast *starFeatureAST) error { return nil}
 
 type defaultFn func(v *build.Expr) error
 type descriptionFn func(v *build.StringExpr) error
 type overridesFn func(rules *overridesWrapper) error
 type importsFn func(imports *importsWrapper) error
+type metadataFn func(ast *starFeatureAST) error
 
 // Traverses a lekko starlark file, running methods on various
 // components of the file. Methods can be provided to read the
@@ -57,6 +60,7 @@ type traverser struct {
 	descriptionFn  descriptionFn
 	overridesFn    overridesFn
 	protoImportsFn importsFn
+	metadataFn     metadataFn
 }
 
 func newTraverser(f *build.File, nv feature.NamespaceVersion) *traverser {
@@ -67,6 +71,7 @@ func newTraverser(f *build.File, nv feature.NamespaceVersion) *traverser {
 		descriptionFn:  descriptionNoop,
 		overridesFn:    rulesNoop,
 		protoImportsFn: importsNoop,
+		metadataFn: metadataNoop,
 	}
 }
 
@@ -90,6 +95,11 @@ func (t *traverser) withProtoImportsFn(fn importsFn) *traverser {
 	return t
 }
 
+func (t *traverser) withMetadataFn(fn metadataFn) *traverser {
+	t.metadataFn = fn
+	return t
+} 
+
 func (t *traverser) traverse() error {
 	imports := t.getProtoImports()
 	if err := t.protoImportsFn(imports); err != nil {
@@ -118,6 +128,9 @@ func (t *traverser) traverse() error {
 	if err := t.descriptionFn(descriptionStr); err != nil {
 		return errors.Wrap(err, "description fn")
 	}
+	if err := t.metadataFn(ast); err != nil {
+		return errors.Wrap(err, "metadata fn")
+	}
 	// rules
 	if err := ast.parseOverrides(t.overridesFn, t.nv); err != nil {
 		return err
@@ -326,6 +339,10 @@ type importVal struct {
 	assignExpr *build.AssignExpr
 }
 
+type metadataWrapper struct {
+	metadataExpr *build.DictExpr
+}
+
 func newOverride(li build.Expr) (*override, error) {
 	tupleV, ok := li.(*build.TupleExpr)
 	if !ok {

pkg/star/static/walk.go

@@ -85,7 +85,8 @@ func (w *walker) Build() (*featurev1beta1.StaticFeature, error) {
 		withDefaultFn(w.buildDefaultFn(ret)).
 		withDescriptionFn(w.buildDescriptionFn(ret)).
 		withOverridesFn(w.buildRulesFn(ret)).
-		withProtoImportsFn(w.buildProtoImportsFn(ret))
+		withProtoImportsFn(w.buildProtoImportsFn(ret)).
+		withMetadataFn(w.buildMetadataFn(ret))
 
 	if err := t.traverse(); err != nil {
 		return nil, errors.Wrap(err, "traverse")
@@ -101,7 +102,8 @@ func (w *walker) Mutate(f *featurev1beta1.StaticFeature) ([]byte, error) {
 	t := newTraverser(ast, w.nv).
 		withDefaultFn(w.mutateDefaultFn(f)).
 		withDescriptionFn(w.mutateDescriptionFn(f)).
-		withOverridesFn(w.mutateOverridesFn(f))
+		withOverridesFn(w.mutateOverridesFn(f)).
+		withMetadataFn(w.mutateMetadataFn(f))
 
 	if err := t.traverse(); err != nil {
 		return nil, errors.Wrap(err, "traverse")
@@ -240,6 +242,27 @@ func (w *walker) buildDescriptionFn(f *featurev1beta1.StaticFeature) description
 	}
 }
 
+func (w *walker) buildMetadataFn(f *featurev1beta1.StaticFeature) metadataFn {
+	return func(ast *starFeatureAST) error {
+		metadataExprPtr, found := ast.get(MetadataAttrName)
+		if !found {
+			return nil
+		}
+		metadataExpr := *metadataExprPtr
+		metadataDict, ok := metadataExpr.(*build.DictExpr)
+		if !ok {
+			return errors.Wrapf(ErrUnsupportedStaticParsing, "metadata kwarg: expected dict, got %T", metadataExpr)
+		}
+		metadataValue, err := w.extractJSONValue(metadataDict)
+		if err != nil {
+			return errors.Wrap(err, "extract metadata")
+		}
+		f.Feature.Metadata = metadataValue
+		f.FeatureOld.Metadata = metadataValue
+		return nil
+	}
+}
+
 func (w *walker) buildRulesFn(f *featurev1beta1.StaticFeature) overridesFn {
 	return func(overridesW *overridesWrapper) error {
 		for i, o := range overridesW.overrides {
@@ -485,6 +508,21 @@ func (w *walker) mutateDescriptionFn(f *featurev1beta1.StaticFeature) descriptio
 	}
 }
 
+func (w *walker) mutateMetadataFn(f *featurev1beta1.StaticFeature) metadataFn {
+	return func(ast *starFeatureAST) error {
+		metadataProto := f.FeatureOld.GetMetadata()
+		if metadataProto == nil {
+			return nil
+		}
+		metadataStarDict, err := w.genJSONValue(metadataProto, nil) 
+		if err != nil {
+			return err
+		}
+		ast.set(MetadataAttrName, metadataStarDict)
+		return nil
+	}
+}
+
 func (w *walker) mutateOverridesFn(f *featurev1beta1.StaticFeature) overridesFn {
 	return func(overridesW *overridesWrapper) error {
 		var newOverrides []override

proto/lekko/feature/v1beta1/static.proto

@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package lekko.feature.v1beta1;
 
+import "google/protobuf/struct.proto";
 import "lekko/feature/v1beta1/feature.proto";
 
 // Represents a statically parsed feature.
@@ -47,6 +48,7 @@ message FeatureStruct {
   string description = 2;
   StarExpr default = 3;
   Rules rules = 4;
+  google.protobuf.Value metadata = 7;
 }
 
 message Rules {