types: add stronger types and helpers for inspecting Paths and Path derivatives

Now, instead of passing types.Paths around all over the place in the schema code, we can know that we've got a Namespace or a commonType or a EntityType and the code becomes easier to understand (IMO).

The new methods on Path and EntityType may also help cedar-go users write more understandable code.

Author: patjakdev

types/entity_uid.go

@@ -14,9 +14,50 @@ import (
 // Path is a series of idents separated by ::
 type Path string
 
+// IsQualified returns whether a Path has any qualifiers (i.e. at least one ::)
+func (p Path) IsQualified() bool {
+	return strings.Contains(string(p), "::")
+}
+
+// Qualifier returns a Path with everything but the last element in the original Path or "" if there is only one element.
+func (p Path) Qualifier() Path {
+	idx := strings.LastIndex(string(p), "::")
+	if idx == -1 {
+		return ""
+	}
+	return p[:idx]
+}
+
+// Basename returns the last element in the original Path
+func (p Path) Basename() string {
+	idx := strings.LastIndex(string(p), "::")
+	if idx == -1 {
+		return string(p)
+	}
+	return string(p[idx+2:])
+}
+
+// Namespace is a type of path with no base name referring to an entity type
+type Namespace Path
+
 // EntityType is the type portion of an EntityUID
 type EntityType Path
 
+// IsQualified reports whether the EntityType contains a namespace qualifier.
+func (e EntityType) IsQualified() bool {
+	return Path(e).IsQualified()
+}
+
+// Namespace returns the namespace for the EntityType or "" if the type is unqualified.
+func (e EntityType) Namespace() Namespace {
+	return Namespace(Path(e).Qualifier())
+}
+
+// Basename returns the unqualified entity type name
+func (e EntityType) Basename() string {
+	return Path(e).Basename()
+}
+
 // An EntityUID is the identifier for a principal, action, or resource.
 type EntityUID struct {
 	Type EntityType

types/entity_uid_test.go

@@ -113,6 +113,47 @@ func TestEntity(t *testing.T) {
 	})
 }
 
+func TestPathQualification(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		path      types.Path
+		qualified bool
+		qualifier types.Path
+		basename  string
+	}{
+		{"NS::User", true, "NS", "User"},
+		{"A::B::C", true, "A::B", "C"},
+		{"User", false, "", "User"},
+		{"", false, "", ""},
+	}
+	for _, tt := range tests {
+		testutil.Equals(t, tt.path.IsQualified(), tt.qualified)
+		testutil.Equals(t, tt.path.Qualifier(), tt.qualifier)
+		testutil.Equals(t, tt.path.Basename(), tt.basename)
+	}
+}
+
+func TestEntityTypeQualification(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		typ       types.EntityType
+		qualified bool
+		namespace types.Namespace
+		basename  string
+	}{
+		{"NS::User", true, "NS", "User"},
+		{"A::B::C", true, "A::B", "C"},
+		{"User", false, "", "User"},
+	}
+	for _, tt := range tests {
+		testutil.Equals(t, tt.typ.IsQualified(), tt.qualified)
+		testutil.Equals(t, tt.typ.Namespace(), tt.namespace)
+		testutil.Equals(t, tt.typ.Basename(), tt.basename)
+	}
+}
+
 func TestEntityUIDSet(t *testing.T) {
 	t.Parallel()
 

x/exp/schema/ast/ast.go

@@ -21,7 +21,7 @@ type Actions map[types.String]Action
 type CommonTypes map[types.Ident]CommonType
 
 // Namespaces maps namespace paths to their definitions.
-type Namespaces map[types.Path]Namespace
+type Namespaces map[types.Namespace]Namespace
 
 // Schema is the top-level Cedar schema AST.
 // The Entities, Enums, Actions, and CommonTypes are for the top-level namespace.

x/exp/schema/ast/ast_test.go

@@ -21,6 +21,30 @@ func TestConstructors(t *testing.T) {
 	testutil.Equals(t, ast.Type("MyType"), ast.TypeRef("MyType"))
 }
 
+func TestEntityTypeRefQualification(t *testing.T) {
+	qualified := ast.EntityTypeRef("NS::User")
+	testutil.Equals(t, qualified.IsQualified(), true)
+	testutil.Equals(t, qualified.Namespace(), types.Namespace("NS"))
+	testutil.Equals(t, qualified.Basename(), "User")
+
+	unqualified := ast.EntityTypeRef("User")
+	testutil.Equals(t, unqualified.IsQualified(), false)
+	testutil.Equals(t, unqualified.Namespace(), types.Namespace(""))
+	testutil.Equals(t, unqualified.Basename(), "User")
+}
+
+func TestTypeRefQualification(t *testing.T) {
+	qualified := ast.TypeRef("NS::MyType")
+	testutil.Equals(t, qualified.IsQualified(), true)
+	testutil.Equals(t, qualified.Namespace(), types.Namespace("NS"))
+	testutil.Equals(t, qualified.Basename(), "MyType")
+
+	unqualified := ast.TypeRef("MyType")
+	testutil.Equals(t, unqualified.IsQualified(), false)
+	testutil.Equals(t, unqualified.Namespace(), types.Namespace(""))
+	testutil.Equals(t, unqualified.Basename(), "MyType")
+}
+
 func TestParentRefFromID(t *testing.T) {
 	ref := ast.ParentRefFromID("view")
 	testutil.Equals(t, ref.ID, types.String("view"))

x/exp/schema/ast/types.go

@@ -81,6 +81,21 @@ type EntityTypeRef types.EntityType
 
 func (EntityTypeRef) isType() { _ = 0 }
 
+// IsQualified reports whether the entity type reference contains a namespace qualifier.
+func (e EntityTypeRef) IsQualified() bool {
+	return types.EntityType(e).IsQualified()
+}
+
+// Namespace returns the namespace portion of a qualified entity type reference, or "" if unqualified.
+func (e EntityTypeRef) Namespace() types.Namespace {
+	return types.EntityType(e).Namespace()
+}
+
+// Basename returns the unqualified entity type name.
+func (e EntityTypeRef) Basename() string {
+	return types.EntityType(e).Basename()
+}
+
 // EntityType returns an EntityTypeRef for the given entity type name.
 func EntityType(name types.EntityType) EntityTypeRef {
 	return EntityTypeRef(name)
@@ -91,6 +106,21 @@ type TypeRef types.Path
 
 func (TypeRef) isType() { _ = 0 }
 
+// IsQualified reports whether the type reference contains a namespace qualifier.
+func (t TypeRef) IsQualified() bool {
+	return types.EntityType(t).IsQualified()
+}
+
+// Namespace returns the namespace portion of a qualified type reference, or "" if unqualified.
+func (t TypeRef) Namespace() types.Namespace {
+	return types.EntityType(t).Namespace()
+}
+
+// Basename returns the unqualified type name.
+func (t TypeRef) Basename() string {
+	return types.EntityType(t).Basename()
+}
+
 // Type returns a TypeRef for the given path.
 func Type(name types.Path) TypeRef {
 	return TypeRef(name)

x/exp/schema/internal/json/json.go

@@ -19,7 +19,7 @@ func (s *Schema) MarshalJSON() ([]byte, error) {
 
 	// Bare declarations go under the empty string key.
 	if hasBareDecls((*ast.Schema)(s)) {
-		ns, err := marshalNamespace("", ast.Namespace{
+		ns, err := marshalNamespace(ast.Namespace{
 			Entities:    s.Entities,
 			Enums:       s.Enums,
 			Actions:     s.Actions,
@@ -32,7 +32,7 @@ func (s *Schema) MarshalJSON() ([]byte, error) {
 	}
 
 	for name, ns := range s.Namespaces {
-		jns, err := marshalNamespace(name, ns)
+		jns, err := marshalNamespace(ns)
 		if err != nil {
 			return nil, err
 		}
@@ -67,7 +67,7 @@ func (s *Schema) UnmarshalJSON(b []byte) error {
 			if result.Namespaces == nil {
 				result.Namespaces = ast.Namespaces{}
 			}
-			result.Namespaces[types.Path(name)] = ns
+			result.Namespaces[types.Namespace(name)] = ns
 		}
 	}
 	*s = Schema(result)
@@ -131,7 +131,7 @@ type jsonAttr struct {
 	Annotations map[string]string `json:"annotations,omitempty"`
 }
 
-func marshalNamespace(name types.Path, ns ast.Namespace) (jsonNamespace, error) {
+func marshalNamespace(ns ast.Namespace) (jsonNamespace, error) {
 	jns := jsonNamespace{
 		EntityTypes: make(map[string]jsonEntityType),
 		Actions:     make(map[string]jsonAction),

x/exp/schema/internal/json/json_internal_test.go

@@ -26,7 +26,7 @@ func TestMarshalRecordTypeError(t *testing.T) {
 }
 
 func TestMarshalNamespaceCommonTypeError(t *testing.T) {
-	_, err := marshalNamespace("", ast.Namespace{
+	_, err := marshalNamespace(ast.Namespace{
 		CommonTypes: ast.CommonTypes{
 			"Bad": ast.CommonType{Type: nil},
 		},
@@ -35,7 +35,7 @@ func TestMarshalNamespaceCommonTypeError(t *testing.T) {
 }
 
 func TestMarshalNamespaceEntityShapeError(t *testing.T) {
-	_, err := marshalNamespace("", ast.Namespace{
+	_, err := marshalNamespace(ast.Namespace{
 		Entities: ast.Entities{
 			"Foo": ast.Entity{
 				Shape: ast.RecordType{
@@ -50,7 +50,7 @@ func TestMarshalNamespaceEntityShapeError(t *testing.T) {
 func TestMarshalNamespaceEntityTagsError(t *testing.T) {
 	// Tags is nil, but the code checks `entity.Tags != nil` first
 	// So we need a non-nil tags that fails. Use SetType{Element: nil}.
-	_, err := marshalNamespace("", ast.Namespace{
+	_, err := marshalNamespace(ast.Namespace{
 		Entities: ast.Entities{
 			"Foo": ast.Entity{Tags: nil},
 		},
@@ -59,7 +59,7 @@ func TestMarshalNamespaceEntityTagsError(t *testing.T) {
 }
 
 func TestMarshalNamespaceEntityTagsError2(t *testing.T) {
-	_, err := marshalNamespace("", ast.Namespace{
+	_, err := marshalNamespace(ast.Namespace{
 		Entities: ast.Entities{
 			"Foo": ast.Entity{Tags: ast.SetType{Element: nil}},
 		},
@@ -68,7 +68,7 @@ func TestMarshalNamespaceEntityTagsError2(t *testing.T) {
 }
 
 func TestMarshalNamespaceActionAnnotations(t *testing.T) {
-	ns, err := marshalNamespace("", ast.Namespace{
+	ns, err := marshalNamespace(ast.Namespace{
 		Actions: ast.Actions{
 			"view": ast.Action{
 				Annotations: ast.Annotations{"doc": "test"},
@@ -80,7 +80,7 @@ func TestMarshalNamespaceActionAnnotations(t *testing.T) {
 }
 
 func TestMarshalNamespaceContextError(t *testing.T) {
-	_, err := marshalNamespace("", ast.Namespace{
+	_, err := marshalNamespace(ast.Namespace{
 		Actions: ast.Actions{
 			"view": ast.Action{
 				AppliesTo: &ast.AppliesTo{

x/exp/schema/internal/parser/parser.go

@@ -141,7 +141,7 @@ func (p *parser) parseSchema() (*ast.Schema, error) {
 }
 
 type parsedNamespace struct {
-	name types.Path
+	name types.Namespace
 	ns   ast.Namespace
 }
 
@@ -150,7 +150,8 @@ func (p *parser) parseNamespace(annotations ast.Annotations) (parsedNamespace, e
 	if err != nil {
 		return parsedNamespace{}, err
 	}
-	if slices.Contains(strings.Split(string(path), "::"), "__cedar") {
+	nsName := types.Namespace(path)
+	if slices.Contains(strings.Split(string(nsName), "::"), "__cedar") {
 		return parsedNamespace{}, fmt.Errorf("%s: the name %q contains \"__cedar\", which is reserved", p.tok.Pos, path)
 	}
 	if err := p.expect(tokenLBrace); err != nil {
@@ -177,7 +178,7 @@ func (p *parser) parseNamespace(annotations ast.Annotations) (parsedNamespace, e
 	ns.Enums = innerSchema.Enums
 	ns.Actions = innerSchema.Actions
 	ns.CommonTypes = innerSchema.CommonTypes
-	return parsedNamespace{name: path, ns: ns}, nil
+	return parsedNamespace{name: nsName, ns: ns}, nil
 }
 
 func (p *parser) parseDecl(annotations ast.Annotations, schema *ast.Schema) error {