feat: add .Imports() method to schema.Module (#573)

This will initially be used by templates to generate import statements.

backend/schema/schema.go

@@ -9,6 +9,7 @@ import (
 	"github.com/alecthomas/errors"
 	"github.com/alecthomas/participle/v2"
 	"github.com/alecthomas/participle/v2/lexer"
+	"golang.org/x/exp/maps"
 	"google.golang.org/protobuf/proto"
 )
 
@@ -230,6 +231,28 @@ func (m *Module) Data() []*Data {
 	return data
 }
 
+// Imports returns the modules imported by this module.
+func (m *Module) Imports() []string {
+	imports := map[string]bool{}
+	_ = Visit(m, func(n Node, next func() error) error {
+		switch n := n.(type) {
+		case *DataRef:
+			if n.Module != "" && n.Module != m.Name {
+				imports[n.Module] = true
+			}
+
+		case *VerbRef:
+			if n.Module != "" && n.Module != m.Name {
+				imports[n.Module] = true
+			}
+
+		default:
+		}
+		return nil
+	})
+	return maps.Keys(imports)
+}
+
 type Schema struct {
 	Pos Position `json:"pos,omitempty" parser:"" protobuf:"1,optional"`
 

backend/schema/validate.go

@@ -89,6 +89,14 @@ func ValidateModule(module *Module) error {
 	}
 	err := Visit(module, func(n Node, next func() error) error {
 		switch n := n.(type) {
+		case *VerbRef:
+			if n.Name == module.Name {
+				merr = append(merr, errors.Errorf("%s: references to Verbs in the same module cannot include a module name", n.Pos))
+			}
+		case *DataRef:
+			if n.Name == module.Name {
+				merr = append(merr, errors.Errorf("%s: references to Data in the same module cannot include a module name", n.Pos))
+			}
 		case *Verb:
 			if !validNameRe.MatchString(n.Name) {
 				merr = append(merr, errors.Errorf("%s: Verb name %q is invalid", n.Pos, n.Name))
@@ -117,8 +125,8 @@ func ValidateModule(module *Module) error {
 				}
 			}
 
-		case *Array, *Bool, *DataRef, *Field, *Float, *Int,
-			*Time, *Map, *Module, *Schema, *String, *VerbRef,
+		case *Array, *Bool, *Field, *Float, *Int,
+			*Time, *Map, *Module, *Schema, *String,
 			*MetadataCalls, *MetadataIngress:
 		case Type, Metadata, Decl: // Union sql.
 		}