feat: support type aliases and redefinitions (#721)

Author: mattjohnsonpint

CHANGELOG.md

@@ -11,6 +11,8 @@
 - fix: remove fallback to default time zone [#706](https://github.com/hypermodeinc/modus/pull/706)
 - feat: improve OpenAI model APIs and examples to better support audio, images, and tool calling
   [#707](https://github.com/hypermodeinc/modus/pull/707)
+- feat: support type aliases and redefinitions
+  [#721](https://github.com/hypermodeinc/modus/pull/721)
 
 ## 2025-01-09 - CLI 0.16.6
 

sdk/go/tools/modus-go-build/extractor/extractor.go

@@ -10,6 +10,7 @@
 package extractor
 
 import (
+	"fmt"
 	"go/types"
 	"sort"
 
@@ -49,8 +50,27 @@ func CollectProgramInfo(config *config.Config, meta *metadata.Metadata) error {
 	sort.Strings(keys)
 	for _, name := range keys {
 		t := requiredTypes[name]
+
+		// resolve type aliases
+		for {
+			if a, ok := t.(*types.Alias); ok {
+				t = a.Rhs()
+			} else {
+				break
+			}
+		}
+
+		resolvedName := name
+		if n, ok := t.(*types.Named); ok {
+			resolvedName = n.String()
+			t = n.Underlying()
+		}
+
 		if s, ok := t.(*types.Struct); ok && !wellKnownTypes[name] {
-			t := transformStruct(name, s, pkgs)
+			t := transformStruct(resolvedName, s, pkgs)
+			if t == nil {
+				return fmt.Errorf("failed to transform struct %s", resolvedName)
+			}
 			t.Id = id
 			meta.Types[name] = t
 		} else {

sdk/go/tools/modus-go-build/extractor/functions.go

@@ -227,6 +227,11 @@ func addRequiredTypes(t types.Type, m map[string]types.Type) bool {
 			m[name] = t
 			return true
 		}
+	case *types.Alias:
+		if addRequiredTypes(t.Rhs(), m) {
+			m[name] = t
+			return true
+		}
 	case *types.Struct:
 		// TODO: handle unnamed structs
 	case *types.Slice:

sdk/go/tools/modus-go-build/extractor/transform.go

@@ -109,6 +109,17 @@ func getStructDeclarationAndType(name string, pkgs map[string]*packages.Package)
 						if typeSpec.Name.Name == objName {
 							if structType, ok := typeSpec.Type.(*ast.StructType); ok {
 								return genDecl, structType
+							} else if ident, ok := typeSpec.Type.(*ast.Ident); ok {
+								typePath := pkgName + "." + ident.Name
+								return getStructDeclarationAndType(typePath, pkgs)
+							} else if selExp, ok := typeSpec.Type.(*ast.SelectorExpr); ok {
+								if pkgIdent, ok := selExp.X.(*ast.Ident); !ok {
+									return nil, nil
+								} else {
+									pkgPath := getFullImportPath(file, pkgIdent.Name)
+									typePath := pkgPath + "." + selExp.Sel.Name
+									return getStructDeclarationAndType(typePath, pkgs)
+								}
 							}
 						}
 					}
@@ -120,6 +131,24 @@ func getStructDeclarationAndType(name string, pkgs map[string]*packages.Package)
 	return nil, nil
 }
 
+func getFullImportPath(file *ast.File, pkgName string) string {
+	for _, imp := range file.Imports {
+		path := strings.Trim(imp.Path.Value, `"`)
+		if imp.Name == nil {
+			parts := strings.Split(path, "/")
+			if len(parts) == 0 {
+				return ""
+			}
+			if parts[len(parts)-1] == pkgName {
+				return path
+			}
+		} else if imp.Name.Name == pkgName {
+			return path
+		}
+	}
+	return ""
+}
+
 func getDocs(comments *ast.CommentGroup) *metadata.Docs {
 	if comments == nil {
 		return nil