Organize backend into product executable and shared Go modules

backend/product/architecture/errors_test.go

@@ -0,0 +1,69 @@
+package architecture
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io/fs"
+	"path/filepath"
+	"strconv"
+	"testing"
+)
+
+// Keep the backend error-model guideline executable, including aliased imports.
+func TestErrorConstructorsUseProjectModel(t *testing.T) {
+	root := filepath.Join("..", "..")
+	err := filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() || filepath.Ext(path) != ".go" {
+			return nil
+		}
+		fset := token.NewFileSet()
+		file, err := parser.ParseFile(fset, path, nil, 0)
+		if err != nil {
+			return err
+		}
+		imports := map[string]string{}
+		for _, imp := range file.Imports {
+			pkg, err := strconv.Unquote(imp.Path.Value)
+			if err != nil {
+				return err
+			}
+			if pkg != "errors" && pkg != "fmt" {
+				continue
+			}
+			alias := pkg
+			if imp.Name != nil {
+				alias = imp.Name.Name
+			}
+			if alias == "." {
+				t.Errorf("%s: dot import obscures error constructors", path)
+			}
+			imports[alias] = pkg
+		}
+		ast.Inspect(file, func(n ast.Node) bool {
+			call, ok := n.(*ast.CallExpr)
+			if !ok {
+				return true
+			}
+			sel, ok := call.Fun.(*ast.SelectorExpr)
+			if !ok {
+				return true
+			}
+			ident, ok := sel.X.(*ast.Ident)
+			if !ok {
+				return true
+			}
+			if (imports[ident.Name] == "errors" && sel.Sel.Name == "New") || (imports[ident.Name] == "fmt" && sel.Sel.Name == "Errorf") {
+				t.Errorf("%s: use backend/shared/errors", fset.Position(call.Pos()))
+			}
+			return true
+		})
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}