Add traverser.AccessSchema to access the Terraform schema elements

Signed-off-by: Alper Rifat Ulucinar <[email protected]>

pkg/schema/traverser/access.go

@@ -0,0 +1,58 @@
+// SPDX-FileCopyrightText: 2024 The Crossplane Authors <https://crossplane.io>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package traverser
+
+import (
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+	"github.com/pkg/errors"
+)
+
+// SchemaAccessor is a function that accesses and potentially modifies a
+// Terraform schema.
+type SchemaAccessor func(*schema.Schema) error
+
+// AccessSchema accesses the schema element at the specified path and calls
+// the given schema accessors in order. Reports any errors encountered by
+// the accessors. The terminal node at the end of the specified path must be
+// a *schema.Resource or an error will be reported. The specified path must
+// have at least one component.
+func AccessSchema(sch any, path []string, accessors ...SchemaAccessor) error {
+	if len(path) == 0 {
+		return errors.New("empty path specified while accessing the Terraform resource schema")
+	}
+	k := path[0]
+	path = path[1:]
+	switch s := sch.(type) {
+	case *schema.Schema:
+		if len(path) == 0 {
+			return errors.Errorf("terminal node at key %q is a *schema.Schema", k)
+		}
+		if k != wildcard {
+			return errors.Errorf("expecting a wildcard key but encountered the key %q", k)
+		}
+		if err := AccessSchema(s.Elem, path, accessors...); err != nil {
+			return err
+		}
+	case *schema.Resource:
+		c := s.Schema[k]
+		if c == nil {
+			return errors.Errorf("schema element for key %q is nil", k)
+		}
+		if len(path) == 0 {
+			for _, a := range accessors {
+				if err := a(c); err != nil {
+					return errors.Wrapf(err, "failed to call the accessor function on the schema element at key %q", k)
+				}
+			}
+			return nil
+		}
+		if err := AccessSchema(c, path, accessors...); err != nil {
+			return err
+		}
+	default:
+		return errors.Errorf("unknown schema element type %T at key %q", s, k)
+	}
+	return nil
+}