WIP: Add schema and from_file classmethod

data_safe_haven/config/backend_settings.py

@@ -5,6 +5,7 @@
 
 import appdirs
 import yaml
+from schema import Schema, SchemaError
 from yaml.parser import ParserError
 
 from data_safe_haven.exceptions import (
@@ -14,6 +15,12 @@
 from data_safe_haven.utility import LoggingSingleton
 
 
+config_directory = pathlib.Path(
+    appdirs.user_config_dir(appname="data_safe_haven")
+).resolve()
+config_file_path = config_directory / "config.yaml"
+
+
 @dataclass
 class Context:
     admin_group_id: str
@@ -35,34 +42,31 @@ class ContextSettings:
         ...
     """
 
-    def __init__(self) -> None:
+    def __init__(self, settings_dict: dict[Any, Any]) -> None:
         self.logger = LoggingSingleton()
 
-        self._settings: dict[Any, Any] | None = None
-
-        config_directory = pathlib.Path(
-            appdirs.user_config_dir(appname="data_safe_haven")
-        ).resolve()
-        self.config_file_path = config_directory / "config.yaml"
+        context_schema = Schema({
+            "name": str,
+            "admin_group_id": str,
+            "location": str,
+            "subscription_name": str,
+        })
+
+        schema = Schema({
+            "selected": str,
+            "contexts": Schema({
+                str: context_schema,
+            }),
+        })
+
+        try:
+            self._settings: schema.validate(settings_dict)
+        except SchemaError as exc:
+            msg = f"Invalid context configuration file.\n{exc}"
+            raise DataSafeHavenParameterError(msg)
 
     @property
     def settings(self) -> dict[Any, Any]:
-        if not self._settings:
-            try:
-                with open(self.config_file_path, encoding="utf-8") as f_yaml:
-                    settings = yaml.safe_load(f_yaml)
-                if isinstance(settings, dict):
-                    self.logger.info(
-                        f"Reading project settings from '[green]{self.config_file_path}[/]'."
-                    )
-                    self._settings = settings
-                    self._context = Context(**settings.get("contexts").get(self._selected))
-            except FileNotFoundError as exc:
-                msg = f"Could not find file {self.config_file_path}.\n{exc}"
-                raise DataSafeHavenConfigError(msg) from exc
-            except ParserError as exc:
-                msg = f"Could not load settings from {self.config_file_path}.\n{exc}"
-                raise DataSafeHavenConfigError(msg) from exc
 
         return self._settings
 
@@ -128,3 +132,21 @@ def write(self) -> None:
         self.logger.info(
             f"Saved context settings to '[green]{self.config_file_path}[/]'."
         )
+
+    @classmethod
+    def from_file(cls) -> None:
+        logger = LoggingSingleton()
+        try:
+            with open(config_file_path, encoding="utf-8") as f_yaml:
+                settings = yaml.safe_load(f_yaml)
+            if isinstance(settings, dict):
+                logger.info(
+                    f"Reading project settings from '[green]{config_file_path}[/]'."
+                )
+                return cls(settings)
+        except FileNotFoundError as exc:
+            msg = f"Could not find file {config_file_path}.\n{exc}"
+            raise DataSafeHavenConfigError(msg) from exc
+        except ParserError as exc:
+            msg = f"Could not load settings from {config_file_path}.\n{exc}"
+            raise DataSafeHavenConfigError(msg) from exc

pyproject.toml

@@ -44,6 +44,7 @@ dependencies = [
   "pytz~=2022.7.0",
   "PyYAML~=6.0",
   "rich~=13.4.2",
+  "schema~=0.7.0",
   "simple-acme-dns~=1.2.0",
   "typer~=0.9.0",
   "websocket-client~=1.5.0",