Updated environment variable handling notes

README.md

@@ -501,6 +501,40 @@ env=prod make change-env
 
 This would copy `.env.prod` to `.env`. By default, running the command without specifying an environment will use the `.env.default` file. In this way, an infinite number of environments could be created and easily switched between.
 
+> [!IMPORTANT]
+> This method of managing environment variables has known security issues. In later projects, this method has been retired in favor of passing in the environment variables directly to Flutter.
+> It is recommended to migrate any existing `dot_env` usage to this newer system. 
+
+Nowadays, environment variables are managed by passing the `.env` file into the Flutter/Dart command directly using `--dart-define-from-file=.env`. This requires a couple of changes, both in how the application is launched and how the environment variables are configured in the code.
+
+If you're using Visual Studio Code, you can simply edit your `launch.json` and include these lines:
+
+```json
+"toolArgs": [
+  "--dart-define-from-file=.env"
+]
+```
+
+Migrating the code allows you to _remove_ code, which is always nice. The `AppEnv` class can be removed, as it is no longer necessary. Now, your `EnvVar` enum can point directly to the environment varibles:
+
+```dart
+enum EnvVar {
+  /// The environment to use for the API calls. Returns either [sandbox] or [prod].
+  ///
+  /// Example `.env` configuration:
+  /// ```
+  /// API_ENVIRONMENT="sandbox"
+  /// ```
+  apiEnvironment(String.fromEnvironment("API_ENVIRONMENT")), // Note the direct reference to the environment variable
+  ;
+
+  /// The environment variable to use when retrieving the value of this [EnvVar].
+  final String value;
+
+  const EnvVar(this.value);
+}
+```
+
 #### Accessing Secrets
 
 Accessing the secrets defined in the environment variables can be done via the `AppEnv`, provided they have been mapped to a corresponding `EnvVar` enum item: