fix(inventory): always use fresh cache on new cached session (#404)

##### SUMMARY

The class scoped `cache` dict was being shared across all
`cached_session`, we now make sure that the cache is instance scoped.

Fixes #403

##### ISSUE TYPE

- Bugfix Pull Request

.ansible-lint

@@ -5,6 +5,7 @@ exclude_paths:
   - .git/
   - .github/
   - changelogs/
+  - examples/
   - tests/integration/targets/certificate
   - tests/integration/targets/firewall
   - tests/integration/targets/floating_ip

changelogs/fragments/fix-inventory-fresh-cache.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - hcloud inventory - Ensure the API client use a new cache for every *cached session*.

examples/use-refresh-inventory.yml

@@ -0,0 +1,35 @@
+---
+- name: Demonstrate the usage of 'refresh_inventory'
+  hosts: localhost
+  connection: local
+
+  tasks:
+    - name: Print hostvars
+      ansible.builtin.debug:
+        var: hostvars
+
+    - name: Create new server
+      hetzner.hcloud.server:
+        name: my-server
+        server_type: cx11
+        image: debian-12
+
+    - name: Refresh inventory
+      ansible.builtin.meta: refresh_inventory
+
+    - name: Run tests
+      block:
+        - name: Print updated inventory
+          ansible.builtin.debug:
+            var: hostvars
+
+        - name: Verify hostvars is not empty
+          ansible.builtin.assert:
+            that:
+              - hostvars != {}
+
+      always:
+        - name: Cleanup server
+          hetzner.hcloud.server:
+            name: my-server
+            state: absent

plugins/module_utils/client.py

@@ -68,7 +68,11 @@ def client_get_by_name_or_id(client: Client, resource: str, param: str | int):
 if HAS_REQUESTS:
 
     class CachedSession(requests.Session):
-        cache: dict[str, requests.Response] = {}
+        cache: dict[str, requests.Response]
+
+        def __init__(self) -> None:
+            super().__init__()
+            self.cache = {}
 
         def send(self, request: requests.PreparedRequest, **kwargs) -> requests.Response:  # type: ignore[no-untyped-def]
             """
@@ -89,7 +93,7 @@ if HAS_REQUESTS:
 
 class Client(ClientBase):
     @contextmanager
-    def cached_session(self) -> None:
+    def cached_session(self):
         """
         Swap the client session during the scope of the context. The session will cache
         all GET requests.
@@ -98,5 +102,7 @@ class Client(ClientBase):
         for long living scopes.
         """
         self._requests_session = CachedSession()
-        yield
-        self._requests_session = requests.Session()
+        try:
+            yield
+        finally:
+            self._requests_session = requests.Session()