Merge pull request #943 from cderici/nested-assumes-on-3x

#943

#### Description

This forward ports the fix for nested assume expressions from #940 into the master branch.

Fixes #938 for `3.x`.

#### QA Steps

Same QA steps can be followed from #940, so copy/pasting the manual QA steps below:

----- 

Unfortunately it's not trivial to write an integration test for this, as the code that's been changed is part of the facade api. So we'll use the `mysql-k8s` charm that's been used in #938.

```
 $ juju version
3.x
 $ juju bootstrap microk8s micro28
 $ juju add-model assumes-test
```

```python
 $ python -m asyncio
asyncio REPL 3.10.12 (main, Jun 11 2023, 05:26:28) [GCC 11.4.0] on linux
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> from juju import model;m=model.Model();await m.connect();await m.deploy("mysql-k8s", channel="8.0/edge", trust=True)
<Application entity_id="mysql-k8s">
>>>
exiting asyncio REPL...
```

#### Notes & Discussion

JUJU-4562

juju/client/facade.py

@@ -661,6 +661,26 @@ async def rpc(self, msg):
 
     @classmethod
     def from_json(cls, data):
+        def _parse_nested_list_entry(expr, result_dict):
+            if isinstance(expr, str):
+                if '>' in expr or '>=' in expr:
+                    # something like juju >= 2.9.31
+                    i = expr.index('>')
+                    _key = expr[:i].strip()
+                    _value = expr[i:].strip()
+                    result_dict[_key] = _value
+                else:
+                    # this is a simple entry
+                    result_dict[expr] = ''
+            elif isinstance(expr, dict):
+                for _, v in expr.items():
+                    _parse_nested_list_entry(v, result_dict)
+            elif isinstance(expr, list):
+                for v in expr:
+                    _parse_nested_list_entry(v, result_dict)
+            else:
+                raise TypeError(f"Unexpected type of entry in assumes expression: {expr}")
+
         if isinstance(data, cls):
             return data
         if isinstance(data, str):
@@ -680,16 +700,7 @@ def from_json(cls, data):
             # check: https://juju.is/docs/sdk/assumes
             # assumes are in the form of a list
             d = {}
-            for entry in data:
-                if '>' in entry or '>=' in entry:
-                    # something like juju >= 2.9.31
-                    i = entry.index('>')
-                    key = entry[:i].strip()
-                    value = entry[i:].strip()
-                    d[key] = value
-                else:
-                    # this is a simple entry
-                    d[entry] = ''
+            _parse_nested_list_entry(data, d)
             return cls(**d)
         return None
 

juju/utils.py

@@ -546,12 +546,13 @@ def should_upgrade_resource(available_resource, existing_resources):
     """
     # should upgrade resource?
     res_name = available_resource.get('Name', available_resource.get('name'))
-    # no, if it's upload
-    if existing_resources[res_name].origin == 'upload':
-        return False
 
-    # no, if we already have it (and upstream doesn't have a newer res available)
+    # do we have it already?
     if res_name in existing_resources:
+        # no upgrade, if it's upload
+        if existing_resources[res_name].origin == 'upload':
+            return False
+        # no upgrade, if upstream doesn't have a newer revision of the resource available
         available_rev = available_resource.get('Revision', available_resource.get('revision', -1))
         u_fields = existing_resources[res_name].unknown_fields
         existing_rev = u_fields.get('Revision', u_fields.get('revision', -1))