fix: get_agent_card tailing slash when agent_card_path="" (#799) (#800)

Made a minor change to A2ACardResolver.get_agent_card() so it doesn't
introduce an spurious trailing slash when agent_card_path is empty. This
allows one to get the card from a card URL without having to break it
into a base and relative card path component, it's arguably a bit odd
but the empty agent_card_path is technically allowed and the result of
that isn't right so I think it's a reasonable improvement, and one that
as far as I can see can't reasonably be not backwards compatible for
anyone.

I changed one existing test, but only in a fashion such that it still
tests the thing that it says it is testing... It is fine IF I understood
the point of the test...

# Description

Thank you for opening a Pull Request!
Before submitting your PR, there are a few things you can do to make
sure it goes smoothly:

- [X] Follow the [`CONTRIBUTING`
Guide](https://github.com/a2aproject/a2a-python/blob/main/CONTRIBUTING.md).
- [X] Make your Pull Request title in the
<https://www.conventionalcommits.org/> specification.
- Important Prefixes for
[release-please](https://github.com/googleapis/release-please):
- `fix:` which represents bug fixes, and correlates to a
[SemVer](https://semver.org/) patch.
- `feat:` represents a new feature, and correlates to a SemVer minor.
- `feat!:`, or `fix!:`, `refactor!:`, etc., which represent a breaking
change (indicated by the `!`) and will result in a SemVer major.
- [X] Ensure the tests and linter pass (Run `bash scripts/format.sh`
from the repository root to format)
- [X] Appropriate docs were updated (if necessary)

Fixes #799

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Iva Sokolaj <102302011+sokoliva@users.noreply.github.com>

Author: 3 people

src/a2a/client/card_resolver.py

@@ -72,7 +72,9 @@ async def get_agent_card(
         else:
             path_segment = relative_card_path.lstrip('/')
 
-        target_url = f'{self.base_url}/{path_segment}'
+        target_url = (
+            f'{self.base_url}/{path_segment}' if path_segment else self.base_url
+        )
 
         try:
             response = await self.httpx_client.get(

tests/client/test_card_resolver.py

@@ -203,7 +203,23 @@ async def test_get_agent_card_root_path(
         mock_response.json.return_value = valid_agent_card_data
         mock_httpx_client.get.return_value = mock_response
         await resolver.get_agent_card(relative_card_path='/')
-        mock_httpx_client.get.assert_called_once_with(f'{base_url}/')
+        mock_httpx_client.get.assert_called_once_with(f'{base_url}')
+
+    @pytest.mark.asyncio
+    async def test_get_agent_card_with_empty_resolver_agent_card_path(
+        self,
+        base_url,
+        resolver,
+        mock_httpx_client,
+        mock_response,
+        valid_agent_card_data,
+    ):
+        """Test fetching agent card when the resolver's agent_card_path is empty."""
+        resolver.agent_card_path = ''
+        mock_response.json.return_value = valid_agent_card_data
+        mock_httpx_client.get.return_value = mock_response
+        await resolver.get_agent_card()
+        mock_httpx_client.get.assert_called_once_with(f'{base_url}')
 
     @pytest.mark.asyncio
     async def test_get_agent_card_http_status_error(