Fix stdio transport not reading the full response (#12)

* Read stdout until newline for stdio transport

Update the stdio transport to read a response from stdout until a newline
or until timing out while waiting for readable data. Notably, this fixes
an issue where the plugin fails when a response is more than 4096 bytes.

* Add ansible-core to tox.ini mypy deps

Rather than relying on ansible-core being installed outside the tox
environment, install it explicitly since it's being used by tox.

Author: gravesm

plugins/plugin_utils/transport.py

@@ -123,18 +123,21 @@ def _stdout_read(self, wait_timeout: int = 5) -> dict:
         """
 
         response = {}
+        buffer = b""
         if self._process:
-            rfd, wfd, efd = select.select([self._process.stdout], [], [], wait_timeout)
-            if not (rfd or wfd or efd):
-                # Process has timeout
-                raise AnsibleConnectionFailure(
-                    f"MCP server response timeout after {wait_timeout} seconds."
-                )
-
-            if self._process.stdout in rfd:
-                response = json.loads(
-                    os.read(self._process.stdout.fileno(), 4096).decode("utf-8").strip()
-                )
+            while True:
+                rfd, wfd, efd = select.select([self._process.stdout], [], [], wait_timeout)
+                if self._process.stdout in rfd:
+                    buffer += os.read(self._process.stdout.fileno(), 4096)
+                    if b"\n" in buffer:
+                        line, buffer = buffer.split(b"\n", 1)
+                        response = json.loads(line.decode("utf-8"))
+                        break
+                else:
+                    # Process has timeout
+                    raise AnsibleConnectionFailure(
+                        f"MCP server response timeout after {wait_timeout} seconds."
+                    )
         return response
 
     def _stdin_write(self, data: dict) -> None:

tox.ini

@@ -7,7 +7,7 @@ deps =
     black
     flake8
     isort
-    mypy
+    {[testenv:mypy]deps}
 skip_install = true
 allowlist_externals =
     {[testenv:mypy]allowlist_externals}
@@ -22,13 +22,14 @@ setenv =
     {[testenv:mypy]setenv}
 
 [testenv:mypy]
-deps = mypy
+deps =
+    mypy
+    ansible-core
 skip_install = true
 allowlist_externals =
     mkdir
     ln
     rm
-    ansible-galaxy
 commands =
     rm -rf {toxinidir}/.collection_root
     ansible-galaxy collection install git+https://github.com/ansible-collections/ansible.utils.git --collections-path {toxinidir}/.collection_root