Improve JSON parsing error handling. (#1221)

changelogs/fragments/1221-cli-json-errors.yml

@@ -0,0 +1,3 @@
+bugfixes:
+  - "CLI-based modules - when parsing JSON output fails, also provide standard error output. Also provide information on the command and its result in machine-readable way
+     (https://github.com/ansible-collections/community.docker/issues/1216, https://github.com/ansible-collections/community.docker/pull/1221)."

plugins/module_utils/_common_cli.py

@@ -197,7 +197,11 @@ class AnsibleDockerClientBase:
             data = json.loads(stdout)
         except Exception as exc:  # pylint: disable=broad-exception-caught
             self.fail(
-                f"Error while parsing JSON output of {self._compose_cmd_str(args)}: {exc}\nJSON output: {to_text(stdout)}"
+                f"Error while parsing JSON output of {self._compose_cmd_str(args)}: {exc}\nJSON output: {to_text(stdout)}\n\nError output:\n{to_text(stderr)}",
+                cmd=self._compose_cmd_str(args),
+                rc=rc,
+                stdout=stdout,
+                stderr=stderr,
             )
         return rc, data, stderr
 
@@ -223,7 +227,11 @@ class AnsibleDockerClientBase:
                     result.append(json.loads(line))
         except Exception as exc:  # pylint: disable=broad-exception-caught
             self.fail(
-                f"Error while parsing JSON output of {self._compose_cmd_str(args)}: {exc}\nJSON output: {to_text(stdout)}"
+                f"Error while parsing JSON output of {self._compose_cmd_str(args)}: {exc}\nJSON output: {to_text(stdout)}\n\nError output:\n{to_text(stderr)}",
+                cmd=self._compose_cmd_str(args),
+                rc=rc,
+                stdout=stdout,
+                stderr=stderr,
             )
         return rc, result, stderr