[2.13] don't ignore templated _raw_params that k=v parser failed to parse (#79913) (#79965)

* don't ignore templated _raw_params that k=v parser failed to parse (#79913)

fixes #79862

* backport test changes

changelogs/fragments/79862-fix-varargs.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- TaskExecutor - don't ignore templated _raw_params that k=v parser failed to parse (https://github.com/ansible/ansible/issues/79862)

lib/ansible/executor/task_executor.py

@@ -534,6 +534,10 @@ class TaskExecutor:
                                     "(see https://docs.ansible.com/ansible/devel/reference_appendices/faq.html#argsplat-unsafe)")
                 variable_params.update(self._task.args)
                 self._task.args = variable_params
+            else:
+                # if we didn't get a dict, it means there's garbage remaining after k=v parsing, just give up
+                # see https://github.com/ansible/ansible/issues/79862
+                raise AnsibleError(f"invalid or malformed argument: '{variable_params}'")
 
         # update no_log to task value, now that we have it templated
         no_log = self._task.no_log

test/integration/targets/tasks/playbook.yml

@@ -0,0 +1,19 @@
+- hosts: localhost
+  gather_facts: false
+  tasks:
+    # make sure tasks with an undefined variable in the name are gracefully handled
+    - name: "Task name with undefined variable: {{ not_defined }}"
+      debug:
+        msg: Hello
+
+    - name: ensure malformed raw_params on arbitrary actions are not ignored
+      debug:
+        garbage {{"with a template"}}
+      ignore_errors: true
+      register: bad_templated_raw_param
+
+    - assert:
+        that:
+        - bad_templated_raw_param is failed
+        - |
+          "invalid or malformed argument: 'garbage with a template'" in bad_templated_raw_param.msg

test/integration/targets/tasks/runme.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+ansible-playbook playbook.yml "$@"
+

test/integration/targets/tasks/tasks/main.yml

@@ -1,4 +0,0 @@
-# make sure tasks with an undefined variable in the name are gracefully handled
-- name: "Task name with undefined variable: {{ not_defined }}"
-  debug:
-    msg: Hello