Cache items when task.loop/with_items is evaluated to set delegate_to vars (#41969)

* If we evaluate task.loop/with_items when calculating delegate_to vars, cache the items. Fixes #28231

* Add comments about caching loop items

* Add test for delegate_to+loop+random

* Be more careful about where we update task.loop

2 files changed, 60 insertions, 0 deletions

diff --git a/test/integration/targets/delegate_to/runme.sh b/test/integration/targets/delegate_to/runme.sh
index 3d2873ee44..38514c37b8 100755
--- a/test/integration/targets/delegate_to/runme.sh
+++ b/test/integration/targets/delegate_to/runme.sh
@@ -6,3 +6,5 @@ ANSIBLE_SSH_ARGS='-C -o ControlMaster=auto -o ControlPersist=60s -o UserKnownHos
     ANSIBLE_HOST_KEY_CHECKING=false ansible-playbook test_delegate_to.yml -i ../../inventory -v "$@"
 
 ansible-playbook test_loop_control.yml -v "$@"
+
+ansible-playbook test_delegate_to_loop_randomness.yml -v "$@"
diff --git a/test/integration/targets/delegate_to/test_delegate_to_loop_randomness.yml b/test/integration/targets/delegate_to/test_delegate_to_loop_randomness.yml
new file mode 100644
index 0000000000..b43e884a0c
--- /dev/null
+++ b/test/integration/targets/delegate_to/test_delegate_to_loop_randomness.yml
@@ -0,0 +1,58 @@
+---
+- name: Integration tests for #28231
+  hosts: localhost
+  gather_facts: false
+  tasks:
+    - name: Add some test hosts
+      add_host:
+        name: "foo{{item}}"
+        groups: foo
+      loop: "{{ range(10)|list }}"
+
+    # We expect all of the next 3 runs to succeeed
+    # this is done multiple times to increase randomness
+    - assert:
+        that:
+          - item in ansible_delegated_vars
+      delegate_to: "{{ item }}"
+      loop:
+        - "{{ groups.foo|random }}"
+      ignore_errors: true
+      register: result1
+
+    - assert:
+        that:
+          - item in ansible_delegated_vars
+      delegate_to: "{{ item }}"
+      loop:
+        - "{{ groups.foo|random }}"
+      ignore_errors: true
+      register: result2
+
+    - assert:
+        that:
+          - item in ansible_delegated_vars
+      delegate_to: "{{ item }}"
+      loop:
+        - "{{ groups.foo|random }}"
+      ignore_errors: true
+      register: result3
+
+    - debug:
+        var: result1
+
+    - debug:
+        var: result2
+
+    - debug:
+        var: result3
+
+    - name: Ensure all of the 3 asserts were successful
+      assert:
+        that:
+          - results is all
+      vars:
+        results:
+          - "{{ (result1.results|first) is successful }}"
+          - "{{ (result2.results|first) is successful }}"
+          - "{{ (result3.results|first) is successful }}"