[advanced_host_list] 100% coverage + fix a bug (#74227)

Change:
- Tests for advanced_host_list; it is now at 100% coverage.
- There was a typo (host vs hostnames) where when the host pattern
  failed to parse, instead of treating the name as a literal as
  intended, it would trigger UnboundLocalError. This didn't fatal
  as there's a global "Exception" handler below, but it did lead to
  an ugly error and incorrect behavior.

Test Plan:
- New tests
- Local experimenting

Signed-off-by: Rick Elrod <rick@elrod.me>

* changelog

Signed-off-by: Rick Elrod <rick@elrod.me>

* fix tests

Signed-off-by: Rick Elrod <rick@elrod.me>

changelogs/fragments/advanced-host-list-ref-before-assignment.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - advanced_host_list inventory plugin - Fixed variable referenced before assignment when hostname/range could not be parsed.

lib/ansible/plugins/inventory/advanced_host_list.py

@@ -53,7 +53,7 @@ class InventoryModule(BaseInventoryPlugin):
                         (hostnames, port) = self._expand_hostpattern(h)
                     except AnsibleError as e:
                         self.display.vvv("Unable to parse address from hostname, leaving unchanged: %s" % to_text(e))
-                        host = [h]
+                        hostnames = [h]
                         port = None
 
                     for host in hostnames:

test/integration/targets/inventory_advanced_host_list/aliases

@@ -0,0 +1 @@
+shippable/posix/group1

test/integration/targets/inventory_advanced_host_list/runme.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+set -eux
+
+export ANSIBLE_INVENTORY_ENABLED=advanced_host_list
+
+# A few things to make it easier to grep against adhoc
+export ANSIBLE_LOAD_CALLBACK_PLUGINS=True
+export ANSIBLE_STDOUT_CALLBACK=oneline
+
+adhoc="$(ansible -i 'local[0:10],' -m ping --connection=local -e ansible_python_interpreter="{{ ansible_playbook_python }}" all -v)"
+
+for i in $(seq 0 10); do
+    grep -qE "local${i} \| SUCCESS.*\"ping\": \"pong\"" <<< "$adhoc"
+done
+
+set +e
+parse_fail="$(ansible -i 'local[1:j],' -m ping --connection=local all -v 2>&1)"
+set -e
+
+grep -q "Failed to parse local\[1:j\], with advanced_host_list" <<< "$parse_fail"
+
+# Intentionally missing comma, ensure we don't fatal.
+no_comma="$(ansible -i 'local[1:5]' -m ping --connection=local all -v 2>&1)"
+grep -q "No inventory was parsed" <<< "$no_comma"
+
+# Intentionally botched range (missing end number), ensure we don't fatal.
+no_end="$(ansible -i 'local[1:],' -m ping --connection=local -e ansible_python_interpreter="{{ ansible_playbook_python }}" all -vvv 2>&1)"
+grep -q "Unable to parse address from hostname, leaving unchanged:" <<< "$no_end"
+grep -q "host range must specify end value" <<< "$no_end"
+grep -q "local\[3:\] \| SUCCESS" <<< "$no_end"
+
+# Unset adhoc stuff
+unset ANSIBLE_LOAD_CALLBACK_PLUGINS ANSIBLE_STDOUT_CALLBACK
+
+ansible-playbook -i 'local100,local[100:110:2]' test_advanced_host_list.yml -v "$@"

test/integration/targets/inventory_advanced_host_list/test_advanced_host_list.yml

@@ -0,0 +1,9 @@
+- hosts: all
+  connection: local
+  vars:
+    ansible_python_interpreter: "{{ ansible_playbook_python }}"
+  tasks:
+    - assert:
+        that:
+          - inventory_hostname in ["local100", "local102", "local104", "local106", "local108", "local110", "local118"]
+          - inventory_hostname not in ["local101", "local103", "local105", "local107", "local109", "local111"]