Remove _load_hosts() from Play initialization as it's no longer needed and it breaks using extra_vars defining a list for hosts (#17699)

Thanks to @jimi-c for the solution

Fixes #16583

test/integration/Makefile

@@ -27,7 +27,7 @@ UNAME := $(shell uname | tr '[:upper:]' '[:lower:]')
 
 all: setup other non_destructive destructive
 
-other: test_test_infra parsing test_var_precedence unicode test_templating_settings environment test_connection test_async_conditional includes blocks pull check_mode test_hash test_handlers test_group_by test_vault test_tags test_lookup_paths no_log test_gathering_facts test_binary_modules
+other: test_test_infra parsing test_var_precedence unicode test_templating_settings environment test_connection test_async_conditional includes blocks pull check_mode test_hash test_handlers test_group_by test_vault test_tags test_lookup_paths no_log test_gathering_facts test_binary_modules test_hosts_field
 
 test_test_infra:
 	# ensure fail/assert work locally and can stop execution with non-zero exit code
@@ -354,3 +354,32 @@ test_async:
 	# Verify that the warning exists by examining debug output.
 	ANSIBLE_DEBUG=1 LC_ALL=bogus ansible-playbook test_async.yml -i localhost, -e ansible_connection=ssh -v $(TEST_FLAGS) \
 	| grep 'bash: warning: setlocale: LC_ALL: cannot change locale (bogus)' > /dev/null
+
+test_hosts_field:
+	# Hosts in playbook has a list of strings consisting solely of digits
+	ansible-playbook test_hosts_field.yml -i inventory.hosts_field -e'target_kv=42' -e'{ "target_json_cli": "42", "target_json_cli_list": ["42", "localhost"] }' -e "@test_hosts_field.json" -t string_digit_host_in_list -v $(TEST_FLAGS) | tee test_hosts_field.out
+	grep 'Running on 42' test_hosts_field.out 2>&1
+	test `grep -c 'ok=1' test_hosts_field.out` = 1
+	# Hosts taken from kv extra_var on the CLI
+	ansible-playbook test_hosts_field.yml -i inventory.hosts_field -e'target_kv=42' -e'{ "target_json_cli": "42", "target_json_cli_list": ["42", "localhost"] }' -e "@test_hosts_field.json" -t hosts_from_kv_string -v $(TEST_FLAGS) | tee test_hosts_field.out
+	grep 'Running on 42' test_hosts_field.out 2>&1
+	test `grep -c 'ok=1' test_hosts_field.out` = 1
+	# hosts is taken from an all digit json extra_vars string on the CLI
+	ansible-playbook test_hosts_field.yml -i inventory.hosts_field -e'target_kv=42' -e'{ "target_json_cli": "42", "target_json_cli_list": ["42", "localhost"] }' -e "@test_hosts_field.json" -t hosts_from_cli_json_string -v $(TEST_FLAGS) | tee test_hosts_field.out
+	grep 'Running on 42' test_hosts_field.out 2>&1
+	test `grep -c 'ok=1' test_hosts_field.out` = 1
+	# hosts is taken from a json list in extra_vars on the CLI
+	ansible-playbook test_hosts_field.yml -i inventory.hosts_field -e'target_kv=42' -e'{ "target_json_cli": "42", "target_json_cli_list": ["42", "localhost"] }' -e "@test_hosts_field.json" -t hosts_from_cli_json_list -v $(TEST_FLAGS) | tee test_hosts_field.out
+	grep 'Running on 42' test_hosts_field.out 2>&1
+	grep 'Running on localhost' test_hosts_field.out 2>&1
+	test `grep -c 'ok=1' test_hosts_field.out` = 2
+	# hosts is taken from a json string in an extra_vars file
+	ansible-playbook test_hosts_field.yml -i inventory.hosts_field -e'target_kv=42' -e'{ "target_json_cli": "42", "target_json_cli_list": ["42", "localhost"] }' -e "@test_hosts_field.json" -t hosts_from_json_file_string -v $(TEST_FLAGS) | tee test_hosts_field.out
+	grep 'Running on 42' test_hosts_field.out 2>&1
+	test `grep -c 'ok=1' test_hosts_field.out` = 1
+	# hosts is taken from a json list in an extra_vars file
+	ansible-playbook test_hosts_field.yml -i inventory.hosts_field -e'target_kv=42' -e'{ "target_json_cli": "42", "target_json_cli_list": ["42", "localhost"] }' -e "@test_hosts_field.json" -t hosts_from_json_file_list -v $(TEST_FLAGS) | tee test_hosts_field.out
+	grep 'Running on 42' test_hosts_field.out 2>&1
+	grep 'Running on localhost' test_hosts_field.out 2>&1
+	test `grep -c 'ok=1' test_hosts_field.out` = 2
+	rm test_hosts_field.out

test/integration/inventory.hosts_field

@@ -0,0 +1,2 @@
+42 ansible_host=127.0.0.42 ansible_connection=local
+

test/integration/test_hosts_field.json

@@ -0,0 +1 @@
+{ "target_json_file": "42", "target_json_file_list": ["42", "localhost"] }

test/integration/test_hosts_field.yml

@@ -0,0 +1,62 @@
+---
+#- name: Host in playbook is an integer
+#  hosts: 42
+#  tags: numeric_host
+#  tasks:
+#    - command: echo 'Running on {{ inventory_hostname }}'
+
+#- name: Host in playbook is a string of digits
+#  hosts: "42"
+#  tags: string_digit_host
+#  tasks:
+#    - command: echo 'Running on {{ inventory_hostname }}'
+
+#- name: Host in playbook is a list of integer
+#  hosts:
+#    - 42
+#  tags: numeric_host_in_list
+#  tasks:
+#    - command: echo 'Running on {{ inventory_hostname }}'
+
+- name: Host in playbook is a list of strings of digits
+  hosts:
+    - "42"
+  gather_facts: False
+  tags: string_digit_host_in_list
+  tasks:
+    - command: echo 'Running on {{ inventory_hostname }}'
+
+- name: Hosts taken from kv extra_var on the CLI
+  hosts: "{{ target_kv }}"
+  gather_facts: False
+  tags: hosts_from_kv_string
+  tasks:
+    - command: echo 'Running on {{ inventory_hostname }}'
+
+- name: Hosts taken from a json string on the CLI
+  hosts: "{{ target_json_cli }}"
+  gather_facts: False
+  tags: hosts_from_cli_json_string
+  tasks:
+    - command: echo 'Running on {{ inventory_hostname }}'
+
+- name: Hosts taken from a json list on the CLI
+  hosts: "{{ target_json_cli_list }}"
+  gather_facts: False
+  tags: hosts_from_cli_json_list
+  tasks:
+    - command: echo 'Running on {{ inventory_hostname }}'
+
+- name: Hosts is taken from a json string in an extra_vars file
+  hosts: "{{ target_json_file }}"
+  gather_facts: False
+  tags: hosts_from_json_file_string
+  tasks:
+    - command: echo 'Running on {{ inventory_hostname }}'
+
+- name: Hosts is taken from a json list in an extra_vars file
+  hosts: "{{ target_json_file_list }}"
+  gather_facts: False
+  tags: hosts_from_json_file_list
+  tasks:
+    - command: echo 'Running on {{ inventory_hostname }}'