Config toggle for duplicate dict key warnings (fixes #56799) (#56805)

changelogs/fragments/56805-duplicate-dict-key-warnings.yml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+  - added config toggle for YAML duplicate dict key warnings

lib/ansible/config/base.yml

@@ -1253,6 +1253,17 @@ DOCSITE_ROOT_URL:
   ini:
   - {key: docsite_root_url, section: defaults}
   version_added: "2.8"
+DUPLICATE_DICT_KEY_WARNINGS:
+  name: Toggle warnings for duplicate dict keys in YAML
+  default: True
+  description:
+    - By default Ansible will issue a warning when a duplicate dict key is encountered in YAML.
+    - These warnings can be silenced by adjusting this setting to False.
+  env: [{name: ANSIBLE_DUPLICATE_DICT_KEY_WARNINGS}]
+  ini:
+  - {key: duplicate_dict_key_warnings, section: defaults}
+  type: boolean
+  version_added: "2.9"
 ERROR_ON_MISSING_HANDLER:
   name: Missing handler error
   default: True

lib/ansible/parsing/yaml/constructor.py

@@ -22,6 +22,7 @@ __metaclass__ = type
 from yaml.constructor import SafeConstructor, ConstructorError
 from yaml.nodes import MappingNode
 
+from ansible import constants as C
 from ansible.module_utils._text import to_bytes
 from ansible.parsing.yaml.objects import AnsibleMapping, AnsibleSequence, AnsibleUnicode
 from ansible.parsing.yaml.objects import AnsibleVaultEncryptedUnicode
@@ -70,8 +71,9 @@ class AnsibleConstructor(SafeConstructor):
                                        "found unacceptable key (%s)" % exc, key_node.start_mark)
 
             if key in mapping:
-                display.warning(u'While constructing a mapping from {1}, line {2}, column {3}, found a duplicate dict key ({0}).'
+                if C.DUPLICATE_DICT_KEY_WARNINGS:
-                                u' Using last defined value only.'.format(key, *mapping.ansible_pos))
+                    display.warning(u'While constructing a mapping from {1}, line {2}, column {3}, found a duplicate dict key ({0}).'
+                                    u' Using last defined value only.'.format(key, *mapping.ansible_pos))
 
             value = self.construct_object(value_node, deep=deep)
             mapping[key] = value