From dae737c8b714f2c6d28663ef0afeab10e6d3a667 Mon Sep 17 00:00:00 2001
From: Andrew Gaffney <andrew@agaffney.org>
Date: Thu, 8 Feb 2018 10:17:28 -0700
Subject: [PATCH] Only template each hostvars var on-demand (fixes #33259)

---
 lib/ansible/parsing/yaml/dumper.py |  7 +++++-
 lib/ansible/plugins/filter/core.py |  4 ++--
 lib/ansible/template/__init__.py   |  6 ++---
 lib/ansible/vars/hostvars.py       | 35 +++++++++++++++++++++++++-----
 4 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/lib/ansible/parsing/yaml/dumper.py b/lib/ansible/parsing/yaml/dumper.py
index 8d8ffe5701e..155d42986ca 100644
--- a/lib/ansible/parsing/yaml/dumper.py
+++ b/lib/ansible/parsing/yaml/dumper.py
@@ -24,7 +24,7 @@ import yaml
 from ansible.module_utils.six import PY3
 from ansible.parsing.yaml.objects import AnsibleUnicode, AnsibleSequence, AnsibleMapping, AnsibleVaultEncryptedUnicode
 from ansible.utils.unsafe_proxy import AnsibleUnsafeText
-from ansible.vars.hostvars import HostVars
+from ansible.vars.hostvars import HostVars, HostVarsVars
 
 
 class AnsibleDumper(yaml.SafeDumper):
@@ -63,6 +63,11 @@ AnsibleDumper.add_representer(
     represent_hostvars,
 )
 
+AnsibleDumper.add_representer(
+    HostVarsVars,
+    represent_hostvars,
+)
+
 AnsibleDumper.add_representer(
     AnsibleSequence,
     yaml.representer.SafeRepresenter.represent_list,
diff --git a/lib/ansible/plugins/filter/core.py b/lib/ansible/plugins/filter/core.py
index d3f2e1424c2..8b9ff7a4c9e 100644
--- a/lib/ansible/plugins/filter/core.py
+++ b/lib/ansible/plugins/filter/core.py
@@ -55,7 +55,7 @@ from ansible.parsing.yaml.dumper import AnsibleDumper
 from ansible.utils.hashing import md5s, checksum_s
 from ansible.utils.unicode import unicode_wrap
 from ansible.utils.vars import merge_hash
-from ansible.vars.hostvars import HostVars
+from ansible.vars.hostvars import HostVars, HostVarsVars
 
 
 UUID_NAMESPACE_ANSIBLE = uuid.UUID('361E6D51-FAEC-444A-9079-341386DA8E2E')
@@ -67,7 +67,7 @@ class AnsibleJSONEncoder(json.JSONEncoder):
     types like HostVars
     '''
     def default(self, o):
-        if isinstance(o, HostVars):
+        if isinstance(o, (HostVars, HostVarsVars)):
             return dict(o)
         elif isinstance(o, (datetime.date, datetime.datetime)):
             return o.isoformat()
diff --git a/lib/ansible/template/__init__.py b/lib/ansible/template/__init__.py
index 4cd9ee8b3f2..1241ed78432 100644
--- a/lib/ansible/template/__init__.py
+++ b/lib/ansible/template/__init__.py
@@ -27,7 +27,7 @@ import pwd
 import re
 import time
 
-from collections import Sequence
+from collections import Sequence, Mapping
 from functools import wraps
 from io import StringIO
 from numbers import Number
@@ -356,7 +356,7 @@ class Templar:
                 clean_list.append(self._clean_data(list_item))
             ret = clean_list
 
-        elif isinstance(orig_data, dict):
+        elif isinstance(orig_data, (dict, Mapping)):
             clean_dict = {}
             for k in orig_data:
                 clean_dict[self._clean_data(k)] = self._clean_data(orig_data[k])
@@ -509,7 +509,7 @@ class Templar:
                     overrides=overrides,
                     disable_lookups=disable_lookups,
                 ) for v in variable]
-            elif isinstance(variable, dict):
+            elif isinstance(variable, (dict, Mapping)):
                 d = {}
                 # we don't use iteritems() here to avoid problems if the underlying dict
                 # changes sizes due to the templating, which can happen with hostvars
diff --git a/lib/ansible/vars/hostvars.py b/lib/ansible/vars/hostvars.py
index d1f1668cca0..4f358737ee2 100644
--- a/lib/ansible/vars/hostvars.py
+++ b/lib/ansible/vars/hostvars.py
@@ -47,7 +47,7 @@ try:
 except ImportError:
     from sha import sha as sha1
 
-__all__ = ['HostVars']
+__all__ = ['HostVars', 'HostVarsVars']
 
 
 # Note -- this is a Mapping, not a MutableMapping
@@ -86,11 +86,9 @@ class HostVars(collections.Mapping):
 
     def __getitem__(self, host_name):
         data = self.raw_get(host_name)
-        sha1_hash = sha1(to_bytes(data)).hexdigest()
-        if sha1_hash not in self._cached_result:
-            templar = Templar(variables=data, loader=self._loader)
-            self._cached_result[sha1_hash] = templar.template(data, fail_on_undefined=False, static_vars=STATIC_VARS)
-        return self._cached_result[sha1_hash]
+        if isinstance(data, Undefined):
+            return data
+        return HostVarsVars(data, loader=self._loader)
 
     def set_host_variable(self, host, varname, value):
         self._variable_manager.set_host_variable(host, varname, value)
@@ -117,3 +115,28 @@ class HostVars(collections.Mapping):
         for host in self._inventory.hosts:
             out[host] = self.get(host)
         return repr(out)
+
+
+class HostVarsVars(collections.Mapping):
+
+    def __init__(self, variables, loader):
+        self._vars = variables
+        self._loader = loader
+
+    def __getitem__(self, var):
+        templar = Templar(variables=self._vars, loader=self._loader)
+        foo = templar.template(self._vars[var], fail_on_undefined=False, static_vars=STATIC_VARS)
+        return foo
+
+    def __contains__(self, var):
+        return (var in self._vars)
+
+    def __iter__(self):
+        for var in self._vars.keys():
+            yield var
+
+    def __len__(self):
+        return len(self._vars.keys())
+
+    def __repr__(self):
+        return repr(self._vars)