Introduce context manager for temporary templar context changes (#60513)

* Introduce context manager for temporary templar context changes. Fixes #60106

* Rename and docstring

* Make set_temporary_context more generic, don't hardcode each thing you can set, apply to template action too

* not None

* linting fix

* Ignore invalid attrs

* Catch the right things, loop the right things

* Use set_temporary_context in a few extra action plugins

changelogs/fragments/60106-templar-contextmanager.yml

@@ -0,0 +1,4 @@
+bugfixes:
+- template lookup - ensure changes to the templar in the lookup, do not
+  affect the templar context outside of the lookup
+  (https://github.com/ansible/ansible/issues/60106)

lib/ansible/plugins/action/ce_template.py

@@ -100,5 +100,5 @@ class ActionModule(_ActionModule):
                     for role in dep_chain:
                         searchpath.append(role._role_path)
         searchpath.append(os.path.dirname(source))
-        self._templar.environment.loader.searchpath = searchpath
-        self._task.args['src'] = self._templar.template(template_data)
+        with self._templar.set_temporary_context(searchpath=searchpath):
+            self._task.args['src'] = self._templar.template(template_data)

lib/ansible/plugins/action/network.py

@@ -160,8 +160,8 @@ class ActionModule(_ActionModule):
                     for role in dep_chain:
                         searchpath.append(role._role_path)
         searchpath.append(os.path.dirname(source))
-        self._templar.environment.loader.searchpath = searchpath
-        self._task.args['src'] = self._templar.template(template_data, convert_data=convert_data)
+        with self._templar.set_temporary_context(searchpath=searchpath):
+            self._task.args['src'] = self._templar.template(template_data, convert_data=convert_data)
 
     def _get_network_os(self, task_vars):
         if 'network_os' in self._task.args and self._task.args['network_os']:

lib/ansible/plugins/action/template.py

@@ -127,27 +127,16 @@ class ActionModule(ActionBase):
                     newsearchpath.append(p)
                 searchpath = newsearchpath
 
-                self._templar.environment.loader.searchpath = searchpath
-                self._templar.environment.newline_sequence = newline_sequence
-                if block_start_string is not None:
-                    self._templar.environment.block_start_string = block_start_string
-                if block_end_string is not None:
-                    self._templar.environment.block_end_string = block_end_string
-                if variable_start_string is not None:
-                    self._templar.environment.variable_start_string = variable_start_string
-                if variable_end_string is not None:
-                    self._templar.environment.variable_end_string = variable_end_string
-                self._templar.environment.trim_blocks = trim_blocks
-                self._templar.environment.lstrip_blocks = lstrip_blocks
-
                 # add ansible 'template' vars
                 temp_vars = task_vars.copy()
                 temp_vars.update(generate_ansible_template_vars(source, dest))
 
-                old_vars = self._templar.available_variables
-                self._templar.available_variables = temp_vars
-                resultant = self._templar.do_template(template_data, preserve_trailing_newlines=True, escape_backslashes=False)
-                self._templar.available_variables = old_vars
+                with self._templar.set_temporary_context(searchpath=searchpath, newline_sequence=newline_sequence,
+                                                         block_start_string=block_start_string, block_end_string=block_end_string,
+                                                         variable_start_string=variable_start_string, variable_end_string=variable_end_string,
+                                                         trim_blocks=trim_blocks, lstrip_blocks=lstrip_blocks,
+                                                         available_variables=temp_vars):
+                    resultant = self._templar.do_template(template_data, preserve_trailing_newlines=True, escape_backslashes=False)
             except AnsibleAction:
                 raise
             except Exception as e:

lib/ansible/plugins/lookup/template.py

@@ -68,8 +68,6 @@ class LookupModule(LookupBase):
         variable_start_string = kwargs.get('variable_start_string', None)
         variable_end_string = kwargs.get('variable_end_string', None)
 
-        old_vars = self._templar.available_variables
-
         for term in terms:
             display.debug("File lookup term: %s" % term)
 
@@ -92,12 +90,6 @@ class LookupModule(LookupBase):
                     searchpath = newsearchpath
                 searchpath.insert(0, os.path.dirname(lookupfile))
 
-                self._templar.environment.loader.searchpath = searchpath
-                if variable_start_string is not None:
-                    self._templar.environment.variable_start_string = variable_start_string
-                if variable_end_string is not None:
-                    self._templar.environment.variable_end_string = variable_end_string
-
                 # The template will have access to all existing variables,
                 # plus some added by ansible (e.g., template_{path,mtime}),
                 # plus anything passed to the lookup with the template_vars=
@@ -105,17 +97,16 @@ class LookupModule(LookupBase):
                 vars = deepcopy(variables)
                 vars.update(generate_ansible_template_vars(lookupfile))
                 vars.update(lookup_template_vars)
-                self._templar.available_variables = vars
 
                 # do the templating
-                res = self._templar.template(template_data, preserve_trailing_newlines=True,
-                                             convert_data=convert_data_p, escape_backslashes=False)
+                with self._templar.set_temporary_context(variable_start_string=variable_start_string,
+                                                         variable_end_string=variable_end_string,
+                                                         available_variables=vars, searchpath=searchpath):
+                    res = self._templar.template(template_data, preserve_trailing_newlines=True,
+                                                 convert_data=convert_data_p, escape_backslashes=False)
 
                 ret.append(res)
             else:
                 raise AnsibleError("the template file %s could not be found for the lookup" % term)
 
-        # restore old variables
-        self._templar.available_variables = old_vars
-
         return ret

lib/ansible/template/__init__.py

@@ -27,6 +27,7 @@ import pwd
 import re
 import time
 
+from contextlib import contextmanager
 from numbers import Number
 
 try:
@@ -512,6 +513,36 @@ class Templar:
         )
         self.available_variables = variables
 
+    @contextmanager
+    def set_temporary_context(self, **kwargs):
+        """Context manager used to set temporary templating context, without having to worry about resetting
+        original values afterward
+
+        Use a keyword that maps to the attr you are setting. Applies to ``self.environment`` by default, to
+        set context on another object, it must be in ``mapping``.
+        """
+        mapping = {
+            'available_variables': self,
+            'searchpath': self.environment.loader,
+        }
+        original = {}
+
+        for key, value in kwargs.items():
+            obj = mapping.get(key, self.environment)
+            try:
+                original[key] = getattr(obj, key)
+                if value is not None:
+                    setattr(obj, key, value)
+            except AttributeError:
+                # Ignore invalid attrs, lstrip_blocks was added in jinja2==2.7
+                pass
+
+        yield
+
+        for key in original:
+            obj = mapping.get(key, self.environment)
+            setattr(obj, key, original[key])
+
     def template(self, variable, convert_bare=False, preserve_trailing_newlines=True, escape_backslashes=True, fail_on_undefined=None, overrides=None,
                  convert_data=True, static_vars=None, cache=True, disable_lookups=False):
         '''