Set Jinja2's keep_trailing_newline=True in template_from_string.

Without this setting, the newline idempotence of scalar strings changes depending on whether
or not they contain any Jinja2 template blocks.

lib/ansible/utils/template.py

@@ -322,7 +322,7 @@ def template_from_string(basedir, data, vars, fail_on_undefined=False):
         def my_finalize(thing):
             return thing if thing is not None else ''
 
-        environment = jinja2.Environment(trim_blocks=True, undefined=StrictUndefined, extensions=_get_extensions(), finalize=my_finalize)
+        environment = jinja2.Environment(trim_blocks=True, keep_trailing_newline=True, undefined=StrictUndefined, extensions=_get_extensions(), finalize=my_finalize)
         environment.filters.update(_get_filters())
         environment.template_class = J2Template
 

test/integration/roles/test_template/tasks/main.yml

@@ -64,3 +64,9 @@
     that: 
       - "file_result.changed != True"
 
+# VERIFY STRING TEMPLATE PRESERVES NEWLINE
+
+- name: ensure template strings preserve newline
+  assert:
+    that:
+      - "newline_no_template_string == newline_template_string"

test/integration/roles/test_template/vars/main.yml

@@ -1 +1,3 @@
 templated_var: templated_var_loaded
+newline_template_string: "Hello {{ 'World' }}\n"
+newline_no_template_string: "Hello World\n"