Add a policy for the ascii literal behavior. Fixes #392

4 files changed, 11 insertions, 12 deletions

diff --git a/jinja2/compiler.py b/jinja2/compiler.py
index 65bffe6c..6595d632 100644
--- a/jinja2/compiler.py
+++ b/jinja2/compiler.py
@@ -1340,7 +1340,7 @@ class CodeGenerator(NodeVisitor):
         self.write(ref)
 
     def visit_Const(self, node, frame):
-        val = node.value
+        val = node.as_const(frame.eval_ctx)
         if isinstance(val, float):
             self.write(str(val))
         else:
diff --git a/jinja2/defaults.py b/jinja2/defaults.py
index 90ccb65f..38c53764 100644
--- a/jinja2/defaults.py
+++ b/jinja2/defaults.py
@@ -41,6 +41,7 @@ DEFAULT_NAMESPACE = {
 
 # default policies
 DEFAULT_POLICIES = {
+    'compiler.ascii_str':   True,
     'urlize.rel':           'noopener',
     'urlize.target':        None,
     'json.dumps_function':  None,
diff --git a/jinja2/lexer.py b/jinja2/lexer.py
index c8dac214..d2ca32fc 100644
--- a/jinja2/lexer.py
+++ b/jinja2/lexer.py
@@ -574,15 +574,6 @@ class Lexer(object):
                 except Exception as e:
                     msg = str(e).split(':')[-1].strip()
                     raise TemplateSyntaxError(msg, lineno, name, filename)
-                # if we can express it as bytestring (ascii only)
-                # we do that for support of semi broken APIs
-                # as datetime.datetime.strftime.  On python 3 this
-                # call becomes a noop thanks to 2to3
-                if PY2:
-                    try:
-                        value = value.encode('ascii')
-                    except UnicodeError:
-                        pass
             elif token == 'integer':
                 value = int(value)
             elif token == 'float':
diff --git a/jinja2/nodes.py b/jinja2/nodes.py
index 4d62cccb..5e0726a3 100644
--- a/jinja2/nodes.py
+++ b/jinja2/nodes.py
@@ -17,7 +17,7 @@ import operator
 
 from collections import deque
 from jinja2.utils import Markup
-from jinja2._compat import izip, with_metaclass, text_type
+from jinja2._compat import izip, with_metaclass, text_type, PY2
 
 
 #: the types we support for context functions
@@ -470,7 +470,14 @@ class Const(Literal):
     fields = ('value',)
 
     def as_const(self, eval_ctx=None):
-        return self.value
+        rv = self.value
+        if PY2 and type(rv) is text_type and \
+           self.environment.policies['compiler.ascii_str']:
+            try:
+                rv = rv.encode('ascii')
+            except UnicodeError:
+                pass
+        return rv
 
     @classmethod
     def from_untrusted(cls, value, lineno=None, environment=None):