Enable access to local variables in extensions

[OddBloke]

As far as I can tell, there is no way for extensions to access local variables from their call site, they can only access the template context (which, for example, excludes loop-local variables).

Template Code

Using the extension at https://review.openstack.org/#/c/568021/5/jenkins_jobs/jinja2_extension.py, and

{% set y = 'foo' %}
{% for x in [1, 2] %}
    {% set z = 'bar' %}
    {% for a in [1, 2] %}
        {% jjb_include_raw 'jinja_jjb_include_raw001.sh.inc' %}
    {% endfor %}
{% endfor %}

the context passed by a ContextReference in _render_template looks like:

>>> context
<Context {'range': <class 'range'>, 'dict': <class 'dict'>, 'lipsum': <function generate_lorem_ipsum at 0x7fb8d23a0840>, 'cycler': <class 'jinja2.utils.Cycler'>, 'joiner': <class 'jinja2.utils.Joiner'>, 'namespace': <class 'jinja2.utils.Namespace'>, 'name': 'test-include_jjb', 'param': 'value', 'template-name': 'test-job-{param}', '': '', 'builders': [OrderedDict([('shell', <jenkins_jobs.local_yaml.Jinja2Loader object at 0x7fb8d5e09198>)])], 'y': 'foo'} of None>
>>> pprint.pprint(dict(context))
{'': '',
 'builders': [OrderedDict([('shell',
                            <jenkins_jobs.local_yaml.Jinja2Loader object at 0x7fb8d5e09198>)])],
 'cycler': <class 'jinja2.utils.Cycler'>,
 'dict': <class 'dict'>,
 'joiner': <class 'jinja2.utils.Joiner'>,
 'lipsum': <function generate_lorem_ipsum at 0x7fb8d23a0840>,
 'name': 'test-include_jjb',
 'namespace': <class 'jinja2.utils.Namespace'>,
 'param': 'value',
 'range': <class 'range'>,
 'template-name': 'test-job-{param}',
 'y': 'foo'}

Note that y is in the context, but none of x, z or a are.

Your Environment

• Python version: 3.6
• Jinja version: trunk

[OddBloke]

For including of templates, the local variables are available because the return value of self.dump_local_context(frame) is passed in to root_render_func when with_context is True (around https://github.com/pallets/jinja/blob/master/jinja2/compiler.py#L918).

[OddBloke]

One solution would be to extend ContextReference to allow locals to be included (whilst still defaulting to the existing behaviour):

diff --git a/jinja2/compiler.py b/jinja2/compiler.py
index 5135a77..6cfe750 100644
--- a/jinja2/compiler.py
+++ b/jinja2/compiler.py
@@ -1670,7 +1670,10 @@ class CodeGenerator(NodeVisitor):
         self.write(node.name)
 
     def visit_ContextReference(self, node, frame):
-        self.write('context')
+        if node.include_locals:
+            self.write(self.derive_context(frame))
+        else:
+            self.write('context')
 
     def visit_Continue(self, node, frame):
         self.writeline('continue', node)
diff --git a/jinja2/nodes.py b/jinja2/nodes.py
index 5ab2b31..61f2dd6 100644
--- a/jinja2/nodes.py
+++ b/jinja2/nodes.py
@@ -943,6 +943,7 @@ class ContextReference(Expr):
         Assign(Name('foo', ctx='store'),
                Getattr(ContextReference(), 'name'))
     """
+    attributes = ('include_locals',)
 
 
 class Continue(Stmt):

[OddBloke]

An alternative would be to use a separate node type to provide the locals, but playing with that locally I just ended up doing the context.derive(locals) call myself; I don't know if there are many cases where extension authors would want the locals without the rest of the context, which is (I think) the only use case that approach would enable that the above diff doesn't.