Extend injected render function to accept context

The context is merged with original render context before passed on to
salt template engine.

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [Unreleased]
 ### Added
 - Add require option to tower.get
+- Experimental: Suppor custom context in template injected `render` function
 
 ## [1.5.2] - 2021-02-10
 ### Fixed

salt_tower/pillar/tower.py

@@ -262,16 +262,21 @@ def _compile(
         ctx["pillar"] = self
         ctx["tower"] = self
 
-        def render(path, renderer="text"):
-            if "basedir" in ctx:
-                path = os.path.join(ctx["basedir"], path)
+        def render(path, context=None, renderer='text'):
+            if isinstance(context, dict):
+                context = {**ctx, **context}
+            else:
+                context = ctx
+
+            if "basedir" in context:
+                path = os.path.join(context["basedir"], path)
 
             file = os.path.abspath(path)
 
             if not os.path.isfile(file):
                 raise FileNotFoundError(errno.ENOENT, os.strerror(errno.ENOENT), file)
 
-            return self._compile(file, renderer, None, None, ctx)
+            return self._compile(file, renderer, None, None, context)
 
         ctx["render"] = render
 

test/pillar/test_tower.py

@@ -505,3 +505,31 @@ def test_render_func_in_top(env):
     })
 
     assert env.ext_pillar() == {'key': 'This is a test.'}
+
+
+def test_render_func_context(env):
+    env.setup({
+        'tower.sls':
+            '''
+            base:
+                - '*':
+                    - key: !include context/test.py
+            ''',
+        'context/test.py':
+            '''
+            #!py
+            import os.path
+            def run():
+                return context["render"](
+                    os.path.join(context["tmplpath"], "../template.j2"),
+                    context={**context, "message": "Hello World!"}
+                )
+            ''',
+        'context/template.j2':
+            '''
+            #!jinja|text strip
+            {{ message }}
+            ''',
+    })
+
+    assert env.ext_pillar() == {'key': 'Hello World!'}