Fix and extend render function

This `render` function can be used to render a template e.g. in jinja
using the tower lookup:

    #! jinja
    {{ render('another_file.j2') }}

This file will be rendered using the same tower rendering pipeline as
all other files. It therefore supprots shebang, any other renderer and
any tower helper.

CHANGELOG.md

@@ -8,6 +8,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 - Added `merge-last`, `merge-first`, `remove` and `overwrite` merge strategies for dictionaries
 - Improve logging source and exception for rendering errors (#10)
+- Extended `render` context function to support relative lookup
+
+### Fixed
+- Fix `render` context function to use correct `basedir` variable
+- Add `basedir` variable when rendering top file
 
 ## [1.2.0] - 2020-01-31
 ### Added

salt_tower/pillar/tower.py

@@ -114,7 +114,7 @@ def run(self, top):
 
         base = os.path.dirname(top)
 
-        for item in self._load_top(top):
+        for item in self._load_top(top, base):
             if isinstance(item, str):
                 self._load_item(base, item)
 
@@ -135,8 +135,8 @@ def _match_minion(self, tgt):
             LOGGER.exception(err)
             return False
 
-    def _load_top(self, top):
-        data = self._compile(top)
+    def _load_top(self, top, base):
+        data = self._compile(top, context={'basedir': base})
 
         if not isinstance(data, dict):
             LOGGER.critical("Tower top must be a dict, but is %s.", type(data))
@@ -256,8 +256,12 @@ def _compile(
         context["tower"] = self
 
         def render(tmpl, renderer="text"):
-            file = os.path.join(context.get("base"), tmpl)
-            file = os.path.abspath(file)
+            if (tmpl.startswith("./") or tmpl.startswith("../")):
+                path = os.path.join(context["tmpldir"], tmpl)
+            elif not tmpl.startswith("/"):
+                path = os.path.join(context["basedir"], tmpl)
+
+            file = os.path.abspath(path)
 
             if not os.path.isfile(file):
                 raise FileNotFoundError(errno.ENOENT, os.strerror(errno.ENOENT), file)

test/pillar/test_tower.py

@@ -430,3 +430,75 @@ def test_error_invalid_file(env):
 
     with pytest.raises(SaltRenderError):
         env.ext_pillar()
+
+
+def test_render_func(env):
+    env.setup({
+        'tower.sls':
+            '''
+            base:
+                - index
+            ''',
+        'index.sls':
+            '''
+            key: !include test/conf.j2
+            ''',
+        'test/conf.j2':
+            '''
+            #! jinja | text strip
+            {{ render('test/conf2.j2') }}
+            ''',
+        'test/conf2.j2':
+            '''
+            This is a test.
+            ''',
+    })
+
+    assert env.ext_pillar() == {'key': 'This is a test.'}
+
+
+def test_render_func_relative(env):
+    env.setup({
+        'tower.sls':
+            '''
+            base:
+                - index
+            ''',
+        'index.sls':
+            '''
+            key: !include test/conf.j2
+            ''',
+        'test/conf.j2':
+            '''
+            #! jinja | text strip
+            {{ render('./conf2.j2') }}
+            ''',
+        'test/conf2.j2':
+            '''
+            This is a test.
+            ''',
+    })
+
+    assert env.ext_pillar() == {'key': 'This is a test.'}
+
+
+def test_render_func_in_top(env):
+    env.setup({
+        'tower.sls':
+            '''
+            base:
+                - '*':
+                    - key: !include test/conf.j2
+            ''',
+        'test/conf.j2':
+            '''
+            #! jinja | text strip
+            {{ render('./conf2.j2') }}
+            ''',
+        'test/conf2.j2':
+            '''
+            This is a test.
+            ''',
+    })
+
+    assert env.ext_pillar() == {'key': 'This is a test.'}