Add Jinja render filter

CHANGES.txt

@@ -4,6 +4,7 @@ Next release
 Features
 --------
 - #119: New Jinja filter: increment_datetime (thanks @jmrgonza)
+- #122: New Jinja filter: render (solves #121)
 
 Internal changes
 ----------------

docs/sphinx/scripts.rst

@@ -389,6 +389,9 @@ increment_datetime
         base.context:
             date_time: "{{ '2022-01-01 00:00:00' | datetime | increment_datetime(days=1, hours=6)}}""
 
+.. versionadded:: 1.1
+    ``increment_datetime`` filter added.
+
 date
     Converts a string to a ``datetime.date`` object::
 
@@ -437,6 +440,26 @@ path_join
         base.echo:
             msg: "{{ ['foo', 'bar.txt'] | path_join }}"
 
+Other filters
+^^^^^^^^^^^^^
+
+render
+    Renders the expression (e.g. a variable) with Jinja2 and the current context. This can be used, for
+    example, to explicitly render context parameters that have been set with the ``!noparse`` tag::
+
+        - base.context:
+            foo: me
+            bar: !noparse "{{ foo }}"
+        - when: "{{ bar|render == 'me' }}"
+          base.echo:
+            msg: "It is {{ bar }}!"
+
+    Without using the ``render`` filter in the example, the ``when`` clause would evaluate to ``false``
+    because the value of ``bar`` would still be ``"{{ foo }}"`` as a consequence of ``!noparse``.
+
+.. versionadded:: 1.1
+    ``render`` filter added.
+
 
 .. _PyYAML: https://pyyaml.org
 .. _RFC5545: https://tools.ietf.org/html/rfc5545

pyproject.toml

@@ -18,7 +18,7 @@ dependencies = [
     "python-dateutil",
     "deepmerge",
     "PyYAML",
-    "jinja2",
+    "jinja2>=3.0.0",
 ]
 
 [project.optional-dependencies]

src/scriptengine/jinja.py

@@ -45,6 +45,11 @@ def path_join(pathlist):
     return os.path.join(*pathlist)
 
 
+@jinja2.pass_context
+def render_filter(context, expression):
+    return render(expression, context)
+
+
 def filters():
     """Return all defined Jinja2 filters by their name and corresponding function"""
     return {
@@ -55,6 +60,7 @@ def filters():
         "dirname": dirname,
         "exists": exists,
         "path_join": path_join,
+        "render": render_filter,
     }
 
 

tests/jobs/test_conditionals.py

@@ -1,5 +1,6 @@
 import yaml
 
+from scriptengine.engines import SimpleScriptEngine
 from scriptengine.yaml.parser import parse
 
 
@@ -31,3 +32,19 @@ def test_when_false(capsys):
     j.run({})
     captured = capsys.readouterr()
     assert "Hello, world!" not in captured.out
+
+
+def test_when_clause_parses_noparse_parameter(capsys):
+    s = from_yaml(
+        """
+        - base.context:
+            foo: me
+            bar: !noparse_jinja "{{ foo }}"
+        - when: "{{ bar|render == 'me' }}"
+          base.echo:
+            msg: Hello!
+        """
+    )
+    SimpleScriptEngine().run(s, context={})
+    captured = capsys.readouterr()
+    assert "Hello!" in captured.out