Add support for a Jinja2 pandoc filter (#82)

.travis.yml

@@ -19,6 +19,10 @@ matrix:
       install: pip install tox
       script: tox -e $TOX_ENV
 
+before_install:
+    - sudo apt update
+    - sudo apt -y install pandoc
+
 install:
     - pip install tox-travis codecov
 

docs/filters.rst

@@ -42,6 +42,17 @@ keyword arguments.
 
 Please view the `Markdown documentation <https://python-markdown.github.io/>`_ for details.
 
+Pandoc
+^^^^^^
+
+``pandoc`` is provided as a filter and can be configured by the
+``pandoc_config`` meta variable, which is passed to the convert_text function
+as keyword arguments.
+
+Please refer `pypandoc project <https://github.com/bebraw/pypandoc>`_ for details.
+
+Note, pypandoc requires pandoc to be installed. It will error without it.
+
 Typogrify
 ^^^^^^^^^
 

exhibition/filters/jinja2.py

@@ -36,6 +36,7 @@
 from jinja2.ext import Extension
 from jinja2.nodes import CallBlock, Const, ContextReference
 from markdown import markdown as md_func
+from pypandoc import convert_text as pandoc_func
 from typogrify.templatetags import jinja_filters as typogrify_filters
 
 EXTENDS_TEMPLATE_TEMPLATE = """{%% extends "%s" %%}
@@ -53,6 +54,10 @@
     "output_format": "html5",
 }
 
+DEFAULT_PANDOC_KWARGS = {
+    "to": "html",
+}
+
 
 def metasort(nodes, key=None, reverse=False):
     """
@@ -86,6 +91,19 @@ def markdown(ctx, text):
     return md_func(text, **kwargs)
 
 
+@contextfilter
+def pandoc(ctx, text, fmt=None):
+    kwargs = DEFAULT_PANDOC_KWARGS.copy()
+    node = ctx[NODE_TMPL_VAR]
+
+    kwargs.update(node.meta.get("pandoc_config", {}))
+
+    if fmt is not None:
+        kwargs["format"] = fmt
+
+    return pandoc_func(text, **kwargs)
+
+
 class RaiseError(Extension):
     """
     Raise an exception during template rendering:
@@ -157,6 +175,7 @@ def content_filter(node, content):
         extensions=[RaiseError, Mark],
         autoescape=True,
     )
+    env.filters["pandoc"] = pandoc
     env.filters["markdown"] = markdown
     env.filters["metasort"] = metasort
     env.filters["metaselect"] = metaselect

exhibition/tests/test_filters.py

@@ -68,6 +68,23 @@
 {% endfilter %}
 """.strip()
 
+
+PANDOC_TEMPLATE = """
+{% filter pandoc("org") %}
+* Hello
+
+This /is/ *text*
+{% endfilter %}
+"""
+
+PANDOC_TEMPLATE_WITHOUT_ARG = """
+{% filter pandoc %}
+* Hello
+
+This /is/ *text*
+{% endfilter %}
+"""
+
 TYPOG_TEMPLATE = """
 {% filter typogrify %}
 Hello -- how are you?
@@ -243,6 +260,33 @@ def test_markdown_filter(self):
         result = jinja_filter(node, MD_TEMPLATE)
         self.assertEqual(result, "<h2>Hello</h2>\n<p>This is <em>text</em></p>")
 
+    def test_pandoc_filter(self):
+        node = Node(mock.Mock(), None, meta={"templates": []})
+        node.is_leaf = False
+        result = jinja_filter(node, PANDOC_TEMPLATE)
+        self.assertEqual(
+            result,
+            "\n<h1 id=\"hello\">Hello</h1>\n"
+            "<p>This <em>is</em> <strong>text</strong></p>\n"
+        )
+
+    def test_pandoc_filter_no_argument(self):
+        meta = {"templates": []}
+        node = Node(mock.Mock(), None, meta=meta)
+        node.is_leaf = False
+
+        # First test with no arguments at all.
+        self.assertRaises(
+            TypeError,
+            jinja_filter,
+            node,
+            PANDOC_TEMPLATE_WITHOUT_ARG
+        )
+
+        node.meta["pandoc_config"] = {"format": "org", "to": "markdown"}
+        result = jinja_filter(node, PANDOC_TEMPLATE_WITHOUT_ARG)
+        self.assertEqual(result, "\nHello\n=====\n\nThis *is* **text**\n")
+
     def test_typogrify_filter(self):
         node = Node(mock.Mock(), None, meta={"templates": []})
         node.is_leaf = False

setup.py

@@ -39,6 +39,7 @@
         "markdown",
         "ruamel.yaml",
         "typogrify",
+        "pypandoc",
     ],
     extras_require={
         "docs": [