From b777a731f172cd06d1e1311ec681b72e9ed14717 Mon Sep 17 00:00:00 2001
From: Elena ``of Valhalla'' Grandi <valhalla@trueelena.org>
Date: Sun, 7 Mar 2021 10:34:06 +0100
Subject: New custom filter for templates: to_yaml.

---
 CHANGELOG.rst            |  3 ++-
 lesana/collection.py     |  4 ++--
 lesana/templating.py     | 27 +++++++++++++++++++++++++++
 tests/test_templating.py | 42 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 73 insertions(+), 3 deletions(-)
 create mode 100644 lesana/templating.py
 create mode 100644 tests/test_templating.py

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 04a8463..c8c2786 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -5,7 +5,8 @@
 Unreleased
 ==========
 
-* New data type: geo (for Geo URIs)
+* New data type: geo (for Geo URIs).
+* New custom filter for templates: to_yaml.
 
 0.8.1
 =====
diff --git a/lesana/collection.py b/lesana/collection.py
index a78de2b..a4546df 100644
--- a/lesana/collection.py
+++ b/lesana/collection.py
@@ -9,7 +9,7 @@ import xapian
 import jinja2
 
 from pkg_resources import resource_string
-from . import types
+from . import types, templating
 
 try:
     import git
@@ -473,7 +473,7 @@ class Collection(object):
         self.update_cache([e.fname for e in changed])
 
     def get_template(self, template_fname, searchpath='.'):
-        env = jinja2.Environment(
+        env = templating.Environment(
             loader=jinja2.FileSystemLoader(
                 searchpath=searchpath, followlinks=True,
             ),
diff --git a/lesana/templating.py b/lesana/templating.py
new file mode 100644
index 0000000..375a6f0
--- /dev/null
+++ b/lesana/templating.py
@@ -0,0 +1,27 @@
+"""
+Custom jinja2 filters and other templating helpers
+"""
+import decimal
+
+import jinja2
+import ruamel.yaml
+
+
+class Environment(jinja2.Environment):
+    """
+    A customized jinja2 environment that includes our filters.
+    """
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self.filters['to_yaml'] = to_yaml
+
+
+def to_yaml(data):
+    """
+    Return the yaml representation of data.
+    """
+    if isinstance(data, decimal.Decimal):
+        data = str(data)
+    return ruamel.yaml.dump(data).strip('...\n').strip()
diff --git a/tests/test_templating.py b/tests/test_templating.py
new file mode 100644
index 0000000..33889ae
--- /dev/null
+++ b/tests/test_templating.py
@@ -0,0 +1,42 @@
+import decimal
+import unittest
+
+from lesana import templating
+
+
+class testFilters(unittest.TestCase):
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def test_to_yaml(self):
+        res = templating.to_yaml(None)
+        self.assertIsInstance(res, str)
+        self.assertEqual(res, 'null')
+
+        s = "A short string"
+        res = templating.to_yaml(s)
+        self.assertEqual(res, s)
+
+        s = """
+        A long, multiline
+        string
+        with multiple
+        lines
+        """
+        res = templating.to_yaml(s)
+        self.assertIsInstance(res, str)
+        self.assertIn('"', res)
+        self.assertIn('\n', res)
+
+        res = templating.to_yaml(10)
+        self.assertEqual(res, '10')
+
+        res = templating.to_yaml(decimal.Decimal('10.1'))
+        self.assertEqual(res, "'10.1'")
+
+
+if __name__ == '__main__':
+    unittest.main()
-- 
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