[formatter] add 'g' conversion to sluGify a string (#2410)

docs/formatting.md

@@ -63,6 +63,12 @@ Conversion specifiers allow to *convert* the value to a different form or type.
     <td><code>{foo!C}</code></td>
     <td><code>Foo Bar</code></td>
 </tr>
+<tr>
+    <td align="center"><code>g</code></td>
+    <td>Slugify a value</td>
+    <td><code>{foo!g}</code></td>
+    <td><code>foo-bar</code></td>
+</tr>
 <tr>
     <td align="center"><code>j</code></td>
     <td>Serialize value to a JSON formatted string</td>

gallery_dl/formatter.py

@@ -381,6 +381,7 @@ _CONVERSIONS = {
     "T": util.datetime_to_timestamp_string,
     "d": text.parse_timestamp,
     "U": text.unescape,
+    "g": text.slugify,
     "S": util.to_string,
     "s": str,
     "r": repr,

gallery_dl/text.py

@@ -39,6 +39,16 @@ def split_html(txt):
         return []
 
 
+def slugify(value):
+    """Convert a string to a URL slug
+
+    Adapted from:
+    https://github.com/django/django/blob/master/django/utils/text.py
+    """
+    value = re.sub(r"[^\w\s-]", "", str(value).lower())
+    return re.sub(r"[-\s]+", "-", value).strip("-_")
+
+
 def ensure_http_scheme(url, scheme="https://"):
     """Prepend 'scheme' to 'url' if it doesn't have one"""
     if url and not url.startswith(("https://", "http://")):

test/test_formatter.py

@@ -58,6 +58,7 @@ class TestFormatter(unittest.TestCase):
         self._run_test("{dt!T}", "1262304000")
         self._run_test("{l!j}", '["a", "b", "c"]')
         self._run_test("{dt!j}", '"2010-01-01 00:00:00"')
+        self._run_test("{a!g}", "hello-world")
 
         with self.assertRaises(KeyError):
             self._run_test("{a!q}", "hello world")

test/test_text.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-# Copyright 2015-2021 Mike Fährmann
+# Copyright 2015-2022 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -75,6 +75,23 @@ class TestText(unittest.TestCase):
         for value in INVALID:
             self.assertEqual(f(value), empty)
 
+    def test_slugify(self, f=text.slugify):
+        self.assertEqual(f("Hello World"), "hello-world")
+        self.assertEqual(f("-HeLLo---World-"), "hello-world")
+        self.assertEqual(f("_-H#e:l#l:o+\t+W?o!rl=d-_"), "hello-world")
+        self.assertEqual(f("_Hello_World_"), "hello_world")
+
+        self.assertEqual(f(""), "")
+        self.assertEqual(f("-"), "")
+        self.assertEqual(f("--"), "")
+
+        self.assertEqual(f(()), "")
+        self.assertEqual(f([]), "")
+        self.assertEqual(f({}), "")
+        self.assertEqual(f(None), "none")
+        self.assertEqual(f(1), "1")
+        self.assertEqual(f(2.3), "23")
+
     def test_ensure_http_scheme(self, f=text.ensure_http_scheme):
         result = "https://example.org/filename.ext"