[formatter] add 'I' format specifier - identity

docs/formatting.md

@@ -375,6 +375,12 @@ Format specifiers can be used for advanced formatting by using the options provi
     <td><code>{date:Olocal/}</code></td>
     <td><code>2010-01-01 01:00:00</code></td>
 </tr>
+<tr>
+    <td><code>I</code></td>
+    <td>Return the current value as is.<br>Do not convert it to <code>str</code></td>
+    <td><code>{num:I}</code></td>
+    <td><code>1</code></td>
+</tr>
 </tbody>
 </table>
 

gallery_dl/formatter.py

@@ -430,6 +430,10 @@ def _parse_maxlen(format_spec, default):
     return mlen
 
 
+def _parse_identity(format_spec, default):
+    return util.identity
+
+
 def _parse_join(format_spec, default):
     separator, _, format_spec = format_spec.partition(_SEPARATOR)
     join = separator[1:].join
@@ -609,6 +613,7 @@ _FORMAT_SPECIFIERS = {
     "A": _parse_arithmetic,
     "C": _parse_conversion,
     "D": _parse_datetime,
+    "I": _parse_identity,
     "J": _parse_join,
     "L": _parse_maxlen,
     "M": _parse_map,

test/test_formatter.py

@@ -369,6 +369,15 @@ class TestFormatter(unittest.TestCase):
         with self.assertRaises(ValueError):
             self._run_test("{t:Mname", "")
 
+    def test_specifier_identity(self):
+        self._run_test("{a:I}", self.kwdict["a"])
+        self._run_test("{i:I}", self.kwdict["i"])
+        self._run_test("{dt:I}", self.kwdict["dt"])
+
+        self._run_test("{t!D:I}", self.kwdict["dt"])
+        self._run_test("{t!D:I/O+01:30}", self.kwdict["dt"])
+        self._run_test("{i:A+1/I}", self.kwdict["i"]+1)
+
     def test_chain_special(self):
         # multiple replacements
         self._run_test("{a:Rh/C/RE/e/RL/l/}", "Cello wOrld")