Add unparse_spec

Author: tomasr8

Lib/test/test_tools/test_i18n.py

@@ -18,7 +18,8 @@
 
 
 with imports_under_tool("i18n"):
-    from pygettext import parse_spec, process_keywords, DEFAULTKEYWORDS
+    from pygettext import (parse_spec, process_keywords, DEFAULTKEYWORDS,
+                           unparse_spec)
 
 
 def normalize_POT_file(pot):
@@ -497,6 +498,8 @@ def test_parse_keyword_spec(self):
         for spec, expected in valid:
             with self.subTest(spec=spec):
                 self.assertEqual(parse_spec(spec), expected)
+                # test unparse-parse round-trip
+                self.assertEqual(parse_spec(unparse_spec(*expected)), expected)
 
         invalid = (
             ('foo:', "Invalid keyword spec 'foo:': missing argument positions"),

Tools/i18n/pygettext.py

@@ -376,6 +376,20 @@ def parse_spec(spec):
     return name, result
 
 
+def unparse_spec(name, spec):
+    """Unparse a keyword spec dictionary into a string."""
+    if spec == {'msgid': 0}:
+        return name
+
+    parts = []
+    for arg, pos in sorted(spec.items(), key=lambda x: x[1]):
+        if arg == 'msgctxt':
+            parts.append(f'{pos + 1}c')
+        else:
+            parts.append(str(pos + 1))
+    return f'{name}:{','.join(parts)}'
+
+
 def process_keywords(keywords, *, no_default_keywords):
     custom_keywords_list = [parse_spec(spec) for spec in keywords]
     custom_keywords = {}