bpo-46105: Honor spec when generating requirement specs with urls and extras. (GH-30151)

1 files changed, 11 insertions, 2 deletions

diff --git a/Lib/importlib/metadata/__init__.py b/Lib/importlib/metadata/__init__.py
index b3e8fb0..ec41ed3 100644
--- a/Lib/importlib/metadata/__init__.py
+++ b/Lib/importlib/metadata/__init__.py
@@ -669,7 +669,7 @@ class Distribution:
         def make_condition(name):
             return name and f'extra == "{name}"'
 
-        def parse_condition(section):
+        def quoted_marker(section):
             section = section or ''
             extra, sep, markers = section.partition(':')
             if extra and markers:
@@ -677,8 +677,17 @@ class Distribution:
             conditions = list(filter(None, [markers, make_condition(extra)]))
             return '; ' + ' and '.join(conditions) if conditions else ''
 
+        def url_req_space(req):
+            """
+            PEP 508 requires a space between the url_spec and the quoted_marker.
+            Ref python/importlib_metadata#357.
+            """
+            # '@' is uniquely indicative of a url_req.
+            return ' ' * ('@' in req)
+
         for section in sections:
-            yield section.value + parse_condition(section.name)
+            space = url_req_space(section.value)
+            yield section.value + space + quoted_marker(section.name)
 
 
 class DistributionFinder(MetaPathFinder):