Store 'provides_extras' as an ordered list to retain order.

3 files changed, 30 insertions, 10 deletions

diff --git a/setuptools/dist.py b/setuptools/dist.py
index ddb1787a..f03f3862 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -31,6 +31,7 @@ from setuptools.extern import packaging
 from setuptools.extern.six.moves import map, filter, filterfalse
 
 from . import SetuptoolsDeprecationWarning
+from .itertools_recipes import unique_everseen
 
 from setuptools.depends import Require
 from setuptools import windows_support
@@ -408,7 +409,7 @@ class Distribution(_Distribution):
     _DISTUTILS_UNSUPPORTED_METADATA = {
         'long_description_content_type': None,
         'project_urls': dict,
-        'provides_extras': set,
+        'provides_extras': list,
     }
 
     _patched_dist = None
@@ -493,14 +494,14 @@ class Distribution(_Distribution):
         if getattr(self, 'python_requires', None):
             self.metadata.python_requires = self.python_requires
 
-        if getattr(self, 'extras_require', None):
-            for extra in self.extras_require.keys():
-                # Since this gets called multiple times at points where the
-                # keys have become 'converted' extras, ensure that we are only
-                # truly adding extras we haven't seen before here.
-                extra = extra.split(':')[0]
-                if extra:
-                    self.metadata.provides_extras.add(extra)
+        # Since this gets called multiple times at points where the
+        # keys have become 'converted' extras, ensure that we are only
+        # truly adding extras we haven't seen before here.
+        raw_extra_names = filter(None, unique_everseen(
+            extra.split(':')[0]
+            for extra in getattr(self, 'extras_require', None) or {}
+        ))
+        self.metadata.provides_extras.extend(raw_extra_names)
 
         self._convert_extras_requirements()
         self._move_install_requirements_markers()
diff --git a/setuptools/itertools_recipes.py b/setuptools/itertools_recipes.py
new file mode 100644
index 00000000..6b611f64
--- /dev/null
+++ b/setuptools/itertools_recipes.py
@@ -0,0 +1,19 @@
+from setuptools.extern.six.moves import filterfalse
+
+
+def unique_everseen(iterable, key=None):
+    "List unique elements, preserving order. Remember all elements ever seen."
+    # unique_everseen('AAAABBBCCDAABBB') --> A B C D
+    # unique_everseen('ABBCcAD', str.lower) --> A B C D
+    seen = set()
+    seen_add = seen.add
+    if key is None:
+        for element in filterfalse(seen.__contains__, iterable):
+            seen_add(element)
+            yield element
+    else:
+        for element in iterable:
+            k = key(element)
+            if k not in seen:
+                seen_add(k)
+                yield element
diff --git a/setuptools/tests/test_dist.py b/setuptools/tests/test_dist.py
index 7409400f..f73eeaea 100644
--- a/setuptools/tests/test_dist.py
+++ b/setuptools/tests/test_dist.py
@@ -169,7 +169,7 @@ def test_read_metadata(name, attrs):
         ('requires', dist_class.get_requires),
         ('classifiers', dist_class.get_classifiers),
         ('project_urls', lambda s: getattr(s, 'project_urls', {})),
-        ('provides_extras', lambda s: getattr(s, 'provides_extras', set())),
+        ('provides_extras', lambda s: getattr(s, 'provides_extras', [])),
     ]
 
     for attr, getter in tested_attrs: