Include file path when Version: missing

Related to pip's github issue pypa/pip#6194.

This has come up in pip's issue tracker (github) multiple times:

  - pypa/pip#6177
  - pypa/pip#6283
  - pypa/pip#6194

1 files changed, 34 insertions, 3 deletions

diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index e8921f95..97e08d68 100644
--- a/pkg_resources/__init__.py
+++ b/pkg_resources/__init__.py
@@ -1403,8 +1403,15 @@ class NullProvider:
     def has_resource(self, resource_name):
         return self._has(self._fn(self.module_path, resource_name))
 
+    def _get_metadata_path(self, name):
+        return self._fn(self.egg_info, name)
+
     def has_metadata(self, name):
-        return self.egg_info and self._has(self._fn(self.egg_info, name))
+        if not self.egg_info:
+            return self.egg_info
+
+        path = self._get_metadata_path(name)
+        return self._has(path)
 
     def get_metadata(self, name):
         if not self.egg_info:
@@ -1868,6 +1875,9 @@ class FileMetadata(EmptyProvider):
     def __init__(self, path):
         self.path = path
 
+    def _get_metadata_path(self, name):
+        return self.path
+
     def has_metadata(self, name):
         return name == 'PKG-INFO' and os.path.isfile(self.path)
 
@@ -2663,8 +2673,12 @@ class Distribution:
         except AttributeError:
             version = self._get_version()
             if version is None:
-                tmpl = "Missing 'Version:' header and/or %s file"
-                raise ValueError(tmpl % self.PKG_INFO, self)
+                path = self._get_metadata_path_for_display(self.PKG_INFO)
+                msg = (
+                    "Missing 'Version:' header and/or {} file at path: {}"
+                ).format(self.PKG_INFO, path)
+                raise ValueError(msg, self)
+
             return version
 
     @property
@@ -2722,6 +2736,23 @@ class Distribution:
                 )
         return deps
 
+    def _get_metadata_path_for_display(self, name):
+        """
+        Return the path to the given metadata file, if available.
+        """
+        try:
+            # We need to access _get_metadata_path() on the provider object
+            # directly rather than through this class's __getattr__()
+            # since _get_metadata_path() is marked private.
+            path = self._provider._get_metadata_path(name)
+
+        # Handle exceptions e.g. in case the distribution's metadata
+        # provider doesn't support _get_metadata_path().
+        except Exception:
+            return '[could not detect]'
+
+        return path
+
     def _get_metadata(self, name):
         if self.has_metadata(name):
             for line in self.get_metadata_lines(name):