Some more yet unused implementation

src/pip/_internal/metadata/base.py

@@ -2,19 +2,40 @@
 
 from pip._vendor.six import add_metaclass
 
+from pip._internal.utils.misc import stdlib_pkgs  # TODO: Move definition here.
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import List, Optional
+    from typing import Container, Iterator, List, Optional
 
 
 @add_metaclass(abc.ABCMeta)
 class BaseDistribution(object):
+    @property
+    def canonical_name(self):
+        # type: () -> str
+        raise NotImplementedError()
+
     @property
     def installer(self):
         # type: () -> str
         raise NotImplementedError()
 
+    @property
+    def editable(self):
+        # type: () -> bool
+        raise NotImplementedError()
+
+    @property
+    def local(self):
+        # type: () -> bool
+        raise NotImplementedError()
+
+    @property
+    def in_usersite(self):
+        # type: () -> bool
+        raise NotImplementedError()
+
 
 @add_metaclass(abc.ABCMeta)
 class BaseEnvironment(object):
@@ -33,3 +54,27 @@ def from_paths(cls, paths):
     def get_distribution(self, name):
         # type: (str) -> Optional[BaseDistribution]
         raise NotImplementedError()
+
+    def iter_distributions(self):
+        # type: () -> Iterator[BaseDistribution]
+        raise NotImplementedError()
+
+    def iter_installed_distributions(
+        self,
+        local_only=True,  # type: bool
+        skip=stdlib_pkgs,  # type: Container[str]
+        include_editables=True,  # type: bool
+        editables_only=False,  # type: bool
+        user_only=False,  # type: bool
+    ):
+        # type: (...) -> Iterator[BaseDistribution]
+        it = self.iter_distributions()
+        if local_only:
+            it = (d for d in it if d.local)
+        if not include_editables:
+            it = (d for d in it if not d.editable)
+        if editables_only:
+            it = (d for d in it if d.editable)
+        if user_only:
+            it = (d for d in it if d.in_usersite)
+        return (d for d in it if d.canonical_name not in skip)

src/pip/_internal/metadata/pkg_resources.py

@@ -1,25 +1,50 @@
 from pip._vendor import pkg_resources
+from pip._vendor.packaging.utils import canonicalize_name
 
+from pip._internal.utils.misc import (
+    dist_in_usersite,
+    dist_is_editable,
+    dist_is_local,
+)
 from pip._internal.utils.packaging import get_installer
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 from .base import BaseDistribution, BaseEnvironment
 
 if MYPY_CHECK_RUNNING:
-    from typing import List, Optional
+    from typing import Iterator, List, Optional
 
 
 class Distribution(BaseDistribution):
     def __init__(self, dist):
         # type: (pkg_resources.Distribution) -> None
         self._dist = dist
 
+    @property
+    def canonical_name(self):
+        # type: () -> str
+        return canonicalize_name(self._dist.project_name)
+
     @property
     def installer(self):
         # type: () -> str
-        # TODO: Move get_installer() implementation here.
         return get_installer(self._dist)
 
+    @property
+    def editable(self):
+        # type: () -> bool
+        return dist_is_editable(self._dist)
+
+    @property
+    def local(self):
+        # type: () -> bool
+        return dist_is_local(self._dist)
+
+    @property
+    def in_usersite(self):
+        # type: () -> bool
+        return dist_in_usersite(self._dist)
+
 
 class Environment(BaseEnvironment):
     def __init__(self, ws):
@@ -44,3 +69,8 @@ def get_distribution(self, name):
         except pkg_resources.DistributionNotFound:
             return None
         return Distribution(dist)
+
+    def iter_distributions(self):
+        # type: () -> Iterator[BaseDistribution]
+        for dist in self._ws:
+            yield Distribution(dist)