Add Distribution.editable and top-level editable()

importlib_metadata/__init__.py

@@ -51,6 +51,7 @@
     'SimplePath',
     'distribution',
     'distributions',
+    'editable',
     'entry_points',
     'files',
     'metadata',
@@ -733,6 +734,18 @@ def url_req_space(req):
     def origin(self):
         return self._load_json('direct_url.json')
 
+    @property
+    def editable(self) -> bool:
+        """
+        Whether the distribution is an editable install (:pep:`660`).
+
+        Reads ``dir_info.editable`` from the :pep:`610` ``direct_url.json``,
+        defaulting to ``False`` when there is no origin or the package was
+        not installed from a local directory.
+        """
+        dir_info = getattr(self.origin, 'dir_info', None)
+        return bool(getattr(dir_info, 'editable', False))
+
     def _load_json(self, filename):
         # Deferred for performance (python/importlib_metadata#503)
         import json
@@ -1112,6 +1125,15 @@ def version(distribution_name: str) -> str:
     return distribution(distribution_name).version
 
 
+def editable(distribution_name: str) -> bool:
+    """Return whether the named distribution is an editable install.
+
+    :param distribution_name: The name of the distribution package to query.
+    :return: True if the package is installed in editable mode (:pep:`660`).
+    """
+    return distribution(distribution_name).editable
+
+
 _unique = functools.partial(
     unique_everseen,
     key=operator.attrgetter('_normalized_name'),

newsfragments/510.feature.rst

@@ -0,0 +1 @@
+Added ``Distribution.editable`` property and top-level ``editable()`` function reporting whether a distribution is an editable install (:pep:`660`).

tests/fixtures.py

@@ -126,6 +126,21 @@ class DistInfoPkgEditable(DistInfoPkg):
     }
 
 
+class DistInfoPkgEditableDirInfo(DistInfoPkg):
+    """
+    Package installed as editable from a local directory (:pep:`660`).
+    """
+
+    files: FilesSpec = {
+        'distinfo_pkg-1.0.0.dist-info': {
+            'direct_url.json': json.dumps({
+                "dir_info": {"editable": True},
+                "url": "file:///path/to/distinfo_pkg",
+            })
+        },
+    }
+
+
 class DistInfoPkgWithDot(OnSysPath, SiteBuilder):
     files: FilesSpec = {
         "pkg_dot-1.0.0.dist-info": {

tests/test_main.py

@@ -489,3 +489,23 @@ def test_origin(self):
         dist = Distribution.from_name('distinfo-pkg')
         assert dist.origin.url.endswith('.whl')
         assert dist.origin.archive_info.hashes.sha256
+
+    def test_not_editable_from_archive(self):
+        # An origin without dir_info (here an archive) is not editable.
+        assert Distribution.from_name('distinfo-pkg').editable is False
+        assert importlib_metadata.editable('distinfo-pkg') is False
+
+
+class EditableDirInfoDistributionTest(
+    fixtures.DistInfoPkgEditableDirInfo, unittest.TestCase
+):
+    def test_editable(self):
+        assert Distribution.from_name('distinfo-pkg').editable is True
+        assert importlib_metadata.editable('distinfo-pkg') is True
+
+
+class NonEditableDistributionTest(fixtures.DistInfoPkg, unittest.TestCase):
+    def test_not_editable_without_origin(self):
+        # No direct_url.json means no origin, so not editable.
+        assert Distribution.from_name('distinfo-pkg').editable is False
+        assert importlib_metadata.editable('distinfo-pkg') is False