Backport 2.x's avoidance of 'import pip'

requirements.txt

@@ -14,4 +14,3 @@ requests>=2.11.0,<3.0.0
 regex>=2017.4.1,<2017.12.1
 ftfy>=4.4.2,<5.0.0
 pytest>=3.0.6,<4.0.0
-pip>=9.0.0,<10.0.0

spacy/cli/link.py

@@ -1,7 +1,7 @@
 # coding: utf8
 from __future__ import unicode_literals
 
-import pip
+import pkg_resources
 from pathlib import Path
 import importlib
 from ..compat import unicode_, symlink_to
@@ -69,10 +69,14 @@ def get_meta(package_path, package):
     meta = util.parse_package_meta(package_path, package)
     return meta
 
-
-def is_package(origin):
-    packages = pip.get_installed_distributions()
+def is_package(name):
+    """Check if string maps to a package installed via pip.
+    name (unicode): Name of package.
+    RETURNS (bool): True if installed package, False if not.
+    """
+    name = name.lower()  # compare package name against lowercase name
+    packages = pkg_resources.working_set.by_key.keys()
     for package in packages:
-        if package.project_name.replace('-', '_') == origin:
+        if package.lower().replace('-', '_') == name:
             return True
     return False

spacy/tests/test_cli.py

@@ -2,6 +2,7 @@
 from __future__ import unicode_literals
 
 from ..cli.download import download, get_compatibility, get_version, check_error_depr
+from ..cli.link import is_package
 
 import pytest
 
@@ -24,3 +25,9 @@ def test_cli_download_get_matching_version_fails(model):
 def test_cli_download_no_model_depr_error(model):
     with pytest.raises(SystemExit):
         check_error_depr(model)
+
+
+@pytest.mark.parametrize('package', ['numpy'])
+def test_cli_link_is_package(package):
+    """Test that an installed package via pip is recognised by link.is_package."""
+    assert is_package(package)