show: add PEP376 INSTALLER information

closes #3517

CHANGES.txt

@@ -14,6 +14,8 @@
 
 * Show classifiers in ``pip show``.
 
+* Show PEP376 Installer in ``pip show`` (:issue:`3517`).
+
 * Unhide completion command (:pull:`1810`).
 
 * Decode requirement files according to their BOM if present (:pull:`3485`,

pip/commands/show.py

@@ -85,6 +85,14 @@ def search_packages_info(query):
             entry_points = dist.get_metadata_lines('entry_points.txt')
             package['entry_points'] = entry_points
 
+        installer = 'UNKNOWN'
+        if dist.has_metadata('INSTALLER'):
+            for line in dist.get_metadata_lines('INSTALLER'):
+                if line.strip():
+                    installer = line.strip()
+                    break
+        package['installer'] = installer
+
         # @todo: Should pkg_resources.Distribution have a
         # `get_pkg_info` method?
         feed_parser = FeedParser()
@@ -124,6 +132,7 @@ def print_results(distributions, list_all_files):
         logger.info("Home-page: %s", dist.get('home-page'))
         logger.info("Author: %s", dist.get('author'))
         logger.info("Author-email: %s", dist.get('author-email'))
+        logger.info("Installer: %s", dist.get('installer'))
         logger.info("License: %s", dist.get('license'))
         logger.info("Location: %s", dist['location'])
         logger.info("Requires: %s", ', '.join(dist['requires']))

tests/functional/test_show.py

@@ -10,7 +10,7 @@ def test_show(script):
     """
     result = script.pip('show', 'pip')
     lines = result.stdout.split('\n')
-    assert len(lines) == 30
+    assert len(lines) == 31
     assert lines[0] == '---', lines[0]
     assert 'Name: pip' in lines
     assert 'Version: %s' % __version__ in lines
@@ -27,7 +27,7 @@ def test_show_with_files_not_found(script, data):
     script.pip('install', '-e', editable)
     result = script.pip('show', '-f', 'SetupPyUTF8')
     lines = result.stdout.split('\n')
-    assert len(lines) == 15
+    assert len(lines) == 16
     assert lines[0] == '---', lines[0]
     assert 'Name: SetupPyUTF8' in lines
     assert 'Version: 0.0.0' in lines
@@ -107,3 +107,15 @@ def test_show_with_classifiers(script, data):
     assert 'Name: pip' in lines
     assert re.search(r"Classifiers:\n(  .+\n)+", result.stdout)
     assert "Intended Audience :: Developers" in result.stdout
+
+
+def test_show_installer(script, data):
+    """
+    Test that the installer is shown (this currently needs a wheel install)
+    """
+    wheel_file = data.packages.join('simple.dist-0.1-py2.py3-none-any.whl')
+    script.pip('install', '--no-index', wheel_file)
+    result = script.pip('show', 'simple.dist')
+    lines = result.stdout.split('\n')
+    assert 'Name: simple.dist' in lines
+    assert 'Installer: pip' in lines