Simplify getting info directories for wheel installation (#7526)

* Edit subdirs of top-level instead of checking in each directory

Previously, we were checking whether the top of the relative path ended
with .data. Now, we do not recurse into those directories, so there's no
need to check every time.

* Store info_dir in separate variable

Instead of working with a list everywhere, we use the single info_dir.

* Separate variables for info_dir and the destination path
* Use destination .dist-info dir only when needed

By initially storing just the name of the folder we ensure our code is
agnostic to the destination, so it'll be easier to install from a zip
later.

* Use os.listdir instead of os.walk for wheel dir population

Since we only execute any code when basedir == '', we only need the
top-level directories.

* Inline data_dirs calculation
* Inline info_dirs calculation

src/pip/_internal/operations/install/wheel.py

@@ -332,9 +332,10 @@ def install_unpacked_wheel(
     else:
         lib_dir = scheme.platlib
 
-    info_dir = []  # type: List[str]
-    data_dirs = []
     source = wheeldir.rstrip(os.path.sep) + os.path.sep
+    subdirs = os.listdir(source)
+    info_dirs = [s for s in subdirs if s.endswith('.dist-info')]
+    data_dirs = [s for s in subdirs if s.endswith('.data')]
 
     # Record details of the files moved
     #   installed = files copied from the wheel to the destination
@@ -374,24 +375,8 @@ def install_unpacked_wheel(
         for dir, subdirs, files in os.walk(source):
             basedir = dir[len(source):].lstrip(os.path.sep)
             destdir = os.path.join(dest, basedir)
-            if is_base and basedir.split(os.path.sep, 1)[0].endswith('.data'):
-                continue
-            for s in subdirs:
-                destsubdir = os.path.join(dest, basedir, s)
-                if is_base and basedir == '' and destsubdir.endswith('.data'):
-                    data_dirs.append(s)
-                    continue
-                elif (
-                    is_base and
-                    basedir == '' and
-                    s.endswith('.dist-info')
-                ):
-                    assert not info_dir, (
-                        'Multiple .dist-info directories: {}, '.format(
-                            destsubdir
-                        ) + ', '.join(info_dir)
-                    )
-                    info_dir.append(destsubdir)
+            if is_base and basedir == '':
+                subdirs[:] = [s for s in subdirs if not s.endswith('.data')]
             for f in files:
                 # Skip unwanted files
                 if filter and filter(f):
@@ -443,21 +428,31 @@ def install_unpacked_wheel(
 
     clobber(source, lib_dir, True)
 
-    assert info_dir, "{} .dist-info directory not found".format(
+    assert info_dirs, "{} .dist-info directory not found".format(
         req_description
     )
 
-    info_dir_name = canonicalize_name(os.path.basename(info_dir[0]))
+    assert len(info_dirs) == 1, (
+        '{} multiple .dist-info directories found: {}'.format(
+            req_description, ', '.join(info_dirs)
+        )
+    )
+
+    info_dir = info_dirs[0]
+
+    info_dir_name = canonicalize_name(info_dir)
     canonical_name = canonicalize_name(name)
     if not info_dir_name.startswith(canonical_name):
         raise UnsupportedWheel(
             "{} .dist-info directory {!r} does not start with {!r}".format(
-                req_description, os.path.basename(info_dir[0]), canonical_name
+                req_description, info_dir, canonical_name
             )
         )
 
+    dest_info_dir = os.path.join(lib_dir, info_dir)
+
     # Get the defined entry points
-    ep_file = os.path.join(info_dir[0], 'entry_points.txt')
+    ep_file = os.path.join(dest_info_dir, 'entry_points.txt')
     console, gui = get_entrypoints(ep_file)
 
     def is_entrypoint_wrapper(name):
@@ -607,16 +602,16 @@ def install_unpacked_wheel(
             logger.warning(msg)
 
     # Record pip as the installer
-    installer = os.path.join(info_dir[0], 'INSTALLER')
-    temp_installer = os.path.join(info_dir[0], 'INSTALLER.pip')
+    installer = os.path.join(dest_info_dir, 'INSTALLER')
+    temp_installer = os.path.join(dest_info_dir, 'INSTALLER.pip')
     with open(temp_installer, 'wb') as installer_file:
         installer_file.write(b'pip\n')
     shutil.move(temp_installer, installer)
     generated.append(installer)
 
     # Record details of all files installed
-    record = os.path.join(info_dir[0], 'RECORD')
-    temp_record = os.path.join(info_dir[0], 'RECORD.pip')
+    record = os.path.join(dest_info_dir, 'RECORD')
+    temp_record = os.path.join(dest_info_dir, 'RECORD.pip')
     with open_for_csv(record, 'r') as record_in:
         with open_for_csv(temp_record, 'w+') as record_out:
             reader = csv.reader(record_in)

tests/functional/test_install_wheel.py

@@ -451,7 +451,7 @@ def test_wheel_install_fails_with_extra_dist_info(script):
     result = script.pip(
         "install", "--no-cache-dir", "--no-index", package, expect_error=True
     )
-    assert "Multiple .dist-info directories" in result.stderr
+    assert "multiple .dist-info directories" in result.stderr
 
 
 def test_wheel_install_fails_with_unrelated_dist_info(script):