Refactor some try..excepts into read_utf8_with_fallback

Extract common pattern for reading a file with UTF-8 into the
unicode_utils module.

setuptools/command/develop.py

@@ -10,7 +10,7 @@
 from setuptools import namespaces
 import setuptools
 
-from ..compat import py39
+from ..unicode_utils import read_utf8_with_fallback
 
 
 class develop(namespaces.DevelopInstaller, easy_install):
@@ -131,14 +131,10 @@ def uninstall_link(self):
         if os.path.exists(self.egg_link):
             log.info("Removing %s (link to %s)", self.egg_link, self.egg_base)
 
-            try:
-                with open(self.egg_link, encoding="utf-8") as egg_link_file:
-                    contents = [line.rstrip() for line in egg_link_file]
-            except UnicodeDecodeError:  # pragma: no cover
-                with open(
-                    self.egg_link, encoding=py39.LOCALE_ENCODING
-                ) as egg_link_file:
-                    contents = [line.rstrip() for line in egg_link_file]
+            contents = [
+                line.rstrip()
+                for line in read_utf8_with_fallback(self.egg_link).splitlines()
+            ]
 
             if contents not in ([self.egg_path], [self.egg_path, self.setup_path]):
                 log.warn("Link points to %s: uninstall aborted", contents)
@@ -165,14 +161,7 @@ def install_egg_scripts(self, dist):
         for script_name in self.distribution.scripts or []:
             script_path = os.path.abspath(convert_path(script_name))
             script_name = os.path.basename(script_path)
-
-            try:
-                with open(script_path, encoding="utf-8") as strm:
-                    script_text = strm.read()
-            except UnicodeDecodeError:  # pragma: no cover
-                with open(script_path, encoding=py39.LOCALE_ENCODING) as strm:
-                    script_text = strm.read()
-
+            script_text = read_utf8_with_fallback(script_path)
             self.install_script(dist, script_name, script_text, script_path)
 
         return None

setuptools/package_index.py

@@ -41,6 +41,7 @@
 from setuptools.extern.more_itertools import unique_everseen
 
 from .compat import py39
+from .unicode_utils import read_utf8_with_fallback
 
 
 EGG_FRAGMENT = re.compile(r'^egg=([-A-Za-z0-9_.+!]+)$')
@@ -1120,12 +1121,7 @@ def local_open(url):
         for f in os.listdir(filename):
             filepath = os.path.join(filename, f)
             if f == 'index.html':
-                try:
-                    with open(filepath, 'r', encoding="utf-8") as fp:
-                        body = fp.read()
-                except UnicodeDecodeError:  # pragma: no cover
-                    with open(filepath, 'r', encoding=py39.LOCALE_ENCODING) as fp:
-                        body = fp.read()
+                body = read_utf8_with_fallback(filepath)
                 break
             elif os.path.isdir(filepath):
                 f += '/'

setuptools/unicode_utils.py

@@ -1,6 +1,8 @@
 import unicodedata
 import sys
 
+from .compat import py39
+
 
 # HFS Plus uses decomposed UTF-8
 def decompose(path):
@@ -42,3 +44,18 @@ def try_encode(string, enc):
         return string.encode(enc)
     except UnicodeEncodeError:
         return None
+
+
+def read_utf8_with_fallback(file: str, fallback_encoding=py39.LOCALE_ENCODING) -> str:
+    """
+    First try to read the file with UTF-8, if there is an error fallback to a
+    different encoding ("locale" by default). Returns the content of the file.
+    Also useful when reading files that might have been produced by an older version of
+    setuptools.
+    """
+    try:
+        with open(file, "r", encoding="utf-8") as f:
+            return f.read()
+    except UnicodeDecodeError:  # pragma: no cover
+        with open(file, "r", encoding=fallback_encoding) as f:
+            return f.read()

setuptools/wheel.py

@@ -18,7 +18,7 @@
 from setuptools.command.egg_info import write_requirements, _egg_basename
 from setuptools.archive_util import _unpack_zipfile_obj
 
-from .compat import py39
+from .unicode_utils import read_utf8_with_fallback
 
 
 WHEEL_NAME = re.compile(
@@ -224,12 +224,7 @@ def _move_data_entries(destination_eggdir, dist_data):
     def _fix_namespace_packages(egg_info, destination_eggdir):
         namespace_packages = os.path.join(egg_info, 'namespace_packages.txt')
         if os.path.exists(namespace_packages):
-            try:
-                with open(namespace_packages, encoding="utf-8") as fp:
-                    namespace_packages = fp.read().split()
-            except UnicodeDecodeError:  # pragma: no cover
-                with open(namespace_packages, encoding=py39.LOCALE_ENCODING) as fp:
-                    namespace_packages = fp.read().split()
+            namespace_packages = read_utf8_with_fallback(namespace_packages).split()
 
             for mod in namespace_packages:
                 mod_dir = os.path.join(destination_eggdir, *mod.split('.'))