Support both isort 4 and isort 5

The API of isort 5 (released on 2020-07-04) is completely different.
We must still support isort 4 because isort 5 dropped the
compatibility with Python 3.5, which pylint still supports.

Note about the `known-standard-library` option: it has been included
in pylint for years. Until now, it was mapped with the option of the
same name in isort. However, isort 5 has changed the meaning of this
option (see https://timothycrosley.github.io/isort/docs/upgrade_guides/5.0.0/#known_standard_library).

Most users of pylint want the meaning of the new
`extra-standard-library` option. To avoid a breaking change in pylint,
the `known-standard-library` pylint option is now mapped to
`known-standard-library` in isort 4, and `extra-standard-library` in
isort 5. Users that really want the _new_ meaning of
`known-standard-library` in isort 4 must disable the
`wrong-import-order` check in pylint and run isort manually, outside
of pylint.

Fix #3722.

1 files changed, 35 insertions, 0 deletions

diff --git a/pylint/utils/utils.py b/pylint/utils/utils.py
index 21dd8d251..d7f1bf052 100644
--- a/pylint/utils/utils.py
+++ b/pylint/utils/utils.py
@@ -1,6 +1,15 @@
 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 # For details: https://github.com/PyCQA/pylint/blob/master/COPYING
 
+try:
+    import isort.api
+
+    HAS_ISORT_5 = True
+except ImportError:  # isort < 5
+    import isort
+
+    HAS_ISORT_5 = False
+
 import codecs
 import os
 import re
@@ -398,3 +407,29 @@ def _ini_format(stream, options):
                 # remove trailing ',' from last element of the list
                 value = value[:-1]
             print("%s=%s" % (optname, value), file=stream)
+
+
+class IsortDriver:
+    """A wrapper around isort API that changed between versions 4 and 5."""
+
+    def __init__(self, config):
+        if HAS_ISORT_5:
+            self.isort5_config = isort.api.Config(
+                # There is not typo here. EXTRA_standard_library is
+                # what most users want. The option has been named
+                # KNOWN_standard_library for ages in pylint and we
+                # don't want to break compatibility.
+                extra_standard_library=config.known_standard_library,
+                known_third_party=config.known_third_party,
+            )
+        else:
+            self.isort4_obj = isort.SortImports(  # pylint: disable=no-member
+                file_contents="",
+                known_standard_library=config.known_standard_library,
+                known_third_party=config.known_third_party,
+            )
+
+    def place_module(self, package):
+        if HAS_ISORT_5:
+            return isort.api.place_module(package, self.isort5_config)
+        return self.isort4_obj.place_module(package)