[flake8-use-pathlib] extend PTH118 with os.sep (#5935)

Closes #5905

Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

crates/ruff/resources/test/fixtures/flake8_use_pathlib/full_name.py

@@ -2,6 +2,7 @@
 import os.path
 
 p = "/foo"
+q = "bar"
 
 a = os.path.abspath(p)
 aa = os.chmod(p)
@@ -21,7 +22,9 @@
 os.readlink(p)
 os.stat(p)
 os.path.isabs(p)
-os.path.join(p)
+os.path.join(p, q)
+os.sep.join([p, q])
+os.sep.join((p, q))
 os.path.basename(p)
 os.path.dirname(p)
 os.path.samefile(p)

crates/ruff/resources/test/fixtures/flake8_use_pathlib/import_as.py

@@ -2,6 +2,7 @@
 import os.path as foo_p
 
 p = "/foo"
+q = "bar"
 
 a = foo_p.abspath(p)
 aa = foo.chmod(p)
@@ -21,7 +22,9 @@
 foo.readlink(p)
 foo.stat(p)
 foo_p.isabs(p)
-foo_p.join(p)
+foo_p.join(p, q)
+foo.sep.join([p, q])
+foo.sep.join((p, q))
 foo_p.basename(p)
 foo_p.dirname(p)
 foo_p.samefile(p)

crates/ruff/resources/test/fixtures/flake8_use_pathlib/import_from.py

@@ -1,9 +1,10 @@
-from os import chmod, mkdir, makedirs, rename, replace, rmdir
+from os import chmod, mkdir, makedirs, rename, replace, rmdir, sep
 from os import remove, unlink, getcwd, readlink, stat
 from os.path import abspath, exists, expanduser, isdir, isfile, islink
 from os.path import isabs, join, basename, dirname, samefile, splitext
 
 p = "/foo"
+q = "bar"
 
 a = abspath(p)
 aa = chmod(p)
@@ -23,7 +24,9 @@
 readlink(p)
 stat(p)
 isabs(p)
-join(p)
+join(p, q)
+sep.join((p, q))
+sep.join([p, q])
 basename(p)
 dirname(p)
 samefile(p)

crates/ruff/resources/test/fixtures/flake8_use_pathlib/import_from_as.py

@@ -1,4 +1,4 @@
-from os import chmod as xchmod, mkdir as xmkdir
+from os import chmod as xchmod, mkdir as xmkdir, sep as s
 from os import makedirs as xmakedirs, rename as xrename, replace as xreplace
 from os import rmdir as xrmdir, remove as xremove, unlink as xunlink
 from os import getcwd as xgetcwd, readlink as xreadlink, stat as xstat
@@ -9,6 +9,7 @@
 from os.path import samefile as xsamefile, splitext as xsplitext
 
 p = "/foo"
+q = "bar"
 
 a = xabspath(p)
 aa = xchmod(p)
@@ -28,7 +29,9 @@
 xreadlink(p)
 xstat(p)
 xisabs(p)
-xjoin(p)
+xjoin(p, q)
+s.join((p, q))
+s.join([p, q])
 xbasename(p)
 xdirname(p)
 xsamefile(p)

crates/ruff/src/rules/flake8_use_pathlib/rules/replaceable_by_pathlib.rs

@@ -57,7 +57,18 @@ pub(crate) fn replaceable_by_pathlib(checker: &mut Checker, expr: &Expr) {
                 // PTH117
                 ["os", "path", "isabs"] => Some(OsPathIsabs.into()),
                 // PTH118
-                ["os", "path", "join"] => Some(OsPathJoin.into()),
+                ["os", "path", "join"] => Some(
+                    OsPathJoin {
+                        module: "path".to_string(),
+                    }
+                    .into(),
+                ),
+                ["os", "sep", "join"] => Some(
+                    OsPathJoin {
+                        module: "sep".to_string(),
+                    }
+                    .into(),
+                ),
                 // PTH119
                 ["os", "path", "basename"] => Some(OsPathBasename.into()),
                 // PTH120