Make ``consider-using-f-string`` skip `format()` with backslash (#5055)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

4 files changed, 45 insertions, 25 deletions

diff --git a/ChangeLog b/ChangeLog
index c078c2ae2..4b2a26008 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -29,6 +29,8 @@ Release date: TBA
 
   Closes #5029
 
+* Don't emit ``consider-using-f-string`` if the variables to be interpolated include a backslash
+
 * Fixed false positive for ``cell-var-from-loop`` when variable is used as the default
   value for a keyword-only parameter.
 
diff --git a/pylint/checkers/refactoring/recommendation_checker.py b/pylint/checkers/refactoring/recommendation_checker.py
index b22f18acd..7e8abcb7e 100644
--- a/pylint/checkers/refactoring/recommendation_checker.py
+++ b/pylint/checkers/refactoring/recommendation_checker.py
@@ -355,6 +355,9 @@ class RecommendationChecker(checkers.BaseChecker):
                             and len(inferred.elts) > 1
                         ):
                             return
+                    # Backslashes can't be in f-string expressions
+                    if "\\" in arg.as_string():
+                        return
 
             elif node.parent.parent.keywords:
                 keyword_args = [
@@ -381,6 +384,10 @@ class RecommendationChecker(checkers.BaseChecker):
             )
 
         elif isinstance(node.parent, nodes.BinOp) and node.parent.op == "%":
+            # Backslashes can't be in f-string expressions
+            if "\\" in node.parent.right.as_string():
+                return
+
             inferred_right = utils.safe_infer(node.parent.right)
 
             # If dicts or lists of length > 1 are used
diff --git a/tests/functional/c/consider/consider_using_f_string.py b/tests/functional/c/consider/consider_using_f_string.py
index 825f3517c..1d5400d5a 100644
--- a/tests/functional/c/consider/consider_using_f_string.py
+++ b/tests/functional/c/consider/consider_using_f_string.py
@@ -1,6 +1,6 @@
 """Test to see if a f-string would be possible and consider-using-f-string should be raised"""
 # pylint: disable=unused-variable, invalid-name, missing-function-docstring, pointless-statement
-# pylint: disable=expression-not-assigned, repeated-keyword
+# pylint: disable=expression-not-assigned, repeated-keyword, too-many-locals
 
 PARAM_1 = PARAM_2 = PARAM_3 = 1
 PARAM_LIST = [PARAM_1, PARAM_2, PARAM_3]
@@ -35,6 +35,11 @@ def print_good():
     print("%(Param_1)s %(Param_2)s" % PARAM_DICT)
     print("%(Param_1)s %(Param_2)s" % return_dict())
     print("{a[Param_1]}{a[Param_2]}".format(a=PARAM_DICT))
+    print("{}".format("\n"))
+    print("{}".format("\n".join(i for i in "string")))
+    print("%s" % "\n")
+    print("%s" % "\n".join(i for i in "string"))
+
 
 def print_bad():
     print("String %f" % PARAM_1)  # [consider-using-f-string]
@@ -63,6 +68,10 @@ def statement_good():
     "%(Param_1)s %(Param_2)s" % PARAM_DICT
     "%(Param_1)s %(Param_2)s" % return_dict()
     "{a[Param_1]}{a[Param_2]}".format(a=PARAM_DICT)
+    "{}".format("\n")
+    "{}".format("\n".join(i for i in "string"))
+    "%s" % "\n"
+    "%s" % "\n".join(i for i in "string")
 
 def statement_bad():
     "String %f" % PARAM_1  # [consider-using-f-string]
@@ -92,6 +101,8 @@ def assignment_good():
     L = "%(Param_1)s %(Param_2)s" % return_dict()
     M = "{a[Param_1]}{a[Param_2]}".format(a=PARAM_DICT)
     N = "{Param}".format
+    O = "%s" % "\n"
+    P = "%s" % "\n".join(i for i in "string")
 
 
 def assignment_bad():
diff --git a/tests/functional/c/consider/consider_using_f_string.txt b/tests/functional/c/consider/consider_using_f_string.txt
index db8f98112..65363cea4 100644
--- a/tests/functional/c/consider/consider_using_f_string.txt
+++ b/tests/functional/c/consider/consider_using_f_string.txt
@@ -1,30 +1,30 @@
-consider-using-f-string:40:10:print_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:41:10:print_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:42:10:print_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:43:10:print_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:44:10:print_bad:Formatting a regular string which could be a f-string:HIGH
 consider-using-f-string:45:10:print_bad:Formatting a regular string which could be a f-string:HIGH
 consider-using-f-string:46:10:print_bad:Formatting a regular string which could be a f-string:HIGH
 consider-using-f-string:47:10:print_bad:Formatting a regular string which could be a f-string:HIGH
 consider-using-f-string:48:10:print_bad:Formatting a regular string which could be a f-string:HIGH
 consider-using-f-string:49:10:print_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:68:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:69:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:70:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:71:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:72:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:73:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:74:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:75:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:76:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:50:10:print_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:51:10:print_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:52:10:print_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:53:10:print_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:54:10:print_bad:Formatting a regular string which could be a f-string:HIGH
 consider-using-f-string:77:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:98:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:99:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:100:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:101:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:102:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:103:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:104:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:105:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:106:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
-consider-using-f-string:107:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:78:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:79:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:80:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:81:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:82:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:83:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:84:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:85:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:86:4:statement_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:109:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:110:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:111:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:112:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:113:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:114:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:115:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:116:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:117:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH
+consider-using-f-string:118:8:assignment_bad:Formatting a regular string which could be a f-string:HIGH