Add is operator to FURB124 (use equal chain)

refurb/checks/common.py

@@ -185,7 +185,7 @@ def get_common_expr_positions(*exprs: Expression) -> tuple[int, int] | None:
 
 
 def get_common_expr_in_comparison_chain(
-    node: OpExpr, oper: str
+    node: OpExpr, oper: str, cmp_oper: str = "=="
 ) -> tuple[Expression, tuple[int, int]] | None:
     """
     This function finds the first expression shared between 2 comparison
@@ -206,9 +206,12 @@ def get_common_expr_in_comparison_chain(
 
     match extract_binary_oper(oper, node):
         case (
-            ComparisonExpr(operators=["=="], operands=[a, b]),
-            ComparisonExpr(operators=["=="], operands=[c, d]),
-        ) if indices := get_common_expr_positions(a, b, c, d):
+            ComparisonExpr(operators=[lhs_oper], operands=[a, b]),
+            ComparisonExpr(operators=[rhs_oper], operands=[c, d]),
+        ) if (
+            lhs_oper == rhs_oper == cmp_oper
+            and (indices := get_common_expr_positions(a, b, c, d))
+        ):
             return a, indices
 
     return None  # pragma: no cover

refurb/checks/logical/use_equal_chain.py

@@ -17,13 +17,23 @@ class ErrorInfo(Error):
     ```
     if x == y and x == z:
         pass
+
+    # and
+
+    if x is None and y is None
+        pass
     ```
 
     Good:
 
     ```
     if x == y == z:
         pass
+
+    # and
+
+    if x is y is None:
+        pass
     ```
 
     Note: if `x` depends on side-effects, then this check should be ignored.
@@ -33,19 +43,24 @@ class ErrorInfo(Error):
     categories = ["logical", "readability"]
 
 
-def create_message(indices: tuple[int, int]) -> str:
+def create_message(indices: tuple[int, int], oper: str = "==") -> str:
     names = ["x", "y", "z"]
     names.insert(indices[1], names[indices[0]])
 
-    expr = f"{names[0]} == {names[1]} and {names[2]} == {names[3]}"
+    expr = f"{names[0]} {oper} {names[1]} and {names[2]} {oper} {names[3]}"
 
-    return f"Replace `{expr}` with `x == y == z`"
+    return f"Replace `{expr}` with `x {oper} y {oper} z`"
 
 
 def check(node: OpExpr, errors: list[Error]) -> None:
-    if data := get_common_expr_in_comparison_chain(node, oper="and"):
-        expr, indices = data
-
-        errors.append(
-            ErrorInfo(expr.line, expr.column, create_message(indices))
-        )
+    for cmp_oper in ("==", "is"):
+        if data := get_common_expr_in_comparison_chain(node, "and", cmp_oper):
+            expr, indices = data
+
+            errors.append(
+                ErrorInfo(
+                    expr.line,
+                    expr.column,
+                    create_message(indices, cmp_oper),
+                )
+            )

test/data/err_124.py

@@ -9,10 +9,18 @@
 _ = x == y and y == z and z == 1
 _ = x == y and z == x
 
+_ = x is None and y is None
+_ = x is None and None is y
+_ = None is x and y is None
+_ = x is None and y is None and True
+
 
 # these should not
 
 _ = x == y and z == 1
 _ = x == y or 1 == z
 _ = x == y or 1 == z
 _ = x == y or x <= z
+
+_ = x is None and y is 1
+_ = x is None or y is None

test/data/err_124.txt

@@ -5,3 +5,7 @@ test/data/err_124.py:8:5 [FURB124]: Replace `x == y and x == z` with `x == y ==
 test/data/err_124.py:9:5 [FURB124]: Replace `x == y and y == z` with `x == y == z`
 test/data/err_124.py:9:16 [FURB124]: Replace `x == y and y == z` with `x == y == z`
 test/data/err_124.py:10:5 [FURB124]: Replace `x == y and z == x` with `x == y == z`
+test/data/err_124.py:12:5 [FURB124]: Replace `x is y and z is y` with `x is y is z`
+test/data/err_124.py:13:5 [FURB124]: Replace `x is y and y is z` with `x is y is z`
+test/data/err_124.py:14:5 [FURB124]: Replace `x is y and z is x` with `x is y is z`
+test/data/err_124.py:15:5 [FURB124]: Replace `x is y and z is y` with `x is y is z`