Further improve error messages

refurb/checks/common.py

@@ -338,6 +338,16 @@ def _stringify(node: Node) -> str:
 
             return f"{name}({args})"
 
+        case IndexExpr(base=base, index=index):
+            return f"{stringify(base)}[{stringify(index)}]"
+
+        case SliceExpr(begin_index=begin_index, end_index=end_index, stride=stride):
+            begin = stringify(begin_index) if begin_index else ""
+            end = stringify(end_index) if end_index else ""
+            stride = f":{stringify(stride)}" if stride else ""  # type: ignore[assignment]
+
+            return f"{begin}:{end}{stride}"
+
         case OpExpr(left=left, op=op, right=right):
             return f"{_stringify(left)} {op} {_stringify(right)}"
 
@@ -352,7 +362,10 @@ def _stringify(node: Node) -> str:
             return " ".join(parts)
 
         case UnaryExpr(op=op, expr=expr):
-            return f"{op} {_stringify(expr)}"
+            if op not in "+-~":
+                op += " "
+
+            return f"{op}{_stringify(expr)}"
 
         case LambdaExpr(
             arg_names=arg_names,

refurb/checks/pathlib/open.py

@@ -2,6 +2,7 @@
 
 from mypy.nodes import CallExpr, NameExpr, StrExpr
 
+from refurb.checks.common import stringify
 from refurb.checks.pathlib.util import is_pathlike
 from refurb.error import Error
 
@@ -56,11 +57,9 @@ def check(node: CallExpr, errors: list[Error]) -> None:
                     mode = f'"{value}"'
                     args = f", {mode}"
 
-            expr = "x" if arg == node.args[0] else "str(x)"
+            inner = stringify(arg)
+            expr = inner if arg == node.args[0] else f"str({inner})"
 
-            errors.append(
-                ErrorInfo.from_node(
-                    open_node,
-                    f"Replace `open({expr}{args})` with `x.open({mode})`",
-                )
-            )
+            msg = f"Replace `open({expr}{args})` with `{inner}.open({mode})`"
+
+            errors.append(ErrorInfo.from_node(open_node, msg))

refurb/checks/pathlib/with_suffix.py

@@ -2,6 +2,7 @@
 
 from mypy.nodes import CallExpr, IndexExpr, NameExpr, OpExpr, SliceExpr, StrExpr
 
+from refurb.checks.common import stringify
 from refurb.error import Error
 
 from .util import is_pathlike
@@ -29,7 +30,6 @@ class ErrorInfo(Error):
 
     name = "use-pathlib-with-suffix"
     code = 100
-    msg: str = "Use `Path(x).with_suffix(y)` instead of slice and concat"
     categories = ("pathlib",)
 
 
@@ -44,6 +44,11 @@ def check(node: OpExpr, errors: list[Error]) -> None:
                 ),
                 index=SliceExpr(begin_index=None),
             ),
-            right=StrExpr(),
+            right=StrExpr() as suffix,
         ) if is_pathlike(arg):
-            errors.append(ErrorInfo.from_node(arg))
+            old = stringify(node)
+            new = f"Path({stringify(arg)}).with_suffix({suffix})"
+
+            msg = f"Replace `{old}` with `{new}`"
+
+            errors.append(ErrorInfo.from_node(arg, msg))

test/data/err_100.txt

@@ -1,3 +1,3 @@
-test/data/err_100.py:6:9 [FURB100]: Use `Path(x).with_suffix(y)` instead of slice and concat
-test/data/err_100.py:9:9 [FURB100]: Use `Path(x).with_suffix(y)` instead of slice and concat
-test/data/err_100.py:11:9 [FURB100]: Use `Path(x).with_suffix(y)` instead of slice and concat
+test/data/err_100.py:6:9 [FURB100]: Replace `str(Path("file.txt"))[:4] + ".pdf"` with `Path(Path("file.txt")).with_suffix(StrExpr(.pdf))`
+test/data/err_100.py:9:9 [FURB100]: Replace `str(p)[:4] + ".pdf"` with `Path(p).with_suffix(StrExpr(.pdf))`
+test/data/err_100.py:11:9 [FURB100]: Replace `str(pathlib.Path("file.txt"))[:4] + ".pdf"` with `Path(pathlib.Path("file.txt")).with_suffix(StrExpr(.pdf))`

test/data/err_117.txt

@@ -1,7 +1,7 @@
-test/data/err_117.py:7:6 [FURB117]: Replace `open(str(x))` with `x.open()`
-test/data/err_117.py:10:6 [FURB117]: Replace `open(str(x))` with `x.open()`
-test/data/err_117.py:13:6 [FURB117]: Replace `open(x)` with `x.open()`
-test/data/err_117.py:16:6 [FURB117]: Replace `open(x)` with `x.open()`
-test/data/err_117.py:19:6 [FURB117]: Replace `open(str(x), "rb")` with `x.open("rb")`
-test/data/err_117.py:22:6 [FURB117]: Replace `open(x, "rb")` with `x.open("rb")`
-test/data/err_117.py:25:5 [FURB117]: Replace `open(str(x))` with `x.open()`
+test/data/err_117.py:7:6 [FURB117]: Replace `open(str(path))` with `path.open()`
+test/data/err_117.py:10:6 [FURB117]: Replace `open(str(Path("filename")))` with `Path("filename").open()`
+test/data/err_117.py:13:6 [FURB117]: Replace `open(Path("filename"))` with `Path("filename").open()`
+test/data/err_117.py:16:6 [FURB117]: Replace `open(path)` with `path.open()`
+test/data/err_117.py:19:6 [FURB117]: Replace `open(str(path), "rb")` with `path.open("rb")`
+test/data/err_117.py:22:6 [FURB117]: Replace `open(path, "rb")` with `path.open("rb")`
+test/data/err_117.py:25:5 [FURB117]: Replace `open(str(path))` with `path.open()`

test/data/err_118.py

@@ -23,10 +23,10 @@
 lambda x, y: x >= y
 lambda x, y: x > y
 
-lambda x: ~ x
-lambda x: - x
+lambda x: ~x
+lambda x: -x
 lambda x: not x
-lambda x: + x
+lambda x: +x
 
 def f(x, y):
     return x + y

test/data/err_118.txt

@@ -20,9 +20,9 @@ test/data/err_118.py:21:1 [FURB118]: Replace `lambda x, y: x == y` with `operato
 test/data/err_118.py:22:1 [FURB118]: Replace `lambda x, y: x != y` with `operator.ne`
 test/data/err_118.py:23:1 [FURB118]: Replace `lambda x, y: x >= y` with `operator.ge`
 test/data/err_118.py:24:1 [FURB118]: Replace `lambda x, y: x > y` with `operator.gt`
-test/data/err_118.py:26:1 [FURB118]: Replace `lambda x: ~ x` with `operator.invert`
-test/data/err_118.py:27:1 [FURB118]: Replace `lambda x: - x` with `operator.neg`
+test/data/err_118.py:26:1 [FURB118]: Replace `lambda x: ~x` with `operator.invert`
+test/data/err_118.py:27:1 [FURB118]: Replace `lambda x: -x` with `operator.neg`
 test/data/err_118.py:28:1 [FURB118]: Replace `lambda x: not x` with `operator.not_`
-test/data/err_118.py:29:1 [FURB118]: Replace `lambda x: + x` with `operator.pos`
+test/data/err_118.py:29:1 [FURB118]: Replace `lambda x: +x` with `operator.pos`
 test/data/err_118.py:31:1 [FURB118]: Replace function with `operator.add`
 test/data/err_118.py:34:1 [FURB118]: Replace function with `operator.neg`

test/data/pathlib.txt

@@ -1,2 +1,2 @@
-test/data/pathlib.py:7:6 [FURB117]: Replace `open(x)` with `x.open()`
-test/data/pathlib.py:10:6 [FURB117]: Replace `open(x)` with `x.open()`
+test/data/pathlib.py:7:6 [FURB117]: Replace `open(folder / "file.txt")` with `folder / "file.txt".open()`
+test/data/pathlib.py:10:6 [FURB117]: Replace `open(folder / "another_folder" / "file.txt")` with `folder / "another_folder" / "file.txt".open()`

test/data/stringify.py

@@ -1,2 +1,9 @@
 # test double star in dict expr
 _ = dict({**{}})
+
+# test different slice exprs
+_ = list([""[0]])
+_ = list([""[1:]])
+_ = list([""[1:2]])
+_ = list([""[1:2:-1]])
+_ = list([""[::-1]])

test/data/stringify.txt

@@ -1 +1,6 @@
 test/data/stringify.py:2:5 [FURB123]: Replace `dict({**{}})` with `{**{}}.copy()`
+test/data/stringify.py:5:5 [FURB123]: Replace `list([""[0]])` with `[""[0]].copy()`
+test/data/stringify.py:6:5 [FURB123]: Replace `list([""[1:]])` with `[""[1:]].copy()`
+test/data/stringify.py:7:5 [FURB123]: Replace `list([""[1:2]])` with `[""[1:2]].copy()`
+test/data/stringify.py:8:5 [FURB123]: Replace `list([""[1:2:-1]])` with `[""[1:2:-1]].copy()`
+test/data/stringify.py:9:5 [FURB123]: Replace `list([""[::-1]])` with `[""[::-1]].copy()`