Improve error message output

refurb/checks/builtin/list_extend.py

@@ -43,7 +43,6 @@ class ErrorInfo(Error):
 
     name = "use-list-extend"
     code = 113
-    msg: str = "Use `x.extend(...)` instead of repeatedly calling `x.append()`"
     categories = ("list",)
 
 
@@ -73,7 +72,12 @@ def check_stmts(stmts: list[Statement], errors: list[Error]) -> None:
                 )
             ) if str(ty).startswith("builtins.list["):
                 if not last.did_error and name == last.name:
-                    errors.append(ErrorInfo(last.line, last.column))
+                    old = f"{name}.append(...); {name}.append(...)"
+                    new = f"{name}.extend((..., ...))"
+                    msg = f"Replace `{old}` with `{new}`"
+
+                    errors.append(ErrorInfo(last.line, last.column, msg))
+
                     last.did_error = True
 
                 last.name = name

refurb/checks/builtin/no_is_type_none.py

@@ -2,7 +2,7 @@
 
 from mypy.nodes import CallExpr, ComparisonExpr, NameExpr
 
-from refurb.checks.common import is_type_none_call
+from refurb.checks.common import is_type_none_call, stringify
 from refurb.error import Error
 
 
@@ -41,12 +41,14 @@ def check(node: ComparisonExpr, errors: list[Error]) -> None:
         case ComparisonExpr(
             operators=["is" | "is not" | "==" | "!=" as oper],
             operands=[
-                CallExpr(callee=NameExpr(fullname="builtins.type")),
+                CallExpr(callee=NameExpr(fullname="builtins.type"), args=[arg]),
                 rhs,
             ],
         ) if is_type_none_call(rhs):
             new = "is" if oper in {"is", "=="} else "is not"
 
-            msg = f"Replace `type(x) {oper} type(None)` with `x {new} None`"
+            expr = stringify(arg)
+
+            msg = f"Replace `type({expr}) {oper} type(None)` with `{expr} {new} None`"
 
             errors.append(ErrorInfo.from_node(node, msg))

refurb/checks/builtin/no_slice_copy.py

@@ -2,6 +2,7 @@
 
 from mypy.nodes import AssignmentStmt, DelStmt, IndexExpr, MypyFile, RefExpr, SliceExpr, Var
 
+from refurb.checks.common import stringify
 from refurb.error import Error
 from refurb.visitor import TraverserVisitor
 
@@ -29,7 +30,6 @@ class ErrorInfo(Error):
 
     name = "no-slice-copy"
     code = 145
-    msg: str = "Replace `x[:]` with `x.copy()`"
     categories = ("readability",)
 
 
@@ -57,8 +57,6 @@ def visit_del_stmt(self, node: DelStmt) -> None:
             self.accept(node.expr)
 
     def visit_index_expr(self, node: IndexExpr) -> None:
-        index = node.index
-
         match node.base:
             case RefExpr(node=Var(type=ty)):
                 if not str(ty).startswith(SEQUENCE_BUILTINS):
@@ -67,11 +65,12 @@ def visit_index_expr(self, node: IndexExpr) -> None:
             case _:
                 return
 
-        if (
-            isinstance(index, SliceExpr)
-            and index.begin_index is index.end_index is index.stride is None
-        ):
-            self.errors.append(ErrorInfo.from_node(node))
+        match node.index:
+            case SliceExpr(begin_index=None, end_index=None, stride=None):
+                base = stringify(node.base)
+                msg = f"Replace `{base}[:]` with `{base}.copy()`"
+
+                self.errors.append(ErrorInfo.from_node(node, msg))
 
 
 def check(node: MypyFile, errors: list[Error]) -> None:

refurb/checks/builtin/use_int_base_zero.py

@@ -2,6 +2,7 @@
 
 from mypy.nodes import ArgKind, CallExpr, IndexExpr, IntExpr, RefExpr, SliceExpr
 
+from refurb.checks.common import stringify
 from refurb.error import Error
 
 
@@ -56,6 +57,7 @@ def check(node: CallExpr, errors: list[Error]) -> None:
             callee=RefExpr(fullname="builtins.int"),
             args=[
                 IndexExpr(
+                    base=index_base,
                     index=SliceExpr(
                         begin_index=IntExpr(value=2),
                         end_index=None,
@@ -69,9 +71,10 @@ def check(node: CallExpr, errors: list[Error]) -> None:
         ):
             kw = "base=" if arg_kinds[1] == ArgKind.ARG_NAMED else ""
 
-            errors.append(
-                ErrorInfo.from_node(
-                    node,
-                    f"Replace `int(x[2:], {kw}{base})` with `int(x, {kw}0)`",
-                )
-            )
+            index_base_expr = stringify(index_base)
+
+            old = f"int({index_base_expr}[2:], {kw}{base})"
+            new = f"int({index_base_expr}, {kw}0)"
+            msg = f"Replace `{old}` with `{new}`"
+
+            errors.append(ErrorInfo.from_node(node, msg))

refurb/checks/pattern_matching/simplify_as_builtin.py

@@ -58,6 +58,12 @@ def check(node: AsPattern, errors: list[Error]) -> None:
                 positionals=[],
                 keyword_keys=[],
                 keyword_values=[],
-            )
-        ) if fullname in BUILTIN_PATTERN_CLASSES:
-            errors.append(ErrorInfo.from_node(node, f"Replace `{name}() as x` with `{name}(x)`"))
+            ),
+            name=as_name,
+        ) if as_name and fullname in BUILTIN_PATTERN_CLASSES:
+            old = f"{name}() as {as_name.name}"
+            new = f"{name}({as_name.name})"
+
+            msg = f"Replace `{old}` with `{new}`"
+
+            errors.append(ErrorInfo.from_node(node, msg))

refurb/checks/readability/no_or_default.py

@@ -13,7 +13,7 @@
     Var,
 )
 
-from refurb.checks.common import extract_binary_oper
+from refurb.checks.common import extract_binary_oper, stringify
 from refurb.error import Error
 
 
@@ -49,38 +49,31 @@ def is_markdown_header(line: str) -> bool:
 
 def check(node: OpExpr, errors: list[Error]) -> None:
     match extract_binary_oper("or", node):
-        case (NameExpr(node=Var(type=ty)), arg):
+        case (NameExpr(node=Var(type=ty)) as lhs, arg):
             match arg:
-                case CallExpr(callee=NameExpr(name=name, fullname=fullname), args=[]):
-                    expr = f"{name}()"
+                case CallExpr(callee=NameExpr(fullname=fullname), args=[]):
+                    pass
 
                 case ListExpr(items=[]):
                     fullname = "builtins.list"
-                    expr = "[]"
 
                 case DictExpr(items=[]):
                     fullname = "builtins.dict"
-                    expr = "{}"
 
                 case TupleExpr(items=[]):
                     fullname = "builtins.tuple"
-                    expr = "()"
 
                 case StrExpr(value=""):
                     fullname = "builtins.str"
-                    expr = '""'
 
                 case BytesExpr(value=""):
                     fullname = "builtins.bytes"
-                    expr = 'b""'
 
                 case IntExpr(value=0):
                     fullname = "builtins.int"
-                    expr = "0"
 
                 case NameExpr(fullname="builtins.False"):
                     fullname = "builtins.bool"
-                    expr = "False"
 
                 case _:
                     return
@@ -89,4 +82,9 @@ def check(node: OpExpr, errors: list[Error]) -> None:
 
             # Must check fullname for compatibility with older Mypy versions
             if fullname and type_name.startswith(fullname):
-                errors.append(ErrorInfo.from_node(node, f"Replace `x or {expr}` with `x`"))
+                lhs_expr = stringify(lhs)
+                rhs_expr = stringify(arg)
+
+                msg = f"Replace `{lhs_expr} or {rhs_expr}` with `{lhs_expr}`"
+
+                errors.append(ErrorInfo.from_node(node, msg))

test/data/err_113.txt

@@ -1,6 +1,6 @@
-test/data/err_113.py:6:1 [FURB113]: Use `x.extend(...)` instead of repeatedly calling `x.append()`
-test/data/err_113.py:13:1 [FURB113]: Use `x.extend(...)` instead of repeatedly calling `x.append()`
-test/data/err_113.py:18:1 [FURB113]: Use `x.extend(...)` instead of repeatedly calling `x.append()`
-test/data/err_113.py:24:5 [FURB113]: Use `x.extend(...)` instead of repeatedly calling `x.append()`
-test/data/err_113.py:29:5 [FURB113]: Use `x.extend(...)` instead of repeatedly calling `x.append()`
-test/data/err_113.py:37:5 [FURB113]: Use `x.extend(...)` instead of repeatedly calling `x.append()`
+test/data/err_113.py:6:1 [FURB113]: Replace `nums.append(...); nums.append(...)` with `nums.extend((..., ...))`
+test/data/err_113.py:13:1 [FURB113]: Replace `nums.append(...); nums.append(...)` with `nums.extend((..., ...))`
+test/data/err_113.py:18:1 [FURB113]: Replace `nums.append(...); nums.append(...)` with `nums.extend((..., ...))`
+test/data/err_113.py:24:5 [FURB113]: Replace `nums.append(...); nums.append(...)` with `nums.extend((..., ...))`
+test/data/err_113.py:29:5 [FURB113]: Replace `nums.append(...); nums.append(...)` with `nums.extend((..., ...))`
+test/data/err_113.py:37:5 [FURB113]: Replace `nums.append(...); nums.append(...)` with `nums.extend((..., ...))`

test/data/err_143.txt

@@ -1,10 +1,10 @@
-test/data/err_143.py:14:5 [FURB143]: Replace `x or set()` with `x`
-test/data/err_143.py:15:5 [FURB143]: Replace `x or frozenset()` with `x`
-test/data/err_143.py:16:5 [FURB143]: Replace `x or []` with `x`
-test/data/err_143.py:17:5 [FURB143]: Replace `x or {}` with `x`
-test/data/err_143.py:18:5 [FURB143]: Replace `x or ()` with `x`
-test/data/err_143.py:19:5 [FURB143]: Replace `x or ()` with `x`
-test/data/err_143.py:20:5 [FURB143]: Replace `x or ""` with `x`
-test/data/err_143.py:21:5 [FURB143]: Replace `x or b""` with `x`
-test/data/err_143.py:22:5 [FURB143]: Replace `x or False` with `x`
-test/data/err_143.py:23:5 [FURB143]: Replace `x or 0` with `x`
+test/data/err_143.py:14:5 [FURB143]: Replace `s or set()` with `s`
+test/data/err_143.py:15:5 [FURB143]: Replace `f or frozenset()` with `f`
+test/data/err_143.py:16:5 [FURB143]: Replace `l or []` with `l`
+test/data/err_143.py:17:5 [FURB143]: Replace `d or {}` with `d`
+test/data/err_143.py:18:5 [FURB143]: Replace `t or ()` with `t`
+test/data/err_143.py:19:5 [FURB143]: Replace `t2 or ()` with `t2`
+test/data/err_143.py:20:5 [FURB143]: Replace `r or ""` with `r`
+test/data/err_143.py:21:5 [FURB143]: Replace `b or b""` with `b`
+test/data/err_143.py:22:5 [FURB143]: Replace `n or False` with `n`
+test/data/err_143.py:23:5 [FURB143]: Replace `i or 0` with `i`

test/data/err_145.txt

@@ -1,3 +1,3 @@
-test/data/err_145.py:7:5 [FURB145]: Replace `x[:]` with `x.copy()`
-test/data/err_145.py:8:5 [FURB145]: Replace `x[:]` with `x.copy()`
-test/data/err_145.py:9:5 [FURB145]: Replace `x[:]` with `x.copy()`
+test/data/err_145.py:7:5 [FURB145]: Replace `nums[:]` with `nums.copy()`
+test/data/err_145.py:8:5 [FURB145]: Replace `t[:]` with `t.copy()`
+test/data/err_145.py:9:5 [FURB145]: Replace `barray[:]` with `barray.copy()`

test/data/err_158.txt

@@ -1,11 +1,11 @@
-test/data/err_158.py:5:14 [FURB158]: Replace `bool() as x` with `bool(x)`
-test/data/err_158.py:6:14 [FURB158]: Replace `bytearray() as x` with `bytearray(x)`
-test/data/err_158.py:7:14 [FURB158]: Replace `bytes() as x` with `bytes(x)`
-test/data/err_158.py:8:14 [FURB158]: Replace `dict() as x` with `dict(x)`
-test/data/err_158.py:9:14 [FURB158]: Replace `float() as x` with `float(x)`
-test/data/err_158.py:10:14 [FURB158]: Replace `frozenset() as x` with `frozenset(x)`
-test/data/err_158.py:11:14 [FURB158]: Replace `int() as x` with `int(x)`
-test/data/err_158.py:12:14 [FURB158]: Replace `list() as x` with `list(x)`
-test/data/err_158.py:13:14 [FURB158]: Replace `set() as x` with `set(x)`
-test/data/err_158.py:14:14 [FURB158]: Replace `str() as x` with `str(x)`
-test/data/err_158.py:15:14 [FURB158]: Replace `tuple() as x` with `tuple(x)`
+test/data/err_158.py:5:14 [FURB158]: Replace `bool() as a` with `bool(a)`
+test/data/err_158.py:6:14 [FURB158]: Replace `bytearray() as b` with `bytearray(b)`
+test/data/err_158.py:7:14 [FURB158]: Replace `bytes() as c` with `bytes(c)`
+test/data/err_158.py:8:14 [FURB158]: Replace `dict() as d` with `dict(d)`
+test/data/err_158.py:9:14 [FURB158]: Replace `float() as e` with `float(e)`
+test/data/err_158.py:10:14 [FURB158]: Replace `frozenset() as f` with `frozenset(f)`
+test/data/err_158.py:11:14 [FURB158]: Replace `int() as g` with `int(g)`
+test/data/err_158.py:12:14 [FURB158]: Replace `list() as h` with `list(h)`
+test/data/err_158.py:13:14 [FURB158]: Replace `set() as i` with `set(i)`
+test/data/err_158.py:14:14 [FURB158]: Replace `str() as j` with `str(j)`
+test/data/err_158.py:15:14 [FURB158]: Replace `tuple() as k` with `tuple(k)`

test/data/err_166.txt

@@ -1,5 +1,5 @@
-test/data/err_166.py:3:5 [FURB166]: Replace `int(x[2:], 2)` with `int(x, 0)`
-test/data/err_166.py:4:5 [FURB166]: Replace `int(x[2:], 8)` with `int(x, 0)`
-test/data/err_166.py:5:5 [FURB166]: Replace `int(x[2:], 16)` with `int(x, 0)`
-test/data/err_166.py:8:5 [FURB166]: Replace `int(x[2:], 2)` with `int(x, 0)`
-test/data/err_166.py:10:5 [FURB166]: Replace `int(x[2:], base=16)` with `int(x, base=0)`
+test/data/err_166.py:3:5 [FURB166]: Replace `int("0b1010"[2:], 2)` with `int("0b1010", 0)`
+test/data/err_166.py:4:5 [FURB166]: Replace `int("0o777"[2:], 8)` with `int("0o777", 0)`
+test/data/err_166.py:5:5 [FURB166]: Replace `int("0xFFFF"[2:], 16)` with `int("0xFFFF", 0)`
+test/data/err_166.py:8:5 [FURB166]: Replace `int(b[2:], 2)` with `int(b, 0)`
+test/data/err_166.py:10:5 [FURB166]: Replace `int("0xFFFF"[2:], base=16)` with `int("0xFFFF", base=0)`

test/data/err_169.py

@@ -11,3 +11,4 @@
 _ = type(123) is type(456)
 _ = type(123) is int
 _ = int is type(None)
+_ = type() is type(None)  # type: ignore

test/data/err_169.txt

@@ -1,4 +1,4 @@
-test/data/err_169.py:3:5 [FURB169]: Replace `type(x) is type(None)` with `x is None`
-test/data/err_169.py:4:5 [FURB169]: Replace `type(x) == type(None)` with `x is None`
-test/data/err_169.py:5:5 [FURB169]: Replace `type(x) is not type(None)` with `x is not None`
-test/data/err_169.py:6:5 [FURB169]: Replace `type(x) != type(None)` with `x is not None`
+test/data/err_169.py:3:5 [FURB169]: Replace `type(123) is type(None)` with `123 is None`
+test/data/err_169.py:4:5 [FURB169]: Replace `type(123) == type(None)` with `123 is None`
+test/data/err_169.py:5:5 [FURB169]: Replace `type(123) is not type(None)` with `123 is not None`
+test/data/err_169.py:6:5 [FURB169]: Replace `type(123) != type(None)` with `123 is not None`