Add use-str-method check

docs/checks.md

@@ -2395,4 +2395,30 @@ control the code, consider using the following type checks instead:
 
 * `dict` -> `collections.abc.MutableMapping`
 * `list` -> `collections.abc.MutableSequence`
-* `str` -> No such conversion exists
+* `str` -> No such conversion exists
+
+## FURB190: `use-str-method`
+
+Categories: `performance` `readability`
+
+Don't use a lambda function to call a no-arg method on a string, use the
+name of the string method directly. It is faster, and often times improves
+readability.
+
+Bad:
+
+```python
+def normalize_phone_number(phone_number: str) -> int:
+    digits = filter(lambda x: x.isdigit(), phone_number)
+
+    return int("".join(digits))
+```
+
+Good:
+
+```python
+def normalize_phone_number(phone_number: str) -> int:
+    digits = filter(str.isdigit, phone_number)
+
+    return int("".join(digits))
+```

refurb/checks/readability/use_str_method.py

@@ -0,0 +1,95 @@
+from dataclasses import dataclass
+
+from mypy.nodes import ArgKind, Block, CallExpr, LambdaExpr, MemberExpr, NameExpr, ReturnStmt, Var
+
+from refurb.checks.common import stringify
+from refurb.error import Error
+
+
+@dataclass
+class ErrorInfo(Error):
+    """
+    Don't use a lambda function to call a no-arg method on a string, use the
+    name of the string method directly. It is faster, and often times improves
+    readability.
+
+    Bad:
+
+    ```
+    def normalize_phone_number(phone_number: str) -> int:
+        digits = filter(lambda x: x.isdigit(), phone_number)
+
+        return int("".join(digits))
+    ```
+
+    Good:
+
+    ```
+    def normalize_phone_number(phone_number: str) -> int:
+        digits = filter(str.isdigit, phone_number)
+
+        return int("".join(digits))
+    ```
+    """
+
+    name = "use-str-method"
+    categories = ("performance", "readability")
+    code = 190
+
+
+STR_FUNCS = frozenset(
+    (
+        "capitalize",
+        "casefold",
+        "isalnum",
+        "isalpha",
+        "isascii",
+        "isdecimal",
+        "isdigit",
+        "isidentifier",
+        "islower",
+        "isnumeric",
+        "isprintable",
+        "isspace",
+        "istitle",
+        "isupper",
+        "lower",
+        "lstrip",
+        "rsplit",
+        "rstrip",
+        "split",
+        "splitlines",
+        "strip",
+        "swapcase",
+        "title",
+        "upper",
+    )
+)
+
+
+def check(node: LambdaExpr, errors: list[Error]) -> None:
+    match node:
+        case LambdaExpr(
+            arg_names=[arg_name],
+            arg_kinds=[ArgKind.ARG_POS],
+            body=Block(
+                body=[
+                    ReturnStmt(
+                        expr=CallExpr(
+                            callee=MemberExpr(
+                                expr=NameExpr(name=member_base_name, node=Var(type=ty)),
+                                name=str_func_name,
+                            ),
+                            args=[],
+                        ),
+                    )
+                ]
+            ),
+        ) if (
+            arg_name == member_base_name
+            and str_func_name in STR_FUNCS
+            and str(ty) in {"Any", "None", "builtins.str"}
+        ):
+            msg = f"Replace `{stringify(node)}` with `str.{str_func_name}`"
+
+            errors.append(ErrorInfo.from_node(node, msg))

test/data/err_190.py

@@ -0,0 +1,43 @@
+# these will match
+
+_ = lambda x: x.capitalize()
+_ = lambda x: x.casefold()
+_ = lambda x: x.isalnum()
+_ = lambda x: x.isalpha()
+_ = lambda x: x.isascii()
+_ = lambda x: x.isdecimal()
+_ = lambda x: x.isdigit()
+_ = lambda x: x.isidentifier()
+_ = lambda x: x.islower()
+_ = lambda x: x.isnumeric()
+_ = lambda x: x.isprintable()
+_ = lambda x: x.isspace()
+_ = lambda x: x.istitle()
+_ = lambda x: x.isupper()
+_ = lambda x: x.lower()
+_ = lambda x: x.lstrip()
+_ = lambda x: x.rsplit()
+_ = lambda x: x.rstrip()
+_ = lambda x: x.split()
+_ = lambda x: x.splitlines()
+_ = lambda x: x.strip()
+_ = lambda x: x.swapcase()
+_ = lambda x: x.title()
+_ = lambda x: x.upper()
+
+
+# these will not
+
+y = ""
+
+lambda *x: x.title()  # type: ignore
+lambda x: y.title()
+lambda: y.title()  # noqa: FURB111
+lambda x, y: x.title()
+
+lambda x: x + 1
+lambda x: x.split("\n")
+lambda x: x.strip().title()
+
+# ignore if we deduce the type of x is non-str
+map(lambda x: x.upper(), [1, 2, 3])  # type: ignore

test/data/err_190.txt

@@ -0,0 +1,24 @@
+test/data/err_190.py:3:5 [FURB190]: Replace `lambda x: x.capitalize()` with `str.capitalize`
+test/data/err_190.py:4:5 [FURB190]: Replace `lambda x: x.casefold()` with `str.casefold`
+test/data/err_190.py:5:5 [FURB190]: Replace `lambda x: x.isalnum()` with `str.isalnum`
+test/data/err_190.py:6:5 [FURB190]: Replace `lambda x: x.isalpha()` with `str.isalpha`
+test/data/err_190.py:7:5 [FURB190]: Replace `lambda x: x.isascii()` with `str.isascii`
+test/data/err_190.py:8:5 [FURB190]: Replace `lambda x: x.isdecimal()` with `str.isdecimal`
+test/data/err_190.py:9:5 [FURB190]: Replace `lambda x: x.isdigit()` with `str.isdigit`
+test/data/err_190.py:10:5 [FURB190]: Replace `lambda x: x.isidentifier()` with `str.isidentifier`
+test/data/err_190.py:11:5 [FURB190]: Replace `lambda x: x.islower()` with `str.islower`
+test/data/err_190.py:12:5 [FURB190]: Replace `lambda x: x.isnumeric()` with `str.isnumeric`
+test/data/err_190.py:13:5 [FURB190]: Replace `lambda x: x.isprintable()` with `str.isprintable`
+test/data/err_190.py:14:5 [FURB190]: Replace `lambda x: x.isspace()` with `str.isspace`
+test/data/err_190.py:15:5 [FURB190]: Replace `lambda x: x.istitle()` with `str.istitle`
+test/data/err_190.py:16:5 [FURB190]: Replace `lambda x: x.isupper()` with `str.isupper`
+test/data/err_190.py:17:5 [FURB190]: Replace `lambda x: x.lower()` with `str.lower`
+test/data/err_190.py:18:5 [FURB190]: Replace `lambda x: x.lstrip()` with `str.lstrip`
+test/data/err_190.py:19:5 [FURB190]: Replace `lambda x: x.rsplit()` with `str.rsplit`
+test/data/err_190.py:20:5 [FURB190]: Replace `lambda x: x.rstrip()` with `str.rstrip`
+test/data/err_190.py:21:5 [FURB190]: Replace `lambda x: x.split()` with `str.split`
+test/data/err_190.py:22:5 [FURB190]: Replace `lambda x: x.splitlines()` with `str.splitlines`
+test/data/err_190.py:23:5 [FURB190]: Replace `lambda x: x.strip()` with `str.strip`
+test/data/err_190.py:24:5 [FURB190]: Replace `lambda x: x.swapcase()` with `str.swapcase`
+test/data/err_190.py:25:5 [FURB190]: Replace `lambda x: x.title()` with `str.title`
+test/data/err_190.py:26:5 [FURB190]: Replace `lambda x: x.upper()` with `str.upper`