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Update StringVar to match Python str behavior (#5417) #6596

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1 change: 1 addition & 0 deletions packages/reflex-base/news/5417.feature.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
`StringVar` now includes `lstrip` and `rstrip` methods. The `strip` method now accepts an optional `chars` argument for consistency with Python’s str API.
86 changes: 76 additions & 10 deletions packages/reflex-base/src/reflex_base/vars/sequence.py
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Original file line number Diff line number Diff line change
Expand Up @@ -674,6 +674,20 @@ def lower(self) -> StringVar:
"""
return string_lower_operation(self)

def lstrip(self, chars: StringVar | str | None = None) -> StringVar:
"""Left strip the string.

Args:
chars: Characters to remove from the left side. If None, strip whitespace.

Returns:
The string lstrip operation.
"""
if chars is not None and not isinstance(chars, (StringVar, str)):
raise_unsupported_operand_types("lstrip", (type(self), type(chars)))

return string_lstrip_operation(self, chars)

def upper(self) -> StringVar:
"""Convert the string to uppercase.

Expand All @@ -698,13 +712,19 @@ def capitalize(self) -> StringVar:
"""
return string_capitalize_operation(self)

def strip(self) -> StringVar:
def strip(self, chars: StringVar | str | None = None) -> StringVar:
"""Strip the string.

Args:
chars: Characters to remove from both ends. If None, strip whitespace.

Returns:
The string strip operation.
"""
return string_strip_operation(self)
if chars is not None and not isinstance(chars, (StringVar, str)):
raise_unsupported_operand_types("strip", (type(self), type(chars)))

return string_strip_operation(self, chars)

def reversed(self) -> StringVar:
"""Reverse the string.
Expand All @@ -714,6 +734,20 @@ def reversed(self) -> StringVar:
"""
return self.split().reverse().join()

def rstrip(self, chars: StringVar | str | None = None) -> StringVar:
"""Right strip the string.

Args:
chars: Characters to remove from the right side. If None, strip whitespace.

Returns:
The string rstrip operation.
"""
if chars is not None and not isinstance(chars, (StringVar, str)):
raise_unsupported_operand_types("rstrip", (type(self), type(chars)))

return string_rstrip_operation(self, chars)

def contains(
self, other: StringVar | str, field: StringVar | str | None = None
) -> BooleanVar:
Expand Down Expand Up @@ -972,16 +1006,48 @@ def string_capitalize_operation(string: StringVar[Any]):


@var_operation
def string_strip_operation(string: StringVar[Any]):
"""Strip a string.
def string_strip_operation(
string: StringVar[Any],
chars: StringVar[Any] | str | None = None,
):
"""Strip a string."""
if str(chars) == "null":
return var_operation_return(js_expression=f"{string}.trim()", var_type=str)

Args:
string: The string to strip.
return var_operation_return(
js_expression=f"{string}.replace(/^[{chars}]+|[{chars}]+$/g, '')",
var_type=str,
)
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@greptile-apps greptile-apps Bot Jun 2, 2026

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P1 Quoted string literal injected directly into regex character class

When chars is a plain Python str (e.g., "abc"), the @var_operation wrapper converts it to LiteralVar.create("abc"), whose JavaScript serialization is "abc" (with quotes). Interpolating that into the regex literal produces /^["abc"]+.../ — the double-quote characters become literal members of the character class, so .strip("abc") would also strip " from the string.

For a StringVar state-variable, the JS variable expression (e.g., state.chars) is embedded verbatim inside the literal regex /.../, which is static syntax — it does not reference the variable at runtime and instead treats the characters of the expression name as the set to strip. The same problem exists identically in string_lstrip_operation and string_rstrip_operation.

Comment on lines +1017 to +1020
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P1 Regex special characters in chars are not escaped

Characters such as ], \, ^, and - carry special meaning inside a regex character class. If chars contains any of them (e.g., strip("a-z") would make - a range operator), the generated JavaScript regex will silently behave differently from Python's character-set strip semantics. There is no escaping of these characters before they are placed between [ and ]. The same applies to string_lstrip_operation and string_rstrip_operation.


Returns:
The stripped string.
"""
return var_operation_return(js_expression=f"{string}.trim()", var_type=str)

@var_operation
def string_lstrip_operation(
string: StringVar[Any],
chars: StringVar[Any] | str | None = None,
):
"""Left strip a string."""
if str(chars) == "null":
return var_operation_return(js_expression=f"{string}.trimStart()", var_type=str)

return var_operation_return(
js_expression=f"{string}.replace(/^[{chars}]+/, '')",
var_type=str,
)


@var_operation
def string_rstrip_operation(
string: StringVar[Any],
chars: StringVar[Any] | str | None = None,
):
"""Right strip a string."""
if str(chars) == "null":
return var_operation_return(js_expression=f"{string}.trimEnd()", var_type=str)

return var_operation_return(
js_expression=f"{string}.replace(/[{chars}]+$/, '')",
var_type=str,
)


@var_operation
Expand Down
2 changes: 2 additions & 0 deletions tests/units/test_var.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1001,8 +1001,10 @@ def test_string_operations():

assert str(basic_string.length()) == '"Hello, World!".split("").length'
assert str(basic_string.lower()) == '"Hello, World!".toLowerCase()'
assert str(basic_string.lstrip()) == '"Hello, World!".trimStart()'
assert str(basic_string.upper()) == '"Hello, World!".toUpperCase()'
assert str(basic_string.strip()) == '"Hello, World!".trim()'
assert str(basic_string.rstrip()) == '"Hello, World!".trimEnd()'
assert str(basic_string.contains("World")) == '"Hello, World!".includes("World")'
assert (
str(basic_string.split(" ").join(",")) == '"Hello, World!".split(" ").join(",")'
Expand Down
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