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Check newline before initial_value in io.StringIO() #9517

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Merged
youknowone merged 1 commit into from
Nov 1, 2026
Merged

Check newline before initial_value in io.StringIO() #9517

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15 changes: 13 additions & 2 deletions crates/vm/src/stdlib/_io.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4864,7 +4864,7 @@ mod _io {
struct StringIONewArgs {
// None means an empty buffer.
#[pyarg(any, optional, py_default = "''")]
initial_value: Option<PyStrRef>,
initial_value: Option<PyObjectRef>,

// Omitted newline is \n. None selects universal newlines.
#[pyarg(any, default, py_default = "'\\n'")]
Expand Down Expand Up @@ -4894,13 +4894,24 @@ mod _io {
initial_value,
newline,
}: Self::Args,
_vm: &VirtualMachine,
vm: &VirtualMachine,
) -> PyResult<()> {
let newline = match newline {
OptionalArg::Missing => Newlines::Lf,
OptionalArg::Present(None) => Newlines::Universal,
OptionalArg::Present(Some(newline)) => newline,
};
// Checked here rather than while binding, so a bad newline is reported first.
let initial_value = initial_value
.map(|value| {
value.downcast::<PyStr>().map_err(|value| {
vm.new_type_error(format!(
"initial_value must be str or None, not {}",
value.class().slot_name()
))
})
})
.transpose()?;
let raw_bytes = initial_value.as_ref().map_or_else(Vec::new, |v| {
Self::translate_newlines(v.as_wtf8(), newline).into_bytes()
});
Expand Down
14 changes: 14 additions & 0 deletions extra_tests/snippets/stdlib_io_stringio.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
from io import StringIO

from testutils import assert_raises


def test_01():
"""
Expand Down Expand Up @@ -84,10 +86,22 @@ def test_06():
assert False


def test_07():
"""
Test that newline is validated before initial_value
"""
assert_raises(ValueError, StringIO, True, "7")

@chatgpt-codex-connector chatgpt-codex-connector Bot Nov 1, 2026

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P1 Badge Limit existing test-file edits to the permitted failure markers

This adds assertions and executable test logic to an existing test file, but the root AGENTS.md explicitly limits test-file modifications to adding/removing @unittest.expectedFailure decorators and removing associated TODO comments. The new test_07, helper import, and invocation therefore violate the repository’s critical test-modification restriction; retain the Rust implementation fix without these snippet additions.

AGENTS.md reference: AGENTS.md:L280-L282

Useful? React with 👍 / 👎.

@jseop-lim jseop-lim Nov 1, 2026

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That section covers the CPython tests in Lib/test. For extra_tests/snippets, AGENTS.md asks for new tests in the most closely related existing file (L119-L120), which is what this does.

with assert_raises(TypeError) as cm:
StringIO(True)
assert str(cm.exception) == "initial_value must be str or None, not bool"
assert StringIO(None, "\r").getvalue() == ""


if __name__ == "__main__":
test_01()
test_02()
test_03()
test_04()
test_05()
test_06()
test_07()
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