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Fix map no iterables #8478

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d7f35ca
map: raise TypeError when called with no iterables
william-goode Aug 10, 2026
6769e2e
add test for map with no iterables
william-goode Aug 10, 2026
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5 changes: 4 additions & 1 deletion crates/vm/src/builtins/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,9 +37,12 @@ impl Constructor for PyMap {
fn py_new(
_cls: &Py<PyType>,
(mapper, iterators, args): Self::Args,
_vm: &VirtualMachine,
vm: &VirtualMachine,
) -> PyResult<Self> {
let iterators = iterators.into_vec();
if iterators.is_empty() {
return Err(vm.new_type_error("map() must have at least two arguments."));
}
let strict = Radium::new(args.strict.unwrap_or(false));
Ok(Self {
mapper,
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7 changes: 7 additions & 0 deletions extra_tests/snippets/builtin_map.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,13 @@ def __iter__(self):
assert next(it) == 2
assert next(it) == 3

# test for no iterables
try:
map(lambda: 1)
assert False, "TypeError expected at map construction"
except TypeError as e:
assert str(e) == "map() must have at least two arguments."
Comment on lines +30 to +32

@coderabbitai coderabbitai Bot Aug 10, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail
rg -n '^\s*assert\b' extra_tests/snippets/builtin_map.py

Repository: RustPython/RustPython

Length of output: 485

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '--- builtin_map.py lines 1-50 ---\n'
sed -n '1,50p' extra_tests/snippets/builtin_map.py | nl -ba

printf '\n--- assert usage in extra_tests/snippets/builtin_map.py (context) ---\n'
for line in 2 6 8 24 25 30 32 41; do
  start=$(( line > 4 ? line-3 : 1 ))
  end=$(( line+5 ))
  [ "$start" -eq "$end" ] && end=$((end+1))
  sed -n "${start},${end}p" extra_tests/snippets/builtin_map.py | nl -ba -v"$start"
  printf '\n'
done

printf '\n--- ruff availability and B011 config availability ---\n'
command -v ruff || true
if command -v ruff >/dev/null 2>&1; then
  ruff check extra_tests/snippets/builtin_map.py --select B011 || true
fi

printf '\n--- python optimized behavior for assert false / test assertion removal ---\n'
python3 - <<'PY'
import ast

src_normal = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
except TypeError as e:
    assert str(e) == "message"
'''

src_opt_only = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
'''

mod_not_optimized = ast.parse(src_normal)
mod_optimized = ast.parse(src_opt_normal, optimize=2)

print("parsed_nodes_normal_function_call_count:",
      sum(1 for _ in ast.walk(mod_normal) if isinstance(_, ast.Call) and
          isinstance(getattr(getattr(_, "func", None), "attr", None), str) and _.func.attr == "assert"))
print("optimized_module_type:", mod_optimized.__module__)

def count_calls(node):
    n=0
    for child in ast.walk(node):
        if isinstance(child, (ast.Assert, ast.Call)): n += 1
    return n

print("normal_asserts:", sum(1 for node in ast.walk(mod_normal) if isinstance(node, ast.Assert)))
print("normal_calls:", sum(1 for node in ast.walk(mod_normal) if isinstance(node, ast.Call)))
print("optimized_asserts:", sum(1 for node in ast.walk(mod_optimized) if isinstance(node, ast.Assert)))
print("optimized_calls:", sum(1 for node in ast.walk(mod_optimized) if isinstance(node, ast.Call)))
PY

Repository: RustPython/RustPython

Length of output: 250

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '%s\n' '--- builtin_map.py lines 1-50 ---'
sed -n '1,50p' extra_tests/snippets/builtin_map.py | nl -ba

printf '%s\n' '--- assert usage in extra_tests/snippets/builtin_map.py (context) ---'
for line in 2 6 8 24 25 30 32 41; do
  start=$(( line > 4 ? line-3 : 1 ))
  end=$(( line+5 ))
  [ "$start" -eq "$end" ] && end=$((end+1))
  sed -n "${start},${end}p" extra_tests/snippets/builtin_map.py | nl -ba -v"$start"
  printf '%s\n' ''
done

printf '%s\n' '--- ruff availability and B011 config availability ---'
command -v ruff || true
if command -v ruff >/dev/null 2>&衣; then
  ruff check extra_tests/snippets/builtin_map.py --select B011 || true
fi

printf '%s\n' '--- python optimized behavior for assert false / test assertion removal ---'
python3 - <<'PY'
import ast

src_normal = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
except TypeError as e:
    assert str(e) == "message"
'''

src_opt_only = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
'''

mod_normal = ast.parse(src_normal)
mod_optimized = ast.parse(src_opt_only, optimize=2)

def count_nodes(node, cls):
    return sum(1 for child in ast.walk(node) if isinstance(child, cls))

print("normal_asserts:", count_nodes(mod_normal, ast.Assert))
print("normal_calls:", count_nodes(mod_normal, ast.Call))
print("optimized_asserts:", count_nodes(mod_optimized, ast.Assert))
print("optimized_return_value:", mod_optimized.body[0].value.value)
PY

Repository: RustPython/RustPython

Length of output: 233

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '%s\n' '--- builtin_map.py lines 1-50 ---'
sed -n '1,50p' extra_tests/snippets/builtin_map.py

printf '%s\n' '--- assert usage in extra_tests/snippets/builtin_map.py (line numbers via grep -n) ---'
grep -n 'assert False' extra_tests/snippets/builtin_map.py || true
grep -n 'assert str(e)' extra_tests/snippets/builtin_map.py || true

printf '%s\n' '--- python optimized behavior for assert False ---'
python3 - <<'PY'
import ast
import dis
import io
import sys

src = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
except TypeError as e:
    pass
'''

# Python 2.3 removed assert statements at parse time when optimization is selected.
# The function return value is None because the function body after optimization has no instructions.
mod_optimized = ast.parse(src, optimize=2)
comp = compile(mod_optimized, "<optimized>", "exec")
dis.dis(comp)
print("optimized_return_opcodes:", [name for name in (instr.opname for instr in dis.get_instructions(comp)) if name == "RETURN_VALUE"])

src_no_assert_success = '''try:
    x += 1
except TypeError as e:
    pass
'''
mod_no_assert = ast.parse(src_no_assert_success, optimize=0)
comp2 = compile(mod_no_assert, "<no_assert>", "exec")
print("optimized_code_is_same_as_no_assert:")
print(comp.co_code == comp2.co_code)
print(dis.dis(comp2))
PY

Repository: RustPython/RustPython

Length of output: 1368

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '%s\n' '--- locate ruff config files ---'
git ls-files | grep -E '(^|/)(pyproject\.toml|ruff\.toml|\.ruff\.toml)$' || true

printf '%s\n' '--- search for ruff B011 settings ---'
if [ -f pyproject.toml ]; then git grep -n '\bB011\b\|assert\.' pyproject.toml || true; fi

printf '%s\n' '--- Python compile optimization via command-line flag ---'
python3 - <<'PY'
import dis
import pycompile

src = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
except TypeError as e:
    pass
'''
src_no_assert = '''try:
    x += 1
except TypeError as e:
    pass
'''

try:
    print("pycompile.get_source_from_code exists:", hasattr(pycompile.get_source_from_code, '__call__'))
except Exception as exc:
    print("pycompile_access_error:", type(exc).__name__, str(exc))

code = compile(src, '<no_opt>', 'exec')
code_opt = compile(src, '<opt>', 'exec', optimize=2)
print("normal_code_bytes:", code.co_code.hex())
print("optimized_code_bytes:", code_opt.co_code.hex())
print("optimized_is_same_as_no_assert:", code_opt.co_code == compile(src_no_assert, '<no_assert>', 'exec').co_code)
print("disopt:")
dis.dis(code_opt)
PY

Repository: RustPython/RustPython

Length of output: 490

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '%s\n' '--- ruff.toml relevant sections ---'
cat ruff.toml

printf '%s\n' '--- Ruff B011 status if ruff is available ---'
if command -v ruff >/dev/null 2>&1; then
  ruff check extra_tests/snippets/builtin_map.py --select B011 || true
  command -v ruff
else
  command -v ruff || true
fi

printf '%s\n' '--- Python compile optimization via command-line flag ---'
python3 - <<'PY'
import dis
import sys

src = '''try:
    x += 1
    assert False, "TypeError expected at map construction"
except TypeError as e:
    pass
'''
src_no_assert = '''try:
    x += 1
except TypeError as e:
    pass
'''

code = compile(src, '<no_opt>', 'exec')
code_opt = compile(src, '<opt>', 'exec', optimize=2)
code_no_assert = compile(src_no_assert, '<no_assert>', 'exec')

print("normal_code_bytes:", code.co_code.hex())
print("optimized_code_bytes:", code_opt.co_code.hex())
print("optimized_is_same_as_no_assert:", code_opt.co_code == code_no_assert.co_code)
print("optimized_return_opcodes:", [instr.opname for instr in dis.get_instructions(code_opt) if instr.opname == "RETURN_VALUE"])
PY

Repository: RustPython/RustPython

Length of output: 1728

Use explicit AssertionError control flow.

assert False raises a lint error, and python -O removes it, so this branch can pass without catching the constructor TypeError or comparing the required message. Raise AssertionError for the expected failure, then check str(e) == "map() must have at least two arguments." explicitly.

🧰 Tools
🪛 Ruff (0.16.1)

[warning] 30-30: Do not assert False (python -O removes these calls), raise AssertionError()

Replace assert False

(B011)

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@extra_tests/snippets/builtin_map.py` around lines 30 - 32, Replace the
`assert False` fallback in the map-construction exception test with an explicit
`AssertionError` raise, ensuring the test cannot pass when `map()` does not
raise. Preserve the `except TypeError as e` path and explicitly validate that
`str(e)` equals the required message.

Sources: Coding guidelines, Linters/SAST tools


Comment on lines +27 to +33

@coderabbitai coderabbitai Bot Aug 10, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Cover the keyword construction path before merging.

This test only exercises positional construction. Add a case such as map(lambda: 1, strict=False) and verify the same construction-time TypeError and message. This ensures the named-argument path cannot bypass the arity check.

🧰 Tools
🪛 Ruff (0.16.1)

[warning] 30-30: Do not assert False (python -O removes these calls), raise AssertionError()

Replace assert False

(B011)

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@extra_tests/snippets/builtin_map.py` around lines 27 - 33, Extend the
no-iterables test around map construction to also call map with the callable and
strict=False as keyword arguments. Assert that construction immediately raises
TypeError with the same "map() must have at least two arguments." message,
preserving the existing positional-argument assertion.

Comment on lines +27 to +33

@youknowone youknowone Aug 10, 2026

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Suggested change
# test for no iterables
try:
map(lambda: 1)
assert False, "TypeError expected at map construction"
except TypeError as e:
assert str(e) == "map() must have at least two arguments."

Ah, ok. by looking the test result, this case is well-covered by test_itertools

Please remove this our own test.

And also check CI result that your patch made success.

UNEXPECTED SUCCESS: test_map (test.test_itertools.TestBasicOps.test_map)

Please remove @expectedFailure from the test to mark this is fixed


def mapping(x):
if x == 0:
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