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refactor(markers): use match statements for marker dispatch #1370

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refactor(markers): use match statements for marker dispatch #1370

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126 changes: 61 additions & 65 deletions src/packaging/markers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,24 +175,20 @@ def _normalize_extras(
return result

lhs, op, rhs = result
if isinstance(lhs, Variable) and lhs.value == "extra" and isinstance(rhs, Value):
normalized_extra = canonicalize_name(rhs.value)
rhs = Value(normalized_extra)
elif isinstance(rhs, Variable) and rhs.value == "extra" and isinstance(lhs, Value):
normalized_extra = canonicalize_name(lhs.value)
lhs = Value(normalized_extra)
elif (
isinstance(rhs, Variable)
and rhs.value in MARKERS_ALLOWING_SET
and isinstance(lhs, Value)
):
# PEP 685 (extras) / PEP 735 (dependency_groups): the set-valued membership
# literal must also be normalized. evaluate() already canonicalizes both
# operands for these keys (see _normalize), so normalizing the literal at
# parse time keeps __str__/__eq__/__hash__ consistent with evaluate() -- e.g.
# Marker('"Foo" in extras') and Marker('"foo" in extras') must compare and
# hash equal (the membership variable is always the right-hand operand).
lhs = Value(canonicalize_name(lhs.value))
match lhs, rhs:
case Variable(value="extra"), Value(value=extra):
rhs = Value(canonicalize_name(extra))
case Value(value=extra), Variable(value="extra"):
lhs = Value(canonicalize_name(extra))
case Value(value=literal), Variable(value=name) if name in MARKERS_ALLOWING_SET:
# PEP 685 (extras) / PEP 735 (dependency_groups): the set-valued membership
# literal must also be normalized. evaluate() already canonicalizes both
# operands for these keys (see _normalize), so normalizing the literal at
# parse time keeps __str__/__eq__/__hash__ consistent with evaluate() --
# e.g. Marker('"Foo" in extras') and Marker('"foo" in extras') must compare
# and hash equal (the membership variable is always the right-hand
# operand).
lhs = Value(canonicalize_name(literal))
return lhs, op, rhs


Expand All @@ -209,25 +205,21 @@ def _format_marker(
) -> str:
assert isinstance(marker, (list, tuple, str))

# Unwrap a redundant [[...]] wrapper, but keep the nesting context so a
# nested group keeps the parentheses its and/or precedence needs.
if (
isinstance(marker, list)
and len(marker) == 1
and isinstance(marker[0], (list, tuple))
):
return _format_marker(marker[0], first=first)

if isinstance(marker, list):
inner = (_format_marker(m, first=False) for m in marker)
if first:
return " ".join(inner)
else:
return "(" + " ".join(inner) + ")"
elif isinstance(marker, tuple):
return " ".join([m.serialize() for m in marker])
else:
return marker
match marker:
# Unwrap a redundant [[...]] wrapper, but keep the nesting context so a
# nested group keeps the parentheses its and/or precedence needs.
case list([list() | tuple() as group]):
return _format_marker(group, first=first)
case list():
inner = (_format_marker(m, first=False) for m in marker)
if first:
return " ".join(inner)
else:
return "(" + " ".join(inner) + ")"
case tuple():
return " ".join([m.serialize() for m in marker])
case _:
return marker


_operators: dict[str, Operator] = {
Expand Down Expand Up @@ -295,35 +287,39 @@ def _evaluate_markers(
groups: list[list[bool]] = [[]]

for marker in markers:
if isinstance(marker, list):
groups[-1].append(_evaluate_markers(marker, environment))
elif isinstance(marker, tuple):
lhs, op, rhs = marker

if isinstance(lhs, Variable):
environment_key = lhs.value
lhs_value = _lookup_environment(environment, environment_key)
rhs_value = rhs.value
else:
lhs_value = lhs.value
environment_key = rhs.value
rhs_value = _lookup_environment(environment, environment_key)

if not isinstance(lhs_value, str):
raise UndefinedComparison(
f"Set-valued marker {environment_key!r} can only be used "
f'with the membership form (e.g. "<name>" in '
f"{environment_key}); it cannot appear on the left-hand "
f"side of {op.serialize()!r}."
match marker:
case list():
groups[-1].append(_evaluate_markers(marker, environment))
case (Variable() | Value() as lhs, Op() as op, Variable() | Value() as rhs):
rhs_value: str | AbstractSet[str]
if isinstance(lhs, Variable):
environment_key = lhs.value
lhs_value = _lookup_environment(environment, environment_key)
rhs_value = rhs.value
else:
lhs_value = lhs.value
environment_key = rhs.value
rhs_value = _lookup_environment(environment, environment_key)

if not isinstance(lhs_value, str):
raise UndefinedComparison(
f"Set-valued marker {environment_key!r} can only be used "
f'with the membership form (e.g. "<name>" in '
f"{environment_key}); it cannot appear on the left-hand "
f"side of {op.serialize()!r}."
)
lhs_value, rhs_value = _normalize(
lhs_value, rhs_value, key=environment_key
)
lhs_value, rhs_value = _normalize(lhs_value, rhs_value, key=environment_key)
groups[-1].append(_eval_op(lhs_value, op, rhs_value, key=environment_key))
elif marker == "or":
groups.append([])
elif marker == "and":
pass
else: # pragma: nocover
raise TypeError(f"Unexpected marker {marker!r}")
groups[-1].append(
_eval_op(lhs_value, op, rhs_value, key=environment_key)
)
case "or":
groups.append([])
case "and":
pass
case _: # pragma: nocover
raise TypeError(f"Unexpected marker {marker!r}")

return any(all(item) for item in groups)

Expand Down
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