#Fix 21316

mypy/semanal_namedtuple.py

@@ -30,6 +30,7 @@
     ExpressionStmt,
     FuncBase,
     FuncDef,
+    IfStmt,
     ListExpr,
     NamedTupleExpr,
     NameExpr,
@@ -48,6 +49,7 @@
     is_StrExpr_list,
 )
 from mypy.options import Options
+from mypy.reachability import ALWAYS_FALSE, ALWAYS_TRUE, infer_condition_value
 from mypy.semanal_shared import (
     PRIORITY_FALLBACKS,
     SemanticAnalyzerInterface,
@@ -139,6 +141,35 @@ def analyze_namedtuple_classdef(
         # This can't be a valid named tuple.
         return False, None
 
+    def iter_reachable_namedtuple_statements(
+        self, statements: list[Statement]
+    ) -> Iterator[Statement]:
+        for stmt in statements:
+            if isinstance(stmt, IfStmt):
+                encountered_unknown = False
+                handled = False
+
+                for expr, body in zip(stmt.expr, stmt.body):
+                    truth = infer_condition_value(expr, self.options)
+
+                    if truth == ALWAYS_TRUE:
+                        yield from self.iter_reachable_namedtuple_statements(body.body)
+                        handled = True
+                        break
+
+                    elif truth == ALWAYS_FALSE:
+                        continue
+
+                    else:
+                        encountered_unknown = True
+
+                if not handled and not encountered_unknown and stmt.else_body is not None:
+                    yield from self.iter_reachable_namedtuple_statements(stmt.else_body.body)
+
+                continue
+
+            yield stmt
+
     def check_namedtuple_classdef(
         self, defn: ClassDef, is_stub_file: bool
     ) -> tuple[list[str], list[Type], dict[str, Expression], list[Statement]] | None:
@@ -157,7 +188,7 @@ def check_namedtuple_classdef(
         types: list[Type] = []
         default_items: dict[str, Expression] = {}
         statements: list[Statement] = []
-        for stmt in defn.defs.body:
+        for stmt in self.iter_reachable_namedtuple_statements(defn.defs.body):
             statements.append(stmt)
             if not isinstance(stmt, AssignmentStmt):
                 # Still allow pass or ... (for empty namedtuples).

test-data/unit/check-namedtuple.test

@@ -1541,3 +1541,255 @@ from foo import DEFERRED_INT, DEFERRED_STR
 DEFERRED_INT = 1
 DEFERRED_STR = "a"
 [builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleFieldPy312]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+    if sys.version_info >= (3, 12):
+        y: str
+
+reveal_type(NT.x)
+reveal_type(NT.y)
+
+[out]
+main:10: note: Revealed type is "builtins.int"
+main:11: note: Revealed type is "builtins.str"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleFieldPy311]
+# flags: --python-version 3.11
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+    if sys.version_info >= (3, 12):
+        y: str
+
+reveal_type(NT.x)
+NT.y
+
+[out]
+main:10: note: Revealed type is "builtins.int"
+main:11: error: "type[NT]" has no attribute "y"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleElseBranch]
+# flags: --python-version 3.11
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+
+    if sys.version_info >= (3, 12):
+        y: str
+    else:
+        z: int
+
+reveal_type(NT.z)
+NT.y
+
+[out]
+main:13: note: Revealed type is "builtins.int"
+main:14: error: "type[NT]" has no attribute "y"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleElseBranchPy312]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+
+    if sys.version_info >= (3, 12):
+        y: str
+    else:
+        z: int
+
+reveal_type(NT.y)
+NT.z
+
+[out]
+main:13: note: Revealed type is "builtins.str"
+main:14: error: "type[NT]" has no attribute "z"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleElif]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+
+    if sys.version_info >= (3, 13):
+        a: int
+    elif sys.version_info >= (3, 12):
+        b: str
+    else:
+        c: bool
+
+reveal_type(NT.b)
+NT.a
+NT.c
+
+[out]
+main:15: note: Revealed type is "builtins.str"
+main:16: error: "type[NT]" has no attribute "a"
+main:17: error: "type[NT]" has no attribute "c"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleNestedIf]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+
+    if sys.version_info >= (3, 12):
+        if sys.version_info >= (3, 12):
+            y: str
+
+reveal_type(NT.y)
+
+[out]
+main:12: note: Revealed type is "builtins.str"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleUnknownCondition]
+from typing import NamedTuple
+
+SOME_FLAG = True
+
+class NT(NamedTuple):
+    x: int
+
+    if SOME_FLAG:
+        y: str
+
+NT.y
+
+[out]
+main:11: error: "type[NT]" has no attribute "y"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleMultipleFields]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    if sys.version_info >= (3, 12):
+        x: int
+        y: str
+
+reveal_type(NT.x)
+reveal_type(NT.y)
+
+[out]
+main:10: note: Revealed type is "builtins.int"
+main:11: note: Revealed type is "builtins.str"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleMultipleElif]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    if sys.version_info >= (3, 14):
+        a: int
+    elif sys.version_info >= (3, 13):
+        b: int
+    elif sys.version_info >= (3, 12):
+        c: str
+    else:
+        d: bool
+
+reveal_type(NT.c)
+NT.a
+NT.b
+NT.d
+
+[out]
+main:15: note: Revealed type is "builtins.str"
+main:16: error: "type[NT]" has no attribute "a"
+main:17: error: "type[NT]" has no attribute "b"
+main:18: error: "type[NT]" has no attribute "d"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleEmptyBranch]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    x: int
+
+    if sys.version_info >= (3, 12):
+        pass
+    else:
+        y: str
+
+NT.y
+
+[out]
+main:13: error: "type[NT]" has no attribute "y"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleUnknownConditionElse]
+from typing import NamedTuple
+
+FLAG = True
+
+class NT(NamedTuple):
+    x: int
+
+    if FLAG:
+        y: str
+    else:
+        z: int
+
+NT.y
+NT.z
+
+[out]
+main:13: error: "type[NT]" has no attribute "y"
+main:14: error: "type[NT]" has no attribute "z"
+
+[builtins fixtures/tuple.pyi]
+
+[case testConditionalNamedTupleDefaultValue]
+# flags: --python-version 3.12
+from typing import NamedTuple
+import sys
+
+class NT(NamedTuple):
+    if sys.version_info >= (3, 12):
+        x: int = 1
+
+reveal_type(NT.x)
+reveal_type(NT().x)
+
+[out]
+main:9: note: Revealed type is "builtins.int"
+main:10: note: Revealed type is "builtins.int"
+
+[builtins fixtures/tuple.pyi]