Ignoring a file with a single # type: ignore comment. (python#6830)

Fixes python#626

(There are potential further features as discussed in the PR, but these are somewhat controversial and may even be excised from PEP 484.)

docs/source/common_issues.rst

@@ -149,6 +149,20 @@ generates spurious errors. Mypy will only look at the stub file
 and ignore the implementation, since stub files take precedence
 over ``.py`` files.
 
+Ignoring a whole file
+---------------------
+
+A ``# type: ignore`` comment at the top of a module (before any statements,
+including imports or docstrings) has the effect of ignoring the *entire* module.
+
+.. code-block:: python
+
+    # type: ignore
+
+    import foo
+
+    foo.bar()
+
 Unexpected errors about 'None' and/or 'Optional' types
 ------------------------------------------------------
 

mypy/fastparse.py

@@ -2,7 +2,7 @@
 import sys
 
 from typing import (
-    Tuple, Union, TypeVar, Callable, Sequence, Optional, Any, Dict, cast, List, overload
+    Tuple, Union, TypeVar, Callable, Sequence, Optional, Any, Dict, cast, List, overload, Set
 )
 MYPY = False
 if MYPY:
@@ -258,7 +258,7 @@ def __init__(self,
         self.is_stub = is_stub
         self.errors = errors
 
-        self.extra_type_ignores = []  # type: List[int]
+        self.type_ignores = set()  # type: Set[int]
 
         # Cache of visit_X methods keyed by type of visited object
         self.visitor_cache = {}  # type: Dict[type, Callable[[Optional[AST]], Any]]
@@ -294,11 +294,29 @@ def translate_expr_list(self, l: Sequence[AST]) -> List[Expression]:
             res.append(exp)
         return res
 
-    def translate_stmt_list(self, l: Sequence[AST]) -> List[Statement]:
+    def get_lineno(self, node: Union[ast3.expr, ast3.stmt]) -> int:
+        if (isinstance(node, (ast3.AsyncFunctionDef, ast3.ClassDef, ast3.FunctionDef))
+                and node.decorator_list):
+            return node.decorator_list[0].lineno
+        return node.lineno
+
+    def translate_stmt_list(self,
+                            stmts: Sequence[ast3.stmt],
+                            ismodule: bool = False) -> List[Statement]:
+        # A "# type: ignore" comment before the first statement of a module
+        # ignores the whole module:
+        if (ismodule and stmts and self.type_ignores
+                and min(self.type_ignores) < self.get_lineno(stmts[0])):
+            self.errors.used_ignored_lines[self.errors.file].add(min(self.type_ignores))
+            block = Block(self.fix_function_overloads(self.translate_stmt_list(stmts)))
+            block.is_unreachable = True
+            return [block]
+
         res = []  # type: List[Statement]
-        for e in l:
-            stmt = self.visit(e)
-            res.append(stmt)
+        for stmt in stmts:
+            node = self.visit(stmt)
+            res.append(node)
+
         return res
 
     op_map = {
@@ -403,13 +421,12 @@ def translate_module_id(self, id: str) -> str:
         return id
 
     def visit_Module(self, mod: ast3.Module) -> MypyFile:
-        body = self.fix_function_overloads(self.translate_stmt_list(mod.body))
-        ignores = [ti.lineno for ti in mod.type_ignores]
-        ignores.extend(self.extra_type_ignores)
+        self.type_ignores = {ti.lineno for ti in mod.type_ignores}
+        body = self.fix_function_overloads(self.translate_stmt_list(mod.body, ismodule=True))
         return MypyFile(body,
                         self.imports,
                         False,
-                        set(ignores),
+                        self.type_ignores,
                         )
 
     # --- stmt ---
@@ -615,7 +632,7 @@ def make_argument(self, arg: ast3.arg, default: Optional[ast3.expr], kind: int,
             elif type_comment is not None:
                 extra_ignore, arg_type = parse_type_comment(type_comment, arg.lineno, self.errors)
                 if extra_ignore:
-                    self.extra_type_ignores.append(arg.lineno)
+                    self.type_ignores.add(arg.lineno)
 
         return Argument(Var(arg.arg), arg_type, self.visit(default), kind)
 
@@ -673,7 +690,7 @@ def visit_Assign(self, n: ast3.Assign) -> AssignmentStmt:
         if n.type_comment is not None:
             extra_ignore, typ = parse_type_comment(n.type_comment, n.lineno, self.errors)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             typ = None
         s = AssignmentStmt(lvalues, rvalue, type=typ, new_syntax=False)
@@ -707,7 +724,7 @@ def visit_For(self, n: ast3.For) -> ForStmt:
         if n.type_comment is not None:
             extra_ignore, target_type = parse_type_comment(n.type_comment, n.lineno, self.errors)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             target_type = None
         node = ForStmt(self.visit(n.target),
@@ -722,7 +739,7 @@ def visit_AsyncFor(self, n: ast3.AsyncFor) -> ForStmt:
         if n.type_comment is not None:
             extra_ignore, target_type = parse_type_comment(n.type_comment, n.lineno, self.errors)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             target_type = None
         node = ForStmt(self.visit(n.target),
@@ -753,7 +770,7 @@ def visit_With(self, n: ast3.With) -> WithStmt:
         if n.type_comment is not None:
             extra_ignore, target_type = parse_type_comment(n.type_comment, n.lineno, self.errors)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             target_type = None
         node = WithStmt([self.visit(i.context_expr) for i in n.items],
@@ -767,7 +784,7 @@ def visit_AsyncWith(self, n: ast3.AsyncWith) -> WithStmt:
         if n.type_comment is not None:
             extra_ignore, target_type = parse_type_comment(n.type_comment, n.lineno, self.errors)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             target_type = None
         s = WithStmt([self.visit(i.context_expr) for i in n.items],

mypy/fastparse2.py

@@ -16,7 +16,7 @@
 """
 import sys
 
-from typing import Tuple, Union, TypeVar, Callable, Sequence, Optional, Any, Dict, cast, List
+from typing import Tuple, Union, TypeVar, Callable, Sequence, Optional, Any, Dict, cast, List, Set
 MYPY = False
 if MYPY:
     import typing  # for typing.Type, which conflicts with types.Type
@@ -163,7 +163,7 @@ def __init__(self,
         # Cache of visit_X methods keyed by type of visited object
         self.visitor_cache = {}  # type: Dict[type, Callable[[Optional[AST]], Any]]
 
-        self.extra_type_ignores = []  # type: List[int]
+        self.type_ignores = set()  # type: Set[int]
 
     def fail(self, msg: str, line: int, column: int, blocker: bool = True) -> None:
         if blocker or not self.options.ignore_errors:
@@ -193,12 +193,28 @@ def translate_expr_list(self, l: Sequence[AST]) -> List[Expression]:
             res.append(exp)
         return res
 
-    def translate_stmt_list(self, l: Sequence[AST]) -> List[Statement]:
+    def get_lineno(self, node: Union[ast27.expr, ast27.stmt]) -> int:
+        if isinstance(node, (ast27.ClassDef, ast27.FunctionDef)) and node.decorator_list:
+            return node.decorator_list[0].lineno
+        return node.lineno
+
+    def translate_stmt_list(self,
+                            stmts: Sequence[ast27.stmt],
+                            module: bool = False) -> List[Statement]:
+        # A "# type: ignore" comment before the first statement of a module
+        # ignores the whole module:
+        if (module and stmts and self.type_ignores
+                and min(self.type_ignores) < self.get_lineno(stmts[0])):
+            self.errors.used_ignored_lines[self.errors.file].add(min(self.type_ignores))
+            block = Block(self.fix_function_overloads(self.translate_stmt_list(stmts)))
+            block.is_unreachable = True
+            return [block]
+
         res = []  # type: List[Statement]
-        for e in l:
-            stmt = self.visit(e)
-            assert isinstance(stmt, Statement)
-            res.append(stmt)
+        for stmt in stmts:
+            node = self.visit(stmt)
+            assert isinstance(node, Statement)
+            res.append(node)
         return res
 
     op_map = {
@@ -304,13 +320,12 @@ def translate_module_id(self, id: str) -> str:
         return id
 
     def visit_Module(self, mod: ast27.Module) -> MypyFile:
+        self.type_ignores = {ti.lineno for ti in mod.type_ignores}
         body = self.fix_function_overloads(self.translate_stmt_list(mod.body))
-        ignores = [ti.lineno for ti in mod.type_ignores]
-        ignores.extend(self.extra_type_ignores)
         return MypyFile(body,
                         self.imports,
                         False,
-                        set(ignores),
+                        self.type_ignores,
                         )
 
     # --- stmt ---
@@ -558,7 +573,7 @@ def visit_Assign(self, n: ast27.Assign) -> AssignmentStmt:
             extra_ignore, typ = parse_type_comment(n.type_comment, n.lineno, self.errors,
                                                    assume_str_is_unicode=self.unicode_literals)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
 
         stmt = AssignmentStmt(self.translate_expr_list(n.targets),
                               self.visit(n.value),
@@ -578,7 +593,7 @@ def visit_For(self, n: ast27.For) -> ForStmt:
             extra_ignore, typ = parse_type_comment(n.type_comment, n.lineno, self.errors,
                                                    assume_str_is_unicode=self.unicode_literals)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             typ = None
         stmt = ForStmt(self.visit(n.target),
@@ -608,7 +623,7 @@ def visit_With(self, n: ast27.With) -> WithStmt:
             extra_ignore, typ = parse_type_comment(n.type_comment, n.lineno, self.errors,
                                                    assume_str_is_unicode=self.unicode_literals)
             if extra_ignore:
-                self.extra_type_ignores.append(n.lineno)
+                self.type_ignores.add(n.lineno)
         else:
             typ = None
         stmt = WithStmt([self.visit(n.context_expr)],

test-data/unit/check-ignore.test

@@ -218,3 +218,43 @@ def f() -> None: pass
 
 [case testCannotIgnoreBlockingError]
 yield  # type: ignore  # E: 'yield' outside function
+
+[case testIgnoreWholeModule1]
+# flags: --warn-unused-ignores
+# type: ignore
+IGNORE # type: ignore  # E: unused 'type: ignore' comment
+
+[case testIgnoreWholeModule2]
+# type: ignore
+if True:
+    IGNORE
+
+[case testIgnoreWholeModule3]
+# type: ignore
+@d
+class C: ...
+IGNORE
+
+[case testIgnoreWholeModule4]
+# type: ignore
+@d
+
+def f(): ...
+IGNORE
+
+[case testDontIgnoreWholeModule1]
+if True:
+    # type: ignore
+    ERROR # E: Name 'ERROR' is not defined
+ERROR # E: Name 'ERROR' is not defined
+
+[case testDontIgnoreWholeModule2]
+@d  # type: ignore
+class C: ...
+ERROR # E: Name 'ERROR' is not defined
+
+[case testDontIgnoreWholeModule3]
+@d  # type: ignore
+
+def f(): ...
+ERROR # E: Name 'ERROR' is not defined