Add stubs for PEP 561.

.gitignore

@@ -7,5 +7,6 @@ tags
 .idea
 .ropeproject
 .cache
+.mypy_cache
 /dist
 /build

lark/exceptions.pyi

@@ -0,0 +1,42 @@
+# -*- coding: utf-8 -*-
+
+from typing import Dict, Iterable, Callable
+from .tree import Tree
+
+
+class LarkError(Exception):
+    pass
+
+
+class GrammarError(LarkError):
+    pass
+
+
+class ParseError(LarkError):
+    pass
+
+
+class LexError(LarkError):
+    pass
+
+
+class UnexpectedInput(LarkError):
+    pos_in_stream: int
+
+    def get_context(self, text: str, span: int = 40):
+        ...
+
+    def match_examples(
+        self,
+        parse_fn: Callable[[str], Tree],
+        examples: Dict[str, Iterable[str]]
+    ):
+        ...
+
+
+class UnexpectedToken(ParseError, UnexpectedInput):
+    pass
+
+
+class UnexpectedCharacters(LexError, UnexpectedInput):
+    pass

lark/lark.pyi

@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+
+from typing import List, Dict, IO, Callable, Union, Optional, Literal
+from .visitors import Transformer
+from .lexer import Lexer, Token
+from .tree import Tree
+
+_Start = Union[None, str, List[str]]
+
+
+class Lark:
+
+    def __init__(
+        self,
+        grammar: Union[str, IO[str]],
+        *,
+        start: _Start = ...,
+        parser: Literal["earley", "lalr", "cyk"] = ...,
+        lexer: Optional[Lexer] = ...,
+        transformer: Optional[Transformer] = ...,
+        postlex: Optional[Literal["standard", "contextual"]] = ...,
+        ambiguity: Literal["explicit", "resolve"] = ...,
+        debug: bool = False,
+        keep_all_tokens: bool = False,
+        propagate_positions: bool = False,
+        maybe_placeholders: bool = False,
+        lexer_callbacks: Dict[str, Callable[[Token], Token]]
+    ):
+        ...
+
+    def parse(self, text: str, start: _Start = None) -> Tree:
+        ...

lark/lexer.pyi

@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+
+from typing import Tuple, Iterator, Sized
+from abc import abstractmethod, ABC
+
+
+class Pattern(ABC):
+
+    @abstractmethod
+    def to_regexp(self) -> str:
+        ...
+
+
+class PatternStr(Pattern):
+
+    def to_regexp(self) -> str:
+        ...
+
+
+class PatternRE(Pattern):
+
+    def to_regexp(self) -> str:
+        ...
+
+
+class TerminalDef:
+    name: str
+    pattern: Pattern
+    priority: int
+
+
+class Token(str):
+    type: str
+    pos_in_stream: int
+    line: int
+    column: int
+    end_line: int
+    end_column: int
+    end_pos: int
+
+
+class Lexer(ABC):
+
+    @abstractmethod
+    def lex(self, stream: Sized) -> Iterator[Token]:
+        ...
+
+
+class TraditionalLexer(Lexer):
+
+    def build(self) -> None:
+        ...
+
+    def match(self, stream: str, pos: int) -> Tuple[str, str]:
+        ...
+
+    def lex(self, stream: Sized) -> Iterator[Token]:
+        ...
+
+
+class ContextualLexer(Lexer):
+
+    def lex(self, stream: Sized) -> Iterator[Token]:
+        ...

lark/reconstruct.pyi

@@ -0,0 +1,13 @@
+# -*- coding: utf-8 -*-
+
+from .lark import Lark
+from .tree import Tree
+
+
+class Reconstructor:
+
+    def __init__(self, parser: Lark):
+        ...
+
+    def reconstruct(self, tree: Tree) -> str:
+        ...

lark/tree.pyi

@@ -0,0 +1,39 @@
+# -*- coding: utf-8 -*-
+
+from typing import List, Callable, Iterator, Union, Optional
+from .lexer import Token
+
+
+class Tree:
+
+    data: str
+    children: List[Union[str, Tree]]
+    meta: Token
+
+    def __init__(self, data: str, children: List[Tree], meta: Optional[Token] = None):
+        ...
+
+    def pretty(self, indent_str: str = ...) -> str:
+        ...
+
+    def find_pred(self, pred: Callable[[Tree], bool]) -> Iterator[Tree]:
+        ...
+
+    def find_data(self, data: str) -> Iterator[Tree]:
+        ...
+
+    def iter_subtrees(self) -> Iterator[Tree]:
+        ...
+
+    def iter_subtrees_topdown(self) -> Iterator[Tree]:
+        ...
+
+    def __eq__(self, other: object) -> bool:
+        ...
+
+    def __hash__(self) -> int:
+        ...
+
+
+class SlottedTree(Tree):
+    pass

lark/visitors.py

@@ -36,8 +36,12 @@ class _Decoratable:
         return cls
 
 
+class _GenericMeta(type):
+    def __getitem__(self, _):
+        return self
 
-class Transformer(_Decoratable):
+
+class Transformer(_Decoratable, metaclass=_GenericMeta):
     """Visits the tree recursively, starting with the leaves and finally the root (bottom-up)
 
     Calls its methods (provided by user via inheritance) according to tree.data
@@ -171,7 +175,7 @@ class VisitorBase:
         return tree
 
 
-class Visitor(VisitorBase):
+class Visitor(VisitorBase, metaclass=_GenericMeta):
     """Bottom-up visitor, non-recursive
 
     Visits the tree, starting with the leaves and finally the root (bottom-up)
@@ -224,7 +228,7 @@ def visit_children_decor(func):
     return inner
 
 
-class Interpreter(_Decoratable):
+class Interpreter(_Decoratable, metaclass=_GenericMeta):
     """Top-down visitor, recursive
 
     Visits the tree, starting with the root and finally the leaves (top-down)

lark/visitors.pyi

@@ -0,0 +1,82 @@
+# -*- coding: utf-8 -*-
+
+from typing import TypeVar, List, Callable, Generic, Type
+from abc import ABC
+from .tree import Tree
+
+_T = TypeVar('_T')
+_R = TypeVar('_R')
+_FUNC = Callable[..., _T]
+
+
+class Transformer(ABC, Generic[_T]):
+
+    def __init__(self, visit_tokens: bool = True):
+        ...
+
+    def transform(self, tree: Tree) -> _T:
+        ...
+
+
+class Transformer_InPlace(Transformer):
+    pass
+
+
+class VisitorBase:
+    pass
+
+
+class Visitor(VisitorBase, ABC, Generic[_T]):
+
+    def visit(self, tree: Tree) -> Tree:
+        ...
+
+    def visit_topdown(self, tree: Tree) -> Tree:
+        ...
+
+
+class Visitor_Recursive(VisitorBase):
+
+    def visit(self, tree: Tree) -> Tree:
+        ...
+
+    def visit_topdown(self, tree: Tree) -> Tree:
+        ...
+
+
+class Interpreter(ABC, Generic[_T]):
+
+    def visit(self, tree: Tree) -> _T:
+        ...
+
+    def visit_children(self, tree: Tree) -> List[_T]:
+        ...
+
+
+_InterMethod = Callable[[Type[Interpreter], _T], _R]
+
+
+def v_args(
+    inline: bool = False,
+    meta: bool = False,
+    tree: bool = False
+) -> Callable[[_FUNC], _FUNC]:
+    ...
+
+
+def visit_children_decor(func: _InterMethod) -> _InterMethod:
+    ...
+
+
+class Discard(Exception):
+    pass
+
+
+# Deprecated
+class InlineTransformer:
+    pass
+
+
+# Deprecated
+def inline_args(obj: _FUNC) -> _FUNC:
+    ...

setup.py

@@ -11,7 +11,7 @@ setup(
     requires = [],
     install_requires = [],
 
-    package_data = { '': ['*.md', '*.lark'] },
+    package_data = { '': ['*.md', '*.lark', '*.pyi'], 'lark': ['py.typed'] },
 
     test_suite = 'tests.__main__',