410 lines
12 KiB
Python
410 lines
12 KiB
Python
"""
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Code for parsing the source (python-alike) code
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"""
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from typing import Dict, Generator, List, Optional, Union, Tuple
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import ast
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from . import wasm
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# pylint: disable=C0103,R0201
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StatementGenerator = Generator[wasm.Statement, None, None]
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WLocals = Dict[str, str]
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class Visitor:
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"""
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Class to visit a Python syntax tree
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Since we need to visit the whole tree, there's no point in subclassing
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the buildin visitor
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"""
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def visit_Module(self, node: ast.Module) -> wasm.Module:
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"""
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Visits a Python module, which results in a wasm Module
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"""
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assert not node.type_ignores
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module = wasm.Module()
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for stmt in node.body:
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if isinstance(stmt, ast.FunctionDef):
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wnode = self.visit_FunctionDef(module, stmt)
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if isinstance(wnode, wasm.Import):
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module.imports.append(wnode)
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else:
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module.functions.append(wnode)
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continue
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raise NotImplementedError(stmt)
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return module
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def visit_FunctionDef(
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self,
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module: wasm.Module,
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node: ast.FunctionDef,
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) -> Union[wasm.Import, wasm.Function]:
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"""
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A Python function definition with the @external decorator is returned as import.
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Other functions are returned as (exported) functions.
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Nested / dynamicly created functions are not yet supported
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"""
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exported = False
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if node.decorator_list:
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assert 1 == len(node.decorator_list)
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decorator = node.decorator_list[0]
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if isinstance(decorator, ast.Name):
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assert 'exported' == decorator.id
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exported = True
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elif isinstance(decorator, ast.Call):
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call = decorator
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assert not node.type_comment
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assert 1 == len(node.body)
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assert isinstance(node.body[0], ast.Expr)
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assert isinstance(node.body[0].value, ast.Ellipsis)
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assert isinstance(call.func, ast.Name)
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assert 'imported' == call.func.id
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assert not call.keywords
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mod, name, intname = _parse_import_decorator(node.name, call.args)
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return wasm.Import(mod, name, intname, _parse_import_args(node.args))
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else:
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raise NotImplementedError
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result = None if node.returns is None else _parse_annotation(node.returns)
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assert not node.args.vararg
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assert not node.args.kwonlyargs
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assert not node.args.kw_defaults
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assert not node.args.kwarg
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assert not node.args.defaults
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params = [
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(a.arg, _parse_annotation(a.annotation), )
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for a in [
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*node.args.posonlyargs,
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*node.args.args,
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]
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]
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wlocals: WLocals = dict(params)
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statements: List[wasm.Statement] = []
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for py_stmt in node.body:
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statements.extend(
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self.visit_stmt(module, node, wlocals, py_stmt)
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)
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return wasm.Function(node.name, exported, params, result, statements)
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def visit_stmt(
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self,
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module: wasm.Module,
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func: ast.FunctionDef,
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wlocals: WLocals,
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stmt: ast.stmt,
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) -> StatementGenerator:
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"""
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Visits a statement node within a function
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"""
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if isinstance(stmt, ast.Return):
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return self.visit_Return(module, func, wlocals, stmt)
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if isinstance(stmt, ast.Expr):
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assert isinstance(stmt.value, ast.Call)
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return self.visit_Call(module, wlocals, "None", stmt.value)
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if isinstance(stmt, ast.If):
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return self.visit_If(module, func, wlocals, stmt)
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raise NotImplementedError(stmt)
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def visit_Return(
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self,
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module: wasm.Module,
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func: ast.FunctionDef,
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wlocals: WLocals,
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stmt: ast.Return,
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) -> StatementGenerator:
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"""
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Visits a Return node
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"""
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assert stmt.value is not None
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return_type = _parse_annotation(func.returns)
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yield from self.visit_expr(module, wlocals, return_type, stmt.value)
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yield wasm.Statement('return')
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def visit_If(
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self,
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module: wasm.Module,
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func: ast.FunctionDef,
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wlocals: WLocals,
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stmt: ast.If,
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) -> StatementGenerator:
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"""
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Visits an If node
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"""
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yield from self.visit_expr(
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module,
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wlocals,
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'bool',
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stmt.test,
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)
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yield wasm.Statement('if')
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for py_stmt in stmt.body:
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yield from self.visit_stmt(module, func, wlocals, py_stmt)
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yield wasm.Statement('else')
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for py_stmt in stmt.orelse:
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yield from self.visit_stmt(module, func, wlocals, py_stmt)
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yield wasm.Statement('end')
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def visit_expr(
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self,
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module: wasm.Module,
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wlocals: WLocals,
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exp_type: str,
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node: ast.expr,
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) -> StatementGenerator:
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"""
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Visit an expression node
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"""
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if isinstance(node, ast.BinOp):
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return self.visit_BinOp(module, wlocals, exp_type, node)
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if isinstance(node, ast.UnaryOp):
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return self.visit_UnaryOp(module, wlocals, exp_type, node)
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if isinstance(node, ast.Compare):
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return self.visit_Compare(module, wlocals, exp_type, node)
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if isinstance(node, ast.Call):
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return self.visit_Call(module, wlocals, exp_type, node)
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if isinstance(node, ast.Constant):
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return self.visit_Constant(exp_type, node)
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if isinstance(node, ast.Name):
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return self.visit_Name(wlocals, exp_type, node)
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raise NotImplementedError(node)
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def visit_UnaryOp(
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self,
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module: wasm.Module,
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wlocals: WLocals,
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exp_type: str,
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node: ast.UnaryOp,
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) -> StatementGenerator:
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"""
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Visits a UnaryOp node as (part of) an expression
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"""
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del module
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del wlocals
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if not isinstance(node.operand, ast.Constant):
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raise NotImplementedError
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return self.visit_Constant(exp_type, node.operand)
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def visit_BinOp(
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self,
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module: wasm.Module,
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wlocals: WLocals,
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exp_type: str,
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node: ast.BinOp,
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) -> StatementGenerator:
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"""
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Visits a BinOp node as (part of) an expression
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"""
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yield from self.visit_expr(module, wlocals, exp_type, node.left)
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yield from self.visit_expr(module, wlocals, exp_type, node.right)
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if isinstance(node.op, ast.Add):
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yield wasm.Statement('{}.add'.format(exp_type))
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return
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raise NotImplementedError(node.op)
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def visit_Compare(
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self,
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module: wasm.Module,
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wlocals: WLocals,
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exp_type: str,
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node: ast.Compare,
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) -> StatementGenerator:
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"""
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Visits a Compare node as (part of) an expression
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"""
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assert 'bool' == exp_type
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if 1 != len(node.ops) or 1 != len(node.comparators):
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raise NotImplementedError
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yield from self.visit_expr(module, wlocals, 'i32', node.left)
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yield from self.visit_expr(module, wlocals, 'i32', node.comparators[0])
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if isinstance(node.ops[0], ast.Lt):
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yield wasm.Statement('i32.lt_s')
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return
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if isinstance(node.ops[0], ast.Gt):
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yield wasm.Statement('i32.gt_s')
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return
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raise NotImplementedError(node.ops)
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def visit_Call(
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self,
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module: wasm.Module,
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wlocals: WLocals,
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exp_type: str,
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node: ast.Call,
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) -> StatementGenerator:
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"""
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Visits a Call node as (part of) an expression
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"""
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assert isinstance(node.func, ast.Name)
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assert not node.keywords
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called_name = node.func.id
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called_func_list = [
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x
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for x in module.functions
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if x.name == called_name
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]
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if called_func_list:
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assert len(called_func_list) == 1
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called_params = called_func_list[0].params
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called_result = called_func_list[0].result
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else:
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called_import_list = [
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x
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for x in module.imports
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if x.name == node.func.id
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]
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if called_import_list:
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assert len(called_import_list) == 1
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called_params = called_import_list[0].params
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called_result = called_import_list[0].result
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else:
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assert 1 == len(called_func_list), \
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'Could not find function {}'.format(node.func.id)
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assert exp_type == called_result
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assert len(called_params) == len(node.args), \
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'{}:{} Function {} requires {} arguments, but {} are supplied'.format(
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node.lineno, node.col_offset,
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called_name, len(called_params), len(node.args),
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)
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for (_, exp_expr_type), expr in zip(called_params, node.args):
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yield from self.visit_expr(module, wlocals, exp_expr_type, expr)
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yield wasm.Statement(
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'call',
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'${}'.format(called_name),
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)
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def visit_Constant(self, exp_type: str, node: ast.Constant) -> StatementGenerator:
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"""
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Visits a Constant node as (part of) an expression
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"""
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if 'i32' == exp_type:
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assert isinstance(node.value, int)
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assert -2147483648 <= node.value <= 2147483647
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yield wasm.Statement(
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'{}.const'.format(exp_type),
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str(node.value)
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)
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return
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raise NotImplementedError(exp_type)
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def visit_Name(self, wlocals: WLocals, exp_type: str, node: ast.Name) -> StatementGenerator:
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"""
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Visits a Name node as (part of) an expression
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"""
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assert node.id in wlocals
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assert exp_type == wlocals[node.id]
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yield wasm.Statement(
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'local.get',
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'${}'.format(node.id),
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)
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def _parse_import_decorator(func_name: str, args: List[ast.expr]) -> Tuple[str, str, str]:
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"""
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Parses an @import decorator
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"""
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assert 0 < len(args) < 3
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str_args = [
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arg.value
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for arg in args
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if isinstance(arg, ast.Constant)
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and isinstance(arg.value, str)
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]
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assert len(str_args) == len(args)
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module = str_args.pop(0)
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if str_args:
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name = str_args.pop(0)
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else:
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name = func_name
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return module, name, func_name
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def _parse_import_args(args: ast.arguments) -> List[Tuple[str, str]]:
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"""
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Parses the arguments for an @imported method
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"""
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assert not args.vararg
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assert not args.kwonlyargs
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assert not args.kw_defaults
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assert not args.kwarg
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assert not args.defaults # Maybe support this later on
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arg_list = [
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*args.posonlyargs,
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*args.args,
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]
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return [
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(arg.arg, _parse_annotation(arg.annotation))
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for arg in arg_list
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]
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def _parse_annotation(ann: Optional[ast.expr]) -> str:
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"""
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Parses a typing annotation
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"""
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assert ann is not None, 'Web Assembly requires type annotations'
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assert isinstance(ann, ast.Name)
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result = ann.id
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assert result in ['i32']
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return result
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