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_ast_util.py
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# mako/_ast_util.py # Copyright 2006-2019 the Mako authors and contributors <see AUTHORS file> # # This module is part of Mako and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """ ast ~~~ This is a stripped down version of Armin Ronacher's ast module. :copyright: Copyright 2008 by Armin Ronacher. :license: Python License. """ from _ast import Add from _ast import And from _ast import AST from _ast import BitAnd from _ast import BitOr from _ast import BitXor from _ast import Div from _ast import Eq from _ast import FloorDiv from _ast import Gt from _ast import GtE from _ast import If from _ast import In from _ast import Invert from _ast import Is from _ast import IsNot from _ast import LShift from _ast import Lt from _ast import LtE from _ast import Mod from _ast import Mult from _ast import Name from _ast import Not from _ast import NotEq from _ast import NotIn from _ast import Or from _ast import PyCF_ONLY_AST from _ast import RShift from _ast import Sub from _ast import UAdd from _ast import USub from mako.compat import arg_stringname BOOLOP_SYMBOLS = {And: "and", Or: "or"} BINOP_SYMBOLS = { Add: "+", Sub: "-", Mult: "*", Div: "/", FloorDiv: "//", Mod: "%", LShift: "<<", RShift: ">>", BitOr: "|", BitAnd: "&", BitXor: "^", } CMPOP_SYMBOLS = { Eq: "==", Gt: ">", GtE: ">=", In: "in", Is: "is", IsNot: "is not", Lt: "<", LtE: "<=", NotEq: "!=", NotIn: "not in", } UNARYOP_SYMBOLS = {Invert: "~", Not: "not", UAdd: "+", USub: "-"} ALL_SYMBOLS = {} ALL_SYMBOLS.update(BOOLOP_SYMBOLS) ALL_SYMBOLS.update(BINOP_SYMBOLS) ALL_SYMBOLS.update(CMPOP_SYMBOLS) ALL_SYMBOLS.update(UNARYOP_SYMBOLS) def parse(expr, filename="<unknown>", mode="exec"): """Parse an expression into an AST node.""" return compile(expr, filename, mode, PyCF_ONLY_AST) def iter_fields(node): """Iterate over all fields of a node, only yielding existing fields.""" # CPython 2.5 compat if not hasattr(node, "_fields") or not node._fields: return for field in node._fields: try: yield field, getattr(node, field) except AttributeError: pass class NodeVisitor(object): """ Walks the abstract syntax tree and call visitor functions for every node found. The visitor functions may return values which will be forwarded by the `visit` method. Per default the visitor functions for the nodes are ``'visit_'`` + class name of the node. So a `TryFinally` node visit function would be `visit_TryFinally`. This behavior can be changed by overriding the `get_visitor` function. If no visitor function exists for a node (return value `None`) the `generic_visit` visitor is used instead. Don't use the `NodeVisitor` if you want to apply changes to nodes during traversing. For this a special visitor exists (`NodeTransformer`) that allows modifications. """ def get_visitor(self, node): """ Return the visitor function for this node or `None` if no visitor exists for this node. In that case the generic visit function is used instead. """ method = "visit_" + node.__class__.__name__ return getattr(self, method, None) def visit(self, node): """Visit a node.""" f = self.get_visitor(node) if f is not None: return f(node) return self.generic_visit(node) def generic_visit(self, node): """Called if no explicit visitor function exists for a node.""" for field, value in iter_fields(node): if isinstance(value, list): for item in value: if isinstance(item, AST): self.visit(item) elif isinstance(value, AST): self.visit(value) class NodeTransformer(NodeVisitor): """ Walks the abstract syntax tree and allows modifications of nodes. The `NodeTransformer` will walk the AST and use the return value of the visitor functions to replace or remove the old node. If the return value of the visitor function is `None` the node will be removed from the previous location otherwise it's replaced with the return value. The return value may be the original node in which case no replacement takes place. Here an example transformer that rewrites all `foo` to `data['foo']`:: class RewriteName(NodeTransformer): def visit_Name(self, node): return copy_location(Subscript( value=Name(id='data', ctx=Load()), slice=Index(value=Str(s=node.id)), ctx=node.ctx ), node) Keep in mind that if the node you're operating on has child nodes you must either transform the child nodes yourself or call the generic visit function for the node first. Nodes that were part of a collection of statements (that applies to all statement nodes) may also return a list of nodes rather than just a single node. Usually you use the transformer like this:: node = YourTransformer().visit(node) """ def generic_visit(self, node): for field, old_value in iter_fields(node): old_value = getattr(node, field, None) if isinstance(old_value, list): new_values = [] for value in old_value: if isinstance(value, AST): value = self.visit(value) if value is None: continue elif not isinstance(value, AST): new_values.extend(value) continue new_values.append(value) old_value[:] = new_values elif isinstance(old_value, AST): new_node = self.visit(old_value) if new_node is None: delattr(node, field) else: setattr(node, field, new_node) return node class SourceGenerator(NodeVisitor): """ This visitor is able to transform a well formed syntax tree into python sourcecode. For more details have a look at the docstring of the `node_to_source` function. """ def __init__(self, indent_with): self.result = [] self.indent_with = indent_with self.indentation = 0 self.new_lines = 0 def write(self, x): if self.new_lines: if self.result: self.result.append("\n" * self.new_lines) self.result.append(self.indent_with * self.indentation) self.new_lines = 0 self.result.append(x) def newline(self, n=1): self.new_lines = max(self.new_lines, n) def body(self, statements): self.new_line = True self.indentation += 1 for stmt in statements: self.visit(stmt) self.indentation -= 1 def body_or_else(self, node): self.body(node.body) if node.orelse: self.newline() self.write("else:") self.body(node.orelse) def signature(self, node): want_comma = [] def write_comma(): if want_comma: self.write(", ") else: want_comma.append(True) padding = [None] * (len(node.args) - len(node.defaults)) for arg, default in zip(node.args, padding + node.defaults): write_comma() self.visit(arg) if default is not None: self.write("=") self.visit(default) if node.vararg is not None: write_comma() self.write("*" + arg_stringname(node.vararg)) if node.kwarg is not None: write_comma() self.write("**" + arg_stringname(node.kwarg)) def decorators(self, node): for decorator in node.decorator_list: self.newline() self.write("@") self.visit(decorator) # Statements def visit_Assign(self, node): self.newline() for idx, target in enumerate(node.targets): if idx: self.write(", ") self.visit(target) self.write(" = ") self.visit(node.value) def visit_AugAssign(self, node): self.newline() self.visit(node.target) self.write(BINOP_SYMBOLS[type(node.op)] + "=") self.visit(node.value) def visit_ImportFrom(self, node): self.newline() self.write("from %s%s import " % ("." * node.level, node.module)) for idx, item in enumerate(node.names): if idx: self.write(", ") self.write(item) def visit_Import(self, node): self.newline() for item in node.names: self.write("import ") self.visit(item) def visit_Expr(self, node): self.newline() self.generic_visit(node) def visit_FunctionDef(self, node): self.newline(n=2) self.decorators(node) self.newline() self.write("def %s(" % node.name) self.signature(node.args) self.write("):") self.body(node.body) def visit_ClassDef(self, node): have_args = [] def paren_or_comma(): if have_args: self.write(", ") else: have_args.append(True) self.write("(") self.newline(n=3) self.decorators(node) self.newline() self.write("class %s" % node.name) for base in node.bases: paren_or_comma() self.visit(base) # XXX: the if here is used to keep this module compatible # with python 2.6. if hasattr(node, "keywords"): for keyword in node.keywords: paren_or_comma() self.write(keyword.arg + "=") self.visit(keyword.value) if getattr(node, "starargs", None): paren_or_comma() self.write("*") self.visit(node.starargs) if getattr(node, "kwargs", None): paren_or_comma() self.write("**") self.visit(node.kwargs) self.write(have_args and "):" or ":") self.body(node.body) def visit_If(self, node): self.newline() self.write("if ") self.visit(node.test) self.write(":") self.body(node.body) while True: else_ = node.orelse if len(else_) == 1 and isinstance(else_[0], If): node = else_[0] self.newline() self.write("elif ") self.visit(node.test) self.write(":") self.body(node.body) else: self.newline() self.write("else:") self.body(else_) break def visit_For(self, node): self.newline() self.write("for ") self.visit(node.target) self.write(" in ") self.visit(node.iter) self.write(":") self.body_or_else(node) def visit_While(self, node): self.newline() self.write("while ") self.visit(node.test) self.write(":") self.body_or_else(node) def visit_With(self, node): self.newline() self.write("with ") self.visit(node.context_expr) if node.optional_vars is not None: self.write(" as ") self.visit(node.optional_vars) self.write(":") self.body(node.body) def visit_Pass(self, node): self.newline() self.write("pass") def visit_Print(self, node): # XXX: python 2.6 only self.newline() self.write("print ") want_comma = False if node.dest is not None: self.write(" >> ") self.visit(node.dest) want_comma = True for value in node.values: if want_comma: self.write(", ") self.visit(value) want_comma = True if not node.nl: self.write(",") def visit_Delete(self, node): self.newline() self.write("del ") for idx, target in enumerate(node): if idx: self.write(", ") self.visit(target) def visit_TryExcept(self, node): self.newline() self.write("try:") self.body(node.body) for handler in node.handlers: self.visit(handler) def visit_TryFinally(self, node): self.newline() self.write("try:") self.body(node.body) self.newline() self.write("finally:") self.body(node.finalbody) def visit_Global(self, node): self.newline() self.write("global " + ", ".join(node.names)) def visit_Nonlocal(self, node): self.newline() self.write("nonlocal " + ", ".join(node.names)) def visit_Return(self, node): self.newline() self.write("return ") self.visit(node.value) def visit_Break(self, node): self.newline() self.write("break") def visit_Continue(self, node): self.newline() self.write("continue") def visit_Raise(self, node): # XXX: Python 2.6 / 3.0 compatibility self.newline() self.write("raise") if hasattr(node, "exc") and node.exc is not None: self.write(" ") self.visit(node.exc) if node.cause is not None: self.write(" from ") self.visit(node.cause) elif hasattr(node, "type") and node.type is not None: self.visit(node.type) if node.inst is not None: self.write(", ") self.visit(node.inst) if node.tback is not None: self.write(", ") self.visit(node.tback) # Expressions def visit_Attribute(self, node): self.visit(node.value) self.write("." + node.attr) def visit_Call(self, node): want_comma = [] def write_comma(): if want_comma: self.write(", ") else: want_comma.append(True) self.visit(node.func) self.write("(") for arg in node.args: write_comma() self.visit(arg) for keyword in node.keywords: write_comma() self.write(keyword.arg + "=") self.visit(keyword.value) if getattr(node, "starargs", None): write_comma() self.write("*") self.visit(node.starargs) if getattr(node, "kwargs", None): write_comma() self.write("**") self.visit(node.kwargs) self.write(")") def visit_Name(self, node): self.write(node.id) def visit_NameConstant(self, node): self.write(str(node.value)) def visit_arg(self, node): self.write(node.arg) def visit_Str(self, node): self.write(repr(node.s)) def visit_Bytes(self, node): self.write(repr(node.s)) def visit_Num(self, node): self.write(repr(node.n)) # newly needed in Python 3.8 def visit_Constant(self, node): self.write(repr(node.value)) def visit_Tuple(self, node): self.write("(") idx = -1 for idx, item in enumerate(node.elts): if idx: self.write(", ") self.visit(item) self.write(idx and ")" or ",)") def sequence_visit(left, right): def visit(self, node): self.write(left) for idx, item in enumerate(node.elts): if idx: self.write(", ") self.visit(item) self.write(right) return visit visit_List = sequence_visit("[", "]") visit_Set = sequence_visit("{", "}") del sequence_visit def visit_Dict(self, node): self.write("{") for idx, (key, value) in enumerate(zip(node.keys, node.values)): if idx: self.write(", ") self.visit(key) self.write(": ") self.visit(value) self.write("}") def visit_BinOp(self, node): self.write("(") self.visit(node.left) self.write(" %s " % BINOP_SYMBOLS[type(node.op)]) self.visit(node.right) self.write(")") def visit_BoolOp(self, node): self.write("(") for idx, value in enumerate(node.values): if idx: self.write(" %s " % BOOLOP_SYMBOLS[type(node.op)]) self.visit(value) self.write(")") def visit_Compare(self, node): self.write("(") self.visit(node.left) for op, right in zip(node.ops, node.comparators): self.write(" %s " % CMPOP_SYMBOLS[type(op)]) self.visit(right) self.write(")") def visit_UnaryOp(self, node): self.write("(") op = UNARYOP_SYMBOLS[type(node.op)] self.write(op) if op == "not": self.write(" ") self.visit(node.operand) self.write(")") def visit_Subscript(self, node): self.visit(node.value) self.write("[") self.visit(node.slice) self.write("]") def visit_Slice(self, node): if node.lower is not None: self.visit(node.lower) self.write(":") if node.upper is not None: self.visit(node.upper) if node.step is not None: self.write(":") if not (isinstance(node.step, Name) and node.step.id == "None"): self.visit(node.step) def visit_ExtSlice(self, node): for idx, item in node.dims: if idx: self.write(", ") self.visit(item) def visit_Yield(self, node): self.write("yield ") self.visit(node.value) def visit_Lambda(self, node): self.write("lambda ") self.signature(node.args) self.write(": ") self.visit(node.body) def visit_Ellipsis(self, node): self.write("Ellipsis") def generator_visit(left, right): def visit(self, node): self.write(left) self.visit(node.elt) for comprehension in node.generators: self.visit(comprehension) self.write(right) return visit visit_ListComp = generator_visit("[", "]") visit_GeneratorExp = generator_visit("(", ")") visit_SetComp = generator_visit("{", "}") del generator_visit def visit_DictComp(self, node): self.write("{") self.visit(node.key) self.write(": ") self.visit(node.value) for comprehension in node.generators: self.visit(comprehension) self.write("}") def visit_IfExp(self, node): self.visit(node.body) self.write(" if ") self.visit(node.test) self.write(" else ") self.visit(node.orelse) def visit_Starred(self, node): self.write("*") self.visit(node.value) def visit_Repr(self, node): # XXX: python 2.6 only self.write("`") self.visit(node.value) self.write("`") # Helper Nodes def visit_alias(self, node): self.write(node.name) if node.asname is not None: self.write(" as " + node.asname) def visit_comprehension(self, node): self.write(" for ") self.visit(node.target) self.write(" in ") self.visit(node.iter) if node.ifs: for if_ in node.ifs: self.write(" if ") self.visit(if_) def visit_excepthandler(self, node): self.newline() self.write("except") if node.type is not None: self.write(" ") self.visit(node.type) if node.name is not None: self.write(" as ") self.visit(node.name) self.write(":") self.body(node.body)