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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,180 @@ | ||
| from ast import parse, NodeVisitor, Name | ||
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| # For error messages (student-facing) only | ||
| _NAMES = { | ||
| 'Add': '+', | ||
| 'And': 'and', | ||
| 'Assert': 'assert', | ||
| 'Assign': '=', | ||
| 'AnnAssign': '=', | ||
| 'AugAssign': 'op=', | ||
| 'BitAnd': '&', | ||
| 'BitOr': '|', | ||
| 'BitXor': '^', | ||
| 'Break': 'break', | ||
| 'Recursion': 'recursive call', | ||
| 'ClassDef': 'class', | ||
| 'Continue': 'continue', | ||
| 'Del': 'del', | ||
| 'Delete': 'delete', | ||
| 'Dict': '{...}', | ||
| 'DictComp': '{...}', | ||
| 'Div': '/', | ||
| 'Ellipsis': '...', | ||
| 'Eq': '==', | ||
| 'ExceptHandler': 'except', | ||
| 'ExtSlice': '[::]', | ||
| 'FloorDiv': '//', | ||
| 'For': 'for', | ||
| 'FunctionDef': 'def', | ||
| 'Filter': 'filter', | ||
| 'GeneratorExp': '(... for ...)', | ||
| 'Global': 'global', | ||
| 'Gt': '>', | ||
| 'GtE': '>=', | ||
| 'If': 'if', | ||
| 'IfExp': '...if...else...', | ||
| 'Import': 'import', | ||
| 'ImportFrom': 'from ... import ...', | ||
| 'In': 'in', | ||
| 'Index': '...[...]', | ||
| 'Invert': '~', | ||
| 'Is': 'is', | ||
| 'IsNot': 'is not ', | ||
| 'LShift': '<<', | ||
| 'Lambda': 'lambda', | ||
| 'List': '[...]', | ||
| 'ListComp': '[...for...]', | ||
| 'Lt': '<', | ||
| 'LtE': '<=', | ||
| 'Mod': '%', | ||
| 'Mult': '*', | ||
| 'NamedExpr': ':=', | ||
| 'Nonlocal': 'nonlocal', | ||
| 'Not': 'not', | ||
| 'NotEq': '!=', | ||
| 'NotIn': 'not in', | ||
| 'Or': 'or', | ||
| 'Pass': 'pass', | ||
| 'Pow': '**', | ||
| 'RShift': '>>', | ||
| 'Raise': 'raise', | ||
| 'Return': 'return', | ||
| 'Set': '{ ... } (set)', | ||
| 'SetComp': '{ ... for ... } (set)', | ||
| 'Slice': '[ : ]', | ||
| 'Starred': '', | ||
| 'Str': 'str', | ||
| 'Sub': '-', | ||
| 'Subscript': '[]', | ||
| 'Try': 'try', | ||
| 'Tuple': '(... , ... )', | ||
| 'UAdd': '+', | ||
| 'USub': '-', | ||
| 'While': 'while', | ||
| 'With': 'with', | ||
| 'Yield': 'yield', | ||
| 'YieldFrom': 'yield from', | ||
| } | ||
|
|
||
| def check(source_file, checked_funcs, disallow, source=None): | ||
| """Checks that AST nodes whose type names are present in DISALLOW | ||
| (an object supporting 'in') are not present in the function(s) named | ||
| CHECKED_FUNCS in SOURCE. By default, SOURCE is the contents of the | ||
| file SOURCE_FILE. CHECKED_FUNCS is either a string (indicating a single | ||
| name) or an object of some other type that supports 'in'. CHECKED_FUNCS | ||
| may contain __main__ to indicate an entire module. Prints reports of | ||
| each prohibited node and returns True iff none are found. | ||
| See ast.__dir__() for AST type names. The special node name 'Recursion' | ||
| checks for overtly recursive calls (i.e., calls of the form NAME(...) where | ||
| NAME is an enclosing def.""" | ||
| return ExclusionChecker(disallow).check(source_file, checked_funcs, source) | ||
|
|
||
| class ExclusionChecker(NodeVisitor): | ||
| """An AST visitor that checks that certain constructs are excluded from | ||
| parts of a program. ExclusionChecker(EXC) checks that AST node types | ||
| whose names are in the sequence or set EXC are not present. Its check | ||
| method visits nodes in a given function of a source file checking that the | ||
| indicated node types are not used.""" | ||
|
|
||
| def __init__(self, disallow=()): | ||
| """DISALLOW is the initial default list of disallowed | ||
| node-type names.""" | ||
| self._disallow = set(disallow) | ||
| self._checking = False | ||
| self._errs = 0 | ||
|
|
||
| def generic_visit(self, node): | ||
| if self._checking and type(node).__name__ in self._disallow: | ||
| self._report(node) | ||
| super().generic_visit(node) | ||
|
|
||
| def visit_Module(self, node): | ||
| if "__main__" in self._checked_funcs: | ||
| self._checking = True | ||
| self._checked_name = self._source_file | ||
| super().generic_visit(node) | ||
|
|
||
| def visit_Call(self, node): | ||
| if 'Recursion' in self._disallow and \ | ||
| type(node.func) is Name and \ | ||
| node.func.id in self._func_nest: | ||
| self._report(node, "should not be recursive") | ||
| self.generic_visit(node) | ||
|
|
||
| def visit_FunctionDef(self, node): | ||
| self._func_nest.append(node.name) | ||
| if self._checking: | ||
| self.generic_visit(node) | ||
| elif node.name in self._checked_funcs: | ||
| self._checked_name = "Function " + node.name | ||
| checking0 = self._checking | ||
| self._checking = True | ||
| super().generic_visit(node) | ||
| self._checking = checking0 | ||
| self._func_nest.pop() | ||
|
|
||
| def _report(self, node, msg=None): | ||
| node_name = _NAMES.get(type(node).__name__, type(node).__name__) | ||
| if msg is None: | ||
| msg = "should not contain '{}'".format(node_name) | ||
| print("{} {}".format(self._checked_name, msg)) | ||
| self._errs += 1 | ||
|
|
||
| def errors(self): | ||
| """Returns the number of number of prohibited constructs found in | ||
| the last call to check.""" | ||
| return self._errs | ||
|
|
||
| def check(self, source_file, checked_funcs, disallow=None, source=None): | ||
| """Checks that AST nodes whose type names are present in DISALLOW | ||
| (an object supporting the contains test) are not present in | ||
| the function(s) named CHECKED_FUNCS in SOURCE. By default, SOURCE | ||
| is the contents of the file SOURCE_FILE. DISALLOW defaults to the | ||
| argument given to the constructor (and resets that value if it is | ||
| present). CHECKED_FUNCS is either a string (indicating a single | ||
| name) or an object of some other type that supports 'in'. | ||
| CHECKED_FUNCS may contain __main__ to indicate an entire module. | ||
| Prints reports of each prohibited node and returns True iff none | ||
| are found. | ||
| See ast.__dir__() for AST type names. The special node name | ||
| 'Recursion' checks for overtly recursive calls (i.e., calls of the | ||
| form NAME(...) where NAME is an enclosing def.""" | ||
|
|
||
| self._checking = False | ||
| self._source_file = source_file | ||
| self._func_nest = [] | ||
| if type(checked_funcs) is str: | ||
| self._checked_funcs = { checked_funcs } | ||
| else: | ||
| self._checked_funcs = set(checked_funcs) | ||
| if disallow is not None: | ||
| self._disallow = set(disallow) | ||
| if source is None: | ||
| with open(source_file, 'r', errors='ignore') as inp: | ||
| source = inp.read() | ||
| p = parse(source, source_file) | ||
| self._errs = 0 | ||
|
|
||
| self.visit(p) | ||
| return self._errs == 0 |
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