Matches a node against a pattern represented by a node.
| 127 | |
| 128 | |
| 129 | class PatternMatcher(gast.NodeVisitor): |
| 130 | """Matches a node against a pattern represented by a node.""" |
| 131 | |
| 132 | def __init__(self, pattern): |
| 133 | self.pattern = pattern |
| 134 | self.pattern_stack = [] |
| 135 | self.matches = True |
| 136 | |
| 137 | def compare_and_visit(self, node, pattern): |
| 138 | self.pattern_stack.append(self.pattern) |
| 139 | self.pattern = pattern |
| 140 | self.generic_visit(node) |
| 141 | self.pattern = self.pattern_stack.pop() |
| 142 | |
| 143 | def no_match(self): |
| 144 | self.matches = False |
| 145 | return False |
| 146 | |
| 147 | def is_wildcard(self, p): |
| 148 | if isinstance(p, (list, tuple)) and len(p) == 1: |
| 149 | p, = p |
| 150 | if isinstance(p, gast.Name) and p.id == '_': |
| 151 | return True |
| 152 | if p == '_': |
| 153 | return True |
| 154 | return False |
| 155 | |
| 156 | def generic_visit(self, node): |
| 157 | if not self.matches: |
| 158 | return |
| 159 | |
| 160 | pattern = self.pattern |
| 161 | for f in node._fields: |
| 162 | if f.startswith('__'): |
| 163 | continue |
| 164 | |
| 165 | if not hasattr(node, f): |
| 166 | if hasattr(pattern, f) and getattr(pattern, f): |
| 167 | return self.no_match() |
| 168 | else: |
| 169 | continue |
| 170 | if not hasattr(pattern, f): |
| 171 | return self.no_match() |
| 172 | |
| 173 | v = getattr(node, f) |
| 174 | p = getattr(pattern, f) |
| 175 | |
| 176 | if self.is_wildcard(p): |
| 177 | continue |
| 178 | if isinstance(v, (list, tuple)): |
| 179 | if not isinstance(p, (list, tuple)) or len(v) != len(p): |
| 180 | return self.no_match() |
| 181 | for v_item, p_item in zip(v, p): |
| 182 | self.compare_and_visit(v_item, p_item) |
| 183 | elif isinstance(v, (gast.AST, ast.AST)): |
| 184 | if not isinstance(v, type(p)) and not isinstance(p, type(v)): |
| 185 | return self.no_match() |
| 186 | self.compare_and_visit(v, p) |