Mercurial > repos > shellac > guppy_basecaller
comparison env/lib/python3.7/site-packages/jinja2/visitor.py @ 0:26e78fe6e8c4 draft
"planemo upload commit c699937486c35866861690329de38ec1a5d9f783"
| author | shellac |
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| date | Sat, 02 May 2020 07:14:21 -0400 |
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| children |
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| -1:000000000000 | 0:26e78fe6e8c4 |
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| 1 # -*- coding: utf-8 -*- | |
| 2 """API for traversing the AST nodes. Implemented by the compiler and | |
| 3 meta introspection. | |
| 4 """ | |
| 5 from .nodes import Node | |
| 6 | |
| 7 | |
| 8 class NodeVisitor(object): | |
| 9 """Walks the abstract syntax tree and call visitor functions for every | |
| 10 node found. The visitor functions may return values which will be | |
| 11 forwarded by the `visit` method. | |
| 12 | |
| 13 Per default the visitor functions for the nodes are ``'visit_'`` + | |
| 14 class name of the node. So a `TryFinally` node visit function would | |
| 15 be `visit_TryFinally`. This behavior can be changed by overriding | |
| 16 the `get_visitor` function. If no visitor function exists for a node | |
| 17 (return value `None`) the `generic_visit` visitor is used instead. | |
| 18 """ | |
| 19 | |
| 20 def get_visitor(self, node): | |
| 21 """Return the visitor function for this node or `None` if no visitor | |
| 22 exists for this node. In that case the generic visit function is | |
| 23 used instead. | |
| 24 """ | |
| 25 method = "visit_" + node.__class__.__name__ | |
| 26 return getattr(self, method, None) | |
| 27 | |
| 28 def visit(self, node, *args, **kwargs): | |
| 29 """Visit a node.""" | |
| 30 f = self.get_visitor(node) | |
| 31 if f is not None: | |
| 32 return f(node, *args, **kwargs) | |
| 33 return self.generic_visit(node, *args, **kwargs) | |
| 34 | |
| 35 def generic_visit(self, node, *args, **kwargs): | |
| 36 """Called if no explicit visitor function exists for a node.""" | |
| 37 for node in node.iter_child_nodes(): | |
| 38 self.visit(node, *args, **kwargs) | |
| 39 | |
| 40 | |
| 41 class NodeTransformer(NodeVisitor): | |
| 42 """Walks the abstract syntax tree and allows modifications of nodes. | |
| 43 | |
| 44 The `NodeTransformer` will walk the AST and use the return value of the | |
| 45 visitor functions to replace or remove the old node. If the return | |
| 46 value of the visitor function is `None` the node will be removed | |
| 47 from the previous location otherwise it's replaced with the return | |
| 48 value. The return value may be the original node in which case no | |
| 49 replacement takes place. | |
| 50 """ | |
| 51 | |
| 52 def generic_visit(self, node, *args, **kwargs): | |
| 53 for field, old_value in node.iter_fields(): | |
| 54 if isinstance(old_value, list): | |
| 55 new_values = [] | |
| 56 for value in old_value: | |
| 57 if isinstance(value, Node): | |
| 58 value = self.visit(value, *args, **kwargs) | |
| 59 if value is None: | |
| 60 continue | |
| 61 elif not isinstance(value, Node): | |
| 62 new_values.extend(value) | |
| 63 continue | |
| 64 new_values.append(value) | |
| 65 old_value[:] = new_values | |
| 66 elif isinstance(old_value, Node): | |
| 67 new_node = self.visit(old_value, *args, **kwargs) | |
| 68 if new_node is None: | |
| 69 delattr(node, field) | |
| 70 else: | |
| 71 setattr(node, field, new_node) | |
| 72 return node | |
| 73 | |
| 74 def visit_list(self, node, *args, **kwargs): | |
| 75 """As transformers may return lists in some places this method | |
| 76 can be used to enforce a list as return value. | |
| 77 """ | |
| 78 rv = self.visit(node, *args, **kwargs) | |
| 79 if not isinstance(rv, list): | |
| 80 rv = [rv] | |
| 81 return rv |