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annotate venv/lib/python2.7/site-packages/jinja2/visitor.py @ 0:d67268158946 draft

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planemo upload commit a3f181f5f126803c654b3a66dd4e83a48f7e203b
author bcclaywell
date Mon, 12 Oct 2015 17:43:33 -0400
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1 # -*- coding: utf-8 -*-
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2 """
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3 jinja2.visitor
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4 ~~~~~~~~~~~~~~
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5
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6 This module implements a visitor for the nodes.
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7
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8 :copyright: (c) 2010 by the Jinja Team.
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9 :license: BSD.
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10 """
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11 from jinja2.nodes import Node
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12
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13
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14 class NodeVisitor(object):
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15 """Walks the abstract syntax tree and call visitor functions for every
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16 node found. The visitor functions may return values which will be
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17 forwarded by the `visit` method.
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18
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19 Per default the visitor functions for the nodes are ``'visit_'`` +
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20 class name of the node. So a `TryFinally` node visit function would
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21 be `visit_TryFinally`. This behavior can be changed by overriding
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22 the `get_visitor` function. If no visitor function exists for a node
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23 (return value `None`) the `generic_visit` visitor is used instead.
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24 """
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25
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26 def get_visitor(self, node):
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27 """Return the visitor function for this node or `None` if no visitor
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28 exists for this node. In that case the generic visit function is
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29 used instead.
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30 """
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31 method = 'visit_' + node.__class__.__name__
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32 return getattr(self, method, None)
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33
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34 def visit(self, node, *args, **kwargs):
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35 """Visit a node."""
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36 f = self.get_visitor(node)
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37 if f is not None:
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38 return f(node, *args, **kwargs)
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39 return self.generic_visit(node, *args, **kwargs)
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40
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41 def generic_visit(self, node, *args, **kwargs):
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42 """Called if no explicit visitor function exists for a node."""
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43 for node in node.iter_child_nodes():
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44 self.visit(node, *args, **kwargs)
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45
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46
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47 class NodeTransformer(NodeVisitor):
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48 """Walks the abstract syntax tree and allows modifications of nodes.
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49
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50 The `NodeTransformer` will walk the AST and use the return value of the
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51 visitor functions to replace or remove the old node. If the return
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52 value of the visitor function is `None` the node will be removed
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53 from the previous location otherwise it's replaced with the return
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54 value. The return value may be the original node in which case no
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55 replacement takes place.
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56 """
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57
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58 def generic_visit(self, node, *args, **kwargs):
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59 for field, old_value in node.iter_fields():
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60 if isinstance(old_value, list):
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61 new_values = []
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62 for value in old_value:
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63 if isinstance(value, Node):
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64 value = self.visit(value, *args, **kwargs)
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65 if value is None:
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66 continue
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67 elif not isinstance(value, Node):
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68 new_values.extend(value)
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69 continue
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70 new_values.append(value)
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71 old_value[:] = new_values
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72 elif isinstance(old_value, Node):
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73 new_node = self.visit(old_value, *args, **kwargs)
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74 if new_node is None:
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75 delattr(node, field)
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76 else:
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77 setattr(node, field, new_node)
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78 return node
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79
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80 def visit_list(self, node, *args, **kwargs):
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81 """As transformers may return lists in some places this method
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82 can be used to enforce a list as return value.
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83 """
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84 rv = self.visit(node, *args, **kwargs)
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85 if not isinstance(rv, list):
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86 rv = [rv]
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87 return rv