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annotate planemo/lib/python3.7/site-packages/jinja2/visitor.py @ 1:56ad4e20f292 draft

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"planemo upload commit 6eee67778febed82ddd413c3ca40b3183a3898f1"
author guerler
date Fri, 31 Jul 2020 00:32:28 -0400
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1 # -*- coding: utf-8 -*-
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2 """API for traversing the AST nodes. Implemented by the compiler and
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3 meta introspection.
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4 """
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5 from .nodes import Node
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6
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7
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8 class NodeVisitor(object):
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9 """Walks the abstract syntax tree and call visitor functions for every
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10 node found. The visitor functions may return values which will be
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11 forwarded by the `visit` method.
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12
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13 Per default the visitor functions for the nodes are ``'visit_'`` +
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14 class name of the node. So a `TryFinally` node visit function would
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15 be `visit_TryFinally`. This behavior can be changed by overriding
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16 the `get_visitor` function. If no visitor function exists for a node
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17 (return value `None`) the `generic_visit` visitor is used instead.
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18 """
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19
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20 def get_visitor(self, node):
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21 """Return the visitor function for this node or `None` if no visitor
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22 exists for this node. In that case the generic visit function is
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23 used instead.
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24 """
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25 method = "visit_" + node.__class__.__name__
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26 return getattr(self, method, None)
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27
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28 def visit(self, node, *args, **kwargs):
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29 """Visit a node."""
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30 f = self.get_visitor(node)
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31 if f is not None:
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32 return f(node, *args, **kwargs)
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33 return self.generic_visit(node, *args, **kwargs)
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34
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35 def generic_visit(self, node, *args, **kwargs):
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36 """Called if no explicit visitor function exists for a node."""
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37 for node in node.iter_child_nodes():
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38 self.visit(node, *args, **kwargs)
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39
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40
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41 class NodeTransformer(NodeVisitor):
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42 """Walks the abstract syntax tree and allows modifications of nodes.
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43
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44 The `NodeTransformer` will walk the AST and use the return value of the
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45 visitor functions to replace or remove the old node. If the return
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46 value of the visitor function is `None` the node will be removed
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47 from the previous location otherwise it's replaced with the return
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48 value. The return value may be the original node in which case no
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49 replacement takes place.
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50 """
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51
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52 def generic_visit(self, node, *args, **kwargs):
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53 for field, old_value in node.iter_fields():
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54 if isinstance(old_value, list):
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55 new_values = []
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56 for value in old_value:
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57 if isinstance(value, Node):
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58 value = self.visit(value, *args, **kwargs)
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59 if value is None:
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60 continue
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61 elif not isinstance(value, Node):
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62 new_values.extend(value)
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63 continue
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64 new_values.append(value)
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65 old_value[:] = new_values
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66 elif isinstance(old_value, Node):
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67 new_node = self.visit(old_value, *args, **kwargs)
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68 if new_node is None:
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69 delattr(node, field)
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70 else:
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71 setattr(node, field, new_node)
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72 return node
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73
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74 def visit_list(self, node, *args, **kwargs):
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75 """As transformers may return lists in some places this method
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76 can be used to enforce a list as return value.
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77 """
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78 rv = self.visit(node, *args, **kwargs)
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79 if not isinstance(rv, list):
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80 rv = [rv]
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81 return rv