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| 1 | +"""This module defines utilities for matching and translation tree templates. |
| 2 | +
|
| 3 | +A tree templates is a tree that contains nodes that are template variables. |
| 4 | +
|
| 5 | +""" |
| 6 | + |
| 7 | +from typing import Union, Optional, Mapping |
| 8 | + |
| 9 | +from lark import Tree, Transformer |
| 10 | + |
| 11 | +TreeOrCode = Union[Tree, str] |
| 12 | + |
| 13 | +class TemplateConf: |
| 14 | + """Template Configuration |
| 15 | +
|
| 16 | + Allows customization for different uses of Template |
| 17 | + """ |
| 18 | + |
| 19 | + def __init__(self, parse=None): |
| 20 | + self._parse = parse |
| 21 | + |
| 22 | + |
| 23 | + def test_var(self, var: Union[Tree, str]) -> Optional[str]: |
| 24 | + """Given a tree node, if it is a template variable return its name. Otherwise, return None. |
| 25 | +
|
| 26 | + This method may be overridden for customization |
| 27 | +
|
| 28 | + Parameters: |
| 29 | + var: Tree | str - The tree node to test |
| 30 | +
|
| 31 | + """ |
| 32 | + if isinstance(var, str) and var.startswith('$'): |
| 33 | + return var.lstrip('$') |
| 34 | + |
| 35 | + if isinstance(var, Tree) and var.data == 'var' and var.children[0].startswith('$'): |
| 36 | + return var.children[0].lstrip('$') |
| 37 | + |
| 38 | + |
| 39 | + def _get_tree(self, template: TreeOrCode): |
| 40 | + if isinstance(template, str): |
| 41 | + assert self._parse |
| 42 | + template = self._parse(template) |
| 43 | + |
| 44 | + assert isinstance(template, Tree) |
| 45 | + return template |
| 46 | + |
| 47 | + def __call__(self, template): |
| 48 | + return Template(template, conf=self) |
| 49 | + |
| 50 | + def _match_tree_template(self, template, tree): |
| 51 | + template_var = self.test_var(template) |
| 52 | + if template_var: |
| 53 | + return {template_var: tree} |
| 54 | + |
| 55 | + if isinstance(template, str): |
| 56 | + if template == tree: |
| 57 | + return {} |
| 58 | + return |
| 59 | + |
| 60 | + assert isinstance(template, Tree), template |
| 61 | + |
| 62 | + if template.data == tree.data and len(template.children) == len(tree.children): |
| 63 | + res = {} |
| 64 | + for t1, t2 in zip(template.children, tree.children): |
| 65 | + matches = self._match_tree_template(t1, t2) |
| 66 | + if matches is None: |
| 67 | + return |
| 68 | + |
| 69 | + res.update(matches) |
| 70 | + |
| 71 | + return res |
| 72 | + |
| 73 | + |
| 74 | + |
| 75 | +class _ReplaceVars(Transformer): |
| 76 | + def __init__(self, conf, vars): |
| 77 | + self._conf = conf |
| 78 | + self._vars = vars |
| 79 | + |
| 80 | + def __default__(self, data, children, meta): |
| 81 | + tree = super().__default__(data, children, meta) |
| 82 | + |
| 83 | + var = self._conf.test_var(tree) |
| 84 | + if var: |
| 85 | + return self._vars[var] |
| 86 | + return tree |
| 87 | + |
| 88 | + |
| 89 | +class Template: |
| 90 | + """Represents a tree templates, tied to a specific configuration |
| 91 | +
|
| 92 | + A tree template is a tree that contains nodes that are template variables. |
| 93 | + Those variables will match any tree. |
| 94 | + (future versions may support annotations on the variables, to allow more complex templates) |
| 95 | + """ |
| 96 | + |
| 97 | + def __init__(self, tree: Tree, conf = TemplateConf()): |
| 98 | + self.conf = conf |
| 99 | + self.tree = conf._get_tree(tree) |
| 100 | + |
| 101 | + def match(self, tree: TreeOrCode): |
| 102 | + """Match a tree template to a tree. |
| 103 | +
|
| 104 | + A tree template without variables will only match ``tree`` if it is equal to the template. |
| 105 | +
|
| 106 | + Parameters: |
| 107 | + tree (Tree): The tree to match to the template |
| 108 | +
|
| 109 | + Returns: |
| 110 | + Optional[Dict[str, Tree]]: If match is found, returns a dictionary mapping |
| 111 | + template variable names to their matching tree nodes. |
| 112 | + If no match was found, returns None. |
| 113 | + """ |
| 114 | + tree = self.conf._get_tree(tree) |
| 115 | + return self.conf._match_tree_template(self.tree, tree) |
| 116 | + |
| 117 | + def search(self, tree: TreeOrCode): |
| 118 | + """Search for all occurances of the tree template inside ``tree``. |
| 119 | + """ |
| 120 | + tree = self.conf._get_tree(tree) |
| 121 | + for subtree in tree.iter_subtrees(): |
| 122 | + res = self.match(subtree) |
| 123 | + if res: |
| 124 | + yield subtree, res |
| 125 | + |
| 126 | + def apply_vars(self, vars: Mapping[str, Tree]): |
| 127 | + """Apply vars to the template tree |
| 128 | + """ |
| 129 | + return _ReplaceVars(self.conf, vars).transform(self.tree) |
| 130 | + |
| 131 | + |
| 132 | +def translate(t1: Template, t2: Template, tree: TreeOrCode): |
| 133 | + """Search tree and translate each occurrance of t1 into t2. |
| 134 | + """ |
| 135 | + tree = t1.conf._get_tree(tree) # ensure it's a tree, parse if necessary and possible |
| 136 | + for subtree, vars in t1.search(tree): |
| 137 | + res = t2.apply_vars(vars) |
| 138 | + subtree.set(res.data, res.children) |
| 139 | + return tree |
| 140 | + |
| 141 | + |
| 142 | + |
| 143 | +class TemplateTranslator: |
| 144 | + """Utility class for translating a collection of patterns |
| 145 | + """ |
| 146 | + |
| 147 | + def __init__(self, translations: Mapping[TreeOrCode, TreeOrCode]): |
| 148 | + assert all( isinstance(k, Template) and isinstance(v, Template) for k, v in translations.items() ) |
| 149 | + self.translations = translations |
| 150 | + |
| 151 | + def translate(self, tree: Tree): |
| 152 | + for k, v in self.translations.items(): |
| 153 | + tree = translate(k, v, tree) |
| 154 | + return tree |
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