59 lines
2.0 KiB
Python
59 lines
2.0 KiB
Python
# from functools import wraps
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from ast import NodeTransformer, AST, copy_location, fix_missing_locations
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from .unparse import unparse
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class BaseMacroExpander(NodeTransformer):
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"""
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A base class for macro expander visitors. After identifying valid macro
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syntax, the actual expander should return the result of calling `_expand()`
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method with the proper arguments.
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"""
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def __init__(self, bindings):
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self.bindings = bindings
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def visit(self, tree):
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"""Short-circuit visit() to avoid expansions if no macros."""
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return super().visit(tree) if self.bindings else tree
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def _expand(self, syntax, target, macroname, tree, kw=None):
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"""
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Transform `target` node, replacing it with the expansion result of
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aplying the named macro on the proper node and recursively treat the
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expansion as well.
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"""
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macro = self.bindings[macroname]
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kw = kw or {}
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kw.update({
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'syntax': syntax,
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'to_source': unparse,
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'expand_macros': self.visit
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})
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expansion = _apply_macro(macro, tree, kw)
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return self._visit_expansion(expansion, target)
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def _visit_expansion(self, expansion, target):
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"""
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Ensures the macro expansions into None (deletions), other nodes or
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list of nodes are expanded too.
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"""
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if expansion is not None:
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is_node = isinstance(expansion, AST)
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expansion = [expansion] if is_node else expansion
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expansion = map(lambda n: copy_location(n, target), expansion)
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expansion = map(fix_missing_locations, expansion)
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expansion = map(self.visit, expansion)
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expansion = list(expansion).pop() if is_node else list(expansion)
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return expansion
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def _ismacro(self, name):
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return name in self.bindings
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def _apply_macro(macro, tree, kw):
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""" Executes the macro on tree passing extra kwargs. """
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return macro(tree, **kw)
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