820 lines
25 KiB
Python
820 lines
25 KiB
Python
# -*- coding: utf-8; -*-
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"""Back-convert a Python AST into source code. Original formatting is disregarded."""
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__all__ = ['UnparserError', 'unparse', 'unparse_with_fallbacks']
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import ast
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import io
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import sys
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from .astdumper import dump # fallback
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from .markers import ASTMarker
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# Large float and imaginary literals get turned into infinities in the AST.
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# We unparse those infinities to INFSTR.
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INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)
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class UnparserError(SyntaxError):
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"""Failed to unparse the given AST."""
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def interleave(inter, f, seq):
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"""Call f on each item in seq, calling inter() in between."""
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seq = iter(seq)
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try:
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f(next(seq))
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except StopIteration:
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pass
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else:
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for x in seq:
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inter()
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f(x)
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class Unparser:
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"""Convert an AST into source code.
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Methods in this class recursively traverse an AST and output source code
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for the abstract syntax. Original formatting is disregarded.
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"""
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def __init__(self, tree, *, file=sys.stdout, debug=False):
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"""Print the source for `tree` to `file`.
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`debug`: bool, print invisible nodes (`Module`, `Expr`).
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The output is then not valid Python, but may better show
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the problem when code produced by a macro mysteriously
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fails to compile (even though the unparse looks ok).
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"""
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self.debug = debug
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self.f = file
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self._indent = 0
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self.dispatch(tree)
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print("", file=self.f)
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self.f.flush()
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def fill(self, text="", *, lineno_node=None):
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"Indent a piece of text, according to the current indentation level."
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self.write("\n")
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if self.debug and isinstance(lineno_node, ast.AST):
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lineno = lineno_node.lineno if hasattr(lineno_node, "lineno") else None
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# In `mcpyrate.debug.step_expansion`, `textwrap.dedent` will strip
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# leading space, so it's better to use something else to always
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# have fixed width.
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#
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# Assume line numbers usually have at most 4 digits, but
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# degrade gracefully for those crazy 5-digit source files.
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self.write(f"L{lineno:5d} " if lineno else "L ---- ")
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self.write(" " * self._indent + text)
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def write(self, text):
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"Append a piece of text to the current line."
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self.f.write(text)
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def enter(self):
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"Print ':', and increase the indentation level."
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self.write(":")
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self._indent += 1
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def leave(self):
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"Decrease the indentation level."
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self._indent -= 1
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def dispatch(self, tree):
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"Dispatcher. Dispatch tree type `T` to method `_T`."
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if isinstance(tree, list):
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for t in tree:
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self.dispatch(t)
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return
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if isinstance(tree, ASTMarker): # mcpyrate and macro communication internal
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self.astmarker(tree)
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return
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methodname = "_" + tree.__class__.__name__
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if not hasattr(self, methodname):
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raise UnparserError(f"Don't know how to unparse AST node type {tree.__class__.__name__}")
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method = getattr(self, methodname)
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method(tree)
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# --------------------------------------------------------------------------------
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# Unparsing methods
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#
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# There should be one method per concrete grammar type.
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# Constructors should be grouped by sum type. Ideally,
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# this would follow the order in the grammar, but
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# currently doesn't.
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def astmarker(self, tree):
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def write_field_value(v):
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if isinstance(v, ast.AST):
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self.dispatch(v)
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else:
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self.write(repr(v))
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self.fill(f"$ASTMarker<{tree.__class__.__name__}>", lineno_node=tree) # markers cannot be eval'd
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self.enter()
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self.write(" ")
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if len(tree._fields) == 1 and tree._fields[0] == "body":
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write_field_value(tree.body)
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else:
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for k, v in ast.iter_fields(tree):
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self.fill(k)
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self.enter()
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self.write(" ")
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write_field_value(v)
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self.leave()
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self.leave()
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def _Module(self, t):
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# TODO: Python 3.8 type_ignores. Since we don't store the source text, maybe ignore that?
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if self.debug:
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self.fill("$Module", lineno_node=t)
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self.enter()
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for stmt in t.body:
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self.dispatch(stmt)
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self.leave()
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else:
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for stmt in t.body:
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self.dispatch(stmt)
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# stmt
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def _Expr(self, t):
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if self.debug:
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self.fill("$Expr", lineno_node=t)
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self.enter()
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self.write(" ")
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self.dispatch(t.value)
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self.leave()
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else:
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self.fill()
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self.dispatch(t.value)
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def _Import(self, t):
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self.fill("import ", lineno_node=t)
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interleave(lambda: self.write(", "), self.dispatch, t.names)
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def _ImportFrom(self, t):
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self.fill("from ", lineno_node=t)
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self.write("." * t.level)
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if t.module:
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self.write(t.module)
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self.write(" import ")
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interleave(lambda: self.write(", "), self.dispatch, t.names)
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def _Assign(self, t):
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self.fill(lineno_node=t)
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for target in t.targets:
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self.dispatch(target)
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self.write(" = ")
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self.dispatch(t.value)
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def _AnnAssign(self, t):
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self.fill(lineno_node=t)
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if not t.simple:
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self.write("(")
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self.dispatch(t.target)
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if not t.simple:
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self.write(")")
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self.write(": ")
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self.dispatch(t.annotation)
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if t.value:
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self.write(" = ")
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self.dispatch(t.value)
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# TODO: Python 3.8 type_comment, ignore it?
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def _AugAssign(self, t):
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self.fill(lineno_node=t)
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self.dispatch(t.target)
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self.write(" " + self.binop[t.op.__class__.__name__] + "= ")
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self.dispatch(t.value)
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def _Return(self, t):
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self.fill("return", lineno_node=t)
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if t.value:
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self.write(" ")
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self.dispatch(t.value)
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def _Pass(self, t):
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self.fill("pass", lineno_node=t)
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def _Break(self, t):
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self.fill("break", lineno_node=t)
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def _Continue(self, t):
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self.fill("continue", lineno_node=t)
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def _Delete(self, t):
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self.fill("del ", lineno_node=t)
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interleave(lambda: self.write(", "), self.dispatch, t.targets)
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def _Assert(self, t):
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self.fill("assert ", lineno_node=t)
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self.dispatch(t.test)
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if t.msg:
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self.write(", ")
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self.dispatch(t.msg)
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def _Global(self, t):
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self.fill("global ", lineno_node=t)
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interleave(lambda: self.write(", "), self.write, t.names)
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def _Nonlocal(self, t):
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self.fill("nonlocal ", lineno_node=t)
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interleave(lambda: self.write(", "), self.write, t.names)
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def _Await(self, t): # expr
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self.write("(")
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self.write("await")
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if t.value:
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self.write(" ")
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self.dispatch(t.value)
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self.write(")")
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def _Yield(self, t): # expr
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self.write("(")
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self.write("yield")
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if t.value:
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self.write(" ")
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self.dispatch(t.value)
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self.write(")")
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def _YieldFrom(self, t): # expr
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self.write("(")
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self.write("yield from")
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if t.value:
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self.write(" ")
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self.dispatch(t.value)
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self.write(")")
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def _Raise(self, t):
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self.fill("raise", lineno_node=t)
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if not t.exc:
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assert not t.cause
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return
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self.write(" ")
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self.dispatch(t.exc)
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if t.cause:
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self.write(" from ")
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self.dispatch(t.cause)
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def _Try(self, t):
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self.fill("try", lineno_node=t)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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for ex in t.handlers:
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self.dispatch(ex)
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if t.orelse:
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self.fill("else")
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self.enter()
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self.dispatch(t.orelse)
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self.leave()
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if t.finalbody:
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self.fill("finally")
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self.enter()
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self.dispatch(t.finalbody)
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self.leave()
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def _ExceptHandler(self, t):
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self.fill("except", lineno_node=t)
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if t.type:
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self.write(" ")
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self.dispatch(t.type)
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if t.name:
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self.write(" as ")
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self.write(t.name)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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def _ClassDef(self, t):
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self.write("\n")
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for deco in t.decorator_list:
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self.fill("@", lineno_node=deco)
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self.dispatch(deco)
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self.fill("class " + t.name, lineno_node=t)
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self.write("(")
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comma = False
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for e in t.bases:
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if comma:
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self.write(", ")
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else:
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comma = True
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self.dispatch(e)
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for e in t.keywords:
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if comma:
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self.write(", ")
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else:
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comma = True
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self.dispatch(e)
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self.write(")")
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self.enter()
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self.dispatch(t.body)
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self.leave()
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def _FunctionDef(self, t):
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self.__FunctionDef_helper(t, "def")
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def _AsyncFunctionDef(self, t):
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self.__FunctionDef_helper(t, "async def")
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def __FunctionDef_helper(self, t, fill_suffix):
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self.write("\n")
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for deco in t.decorator_list:
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self.fill("@", lineno_node=deco)
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self.dispatch(deco)
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def_str = fill_suffix + " " + t.name + "("
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self.fill(def_str, lineno_node=t)
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self.dispatch(t.args)
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self.write(")")
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if t.returns:
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self.write(" -> ")
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self.dispatch(t.returns)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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# TODO: Python 3.8 type_comment, ignore it?
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def _For(self, t):
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self.__For_helper("for ", t)
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def _AsyncFor(self, t):
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self.__For_helper("async for ", t)
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def __For_helper(self, fill, t):
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self.fill(fill, lineno_node=t)
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self.dispatch(t.target)
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self.write(" in ")
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self.dispatch(t.iter)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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if t.orelse:
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self.fill("else")
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self.enter()
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self.dispatch(t.orelse)
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self.leave()
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# TODO: Python 3.8 type_comment, ignore it?
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def _If(self, t):
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self.fill("if ", lineno_node=t)
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self.dispatch(t.test)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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# collapse nested ifs into equivalent elifs.
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while (t.orelse and len(t.orelse) == 1 and
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isinstance(t.orelse[0], ast.If)):
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t = t.orelse[0]
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self.fill("elif ")
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self.dispatch(t.test)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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# final else
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if t.orelse:
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self.fill("else")
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self.enter()
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self.dispatch(t.orelse)
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self.leave()
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def _While(self, t):
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self.fill("while ", lineno_node=t)
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self.dispatch(t.test)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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if t.orelse:
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self.fill("else")
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self.enter()
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self.dispatch(t.orelse)
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self.leave()
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def _With(self, t):
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self.fill("with ", lineno_node=t)
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interleave(lambda: self.write(", "), self.dispatch, t.items)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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# TODO: Python 3.8 type_comment, ignore it?
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def _AsyncWith(self, t):
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self.fill("async with ", lineno_node=t)
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interleave(lambda: self.write(", "), self.dispatch, t.items)
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self.enter()
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self.dispatch(t.body)
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self.leave()
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# expr
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def _NamedExpr(self, t): # Python 3.8+
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self.write("(")
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self.dispatch(t.target)
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self.write(" := ")
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self.dispatch(t.value)
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self.write(")")
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def _Constant(self, t): # Python 3.8+
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# Actually added in 3.6, but Python's parser only produces them starting with 3.8.
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# Replaces the node types Bytes, Str, Num, NameConstant, and Ellipsis.
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if hasattr(t, "kind") and t.kind == "u": # 3.8+: u"..." vs. "..."
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self.write("u")
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if type(t.value) in (int, float, complex):
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# Represent AST infinity as an overflowing decimal literal.
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v = repr(t.value).replace("inf", INFSTR)
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elif t.value is Ellipsis:
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v = "..."
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else:
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v = repr(t.value)
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self.write(v)
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def _Bytes(self, t): # up to Python 3.7
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self.write(repr(t.s))
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def _Str(self, tree): # up to Python 3.7
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self.write(repr(tree.s))
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def _Name(self, t):
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self.write(t.id)
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def _NameConstant(self, t): # up to Python 3.7
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self.write(repr(t.value))
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def _Num(self, t): # up to Python 3.7
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# Represent AST infinity as an overflowing decimal literal.
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self.write(repr(t.n).replace("inf", INFSTR))
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def _List(self, t):
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self.write("[")
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interleave(lambda: self.write(", "), self.dispatch, t.elts)
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self.write("]")
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def _ListComp(self, t):
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self.write("[")
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self.dispatch(t.elt)
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for gen in t.generators:
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self.dispatch(gen)
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self.write("]")
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def _GeneratorExp(self, t):
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self.write("(")
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self.dispatch(t.elt)
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for gen in t.generators:
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self.dispatch(gen)
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self.write(")")
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def _SetComp(self, t):
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self.write("{")
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self.dispatch(t.elt)
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for gen in t.generators:
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self.dispatch(gen)
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self.write("}")
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def _DictComp(self, t):
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self.write("{")
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self.dispatch(t.key)
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self.write(": ")
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self.dispatch(t.value)
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for gen in t.generators:
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self.dispatch(gen)
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self.write("}")
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def _comprehension(self, t):
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if t.is_async:
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self.write(" async")
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self.write(" for ")
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self.dispatch(t.target)
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self.write(" in ")
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self.dispatch(t.iter)
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for if_clause in t.ifs:
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self.write(" if ")
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self.dispatch(if_clause)
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def _IfExp(self, t):
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self.write("(")
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self.dispatch(t.body)
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self.write(" if ")
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self.dispatch(t.test)
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self.write(" else ")
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self.dispatch(t.orelse)
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self.write(")")
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def _Set(self, t):
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assert(t.elts) # should be at least one element
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self.write("{")
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interleave(lambda: self.write(", "), self.dispatch, t.elts)
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self.write("}")
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def _Dict(self, t):
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self.write("{")
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def write_pair(pair):
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(k, v) = pair
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self.dispatch(k)
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self.write(": ")
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self.dispatch(v)
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interleave(lambda: self.write(", "), write_pair, zip(t.keys, t.values))
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self.write("}")
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def _Tuple(self, t):
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self.write("(")
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if len(t.elts) == 1:
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(elt,) = t.elts
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self.dispatch(elt)
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self.write(",")
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else:
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interleave(lambda: self.write(", "), self.dispatch, t.elts)
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self.write(")")
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unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
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def _UnaryOp(self, t):
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self.write("(")
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self.write(self.unop[t.op.__class__.__name__])
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self.write(" ")
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self.dispatch(t.operand)
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self.write(")")
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binop = {"Add": "+", "Sub": "-", "Mult": "*", "MatMult": "@", "Div": "/", "Mod": "%",
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"LShift": "<<", "RShift": ">>", "BitOr": "|", "BitXor": "^", "BitAnd": "&",
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"FloorDiv": "//", "Pow": "**"}
|
|
def _BinOp(self, t):
|
|
self.write("(")
|
|
self.dispatch(t.left)
|
|
self.write(" " + self.binop[t.op.__class__.__name__] + " ")
|
|
self.dispatch(t.right)
|
|
self.write(")")
|
|
|
|
cmpops = {"Eq": "==", "NotEq": "!=", "Lt": "<", "LtE": "<=", "Gt": ">", "GtE": ">=",
|
|
"Is": "is", "IsNot": "is not", "In": "in", "NotIn": "not in"}
|
|
def _Compare(self, t):
|
|
self.write("(")
|
|
self.dispatch(t.left)
|
|
for o, e in zip(t.ops, t.comparators):
|
|
self.write(" " + self.cmpops[o.__class__.__name__] + " ")
|
|
self.dispatch(e)
|
|
self.write(")")
|
|
|
|
boolops = {ast.And: 'and', ast.Or: 'or'}
|
|
def _BoolOp(self, t):
|
|
self.write("(")
|
|
s = " %s " % self.boolops[t.op.__class__]
|
|
interleave(lambda: self.write(s), self.dispatch, t.values)
|
|
self.write(")")
|
|
|
|
def _Attribute(self, t):
|
|
v = t.value
|
|
self.dispatch(v)
|
|
# Special case: 3.__abs__() is a syntax error, so if t.value
|
|
# is an integer literal then we need to either parenthesize
|
|
# it or add an extra space to get 3 .__abs__().
|
|
if ((isinstance(v, ast.Constant) and isinstance(v.value, int)) or
|
|
(isinstance(v, ast.Num) and isinstance(v.n, int))):
|
|
self.write(" ")
|
|
self.write(".")
|
|
self.write(t.attr)
|
|
|
|
def _Call(self, t):
|
|
self.dispatch(t.func)
|
|
self.write("(")
|
|
comma = False
|
|
for e in t.args:
|
|
if comma:
|
|
self.write(", ")
|
|
else:
|
|
comma = True
|
|
self.dispatch(e)
|
|
for e in t.keywords:
|
|
if comma:
|
|
self.write(", ")
|
|
else:
|
|
comma = True
|
|
self.dispatch(e)
|
|
self.write(")")
|
|
|
|
def _FormattedValue(self, t):
|
|
# Node representing a single formatting field in an f-string. If the
|
|
# string contains a single formatting field and nothing else the node
|
|
# can be isolated otherwise it appears in `JoinedStr`.
|
|
self.write("f'")
|
|
self._FormattedValue_helper(t)
|
|
self.write("'")
|
|
|
|
def _FormattedValue_helper(self, t):
|
|
self.write("{")
|
|
self.dispatch(t.value)
|
|
if t.conversion == 115:
|
|
self.write("!s")
|
|
elif t.conversion == 114:
|
|
self.write("!r")
|
|
elif t.conversion == 97:
|
|
self.write("!a")
|
|
elif t.conversion == -1: # no formatting
|
|
pass
|
|
else:
|
|
raise ValueError(f"Don't know how to unparse conversion code {t.conversion}")
|
|
if t.format_spec:
|
|
self.write(":")
|
|
self._JoinedStr_helper(t.format_spec)
|
|
self.write("}")
|
|
|
|
def _JoinedStr(self, t):
|
|
self.write("f'")
|
|
self._JoinedStr_helper(t)
|
|
self.write("'")
|
|
|
|
def _JoinedStr_helper(self, t):
|
|
def escape(s):
|
|
return s.replace("'", r"\'").replace("\n", r"\n")
|
|
for v in t.values:
|
|
# Omit the surrounding quotes in string snippets
|
|
if type(v) is ast.Constant:
|
|
self.write(escape(v.value))
|
|
elif type(v) is ast.Str: # up to Python 3.7
|
|
self.write(escape(v.s))
|
|
elif type(v) is ast.FormattedValue:
|
|
self._FormattedValue_helper(v)
|
|
else:
|
|
raise ValueError(f"Don't know how to unparse {t!r} inside an f-string")
|
|
|
|
def _Subscript(self, t):
|
|
self.dispatch(t.value)
|
|
self.write("[")
|
|
self.dispatch(t.slice)
|
|
self.write("]")
|
|
|
|
def _Starred(self, t):
|
|
self.write("*")
|
|
self.dispatch(t.value)
|
|
|
|
# slice
|
|
def _Ellipsis(self, t): # up to Python 3.7
|
|
self.write("...")
|
|
|
|
def _Index(self, t):
|
|
self.dispatch(t.value)
|
|
|
|
def _Slice(self, t):
|
|
if t.lower:
|
|
self.dispatch(t.lower)
|
|
self.write(":")
|
|
if t.upper:
|
|
self.dispatch(t.upper)
|
|
if t.step:
|
|
self.write(":")
|
|
self.dispatch(t.step)
|
|
|
|
def _ExtSlice(self, t):
|
|
interleave(lambda: self.write(', '), self.dispatch, t.dims)
|
|
|
|
# argument
|
|
def _arg(self, t):
|
|
self.write(t.arg)
|
|
if t.annotation:
|
|
self.write(": ")
|
|
self.dispatch(t.annotation)
|
|
|
|
# others
|
|
def _arguments(self, t):
|
|
first = True
|
|
|
|
# positional-only, and positional-or-keyword arguments
|
|
nposargs = len(t.args)
|
|
if hasattr(t, "posonlyargs"):
|
|
nposonlyargs = len(t.posonlyargs)
|
|
nposargs += nposonlyargs
|
|
defaults = [None] * (nposargs - len(t.defaults)) + t.defaults
|
|
|
|
if hasattr(t, "posonlyargs"):
|
|
args_sets = [t.posonlyargs, t.args]
|
|
defaults_sets = [defaults[:nposonlyargs], defaults[nposonlyargs:]]
|
|
set_separator = ', /'
|
|
else:
|
|
args_sets = [t.args]
|
|
defaults_sets = [defaults]
|
|
set_separator = ''
|
|
|
|
for args, defaults in zip(args_sets, defaults_sets):
|
|
for a, d in zip(args, defaults):
|
|
if first:
|
|
first = False
|
|
else:
|
|
self.write(", ")
|
|
self.dispatch(a)
|
|
if d:
|
|
self.write("=")
|
|
self.dispatch(d)
|
|
self.write(set_separator)
|
|
|
|
# varargs, or bare '*' if no varargs but keyword-only arguments present
|
|
if t.vararg or t.kwonlyargs:
|
|
if first:
|
|
first = False
|
|
else:
|
|
self.write(", ")
|
|
self.write("*")
|
|
if t.vararg:
|
|
self.write(t.vararg.arg)
|
|
if t.vararg.annotation:
|
|
self.write(": ")
|
|
self.dispatch(t.vararg.annotation)
|
|
|
|
# keyword-only arguments
|
|
if t.kwonlyargs:
|
|
for a, d in zip(t.kwonlyargs, t.kw_defaults):
|
|
if first:
|
|
first = False
|
|
else:
|
|
self.write(", ")
|
|
self.dispatch(a),
|
|
if d:
|
|
self.write("=")
|
|
self.dispatch(d)
|
|
|
|
# kwargs
|
|
if t.kwarg:
|
|
if first:
|
|
first = False
|
|
else:
|
|
self.write(", ")
|
|
self.write("**" + t.kwarg.arg)
|
|
if t.kwarg.annotation:
|
|
self.write(": ")
|
|
self.dispatch(t.kwarg.annotation)
|
|
|
|
def _keyword(self, t):
|
|
if t.arg is None:
|
|
self.write("**")
|
|
else:
|
|
self.write(t.arg)
|
|
self.write("=")
|
|
self.dispatch(t.value)
|
|
|
|
def _Lambda(self, t):
|
|
self.write("(")
|
|
self.write("lambda ")
|
|
self.dispatch(t.args)
|
|
self.write(": ")
|
|
self.dispatch(t.body)
|
|
self.write(")")
|
|
|
|
def _alias(self, t):
|
|
self.write(t.name)
|
|
if t.asname:
|
|
self.write(" as " + t.asname)
|
|
|
|
def _withitem(self, t):
|
|
self.dispatch(t.context_expr)
|
|
if t.optional_vars:
|
|
self.write(" as ")
|
|
self.dispatch(t.optional_vars)
|
|
|
|
|
|
def unparse(tree, *, debug=False):
|
|
"""Convert the AST `tree` into source code. Return the code as a string.
|
|
|
|
`debug`: bool, print invisible nodes (`Module`, `Expr`).
|
|
|
|
The output is then not valid Python, but may better show
|
|
the problem when code produced by a macro mysteriously
|
|
fails to compile (even though the unparse looks ok).
|
|
|
|
Upon invalid input, raises `UnparserError`.
|
|
"""
|
|
try:
|
|
with io.StringIO() as output:
|
|
Unparser(tree, file=output, debug=debug)
|
|
code = output.getvalue().strip()
|
|
return code
|
|
except UnparserError as err: # fall back to an AST dump
|
|
try:
|
|
astdump = dump(tree, multiline=True)
|
|
sep = " " if "\n" not in astdump else "\n"
|
|
msg = f"unparse failed, likely invalid AST; here's an AST dump instead:{sep}{astdump}"
|
|
raise UnparserError(msg) from err
|
|
except TypeError: # fall back to repr
|
|
representation = repr(tree)
|
|
sep = " " if "\n" not in representation else "\n"
|
|
msg = f"unparse failed, fallback AST dump failed, likely not an AST; here's the type and repr instead:{sep}{type(tree)}{sep}{representation}"
|
|
raise UnparserError(msg) from err
|
|
|
|
|
|
def unparse_with_fallbacks(tree, *, debug=False):
|
|
"""Like `unparse`, but upon error, don't raise; return the error message.
|
|
|
|
Usually you'll want the exception to be raised. This is mainly useful to
|
|
compactly express "just give me something to work with" (e.g. for including
|
|
source code into an error message) without having to care about exceptions
|
|
at the receiving end.
|
|
"""
|
|
try:
|
|
text = unparse(tree, debug=debug)
|
|
except UnparserError as err:
|
|
text = err.args[0]
|
|
except Exception as err:
|
|
# This can only happen if there is a bug in the unparser, but we don't
|
|
# want to lose the macro use site filename and line number if this
|
|
# occurs during macro expansion, because having that information makes
|
|
# it much easier to create a minimal example for filing a bug report.
|
|
# TODO: maybe use `traceback.format_exception` here?
|
|
text = f"Internal error in unparser: {type(err)}: {str(err)}"
|
|
return text
|