bpo-28850: Fix PrettyPrinter.format overrides being ignored for contents of small containers #22120
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…the buggy behaviour
…t part of the PrettyPrinter class (no functional change)
…on container contents
ZackerySpytz
reviewed
Nov 4, 2020
Misc/NEWS.d/next/Library/2020-09-06-21-55-44.bpo-28850.HJNggD.rst
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| def saferepr(object): | ||
| """Version of repr() which can handle recursive data structures.""" | ||
| return _safe_repr(object, {}, None, 0, True)[0] | ||
| return PrettyPrinter()._safe_repr(object, {}, None, 0)[0] | ||
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| def isreadable(object): | ||
| """Determine if saferepr(object) is readable by eval().""" | ||
| return _safe_repr(object, {}, None, 0, True)[1] | ||
| return PrettyPrinter()._safe_repr(object, {}, None, 0)[1] | ||
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| def isrecursive(object): | ||
| """Determine if object requires a recursive representation.""" | ||
| return _safe_repr(object, {}, None, 0, True)[2] | ||
| return PrettyPrinter()._safe_repr(object, {}, None, 0)[2] |
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It seems rather unfortunate that a PrettyPrinter() instance is now created here for every function call.
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I know. We could:
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leave _safe_repr where it was and pass in a function that it should call when it needs to recurse (default is it calls itself, but PrettyPrinter passes in self.format)
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move _safe_repr to a stateless superclass of PrettyPrinter, and instantiate a module level _defaultPrettyPrinter instance of this superclass for use in these functions.
Any other options?
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IMO this is fine, and better than the alternatives.
adorilson
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Mar 13, 2021
… small containers (pythonGH-22120)
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This PR fixes a bug where subclassing PrettyPrinter and overriding format doesn't work for container contents (see issue 28850 for details).
The solution suggested here is to make _safe_repr a method of PrettyPrinter, and make it call self.format() when it needs to recurse on container contents.
The diff looks substantial, but that's mostly due to the indentation of _safe_repr code. To make it easier to review, I split it into several commits, where the indentation is done in one commit as a noop change. The other commits have much smaller diffs.
https://bugs.python.org/issue28850