While doing a cleanup of some other IndentationError questions, I closed a bunch of questions - including IndentationError during `ast.parse` and `ast.walk` of a function which is a method inside class - as duplicates of Does Python have a built-in function for unindenting a multiline string? . The idea is: the goal in the questions I closed is to analyze the structure of some indented code with ast.parse, but this doesn't work because ast.parse expects code that would be valid on its own. For example, the input could be the source code of a method in a class; while that code could just as well be interpreted as a free-standing function, each line starts with additional leading whitespace. The obvious approach to solving the problem is to unindent the code string, as in the Q&A I linked.
But these closures were wrong (mea culpa), because this does not solve the problem - and I didn't keep a good record of what I closed this way. Simply unindenting the code via textwrap.dedent isn't sufficient, because the code can contain dedented physical lines (in a docstring, logical line continued with \ at the end of a physical line, or logical line continued implicitly within open brackets) that defeat the detection of how far to dedent.
In fact, I found at least two reports of niche bugs caused by popular libraries overlooking the same problem:
in Scrapy: Scrapy Request 'IndentationError: unexpected indent' on parse callback
in Numba/Cuda: python cuda, adding @autojit before class functions
(It's actually a bit tricky to solve the problem properly. Adding a dummy if True: line above the code is a common workaround. It works regardless of the amount of common leading indentation, because Python's indentation processing rules will turn that into a single indent. However, that added code then has to be accounted for in the ast.parse result.)
However, there are still many questions here which still clearly duplicate each other. I am looking for assistance in identifying any existing canonical Q&A for the issue; failing that, I'm hoping to solicit someone to write it up. (It could be that IndentationError during `ast.parse` and `ast.walk` of a function which is a method inside class is already the best version of the question, but I am interested in other opinions. At any rate, it could use a better title if it's selected - and a proper answer; I'm more than willing to place a bounty.) I could also use help to identify and move the right duplicates afterward.
