Re: [RFC 0/1] Leading whitespace as a function identification heuristic?

From: Jeff King <peff@peff.net>
Date: Sep 25, 2020, 18:43 UTC
Message-ID: <20200925184319.GA660343@coredump.intra.peff.net>
In-Reply-To: <1c03faa0-011c-39c2-acb6-d09a5fcfc818@gmail.com>

On Fri, Sep 25, 2020 at 10:11:33AM +0100, Phillip Wood wrote:

Show 20 quoted lines

> If I've understood correctly when ...code 2... contains changes that are
> themselves indented then we'll pick the wrong function header for example
> 
> 	void foo() {
> 		void bar() {
> 			...code 1...
> 		}
> 		for (...) {
> 			// if this line is changed we pick bar rather
> 			// than foo because it is the first function
> 			// header with a smaller indentation than the
> 			// first changed line.
> 		}
> 	}
> 
> Unfortunately I suspect code like that is not uncommon and the diff would
> regress with this simple heuristic. It might be possible to recalculate the
> required indentation as we walk backwards up the file though, so when we hit
> the "for" line we reduce the maximum indentation allowed for a match and so
> skip "bar" as a function header.

Thanks, that's a great counter-example I hadn't considered.

Yes, I agree that adjusting the desired indentation as we walk backwards would work. That's assuming indentation is hierarchical, but I think that's implied by the existence of this feature at all.

Another possible corner case: tabs vs spaces. If I have:

  <space><space><space><space><space><space><space><space>foo
  <tab><tab>bar

which is more indented? Counting isspace(), it is the first one. But visually, it would _usually_ be the second one. But of course it would depend on your tabstops.

The above example is obviously stupid and contrived, but I wonder if there are legitimate confusing cases where people mix tabs and spaces (e.g., mixed tabs and spaces to align function parameters, etc).

-Peff