Fix formatting crosstalk

[MrDOS]

Describe the PR

Fixes formatting crosstalk (#1314) by modelling and applying formatting changes as byte-range edits rather than find/replace operations, which could accidentally clobber identical (correctly-formatted) comment lines.

Relation issue

Resolves #1314.

Additional comments

Of course, everyone's experience will vary, but in the codebase I'm working in with – 4,132 attribute comments across 450 comment groups – this fix changes 8 comment lines. Those changes are pretty obvious and desirable, but I also don't anticipate that this will generate huge waves of changes in existing codebases.

[codecov]

Codecov Report

Merging #1317 (21e660d) into master (e7ccdf4) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1317      +/-   ##
==========================================
+ Coverage   95.61%   95.63%   +0.01%     
==========================================
  Files          14       14              
  Lines        2851     2863      +12     
==========================================
+ Hits         2726     2738      +12     
  Misses         70       70              
  Partials       55       55              

Impacted Files	Coverage Δ
formatter.go	100.00% <100.00%> (ø)

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[ubogdan]

Please update according to my comments if you like to see some performance in a large code base.

[MrDOS]

Thanks for the feedback. I've changed things around to preallocate the edit list.

swag/formatter.go

Lines 62 to 66 in 21e660d

	maxEdits := 0
	for _, comment := range ast.Comments {
	maxEdits += len(comment.List)
	}
	edits := make(edits, 0, maxEdits)

I couldn't make the exact edits you asked for, as the outer edit list may contain up to as many entries as there are comment lines, but probably won't: there will likely be comment lines that don't contain Swag attributes, and we don't create edit entries for those. Also, allocating this with

edits := make(edits, 0, len(ast.Comments))

would only allocate space for one edit per group.

Instead of allocating this slice with its size as the maximum possible number of entries, I'm instead allocating it with the maximum necessary capacity, and a size of 0. This lets me use append normally to gradually grow the size of the slice but without requiring further allocations. That way, I don't need to separately keep track of how many things I've put into the slice – the slice's natural size tracks that for me.

swag/formatter.go

Line 101 in 21e660d

func formatFuncDoc(fileSet *token.FileSet, commentList []*ast.Comment, edits *edits) {

Instead of allocating another edit list inside the formatting function, I'm now just passing in the overall edit list and appending to it directly. This removes the need to allocate a temporary slice of edits per comment group.

[ubogdan]

@MrDOS You're welcome. Your last implementation looks even better.

[ubogdan]

LGTM

[ubogdan]

@MrDOS Thanks for your contribution.