Add operationId uniqueness check

[idexter]

Describe the PR

Add operationId uniqueness check, in accordance with OpenAPI v2 Specification

Relation issue

Closes #731

Additional context

I added a uniqueness check after the parsing phase, so it shows a path when an error happens (E.g. GET /foo/bar) but did not show the file where duplication happens.

I did that in this way because I did not succeed adding check inside ParseRouterAPIInfo(). The reason I did not succeed is that because when you are going through this range:

swag/parser.go

Lines 171 to 175 in 67cb097

	for fileName, astFile := range parser.files {
	if err := parser.ParseRouterAPIInfo(fileName, astFile); err != nil {
	return err
	}
	}

parser.files can contain the same file twice. Once with absolute path and once with a relative path. So in some situations, errors happens even if there are no duplications in operationId

[codecov-commenter]

Codecov Report

Merging #732 into master will increase coverage by 2.14%.
The diff coverage is 48.83%.

@@            Coverage Diff             @@
##           master     #732      +/-   ##
==========================================
+ Coverage   81.50%   83.65%   +2.14%     
==========================================
  Files           8        7       -1     
  Lines        1665     1835     +170     
==========================================
+ Hits         1357     1535     +178     
+ Misses        195      189       -6     
+ Partials      113      111       -2     

Impacted Files	Coverage Δ
parser.go	78.41% <48.83%> (+1.28%)	⬆️
operation.go	87.56% <0.00%> (-0.90%)	⬇️
types.go
packages.go
property.go	91.66% <0.00%> (ø)
schema.go	96.82% <0.00%> (+10.07%)	⬆️

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[sdghchj]

LGTM in function.
however, operationsIds is better to be in a local scope.

[idexter]

however, operationsIds is better to be in a local scope.

@sdghchj I tried to move it inside the checkOperationIDUniqueness() function. Is that thing you was talking about?

https://github.com/swaggo/swag/pull/732/files#diff-f615844d3497ff38db57e459d6ef657bR1508-R1521

[sdghchj]

however, operationsIds is better to be in a local scope.

@sdghchj I tried to move it inside the checkOperationIDUniqueness() function. Is that thing you was talking about?

https://github.com/swaggo/swag/pull/732/files#diff-f615844d3497ff38db57e459d6ef657bR1508-R1521

That's it

[sdghchj]

LGTM

[easonlin404]

@idexter Thanks for your contributions.