Consider adding attribute text position info to HtmlTagToken

[yufeih]

We are using AngleSharp to manipulate HTML in an authoring workflow, so we want to preserve the original HTML content as much as possible, including all the spaces and bad syntax, etc.

With #636 , I am able to retrieve source text position information for tags, but Attributes does not currently have position info, this prevents us from doing stuff like changing all the link urls without touching other parts of HTML.

HtmlAgilityPack has a ValueStartIndex and ValueStartLength property for each attribute.

The proposal is to provide the same text position information to HTML attributes in the tokenization layer.

[FlorianRappl]

I think this should be doable. Thanks for the suggestion!

[FlorianRappl]

Landed in devel.

[yufeih]

@FlorianRappl , HtmlAttributeToken.Position currently points to attribute name start index, can there be an HtmlAttributeToken.ValuePosition that points to attribute value start index?

[FlorianRappl]

@yufeih good suggestion; I think this should be doable.