New Rules: S5842, S5856, S6326

[Corniel]

I implemented 3 regular expression related rules:

• S5842
• S5856
• S6326

I combined them, as I was searching for a way how the different regex rules could reuse code to reduce the required plumbing. I investigated the (re)use of MS internal RegexTree. Unfortunately, that did not help much. The real showstopper in the end is that the RegexNode's in MS's regex tree, do not make a distinction between AAA and A{3}, or A+ and A{1,}. This makes that most analysis can not performed.

The regex helper types I introduced:

RegexTree

Allows to analyze a regex (in relation to its RegexOptions).

RegexNode

Contains the Regex pattern and Regex options related SyntaxNode's. Has factory methods to construct from

• ObjectCreationExpressions (new Regex())
• InvocationExpression (Regex.*)
• Attribute ([System.ComponentModel.DataAnnotations.RegularExpression])

The generated regex attribute should also be taken into account. That is on my TODO.

The 3 rules I choose, do not require a (full) parsing of the regular expression itself. That would blown up this PR too much.

[pavel-mikula-sonarsource]

Hi @Corniel,

this looks good from a first quick view on the overall structure.

Can you please split it into 3 PRs, one for each rule? You can keep this all together in a separate branch in your repo, so I have a reference for shared code and avoid complaining about unused stuff.

To give you more context on the Regex, there exist a Java-based engine to report more complex structures inside the regex itself. So please do not implement rules that would require more complex logic or sematnic understanding of the regex. These 3 looks simple (simple string based), so they are fine.

Thanks

[Corniel]

@pavel-mikula-sonarsource I'll try to split them. I had a look at the Java code. As mentioned, on purpose, I choose 3 rules that did not need more then simple string based rules.

[pavel-mikula-sonarsource]

Hi @Corniel,

Do you plan to work on the last rule S6326? That one should be easy to do with the scaffolding that is already in place.

[Corniel]

@pavel-mikula-sonarsource Yes, I've plans to so.

[Corniel]

@pavel-mikula-sonarsource See: #7345