feat(dotnet): [JsiiOptional] attribute on properties that are optionals + Roslyn Analyzer

[assyadh]

On properties that are optionals, we now add a [JsiiOptional] attribute.

Ex:

[JsiiProperty(name: "optional1", typeJson: "{\"primitive\":\"string\"}", isOptional: true, isOverride: true)]
[System.Obsolete()]
[JsiiOptional]
public string Optional1
{
        get;
        set;
}

Also, This introduces a new package which needs to be pushed to NuGet: Amazon.Jsii.Analyzers.

It includes a Roslyn Analyzer which makes sure that inside nested props object initializations, all required properties are passed by the developer, and are not passed as null (syntax check only).

Example in Rider with a required property not passed:

Whit a required property passed with a null value:

With the required property correctly passed:

The idea here is to check inline initialization of data types within jsii classes.

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[RomainMuller]

Should this be copied to dist instead?

[assyadh]

I based this file on the jsii-dotnet-runtime's one. It does not have a dist directory?

[RomainMuller]

Wish the runtime library was full of those, too... ❤️

[assyadh]

Pretty useful indeed. It can be tricky as everything has to be declared in a single file so that the diagnostic works (no references), but it works fine

[RomainMuller]

What's the use of this? How are people supposed to be using this?

[assyadh]

The only (ugly way) to use an analyzer inside an IDE is to reference its dll directly.

So, in order to avoid that, Microsoft gave Roslyn Analyzers vended by NuGet packages the option to be installed as analyzers, which really just adds this dll reference (not visible in the csproj though).

This is done by adding an install and uninstall scripts in the nupkg. When the analyzer is pulled from NuGet, it gets installed using that script in tools/install.ps1

I have tested this with Rider and Visual Studio.

See: https://docs.microsoft.com/fr-fr/nuget/guides/analyzers-conventions

And

https://blog.jetbrains.com/dotnet/2018/03/22/roslyn-analyzer-support-rider-2018-1-eap/

[assyadh]

Made some changes on the analyzer rules following our meeting this morning.

See the Unit tests comments for some background :-)

Pull request has been modified.

[assyadh]

Travis build is blocked due to a transient issue:

Error downloading packages:
geronimo-jms-1.1.1-19.amzn2.noarch: [Errno 256] No more mirrors to try.

[costleya]

[SuppressMessage("Usage", "JSII001")] is probably not quite what you want. Should we make it "Amazon.JSII" as the category?

[assyadh]

[SuppressMessage("Usage", "JSII001")] is probably not quite what you want. Should we make it "Amazon.JSII" as the category?

It looks correct to me:

https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.codeanalysis.suppressmessageattribute.-ctor?view=netframework-4.8#System_Diagnostics_CodeAnalysis_SuppressMessageAttribute__ctor_System_String_System_String_

Pull request has been modified.

Pull request has been modified.

[mergify]

Thank you for contributing! ❤️ I will now look into making sure the PR is up-to-date, then proceed to try and merge it!