Intellisense doesn't work for XML literals using a schema definition

[VBAndCs]

Version Used:
VS.NET 2019 Community

Steps to Reproduce:
I am trying a sample to provide intellisense for XML literals, by using a schema definition.
But, when I tested with the simple example described here:
https://docs.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2013/bb531325%28v%3dvs.120%29#enabling-xml-intellisense-in-visual-basic
intellisense didn't show any completion at all, both in .NET framework and .NET Core apps.
This is the xsd file I used:

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" 
           elementFormDefault="qualified" 
           targetNamespace="http://SamplePurchaseOrder" 
           xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="PurchaseOrders">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="PurchaseOrder">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="Address" />
              <xs:element name="Items" />
              <xs:element name="Comment" />
            </xs:sequence>
            <xs:attribute name="PurchaseOrderNumber" type="xs:unsignedShort" use="required" />
            <xs:attribute name="OrderDate" type="xs:string" use="required" />
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

and this is VB code I tested:

Imports <xmlns="http://SamplePurchaseOrder">

Module Module1

    Sub Main()
        Dim po = <PurchaseOrder/>


        Dim x = <?xml version="1.0"?>
                <PurchaseOrders>
                    <PurchaseOrder PurchaseOrderNumber="12345" OrderDate="2000-1-1">
                        <Address/>
                        <Items/>
                        <Comment/>
                    </PurchaseOrder>
                </PurchaseOrders>
    End Sub

End Module

Did I do something wrong, or this feature stopped working in Roslyn?

Expected Behavior:
Auto complete list should appear and offer the names defined in the schema.

Actual Behavior:
No auto complete whatever.

[vatsalyaagrawal]

@dpoeschl is this a regression?

[VBAndCs]

I think this feature was forgotten while moving to Roslyn.
But the label Feature Request is misleading. It is a bug because it breaks the old behavior. A feature request may or may not happen, but this is a lost feature and I think it must be restored as soon as possible.

[CyrusNajmabadi]

@VBAndCs at this point, it would be a feature request to return this behavior.

[dpoeschl]

@vatsalyaagrawal I think it's a "regression" from the pre-Roslyn days.

[CyrusNajmabadi]

IIRC, this was a known and intentional thing that was not brought over.

[VBAndCs]

So, is this a bug or not? If it is a bug, is there a plan to be fixed?
Please, I need this feature back ASAP. Is there any workaround?

[jmarolf]

So, is this a bug or not? If it is a bug, is there a plane to be fixed?

I believe this is "by design" in that we intentionally didn't add this feature in 2015 for the 1.0 release of roslyn because we wanted to see how many people missed it.

Is there any workaround?

There is no workaround, the feature is not implemented

[VBAndCs]

This issue is not XML literal specific. Intelligence also ignores xsd schemas used to verify xml documents oppened in xml editor. Html also has the same issue with xsd schemas defined in package/schemes folder in Vs folder. And maybe more. There could be many reports about this but in other places of. Net.
So, this is a wide spread issue related to roslyn and vs, and I don not think it was intended.
This issue wouldn't break old code, but it makes xml literal useless, and using stribg literal can be easier as long as there is no intellisense available.
I hope you restore this feature soon, and consider a more customizable design of vs.ner editors so that we apply them on any part of string or xml literals, with coloring and auto complete and syntax check. There are a punsh of vs powerful editors, and it is a waste of effort to write new extension just to apply them in vb or cs files. I am facing these difficulties now in two different projets vaspr and zml. I think roslyn can offer a mechanism to attach some built in editor in a definite scope inside another.

[CyrusNajmabadi]

This issue is not XML literal specific. Intelligence also ignores xsd schemas used to verify xml documents oppened in xml editor. Html also has the same issue with xsd schemas defined in package/schemes folder in Vs folder.

Roslyn doesn't power the xml editor or html editor.

So, this is a wide spread issue related to roslyn and vs,

Please file an suggestion here if you would like this to be supported. The Xml and Html editor teams can decide if they want to invest in this:

I think roslyn can offer a mechanism to attach some built in editor in a definite scope inside another.

I would be happy to work with you to provide such an extensibility model. I can point you at the places you can look at to make this possible.

[VBAndCs]

@CyrusNajmabadi

The Xml and Html editor teams can decide if they want to invest in this:

I am not requesting a new features. Documentations state that theses are already working features but they are not! The xml editor successfully uses the XSD schema to validate the xml file, but doesn't offer tag and attributes names in auto complete. It seems as a general issue in intellisense, and should be addressed by the team who is programming the "Intellisense Provider / Engine" if this is its name.

I can point you at the places you can look at to make this possible.

I have no background about this. Are there any preliminary resources to read about this topic?

[jmarolf]

should be addressed by the team who is programming the "Intellisense Provider / Engine" if this is its name.

Unfortunately that team is not on github. As @CyrusNajmabadi says filing a feedback item is the fastest way to get this fixed. If you reply on here with a link to the feedback item I can make sure the right teams see it.

[CyrusNajmabadi]

I am not requesting a new features. Documentations state that theses are already working features but they are not! The xml editor successfully uses the XSD schema to validate the xml file, but doesn't offer tag and attributes names in auto complete. It seems as a general issue in intellisense, and should be addressed by the team who is programming the "Intellisense Provider / Engine" if this is its name.

This is not the roslyn team, as i already stated. If you want these teams to fix these issues please follow the steps i listed above.

I have no background about this. Are there any preliminary resources to read about this topic?

No. But i'm happy to help walk you through how this could work. Feel free to reach out on gitter.im if you do want to try adding support for this.

[VBAndCs]

@jmarolf

If you reply on here with a link to the feedback item I can make sure the right teams see it.

Here it is:
https://developercommunity.visualstudio.com/content/problem/554115/intellisense-ignores-xsd-schema-definitions.html

Thanks.

[VBAndCs]

Any hope about this after nearly one year?

[CyrusNajmabadi]

@VBAndCs it hasn't been a priority. If you would like to contribute a pr here, I would be happy to review it!

[VBAndCs]

I am looking in xsd format now, and I will try to implement it in a VS extention myself.
Thanks.

[CyrusNajmabadi]

Sounds good. I'm closing this. We have CompletionProvider which can eb used to create completions, and we have DiagnosticAnalyzer which can be used to report schema validation errors.

This a prime example of a use case we built these extension points for for third parties like yourself.

Good luck!

[VBAndCs]

@lorcanmooney @sharwell @dibarbet @tmat @mattwar @jmarolf
I think it will be easy to write the xsd completion provider for XML literals based on XML Document cooments already working.
I am trying to do it, but I have no experience in the matter.

[VBAndCs]

@atsalyaagrawal @dpoeschl @CyrusNajmabadi @marolf @inujoseph lorcanmooney @sharwell @dibarbet @tmat @mattwar @jmarolf
I made most of the work, and you can take it from there if you are willing to solve this issue:
I added a VbXmlCompletionProvider to this repo
You can add these two files to the in your Roslyn fork, in the folder Completion/CompletionProviders in the project Microsoft.CodeAnalysis.VisualBasic.Features

It will provide HTML5 auto completion in VB.NET XML Literals, but only inside the <vbxml></vbxml> tag.

I did this for two reasons:

1. not to mess with other xml literals that doesn't deal with html.
2. to support Vazor.

I will make a VSIX for this to allow install it as a VS extension (in progress now), but my aim from publishing this, is to allow contributors to build upon to provide a generic XML literals completion provider, based on the xsd that user supplies in the context as this missing feature was described in the docs

[CyrusNajmabadi]

Great. I'm glad you got it working. Good luck with the extension! :-)

[VBAndCs]

@CyrusNajmabadi
The VSIX is available now dotnet/vblang#527 (comment)
Thanks for your help.
My work is done here. a few lines of code can make this provider work for any given xsd file instead of just html_5.xsd file.
Hope you give VB.NET a Span(Of your_attention) :). At least consider the ration between C# issues and VB issues when doing fixes. And note that MS said it will maintain enhancing VB.NET experience in VS.NET.
Thanks.