Unable to remap projected document edits if they fall outside of known list of source mappings

[TanayParikh]

@ajaybhargavb and I were looking into why some edits were being lost during formatting. Issue seems to be due to how we handle projections which come at the end of a document / @code block.

Passing edits into the formatter which go beyond the last line of generated C# fails. This is because the edit starts 1 line after the last source mapping, and consequently the projection mapping fails.

Call here.

@NavMenuCssClass

@(NavMenuCssClass)

@code {
    int counter = 3;
}

Note: Code actions do not work with single line @code blocks as the mapping fails.

Edited C# & Generated C#

Edited C#:

// <auto-generated/>
#pragma warning disable 1591
namespace blazorserver6.Pages
{
    #line hidden
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Threading.Tasks;
    using Microsoft.AspNetCore.Components;
#nullable restore
#line 1 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using System.Net.Http;

#line default
#line hidden
#nullable disable
#nullable restore
#line 2 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Authorization;

#line default
#line hidden
#nullable disable
#nullable restore
#line 3 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Authorization;

#line default
#line hidden
#nullable disable
#nullable restore
#line 4 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Forms;

#line default
#line hidden
#nullable disable
#nullable restore
#line 5 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Routing;

#line default
#line hidden
#nullable disable
#nullable restore
#line 6 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Web;

#line default
#line hidden
#nullable disable
#nullable restore
#line 7 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.JSInterop;

#line default
#line hidden
#nullable disable
#nullable restore
#line 8 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using blazorserver6;

#line default
#line hidden
#nullable disable
#nullable restore
#line 9 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using blazorserver6.Shared;

#line default
#line hidden
#nullable disable
    public partial class Component : Microsoft.AspNetCore.Components.ComponentBase
    {
        #pragma warning disable 219
        private void __RazorDirectiveTokenHelpers__() {
        }
        #pragma warning restore 219
        #pragma warning disable 0414
        private static System.Object __o = null;
        #pragma warning restore 0414
        #pragma warning disable 1998
        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
        {
#nullable restore
#line 1 "c:/Users/taparik/dev/blazorserver6/Pages/Component.razor"
__o = NavMenuCssClass;

#line default
#line hidden
#nullable disable
#nullable restore
#line 3 "c:/Users/taparik/dev/blazorserver6/Pages/Component.razor"
__o = NavMenuCssClass;

#line default
#line hidden
#nullable disable
        }
        #pragma warning restore 1998
#nullable restore
#line 5 "c:/Users/taparik/dev/blazorserver6/Pages/Component.razor"
       
    int foo = 3;

        public Component(int foo)
        {
            this.foo = foo;
        }

#line default
#line hidden
#nullable disable
    }
}
#pragma warning restore 1591

Original:

// <auto-generated/>
#pragma warning disable 1591
namespace blazorserver6.Pages
{
    #line hidden
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Threading.Tasks;
    using Microsoft.AspNetCore.Components;
#nullable restore
#line 1 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using System.Net.Http;

#line default
#line hidden
#nullable disable
#nullable restore
#line 2 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Authorization;

#line default
#line hidden
#nullable disable
#nullable restore
#line 3 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Authorization;

#line default
#line hidden
#nullable disable
#nullable restore
#line 4 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Forms;

#line default
#line hidden
#nullable disable
#nullable restore
#line 5 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Routing;

#line default
#line hidden
#nullable disable
#nullable restore
#line 6 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.AspNetCore.Components.Web;

#line default
#line hidden
#nullable disable
#nullable restore
#line 7 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using Microsoft.JSInterop;

#line default
#line hidden
#nullable disable
#nullable restore
#line 8 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using blazorserver6;

#line default
#line hidden
#nullable disable
#nullable restore
#line 9 "c:/Users/taparik/dev/blazorserver6/_Imports.razor"
using blazorserver6.Shared;

#line default
#line hidden
#nullable disable
    public partial class Component : Microsoft.AspNetCore.Components.ComponentBase
    {
        #pragma warning disable 219
        private void __RazorDirectiveTokenHelpers__() {
        }
        #pragma warning restore 219
        #pragma warning disable 0414
        private static System.Object __o = null;
        #pragma warning restore 0414
        #pragma warning disable 1998
        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
        {
#nullable restore
#line 1 "c:/Users/taparik/dev/blazorserver6/Pages/Component.razor"
__o = NavMenuCssClass;

#line default
#line hidden
#nullable disable
#nullable restore
#line 3 "c:/Users/taparik/dev/blazorserver6/Pages/Component.razor"
__o = NavMenuCssClass;

#line default
#line hidden
#nullable disable
        }
        #pragma warning restore 1998
#nullable restore
#line 5 "c:/Users/taparik/dev/blazorserver6/Pages/Component.razor"
       
    int foo = 3;

#line default
#line hidden
#nullable disable
    }
}
#pragma warning restore 1591

Another manifestation of this issue:

@functions {
    class Foo
    {

    }
}

Invoke generate constructor code action.

Expected:

@functions {
    class Foo
    {
        public Foo()
        {

        }
    }
}

Actual:

@functions {
    {
        public Foo()
        {
        }
    }
}

[ajaybhargavb]

Updating the issue title to better represent the underlying problem.

This is more of a design limitation than a bug. Essentially, the issue is that we can't map a position/range that is not in our SourceMappings. In some cases, edits returned by Roslyn for code actions end up going to places we don't have mapping for and thus doesn't get applied. There is no easy way to get around this unless we make our mapping system more complex and make it understand more than verbatim source mappings.

[TanayParikh]

https://github.com/dotnet/aspnetcore/issues/26867 contains a targeted quick mitigation for this. The long term solution for code actions will involve heuristically determining the correct place within the razor syntax tree to insert the complete code action.

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.