Cannot hit breakpoints in parameter mapped locations #43432

NTaylorMullen · 2020-04-16T23:38:50Z

This ends up impacting Blazor scenarios where Blazor generates @currentCount as:

And then attempting to set a breakpoints results in a failure to bind or step over:

/cc @tmat

The text was updated successfully, but these errors were encountered:

CyrusNajmabadi · 2020-04-17T03:26:10Z

Does razor forward this call along to Roslyn?

NTaylorMullen · 2020-04-17T04:13:48Z

Does razor forward this call along to Roslyn?

Sorry I don't understand the question, could you elaborate?

jcouv · 2020-04-18T00:53:23Z

@NTaylorMullen Is this a new problem? I'm not sure what I would have expected, but probably nothing good. One issue is that breakpoints are set on statements (which the exception of switch expressions, just recently) but you're clicking on an expression and setting a breakpoint. I'm not sure which line map would count.

Tagging @tmat @ivanbasov @cston in case something to add.

tmat · 2020-04-18T01:37:13Z

I'll investigate.

NTaylorMullen · 2020-04-19T00:54:00Z

@NTaylorMullen Is this a new problem? I'm not sure what I would have expected, but probably nothing good. One issue is that breakpoints are set on statements (which the exception of switch expressions, just recently) but you're clicking on an expression and setting a breakpoint. I'm not sure which line map would count.

Nope not a new problem, it's always been there since Blazor's beginnings. Something we just haven't had more time to dig into until recently 😄

I'll investigate.

❤️ 😍 💪

davidwengier · 2021-03-25T05:43:12Z

@NTaylorMullen Can you confirm where this breakpoint is supposed to be in "real" C#? Your screenshot of the Counter.razor.g.cs file matches whats on my disk (default Blazor app template), but the tree we get from Razor looks like this:

// <auto-generated/>
#pragma warning disable 1591
namespace BlazorApp1.Pages
{
    #line hidden
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Threading.Tasks;
    using Microsoft.AspNetCore.Components;
#nullable restore
#line 1 "e:/Scratch/BlazorApp1/_Imports.razor"
using System.Net.Http;

#line default
#line hidden
#nullable disable
#nullable restore
#line 2 "e:/Scratch/BlazorApp1/_Imports.razor"
using Microsoft.AspNetCore.Authorization;

#line default
#line hidden
#nullable disable
#nullable restore
#line 3 "e:/Scratch/BlazorApp1/_Imports.razor"
using Microsoft.AspNetCore.Components.Authorization;

#line default
#line hidden
#nullable disable
#nullable restore
#line 4 "e:/Scratch/BlazorApp1/_Imports.razor"
using Microsoft.AspNetCore.Components.Forms;

#line default
#line hidden
#nullable disable
#nullable restore
#line 5 "e:/Scratch/BlazorApp1/_Imports.razor"
using Microsoft.AspNetCore.Components.Routing;

#line default
#line hidden
#nullable disable
#nullable restore
#line 6 "e:/Scratch/BlazorApp1/_Imports.razor"
using Microsoft.AspNetCore.Components.Web;

#line default
#line hidden
#nullable disable
#nullable restore
#line 7 "e:/Scratch/BlazorApp1/_Imports.razor"
using Microsoft.JSInterop;

#line default
#line hidden
#nullable disable
#nullable restore
#line 8 "e:/Scratch/BlazorApp1/_Imports.razor"
using BlazorApp1;

#line default
#line hidden
#nullable disable
#nullable restore
#line 9 "e:/Scratch/BlazorApp1/_Imports.razor"
using BlazorApp1.Shared;

#line default
#line hidden
#nullable disable
    [Microsoft.AspNetCore.Components.RouteAttribute("/counter")]
    public partial class Counter : Microsoft.AspNetCore.Components.ComponentBase
    {
        #pragma warning disable 219
        private void __RazorDirectiveTokenHelpers__() {
        ((System.Action)(() => {
#nullable restore
#line 1 "e:/Scratch/BlazorApp1/Pages/Counter.razor"
global::System.Object __typeHelper = "/counter";

#line default
#line hidden
#nullable disable
        }
        ))();
        }
        #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 5 "e:/Scratch/BlazorApp1/Pages/Counter.razor"
             __o = currentCount;

#line default
#line hidden
#nullable disable
            __o = Microsoft.AspNetCore.Components.EventCallback.Factory.Create<Microsoft.AspNetCore.Components.Web.MouseEventArgs>(this, 
#nullable restore
#line 7 "e:/Scratch/BlazorApp1/Pages/Counter.razor"
                                          IncrementCount

#line default
#line hidden
#nullable disable
            );
        }
        #pragma warning restore 1998
#nullable restore
#line 9 "e:/Scratch/BlazorApp1/Pages/Counter.razor"
       
    private int currentCount = 0;

    private void IncrementCount()
    {

        currentCount++;
    }

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

I don't see that physical file anywhere, so I'm guessing this is the new source generator at work?

Given the above file though, it looks like Roslyn is doing the right thing. We're resolving the breakpoint for the statement __o = currentCount;, which comes from the right spot in the source razor file (ie, the line pragma is 5), so we return line 98, col 13..32. That then goes to the mapToDocumentRanges LSP method, which comes back with -1, -1.

I'm not exactly sure what is expected on the Razor side, and can't see too much in the debugger, but I did notice that in TryMapFromProjectedDocumentRangeStrict it calls codeDocument.GetCSharpDocument().GeneratedCode:
https://github.com/dotnet/aspnetcore-tooling/blob/067bd1bbfc26651af82be3b48d99e39799d456ba/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/DefaultRazorDocumentMappingService.cs#L273

It then passes the mapped position from that to TryMapFromProjectedDocumentPosition which calls codeDocument.GetCSharpDocument() to get the mappings, but then doesn't find anything. Does GetCSharpDocument().SourceMappings and GetCSharpDocument().GeneratedCode refer to the same generated code? I can't see where they are defined is defined, so I'm not sure, I'm just guessing based on the fact that you pasted in the other generated code above. Is there supposed to be two?

NTaylorMullen · 2021-03-25T19:59:38Z

@davidwengier We disabled this in the LSP editor so that you wouldn't even get the "red" breakpoint location. Try turning off the experimental Razor editor and do the same thing (it uses a different mechanism to map breakpoints)

As for what line it associates with that's:

#nullable restore
#line 5 "e:/Scratch/BlazorApp1/Pages/Counter.razor"
             __o = currentCount;

#line default
#line hidden

At design time and at runtime that __o goes away and is replaced with all sorts of __builder.Add... magic. Not sure which piece (runtime or designtime) matters

tmat · 2021-03-25T20:03:49Z

The IDE only sees design-time source when calculating break point locations when you place them.

NTaylorMullen · 2021-03-25T20:18:38Z

The IDE only sees design-time source when calculating break point locations when you place them.

Oh totally get that part, I was more referring to what happens when the breakpoint is set to be "hit".

For instance, if you use the old editor you can set a breakpoint there where as in the new editor we restricted setting the breakpoint there because we didn't want to give false hope to folks.

Old Editor:

tmat · 2021-03-25T20:33:54Z

Breakpoints are likely to be quite broken, especially when you start editing the files in EnC. The fact that runtime does not match design-time will definitely throw it off.

NTaylorMullen · 2021-03-25T20:37:55Z

Breakpoints are likely to be quite broken, especially when you start editing the files in EnC. The fact that runtime does not match design-time will definitely throw it off.

Sure but it works for all sorts of other things where it doesn't match 😄

tmat · 2021-03-25T20:42:26Z

Not sure what you mean. I'm just saying that we need to review EnC and see if its active statement mapping works for #line mapped spans. There might be issues there. Even then, once we fix those, it might turn out that supporting different runtime and compile time code is just not reasonable.

davidwengier · 2021-03-25T21:39:41Z

Alright, I'll turn off the LSP editor and see if that reveals any secrets.

It's worth nothing I wasn't doing any of this at runtime, this was just opening the razor file in the editor and hitting F9. Let me know if thats not the right repro.

davidwengier · 2021-03-25T21:55:28Z

Okay, now I'm confused. With the LSP editor off, clicking to set a breakpoint on line 5 works. What am I missing here? Is this a problem when setting breakpoints, or at runtime?

davidwengier · 2021-03-25T22:09:49Z

Alright, apologies for my confusion, the issue is at runtime the breakpoints aren't hit. The inability to create them in the LSP editor is a known thing that is irrelevant for this bug, for all intents and purposes.

tmat · 2021-04-05T21:30:48Z

This behavior in C# compiler is by design. The code that Razor emits can't work.

#line directives do not have an effect in the middle of a statement. They only affect the next sequence point. Sequence points can only be places on IL instruction where the evaluation stack is empty. Thus they can't be placed in the middle of statements and the #line directive emitted by Razor therefore has no effect.

tmat · 2021-04-05T21:34:14Z

To achieve the desired behavior we would need a new C# language feature:

#line <start line> <start column> <end line> <end column> <file name>

and then Razor could emit something like

#line 5 15 5 27 "Counter.razor"
__builder.AddContent(3, currentCount);
#line hidden

tmat · 2021-04-05T21:35:24Z

BTW, #line default immediately followed by #line hidden also has no effect since there is no sequence point in between these directives.

NTaylorMullen · 2021-04-05T22:39:58Z

Ahhhh ok ya that sounds like a super awesome idea and also makes me think about #46526 too

jcouv added Area-Compilers Interactive-Debugging labels Apr 18, 2020

tmat self-assigned this Apr 18, 2020

NTaylorMullen mentioned this issue Aug 3, 2020

Expand #line to support columns #46526

Closed

NTaylorMullen mentioned this issue Nov 23, 2020

[Debugging] Breakpoints in .razor files, which are not in the @code block won't bind mono/mono#19339

Closed

tmat mentioned this issue May 13, 2021

[Proposal]: Enhanced #line directives dotnet/csharplang#4747

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Cannot hit breakpoints in parameter mapped locations #43432

Cannot hit breakpoints in parameter mapped locations #43432

NTaylorMullen commented Apr 16, 2020

CyrusNajmabadi commented Apr 17, 2020

NTaylorMullen commented Apr 17, 2020

jcouv commented Apr 18, 2020

tmat commented Apr 18, 2020

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NTaylorMullen commented Apr 5, 2021

Cannot hit breakpoints in parameter mapped locations #43432

Cannot hit breakpoints in parameter mapped locations #43432

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NTaylorMullen commented Apr 16, 2020

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