Blazor WASM debugger faults when stepping through code #49218

RobertBouillon · 2021-03-05T15:55:30Z

Describe the bug

Stepping through code causes fault (failed assertion) in mono.

To Reproduce

Create a new Blazor WASM project
Add a new .NET library project to the solution
Add the Foo class to the library with the code below
Add a reference to the .NET library project from the WASM project
Update the FetchData.razor page with the code below.
Add breakpoints at FetchData.razor:42 (Console.WriteLine...)
Add this.Bar to the watch window.
Start debugging. Wait for the debugger to attach before doing anything.
Click on the "Fetch Data" link in the window
The program should break in the FetchData.razor page. Press F5 to continue.
Click on the "Home" link and then the "Fetch Data" link again
The program should break in the FetchData.razor page. Press F11 twice to Step Into.

Expected Results

The debugger will step over the current statement

Actual Results

The debugger becomes unusable and must be restarted.

Comments

The problem appears to be caused by the expression this.Bar in the watch window: I'm unable to reproduce the error when the expression is removed.

Foo.cs

using System;
using System.Linq;
using System.Collections.Generic;

namespace BlazorBugsLib
{
  public class Foo
  {
    //public string Bar => "sample-data/weather.json";
    public string Bar => Stuffs.First(x => x.Name.StartsWith('S')).Name;
    public string Lorem { get; set; } = "Safe";
    public string Ipsum { get; set; } = "Side";
    public Something What { get; } = new Something();
    public List<Something> Stuffs { get; } = Enumerable.Range(0, 10).Select(x => new Something()).ToList();

    public int Bart()
    {
      int ret;
      if (Lorem.StartsWith('S'))
        ret = 0;
      else
        ret = 1;

      return ret;
    }
  }
}

FetchData.razor

  protected override async Task OnInitializedAsync()
  {
    Console.WriteLine(new BlazorBugsLib.Foo().Bart());
    forecasts = await Http.GetFromJsonAsync<WeatherForecast[]>("Bad URI");
  }

Output Window

mono_wasm_runtime_ready fe00e07a-5519-4dfe-b35a-f867dbaf2e28
0
crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
System.Text.Json.JsonException: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
 ---> System.Text.Json.JsonReaderException: '<' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.Serialization.JsonConverter`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
   at System.Text.Json.Serialization.JsonConverter`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[WeatherForecast[]](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[WeatherForecast[]](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
   at System.Text.Json.JsonSerializer.<ReadAsync>d__20`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at System.Net.Http.Json.HttpContentJsonExtensions.<ReadFromJsonAsyncCore>d__3`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at System.Net.Http.Json.HttpClientJsonExtensions.<GetFromJsonAsyncCore>d__9`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at BlazorBugs2.Pages.FetchData.OnInitializedAsync() in C:\Users\rober\source\repos\BlazorBugs2\BlazorBugs2\Pages\FetchData.razor:line 43
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle)
>> mono_wasm_start_single_stepping 0
>> mono_wasm_start_single_stepping 0
: * Assertion at /__w/1/s/src/mono/mono/mini/debugger-engine.c:769, condition `<disabled>' not met

: * Assertion at /__w/1/s/src/mono/mono/mini/debugger-engine.c:769, condition `<disabled>' not met

Uncaught ExitStatusThe thread 0x2c50 has exited with code 0 (0x0).

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

ghost · 2021-03-05T17:07:29Z

Tagging subscribers to this area: @eiriktsarpalis, @layomia
See info in area-owners.md if you want to be subscribed.

Issue Details

Describe the bug

Stepping through code causes fault (failed assertion) in mono.

To Reproduce

Create a new Blazor WASM project
Add a new .NET library project to the solution
Add the Foo class to the library with the code below
Add a reference to the .NET library project from the WASM project
Update the FetchData.razor page with the code below.
Add breakpoints at FetchData.razor:42 (Console.WriteLine...)
Add this.Bar to the watch window.
Start debugging. Wait for the debugger to attach before doing anything.
Click on the "Fetch Data" link in the window
The program should break in the FetchData.razor page. Press F5 to continue.
Click on the "Home" link and then the "Fetch Data" link again
The program should break in the FetchData.razor page. Press F11 twice to Step Into.

Expected Results

The debugger will step over the current statement

Actual Results

The debugger becomes unusable and must be restarted.

Comments

The problem appears to be caused by the expression this.Bar in the watch window: I'm unable to reproduce the error when the expression is removed.

Foo.cs

using System;
using System.Linq;
using System.Collections.Generic;

namespace BlazorBugsLib
{
  public class Foo
  {
    //public string Bar => "sample-data/weather.json";
    public string Bar => Stuffs.First(x => x.Name.StartsWith('S')).Name;
    public string Lorem { get; set; } = "Safe";
    public string Ipsum { get; set; } = "Side";
    public Something What { get; } = new Something();
    public List<Something> Stuffs { get; } = Enumerable.Range(0, 10).Select(x => new Something()).ToList();

    public int Bart()
    {
      int ret;
      if (Lorem.StartsWith('S'))
        ret = 0;
      else
        ret = 1;

      return ret;
    }
  }
}

FetchData.razor

  protected override async Task OnInitializedAsync()
  {
    Console.WriteLine(new BlazorBugsLib.Foo().Bart());
    forecasts = await Http.GetFromJsonAsync<WeatherForecast[]>("Bad URI");
  }

Output Window

mono_wasm_runtime_ready fe00e07a-5519-4dfe-b35a-f867dbaf2e28
0
crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
System.Text.Json.JsonException: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
 ---> System.Text.Json.JsonReaderException: '<' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.Serialization.JsonConverter`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
   at System.Text.Json.Serialization.JsonConverter`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[WeatherForecast[]](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[WeatherForecast[]](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
   at System.Text.Json.JsonSerializer.<ReadAsync>d__20`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at System.Net.Http.Json.HttpContentJsonExtensions.<ReadFromJsonAsyncCore>d__3`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at System.Net.Http.Json.HttpClientJsonExtensions.<GetFromJsonAsyncCore>d__9`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at BlazorBugs2.Pages.FetchData.OnInitializedAsync() in C:\Users\rober\source\repos\BlazorBugs2\BlazorBugs2\Pages\FetchData.razor:line 43
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle)
>> mono_wasm_start_single_stepping 0
>> mono_wasm_start_single_stepping 0
: * Assertion at /__w/1/s/src/mono/mono/mini/debugger-engine.c:769, condition `<disabled>' not met

: * Assertion at /__w/1/s/src/mono/mono/mini/debugger-engine.c:769, condition `<disabled>' not met

Uncaught ExitStatusThe thread 0x2c50 has exited with code 0 (0x0).

Author:	RobertBouillon
Assignees:	-
Labels:	`area-System.Text.Json`, `untriaged`
Milestone:	-

ghost · 2021-03-05T17:07:41Z

Tagging subscribers to this area: @thaystg
See info in area-owners.md if you want to be subscribed.

Issue Details

Describe the bug

Stepping through code causes fault (failed assertion) in mono.

To Reproduce

Create a new Blazor WASM project
Add a new .NET library project to the solution
Add the Foo class to the library with the code below
Add a reference to the .NET library project from the WASM project
Update the FetchData.razor page with the code below.
Add breakpoints at FetchData.razor:42 (Console.WriteLine...)
Add this.Bar to the watch window.
Start debugging. Wait for the debugger to attach before doing anything.
Click on the "Fetch Data" link in the window
The program should break in the FetchData.razor page. Press F5 to continue.
Click on the "Home" link and then the "Fetch Data" link again
The program should break in the FetchData.razor page. Press F11 twice to Step Into.

Expected Results

The debugger will step over the current statement

Actual Results

The debugger becomes unusable and must be restarted.

Comments

The problem appears to be caused by the expression this.Bar in the watch window: I'm unable to reproduce the error when the expression is removed.

Foo.cs

using System;
using System.Linq;
using System.Collections.Generic;

namespace BlazorBugsLib
{
  public class Foo
  {
    //public string Bar => "sample-data/weather.json";
    public string Bar => Stuffs.First(x => x.Name.StartsWith('S')).Name;
    public string Lorem { get; set; } = "Safe";
    public string Ipsum { get; set; } = "Side";
    public Something What { get; } = new Something();
    public List<Something> Stuffs { get; } = Enumerable.Range(0, 10).Select(x => new Something()).ToList();

    public int Bart()
    {
      int ret;
      if (Lorem.StartsWith('S'))
        ret = 0;
      else
        ret = 1;

      return ret;
    }
  }
}

FetchData.razor

  protected override async Task OnInitializedAsync()
  {
    Console.WriteLine(new BlazorBugsLib.Foo().Bart());
    forecasts = await Http.GetFromJsonAsync<WeatherForecast[]>("Bad URI");
  }

Output Window

mono_wasm_runtime_ready fe00e07a-5519-4dfe-b35a-f867dbaf2e28
0
crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
System.Text.Json.JsonException: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
 ---> System.Text.Json.JsonReaderException: '<' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.Serialization.JsonConverter`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
   at System.Text.Json.Serialization.JsonConverter`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[WeatherForecast[]](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore[WeatherForecast[]](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
   at System.Text.Json.JsonSerializer.<ReadAsync>d__20`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at System.Net.Http.Json.HttpContentJsonExtensions.<ReadFromJsonAsyncCore>d__3`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at System.Net.Http.Json.HttpClientJsonExtensions.<GetFromJsonAsyncCore>d__9`1[[BlazorBugs2.Pages.FetchData.WeatherForecast[], BlazorBugs2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext()
   at BlazorBugs2.Pages.FetchData.OnInitializedAsync() in C:\Users\rober\source\repos\BlazorBugs2\BlazorBugs2\Pages\FetchData.razor:line 43
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle)
>> mono_wasm_start_single_stepping 0
>> mono_wasm_start_single_stepping 0
: * Assertion at /__w/1/s/src/mono/mono/mini/debugger-engine.c:769, condition `<disabled>' not met

: * Assertion at /__w/1/s/src/mono/mono/mini/debugger-engine.c:769, condition `<disabled>' not met

Uncaught ExitStatusThe thread 0x2c50 has exited with code 0 (0x0).

Author:	RobertBouillon
Assignees:	-
Labels:	`arch-wasm`, `area-Debugger-mono`
Milestone:	-

mkArtakMSFT · 2021-03-05T17:07:45Z

@lewing FYI

lewing · 2021-07-14T18:48:55Z

we've updated the stepping logic, this may be resolved.

thaystg · 2021-07-19T15:50:20Z

It's fixed.

@radical

* Creating test to close 49143. * Creating test to close #49141 * Adding test for #49218. * Fix behavior of step to be the same of what we see when debugging using debugger-libs+mono or coreclr. Fix error message of evaluate calling methods. Adding test for #49142 * Improving test to test what @radical asked. * Changing what was suggested by @radical.

mkArtakMSFT transferred this issue from dotnet/aspnetcore Mar 5, 2021

dotnet-issue-labeler bot added area-System.Text.Json untriaged New issue has not been triaged by the area owner labels Mar 5, 2021

mkArtakMSFT added arch-wasm WebAssembly architecture area-Debugger-mono and removed area-System.Text.Json untriaged New issue has not been triaged by the area owner labels Mar 5, 2021

lewing assigned thaystg Mar 5, 2021

lewing added this to the 6.0.0 milestone Jun 17, 2021

lewing assigned radical Jun 17, 2021

lewing unassigned radical Jul 14, 2021

thaystg added a commit to thaystg/runtime that referenced this issue Jul 19, 2021

Adding test for dotnet#49218.

c4ee906

thaystg closed this as completed Jul 19, 2021

thaystg mentioned this issue Jul 19, 2021

[wasm][debugger] Fix step behavior #55915

Merged

ghost added the in-pr There is an active PR which will close this issue when it is merged label Jul 19, 2021

ghost removed the in-pr There is an active PR which will close this issue when it is merged label Jul 21, 2021

ghost locked as resolved and limited conversation to collaborators Aug 20, 2021

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Blazor WASM debugger faults when stepping through code #49218

Blazor WASM debugger faults when stepping through code #49218

RobertBouillon commented Mar 5, 2021

ghost commented Mar 5, 2021

Describe the bug

To Reproduce

Expected Results

Actual Results

Comments

Foo.cs

FetchData.razor

Output Window

ghost commented Mar 5, 2021

Describe the bug

To Reproduce

Expected Results

Actual Results

Comments

Foo.cs

FetchData.razor

Output Window

mkArtakMSFT commented Mar 5, 2021

lewing commented Jul 14, 2021

thaystg commented Jul 19, 2021