launchSettings.json no longer allows comments after System.Text.Json migration

As part of the migration to System.Text.Json, it looks like Comment handling in launchSettings.json was lost. This issue does not repro on SDK 2.2.203.

System.Text.Json supports comment handling, but it has to be enabled in the options. It looks like the current code does not pass in any options: https://github.com/dotnet/cli/blob/0cb36481ad4e628079374447c8ae313006e3f602/src/dotnet/commands/dotnet-run/LaunchSettings/LaunchSettingsManager.cs#L28

Steps to reproduce

1. dotnet new web
2. Edit .\Properties\launchSettings.json to include a comment: // Spicy Comments
3. dotnet run

Expected behavior

It runs, spicy comments and all. Any launch settings (environment variables, etc.) are applied.

Actual behavior

The launch profile "(Default)" could not be applied.
An error was encountered when reading launchSettings.json.
'/' is invalid after a value. Expected either ',', '}', or ']'. LineNumber: 1 | BytePositionInLine: 2

The application does launch, but launch settings are ignored.

😢

Environment data

dotnet --info output:

.NET Core SDK (reflecting any global.json):
 Version:   2.2.203
 Commit:    e5bab63eca

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18865
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.2.203\

Host (useful for support):
  Version: 3.0.0-preview6-27804-01
  Commit:  fdf81c6faf

.NET Core SDKs installed:
  2.1.602 [C:\Program Files\dotnet\sdk]
  2.1.603 [C:\Program Files\dotnet\sdk]
  2.1.700-preview-009601 [C:\Program Files\dotnet\sdk]
  2.1.700-preview-009618 [C:\Program Files\dotnet\sdk]
  2.1.700 [C:\Program Files\dotnet\sdk]
  2.1.800-preview-009677 [C:\Program Files\dotnet\sdk]
  2.1.800-preview-009696 [C:\Program Files\dotnet\sdk]
  2.2.203 [C:\Program Files\dotnet\sdk]
  3.0.100-preview6-012264 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.10 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.10 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.0-preview6.19307.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0-preview6-27804-01 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0-preview6-27804-01 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

[tds01088]

I have encountered the same issue, and after some investigation, I simply edited the launchSettings.json file and saved it again

[nguerrera]

Comments should be allowed in any config file that a user can edit. Strictness in trailing commas is a nuisance but not the same as forbidding comments in user hostility.