Debugging docker image in VS code : cs file cannot be found: - docker

Question

I am trying to debug a docker image using the given description in this article.
I have created a Dockerfile like this :
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
RUN apt update && \
apt install procps -y && \
apt install unzip && \
curl -sSL https://aka.ms/getvsdbgsh | /bin/sh /dev/stdin -v latest -l /vsdbg
WORKDIR /app
EXPOSE 80
EXPOSE 443
FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
WORKDIR /src
COPY *.sln ./
COPY server/Business/NotificationModule.Business.csproj server/Business/
COPY server/Common/NotificationModule.Common.csproj server/Common/
COPY server/Data/NotificationModule.Data.csproj server/Data/
COPY server/DomainModel/NotificationModule.DomainModel.csproj server/DomainModel/
COPY server/Host/NotificationModule.Host.csproj server/Host/
RUN dotnet restore
COPY . .
WORKDIR "/src/server/Host/"
RUN dotnet build "NotificationModule.Host.csproj" -c Debug -o /app/build
FROM build AS publish
RUN dotnet publish "NotificationModule.Host.csproj" -c Debug -o /app/publish
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "NotificationModule.dll"]
and I have added the entry for debugging docker images in launch.json like this :
{
"name": ".NET Core Docker Attach",
"type": "coreclr",
"request": "attach",
"processId": "${command:pickRemoteProcess}",
"pipeTransport": {
"pipeProgram": "docker",
"pipeArgs": [ "exec", "-i", "objective_torvalds" ],
"debuggerPath": "/vsdbg/vsdbg",
"pipeCwd": "${workspaceRoot}",
"quoteArgs": false
}
},
It seems that it is working and I can attach the debugger to my process but the problem is that when the debugger hits a breakpoint it can not find any cs files and shows an empty cs file instead.
I would like to ask if you know what I have done wrong.
UPDATE :
I have noticed that the debugger is looking for my cs files under src folder which apparantly doens't exist neither in my working directory nor in the image itself . So the question is why it is looking there.

Answer 1

OK I've got it . That was my mistake because I was using the same docker file that we have for production to copy pdb files into the docker image and those pdb files have been built on a docker container in a src directory so it was looking there .
I just copied the files from my bin/debug into the docker image and now it is workng perfectly.( and later I noticed that it was also mentioned in the article).
so here is the new DockerFile :
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
RUN apt update && \
apt install procps -y && \
apt install unzip && \
curl -sSL https://aka.ms/getvsdbgsh | /bin/sh /dev/stdin -v latest -l /vsdbg
WORKDIR /app
EXPOSE 80
EXPOSE 443
COPY bin/debug .
ENTRYPOINT ["dotnet", "NotificationModule.dll"]
and BTW you shouldn't add bin into your .dockerignore file

Answer 2

I had the same problem - debugger worked (I could see variables values), but the debugger couldn't find my .cs files:
It turned out that the default value of sourceFileMap in launch.json was incorrect, I found information how to use it properly at OmniSharp Github.
Here's how to fix the issue:
After I clicked Create File button in the popup with the error I was able to check where the debugger was looking for the source file. In my case the error message was:
Unable to write file '/out/src/MyApp/WebDriverFactory/WebDriverFactory.cs' (Unknown (FileSystemError): Error: EROFS: read-only file system, mkdir '/out')
I could use the message above to use fix my paths in sourceFileMap:
{
"version": "0.2.0",
"configurations": [
{
"name": "Docker .NET Core Attach (Preview)",
"type": "docker",
"request": "attach",
"platform": "netCore",
"sourceFileMap": {
"/out/src/": "${workspaceFolder}/src"
}
}
]
}
I used .NET 6 with Alpine images:
mcr.microsoft.com/dotnet/runtime:6.0-alpine3.14-amd64