[Solved] OmniSharp RpcErrorException in VS Code Dev Containers for PowerShell-based Azure Functions

Apr 16, 2023 · 2 min read ·

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I recently got into VS Code Dev Containers and Azure Functions, and I love them. Unfortunately, the PowerShell Azure Functions pretty much come out of the box with a high likelihood of throwing Ominsharp exceptions when debugging.

Exception of type 'OmniSharp.Extensions.JsonRpc.RpcErrorException' was thrown

Two of the files the setup process generates, launch.json and tasks.json, use the func Azure Function type.

launch.json

 1{
 2  "version": "0.2.0",
 3  "configurations": [
 4    {
 5      "name": "Attach to PowerShell Functions",
 6      "type": "PowerShell",
 7      "request": "attach",
 8      "customPipeName": "AzureFunctionsPSWorker",
 9      "runspaceId": 1,
10      "preLaunchTask": "func: host start"
11    }
12  ]
13}

tasks.json

 1{
 2  "version": "2.0.0",
 3  "tasks": [
 4    {
 5      "type": "func",
 6      "command": "host start",
 7      "problemMatcher": "$func-powershell-watch",
 8      "isBackground": true
 9    }
10  ]
11}

Fixed code

Initially, I reduced the number of OmniSharp errors by changing the PowerShell path in various config files, but it wasn't 100% effective. After running into the exception one too many times, I searched for a solution yet again and finally found the post I needed.

This GitHub comment provided the solution, which was initially found on StackOverflow. It took me so long to find this solution, I wanted to repost it for everyone's future reference.

Ultimately, the Azure Function type should be changed from func to shell. Here's what I finally ended up on:

launch.json

 1{
 2  "version": "0.2.0",
 3  "configurations": [
 4    {
 5      "name": "Attach to PowerShell Functions",
 6      "type": "PowerShell",
 7      "request": "attach",
 8      "customPipeName": "AzureFunctionsPSWorker",
 9      "runspaceId": 1,
10      "processId": "${command:azureFunctions.pickProcess}",
11      "preLaunchTask": "func: host start"
12    }
13  ]
14}

tasks.json

 1{
 2  "version": "2.0.0",
 3  "tasks": [
 4    {
 5      "label": "func: host start",
 6      "type": "shell",
 7      "command": "func host start --powershell --verbose",
 8      "problemMatcher": "$func-powershell-watch",
 9      "isBackground": true,
10      "options": {
11        "cwd": "${workspaceFolder}/functions"
12      }
13    }
14  ]
15}

So far, this change has solved 100% of my OminiSharp crashes.