How to debug single file with Rails environment loaded - ruby-on-rails

Question

I've been learning Ruby and now Rails.
I know in VS Code you configure the debugger with the following config
{
"name": "Debug Ruby",
"type": "Ruby",
"request": "launch",
"cwd": "${workspaceRoot}",
"program": "${file}",
},
It works just like ruby xxx.rb and pauses at breakpoints.
But I want to be able to do the same for any file in my rails project. For example, I just wrote a model user.rb for my project and i want to test and debug some functions.I tried the following:
{
"name": "Rails run",
"type": "Ruby",
"request": "launch",
"cwd": "${workspaceRoot}",
"program": "${workspaceRoot}/bin/rails",
"args": [
"runner",
"${file}"
]
},
but this wont stop at the breakpoints. there's also rails server option but that's for running the whole app but i just want to test&debug one single piece of code.

Answer 1

I think it doesnt work because rdebug doesnt attach to any subprocesses that the runner spins up to run the script. You could try launching the debugger directly from the ruby file you want the runner to use. You'd need to add an attach use-case in the debugger options:
For example:
.vscode/launch.json:
{
"name" : "Attach to rdebug-ide",
"type": "Ruby",
"request": "attach",
"cwd": "${workspaceRoot}",
"remoteHost": "127.0.0.1",
"remotePort": "1234",
"remoteWorkspaceRoot": "${workspaceRoot}"
},
Than in xxx.rb add the following to the top of the file:
require 'ruby-debug-ide'
require 'resource-struct'
options = ResourceStruct::FlexStruct.new({
host: '127.0.0.1',
port: '1234'
})
### Anything above this line will get run twice
Debugger.debug_program(options) unless Debugger.started?
### Rest of code you want to debug
Next run rails r xxx.rb it displays something like:
Fast Debugger (ruby-debug-ide 0.7.3, debase 0.2.4.1, file filtering is supported) listens on 127.0.0.1:1234
Lastly attached your debugger.