How to escape a comma in json passed as args in a VSCode launcher.json command? - flutter

Question

I would like to debug an APP and need to pass a in-line json as arg.
I did the following:
"configurations": [
{
"name": "app DEV",
"program": "lib/main.dart",
"request": "launch",
"type": "dart",
"args": [
"--dart-define=APP_BACKENDS={[{\"id\":\"default\",\"url\":\"https://localhost\",\"port\": \"8080\"},]}",
]
}
but the APP_BACKENDS const value is getting stripped in the first comma. lock the print of it: {[{"id":"default"
just to be clear. that is the way I'm getting the value I've printed:
static const _APP_BACKENDS =
String.fromEnvironment('APP_BACKENDS', defaultValue: '{}');

Answer 1

After going through a lot of links and reading, finally I found a GitHub issue https://github.com/microsoft/vscode/issues/98471 which solved my similar problem. If you go through the link and read the second last comment it explains the things regarding shell quoting.
"configurations": [
{
"name": "app DEV",
"program": "lib/main.dart",
"request": "launch",
"type": "dart",
"args": [
"--dart-define=APP_BACKENDS={[{\"id\":\"default\",\"url\":\"https://localhost\",\"port\": \"8080\"},]}",
],
"argsExpansion": "none"
}
"argsExpansion": "none" after adding this to my launch.json file I was able to run the code without adding extra \ or spaces as mentioned in other answers. I tried searching for this configuration in vscode docs but did not find any reference, however it worked for me.

Answer 2

I had the same issue - trying to pass a json string as a command line arg to a python script. Works fine from shell, but couldn't do the same from launch.json. VS Code was intepreting the commas as multiple arguments and passing multiple -b args into my program (4x separate -b args in my case).
Answer: add a space " " to the end of the arg value.
I fail to understand why this works, but it does. Note I'm single-slash escaping the double-quotes.
{
"name": "Test my python code",
"type": "python",
"request": "launch",
"program": "${file}",
"args": [
"-r=/store/purchase",
"-b={\"items\":[\"cake\",\"coffee\",\"toilet roll\",\"masks\"]} "
],
"console": "integratedTerminal"
},

Answer 3

After reading this documentation: Launch JSON Reference, specifically
this reference, I got to know that, you need to use \\\ to achieve what you want. For example. In the documentation only this is given
JSON array of command-line arguments to pass to the program when it is launched. Example ["arg1", "arg2"]. If you are escaping characters, you will need to double escape them. For example, ["{\\\"arg1\\\": true}"] will send {"arg1": true} to your application
So, after looking at this, you must pass your JSON to your args in a proper format
args: [
"--dart-define=APP_BACKENDS={[{\\\"id\\\":\\\"default\\\",\\\"url\\\":\\\"https://localhost\\\",\\\"port\\\": \\\"8080\\\"}]}"
]
This will do your job!