Add JSON comment support to Lune APIs

[ghostnaps]

Lune's APIs for decoding JSON (net.jsonDecode and serde.decode("json", ...)) error when given a JSON string with comments.

This is a problem for me as I don't control the JSON files I'm reading, so I can't enforce which JSON schema is used.

Repro steps

Create two json files:

pass.json

{
  "foo": true,
  "bar": "str"
}

fail.json

// Comment at the top
{
  "foo": true,
  "bar": "str", // <-- trailing comma
}

Create a script with the following contents:

local fs = require("@lune/fs")
local net = require("@lune/net")
local serde = require("@lune/serde")

local pass = fs.readFile("pass.json")
local fail = fs.readFile("fail.json")

local success, result = pcall(net.jsonDecode, pass)
print(success, result)
success, result = pcall(net.jsonDecode, fail)
print(success, result)
success, result = pcall(serde.decode, "json", pass)
print(success, result)
success, result = pcall(serde.decode, "json", fail)
print(success, result)

Run the script. Then from the output you can see where both functions fail:

true {
    bar = "str",
    foo = true,
}
false expected value at line 1 column 1
[Stack Begin]
    Script '[C]' - function pcall
    Script 'server/server', Line 29
[Stack End]
true {
    bar = "str",
    foo = true,
}
false expected value at line 1 column 1
[Stack Begin]
    Script '[C]' - function pcall
    Script 'server/server', Line 33
[Stack End]

Considerations

If Lune doesn't want to support other JSON formats, would there be a good alternative? I'm considering spawning a separate process for JSON parsing to handle these edge cases, though I would much prefer to do everything from within Lune.

[CompeyDev]

Having json5 support would be cool! +1