feat(plugins): add JSON parsing/serialization (#6420)

Reviewed-by: Mm2PL <mm2pl+gh@kotmisia.pl>
Reviewed-by: pajlada <rasmus.karlsson@pajlada.com>

tests/lua/json/stringify.lua

@@ -0,0 +1,137 @@
+local json = require('chatterino.json')
+
+local function check_err(...)
+    local ok = pcall(json.stringify, ...)
+    assert(not ok, "expected an error")
+end
+
+---@param input any
+---@param expected string|string[]
+---@vararg { pretty: boolean, indent_char: string, indent_size: number }|any
+local function check_ok(input, expected, ...)
+    local got = json.stringify(input, ...)
+    if type(expected) == "string" then
+        assert(got == expected, "Failed:\n\texpected: " .. expected .. "\n\tgot: " .. got .. "\n")
+    else
+        local ok = false
+        for _, it in ipairs(expected) do
+            if it == got then
+                ok = true
+                break
+            end
+        end
+        assert(ok, "Output did not match any of the expected values")
+    end
+end
+
+assert(type(json.null) == "userdata")
+
+-- empty
+check_ok({}, "{}")
+check_ok({ [0] = json.null }, '[]')
+
+-- scalars
+check_ok(1, "1")
+check_ok("foo", '"foo"')
+check_ok("foo\n", '"foo\\n"')
+check_ok(true, "true")
+check_ok(false, "false")
+check_ok(nil, "null")
+check_ok(json.null, "null")
+check_ok(1.23, "1.23")
+
+-- arrays
+check_ok({ 1, 2 }, "[1,2]")
+check_ok({ 1, 2, nil }, "[1,2]")
+check_ok({ 1, 2, json.null }, "[1,2,null]")
+check_ok({ 1, nil, 2 }, "[1,null,2]")
+check_ok({ 1, [10] = 2 }, "[1,null,null,null,null,null,null,null,null,2]")
+check_ok({ [10 / 2] = 1 }, '[null,null,null,null,1]')
+check_ok({ { { { { 1 } } } } }, "[[[[[1]]]]]")
+check_ok({ { { { { 1 } } }, { foo = 1 } } }, '[[[[[1]]],{"foo":1}]]')
+
+-- objects
+check_ok({ ok = { baz = "str", [""] = { 1, 2 } } }, {
+    '{"ok":{"baz":"str","":[1,2]}}',
+    '{"ok":{"":[1,2],"baz":"str"}}',
+})
+check_ok({ ok = { 1, 2 } }, '{"ok":[1,2]}')
+check_ok({ ['\n\tlol'] = { 1, 2 } }, '{"\\n\\tlol":[1,2]}')
+check_ok({ foo = nil }, '{}')
+check_ok({ foo = json.null }, '{"foo":null}')
+
+local meta_haver = {}
+local my_meta = {
+    foo = 42,
+    __index = function()
+        return 1
+    end
+}
+setmetatable(meta_haver, my_meta)
+assert(meta_haver.xd == 1)
+check_ok(meta_haver, '{}')
+meta_haver.xd = 2 -- uses __newindex
+check_ok(meta_haver, '{"xd":2}')
+
+-- limits
+local big_obj = {}
+; (function()
+    local it = big_obj
+    for _ = 1, 255 do
+        it.x = {}
+        it = it.x
+    end
+    it.x = "hey"
+end)()
+check_ok(big_obj, string.rep('{"x":', 256) .. '"hey"' .. string.rep('}', 256))
+check_err({ x = big_obj })
+
+local big_arr = {}
+; (function()
+    local it = big_arr
+    for _ = 1, 255 do
+        it[1] = {}
+        it = it[1]
+    end
+    it[1] = 1
+end)()
+check_ok(big_arr, string.rep('[', 256) .. '1' .. string.rep(']', 256))
+check_err({ big_arr })
+
+-- errors
+check_err(c2.Message.new({}))
+check_err(coroutine.create(function() end))
+check_err({ 1, 2, bar = "lol" })
+check_err({ [-1] = 3 })
+check_err({ [0] = 3 })
+check_err({ [0] = "42" })
+check_err({ [-1] = json.null })
+check_err({ [1.1] = 3 })
+check_err()
+local recurse = {}
+recurse.recurse = recurse
+check_err(recurse) -- hits the depth limit
+
+check_err(math.huge)
+check_err(-math.huge)
+check_err(0/0)
+check_err(-(0/0))
+
+-- ✨ pretty ✨
+
+check_ok(1, "1", { pretty = true })
+check_ok(false, "false", { pretty = true })
+check_ok(nil, "null", { pretty = true })
+check_ok("xd", '"xd"', { pretty = true })
+check_ok({ 1 }, '[\n    1\n]', { pretty = true })
+check_ok({ foo = "bar" }, '{\n    "foo": "bar"\n}', { pretty = true })
+check_ok({ foo = "bar", baz = 1 }, { [[{
+    "foo": "bar",
+    "baz": 1
+}]], [[{
+    "baz": 1,
+    "foo": "bar"
+}]] }, { pretty = true })
+check_ok({ foo = "bar" }, '{\n "foo": "bar"\n}', { pretty = true, indent_size = 1 })
+check_ok({ foo = "bar" }, '{\n\t"foo": "bar"\n}', { pretty = true, indent_size = 1, indent_char = '\t' })
+check_ok({ foo = "bar" }, '{"foo":"bar"}', { indent_size = 1, indent_char = '\tlol' })