Upgrade prettyValue to preview tables

packages/lest/src/lua/utils/prettyValue.lua

@@ -1,7 +1,39 @@
---- Formats a value to look prettier
+local MAX_TABLE_FIELDS = 3
+
+--- Iterator function which returns elements in numeric then lexicographic order
+---@param tbl table
+---@return fun(): any, any
+local function sortedPairs(tbl)
+	local keys = {}
+	for key in pairs(tbl) do
+		table.insert(keys, key)
+	end
+
+	table.sort(keys, function(a, b)
+		local aIsNumber = type(a) == "number"
+		local bIsNumber = type(b) == "number"
+
+		if aIsNumber then
+			return not bIsNumber or a < b
+		end
+
+		return not bIsNumber and tostring(a) < tostring(b)
+	end)
+
+	local i = 1
+	return function()
+		local key = keys[i]
+		if key ~= nil then
+			i = i + 1
+			return key, tbl[key]
+		end
+	end
+end
+
+--- Renders a primitive value, or table with tostring
 ---@param value any
 ---@return string
-return function(value)
+local function renderPrimitive(value)
 	if type(value) == "string" then
 		return '"' .. value .. '"'
 	end
@@ -20,3 +52,60 @@ return function(value)
 
 	return tostring(value)
 end
+
+--- Renders an inline truncated table
+---@param tbl table
+---@return string
+local function renderTable(tbl)
+	local renderedFields = {}
+	local totalFields = 0
+
+	for key, value in sortedPairs(tbl) do
+		if #renderedFields < MAX_TABLE_FIELDS then
+			if type(key) == "number" then
+				table.insert(renderedFields, renderPrimitive(value))
+			elseif
+				type(key) == "string" and string.match(key, "^[_%a][_%a%d]*$")
+			then
+				table.insert(
+					renderedFields,
+					string.format("%s = %s", key, renderPrimitive(value))
+				)
+			else
+				table.insert(
+					renderedFields,
+					string.format(
+						"[%s] = %s",
+						renderPrimitive(key),
+						renderPrimitive(value)
+					)
+				)
+			end
+		end
+
+		totalFields = totalFields + 1
+	end
+
+	if #renderedFields < totalFields then
+		table.insert(
+			renderedFields,
+			string.format("...%d more", totalFields - #renderedFields)
+		)
+	end
+
+	return string.format("{ %s }", table.concat(renderedFields, ", "))
+end
+
+--- Formats a value to look prettier
+---@param value any
+---@return string
+return function(value)
+	if
+		type(value) == "table"
+		and string.match(tostring(value), "table: [%a%d]+")
+	then
+		return renderTable(value)
+	end
+
+	return renderPrimitive(value)
+end

packages/lest/src/lua/utils/tests/pretty-value.test.lua

@@ -0,0 +1,49 @@
+local prettyValue = require("utils.prettyValue")
+
+test.each({
+	{ "string", "foo", [["foo"]] },
+	{ "number", 123, [[123]] },
+	{ "boolean", true, [[true]] },
+	{ "positive infinity", math.huge, [[inf]] },
+	{ "negative infinity", -math.huge, [[-inf]] },
+	{ "NaN", 0 / 0, [[NaN]] },
+	{
+		"table with tostring metamethod",
+		setmetatable({}, {
+			__tostring = function()
+				return "Blah"
+			end,
+		}),
+		[[Blah]],
+	},
+	{ "array-like table", { 1, "foo", 3 }, [[{ 1, "foo", 3 }]] },
+	{
+		"object-like table",
+		{ foo = true, ["b-ar"] = false },
+		[[{ ["b-ar"] = false, foo = true }]],
+	},
+	{
+		"mixed table",
+		{ 1, foo = 2, [true] = 3 },
+		[[{ 1, foo = 2, [true] = 3 }]],
+	},
+	{
+		"truncated array-like table",
+		{ 1, 2, 3, 4, 5 },
+		[[{ 1, 2, 3, ...2 more }]],
+	},
+	{
+		"truncated object-like table",
+		{ a = 1, ["b"] = 2, ["c-"] = 3, d = 4 },
+		[[{ a = 1, b = 2, ["c-"] = 3, ...1 more }]],
+	},
+	{
+		"truncated mixed table",
+		{ 1, foo = "bar", 2, 3, 4, 5, 6 },
+		[[{ 1, 2, 3, ...4 more }]],
+	},
+})("prettifies %s", function(_, value, expected)
+	local rendered = prettyValue(value)
+
+	expect(rendered).toBe(expected)
+end)