Stringify errors before processing

CHANGELOG.md

@@ -8,6 +8,9 @@
   * Limitations:
     * `expect.extend` cannot be called from within `describe` blocks
     * Custom matcher names cannot overwrite pre-existing matchers, including default matchers and matchers introduces from previous `expect.extend` calls.
+* Change the way errors are collected to call tostring on them before further processing.
+  * Luau allows non-string errors, but not concatenating non-strings or passing non-strings to `debug.traceback` as a message, so TestRunner needs to do that step. This is a temporary fix as the better solution would be to retain the error in object form for as long as possible to give the reporter more to work with.
+  * This also makes a slight change to what's in the traceback to eliminate the unnecessary line mentioning the error collection function.
 
 ## 0.3.3 (2020-09-25)
 * Remove the lifecycle hooks from the session tree. This prevents the `[?]` spam from the reporter not recognizing these nodes.

src/TestPlan.lua

@@ -196,7 +196,9 @@ function TestNode:expand()
 	end
 	setfenv(self.callback, callbackEnv)
 
-	local success, result = xpcall(self.callback, debug.traceback)
+	local success, result = xpcall(self.callback, function(message)
+		return debug.traceback(tostring(message), 2)
+	end)
 
 	if not success then
 		self.loadError = result

src/TestRunner.lua

@@ -74,7 +74,7 @@ function TestRunner.runPlanNode(session, planNode, lifecycleHooks)
 			end
 
 			success = false
-			errorMessage = messagePrefix .. message .. "\n" .. debug.traceback()
+			errorMessage = messagePrefix .. debug.traceback(tostring(message), 2)
 		end
 
 		testEnvironment.expect = wrapExpectContextWithPublicApi(session:getExpectationContext())
@@ -86,7 +86,7 @@ function TestRunner.runPlanNode(session, planNode, lifecycleHooks)
 				callback(context)
 			end,
 			function(message)
-				return messagePrefix .. message .. "\n" .. debug.traceback()
+				return messagePrefix .. debug.traceback(tostring(message), 2)
 			end
 		)
 

tests/errorTypes.lua

@@ -0,0 +1,45 @@
+local TestEZ = require(script.Parent.Parent.TestEZ)
+
+local function check(str, test)
+	local plan = TestEZ.TestPlanner.createPlan({
+		{
+			-- This function environment hack is needed because the test
+			-- function is not defined or required from within a test. This
+			-- shouldn't come up in real tests.
+			method = function()
+				setfenv(test, getfenv())
+				test()
+			end,
+			path = {'errorTypeTests'}
+		}
+	})
+
+	local results = TestEZ.TestRunner.runPlan(plan)
+
+	assert(#results.errors > 0, "Expected some errors, got none.")
+	for _, err in ipairs(results.errors) do
+		local find = string.find(err, str)
+		assert(find, string.format("Expected errors containing [%s], found [%s]", str, err))
+	end
+end
+
+return {
+	["Error message should show up in output"] = function()
+		check("FOO", function()
+			error("FOO")
+		end)
+	end,
+	["Erroring with an object should mention the object"] = function()
+		check("table:", function()
+			error({})
+		end)
+	end,
+	["Erroring with an object with __tostring should show the string"] = function()
+		check("FOO", function()
+			local obj = setmetatable({}, {__tostring=function()
+				return "FOO"
+			end})
+			error(obj)
+		end)
+	end,
+}