tests: Test that the legacy naughty popup is used when the new API fails

Displaying errors is important. If the notification popup caused the
error, it was likely nothing could be displayed.

tests/test-naughty-legacy.lua

@@ -8,6 +8,8 @@ local cairo     = require("lgi"        ).cairo
 local beautiful = require("beautiful")
 local Gio       = require("lgi"        ).Gio
 local GLib      = require("lgi"        ).GLib
+local gpcall    = require("gears.protected_call")
+local dwidget   = require("naughty.widget._default")
 
 -- This module test deprecated APIs
 require("gears.debug").deprecate = function() end
@@ -1000,6 +1002,82 @@ table.insert(steps, function()
     return true
 end)
 
+-- Add a "new API" handler.
+local current_template, had_error, handler_called = nil
+
+table.insert(steps, function()
+    assert(naughty.has_display_handler == false)
+
+    naughty.connect_signal("request::display", function(n)
+        handler_called = true
+
+        naughty.layout.box {
+            notification    = n,
+            widget_template = current_template
+        }
+    end)
+
+    return true
+end)
+
+-- Make sure the legacy popup is used when the new APIs fails.
+table.insert(steps, function()
+    assert(naughty.has_display_handler == true)
+
+    function gpcall._error_handler()
+        had_error = true
+    end
+
+    local n = naughty.notification {
+        title   = nil,
+        message = nil,
+        timeout = 25000,
+    }
+
+    assert(handler_called)
+    assert(not had_error)
+    assert(not n._private.widget_template_failed)
+    assert(not n.box)
+
+    n:destroy()
+    handler_called = false
+
+    -- Try with a broken template.
+    current_template = {widget = function() assert(false) end}
+
+    n = naughty.notification {
+        title   = "foo",
+        message = "bar",
+        timeout = 25000,
+    }
+
+    assert(handler_called)
+    assert(had_error)
+    assert(not n.box)
+
+    handler_called = false
+    had_error      = false
+
+    -- Break the default template
+    assert(dwidget.widget)
+    dwidget.widget = nil
+    dwidget.layout = function() assert(false) end
+    table.remove(dwidget, 1)
+
+    n = naughty.notification {
+        title   = "foo",
+        message = "bar",
+        timeout = 25000,
+    }
+
+    assert(handler_called)
+    assert(n._private.widget_template_failed)
+    assert(had_error)
+    assert(n.box)
+
+    return true
+end)
+
 -- Test many screens.
 
 require("_runner").run_steps(steps)