Raise ArgumentError when turbo_stream_from helper gets passed blank s…

…treamables (#661)

* Handle blank streamable in turbo_stream_for helper

* turbo_stream_from requires at least one non-blank streamable

app/helpers/turbo/streams_helper.rb

@@ -48,7 +48,13 @@ def turbo_stream
   # It is also possible to pass additional parameters to the channel by passing them through `data` attributes:
   #
   #   <%= turbo_stream_from "room", channel: RoomChannel, data: {room_name: "room #1"} %>
+  #
+  # Raises an +ArgumentError+ if all streamables are blank
+  #
+  #   <%= turbo_stream_from("") %> # => ArgumentError: streamables can't be blank
+  #   <%= turbo_stream_from("", nil) %> # => ArgumentError: streamables can't be blank
   def turbo_stream_from(*streamables, **attributes)
+    raise ArgumentError, "streamables can't be blank" unless streamables.any?(&:present?)
     attributes[:channel] = attributes[:channel]&.to_s || "Turbo::StreamsChannel"
     attributes[:"signed-stream-name"] = Turbo::StreamsChannel.signed_stream_name(streamables)
 

test/streams/streams_helper_test.rb

@@ -11,6 +11,26 @@ class Turbo::StreamsHelperTest < ActionView::TestCase
       turbo_stream_from("messages")
   end
 
+  test "with multiple streamables, some blank" do
+    assert_dom_equal \
+      %(<turbo-cable-stream-source channel="Turbo::StreamsChannel" signed-stream-name="#{Turbo::StreamsChannel.signed_stream_name(["channel", nil, "", "messages"])}"></turbo-cable-stream-source>),
+      turbo_stream_from("channel", nil, "", "messages")
+  end
+
+  test "with invalid streamables" do
+    assert_raises ArgumentError, "streamables can't be blank" do
+      turbo_stream_from("")
+    end
+
+    assert_raises ArgumentError, "streamables can't be blank" do
+      turbo_stream_from(nil)
+    end
+
+    assert_raises ArgumentError, "streamables can't be blank" do
+      turbo_stream_from("", nil)
+    end
+  end
+
   test "with streamable and html attributes" do
     assert_dom_equal \
       %(<turbo-cable-stream-source channel="Turbo::StreamsChannel" signed-stream-name="#{Turbo::StreamsChannel.signed_stream_name("messages")}" data-stream-target="source"></turbo-cable-stream-source>),