I'm trying to copy and paste a chat from Messages.app into an email (macOS Mojave 10.14.5, Messages 12.0 (5500)). When I go into Messages and select all using command+A, the entire conversation is highlighted as if it's all selected. However, when I then copy and paste, only the very first selected message gets pasted. I tried selecting manually with the mouse, using Edit > Select All, and doing all of the above with the message opened in a separate window, but none of those changed the result.
I came up with one kludgey solution of making a PDF to share by selecting File > Print… and then PDF > Save as PDF. That creates a PDF that can be shared but copying and pasting from it remains a mess.
If I'm not mistaken, this was possible in earlier versions of macOS (I seem to even remember the formatting pasting quite nicely).
So how do you copy the entire chat in Messages?