How to debug applescript when an Application's class methods don't respond

In Applescript, I'm trying to change which text editor I'm using. TextEdit works fine, providing the document name, and it opens in MacVim. However, when I try the exact same get path of document 1 command in MacVim, it stays undefined, and terminal shows error: > execution error: MacVim got an error: Can’t get document 1. Invalid index. (-1719) The MacVim library claims it uses the same document object, both really coming from the 'Standard Suite'. What's my next debug step? **All the Details Below Here** Applescript code to "toggle text editing apps" of the currently open and focused file:

on run argv
	set my_arg to argv
	set the_path to "error - not found"
	
	if (my_arg contains "v") then
		set the_path to from_app("TextEdit")
		open_in_app("MacVim", the_path)
	else if (my_arg contains "e") then
		set the_path to from_app("MacVim")
		open_in_app("TextEdit", the_path)
	else
		display dialog "Error: Use argument 'e' or 'v' to switch TO textEditor or macVim"
	end if
end run

on from_app(from_app)
	tell application from_app
		activate
		set my_path to get path of document 1
		close document 1
	end tell
	
	return my_path
end from_app

on open_in_app(to_app, my_path)
	tell application to_app
		activate
		open my_path
	end tell
end open_in_app

Standard Suite in TextEdit > document n [inh. item; see also TextEdit suite] : A document. > elements: contained by application, application. properties: path > (text) : The document's path. TextEdit suite in TextEdit > document n [see also Standard Suite] : A TextEdit document. > properties: text (text) : The text of the document. Standard Suite in MacVim > document n [inh. item] : A document. elements: contained by > application. properties: path (text) : The document's path. Not seeing how to make these images smaller yet... **How I call the script to get the error**

user@userMBP % osascript ~/toggle-text-editor.apple.scpt e

**Versions** MacVim was installed with brew install macvim, Custom Version 9.0.65 (173). Mac is Bug Sur version 11.6.8 (20G730) **Answers to questions** > Does homebrew install a gui "MacVim"? Is it launched when the script runs? Yes, MacVim includes a GUI, and it is successfully launched when the script runs. > What returns from path to application "MacVim"? Is it correct? Not sure what you mean. open my_path successfully opens the right document in MacVim. set my_path to get path of document 1 fails. > What returns from tell application "Macvim" to documents? Again, not sure what you mean. There are 2 lines that can issue a tell application MacVim. One is successful (opening document), one fails (asking MacVim the name of currently open document). Thank you @Mockman and @CJK. Opened [issue1226](https://github.com/macvim-dev/macvim/issues/1266) on MacVim github.