How to identify the script that's calling a user command?

Question

I have a problem: I need to pass « any » caller-session trace into a user command… Was trying with:

command WantToKnowWhosCalling call Impl("\<SID>",
    \ expand("<SID>"), eval('expand("<SID>")'),
    \ expand('<sfile>'))

all methods were failing — <SID> because it's fixed-straight (it's almost like if Bram was brushing some potential security issues…) to point to the «command-defining» session. <sfile> was ·almost· there, however… It returns the script-file path (a very good ID…) only at the time of the :source, later, when expanded from the script-defined functions, it's ≈ <stack>…

Has someone any more ideas? I need to: « identify the command-caller », basically… It can be a random-ID, but stable-assigned and unique. The goal is to know that it's a « client script-A returning », i.e.: recognized and associated with its previous calls to the custom :Command.

Answer 1

By throwing an exception you should be able to obtain the full (functions) callstack. I've described part the process in a section of the documentation of my library plugin along with the related functions I provide to decode v:throwpoint. IIRC, there is another Q/A where I delved more in details about how its works... Found it! And also here.

There are a few limitations: it only returns calling functions. If your function is called only through commands or mappings, you won't see anything useful. It's also extremely slow: do not abuse of the feature.

EDIT: it seems that v:throwpoint and Vim 8.2.1297 expand('<stack>') return a string (almost) in the same format. Split it at ... Then each element will contain a function name (and may a line number). From there the best way to know where it's defined is with verbose function {funcname}. The difficulty is that the message will be localized, and sometimes anonymous functions have already been garbage collected (or why I don't use them any more).

My library already takes care of all these issues. I'll eventually upgrade it to use expand('<stack>') whenever it's possible as I expect better performances.