AppleScript that will save all documents with unsaved changes when BBEdit loses focus.

ReadMe.rst

BBEdit ApplicationWillSwitchOut Attachment Script

The script itself has most of the documentation. Just know that there are two scripts here:

1. A plain-text version (.applescript)
2. A compiled version (.scpt)

The plain text is here so you can actually see the script before downloading. However, BBEdit will need a compiled version. So either download the .scpt file and save it to the proper location, or copy the contents of the .applescript file, open AppleScript Editor, paste it in a new document, and save it as a .scpt in the proper location.

Application.applicationWillSwitchOut.applescript

(*

File:
    Application.applicationWillSwitchOut.scpt

Abstract:
    This script will automatically save all on-disk text documents with unsaved
    changes when BBEdit loses focus.

Version:
    0.9.2

Author:
    Ben Spaulding <http://benspaulding.us/>

Details:
    This is an application attachment point script which, when saved to the
    proper location, will automatically save all text documents with unsaved
    changes when the application is put in the background.

    This script must be saved to  the `Attachment Scripts` directory within
    BBEdit's `Application Support` folder.

    For more information, see:

        - http://groups.google.com/group/bbedit/msg/a817516ca10a217b
        - BBEdit User Manual

*)

on applicationWillSwitchOut(theApp)

    -- Some BBEdit-specific properties, such as the document class's `on disk`
    -- property, require that they be contained in a tell block. To prevent
    -- frustration, simply wrap the whole thing in the tell block.
    tell application "BBEdit"

        -- Save all on-disk text documents with un-saved changes.
        -- -----------------------------------------------------
        set docList to every text document in theApp

        repeat with doc in docList

            (* Note that we verify that the doc is on disk. This is because
               backgrounding BBEdit yeilds a bonk and dialog to save files with
               changes that are not on disk. That is less than effective as the
               purpose of saving when backgrounding is to save keystrokes when
               testing/previewing code. Off-disk docs will rarely be a part of
               that workflow. What's more, they are not at risk of being lost
               because of BBEdit's state and un-saved change handling when the
               app is closed. *)

            if doc is modified then
                if doc is on disk then
                    -- This is a normal, modified, on-disk file, so save it.
                    save doc
                else
                    -- When the command line tool ``bbedit`` is given a path
                    -- to a non-existent file, it opens a window that, when
                    -- saved, will save to the given path. Unfortunately the
                    -- file is marked as not on disk, and there is no file
                    -- property either. However, files opened this way do have
                    -- their name set to read-only, like on-disk files do. So
                    -- trying to set it will throw an error, which lets us know
                    -- that this is one of those files.
                    try
                        set name of doc to (name of doc) as string
                    on error
                        save doc
                    end try
                end if -- doc is on disk
            end if -- doc is modified

        end repeat

    end tell

end applicationWillSwitchOut

Application.applicationWillSwitchOut.scpt

Does this still work?

It doesn't seem to work now on Mojave 10.14.4, and BBEdit 12.6.3, unfortunately.

The following script works:

const app = Application.currentApplication()
app.documents()
	.filter(doc => doc.modified() && doc.file())
	.forEach(doc => app.save(doc))

With Script Editor save it as a JavaScript script as ~/Library/Application Support/BBEdit/Attachment Scripts/Application.applicationWillSwitchOut.scpt.