"g@" does not pass "v:register" to the opfunc when operating on a custom text-object

[lacygoill]

Describe the bug

g@ does not pass v:register to the opfunc when operating on a custom text-object.

To Reproduce

Run this shell command:

vim -es -Nu NONE -S <(cat <<'EOF'
    fu Opfunc(...)
        if !a:0
            let &opfunc = 'Opfunc'
            return 'g@'
        endif
        pu=v:register
    endfu
    nno <expr> <c-b> Opfunc()
    xno io iw
    ono io :normal vio<cr>
    call feedkeys('"r'.."\<c-b>"..'io', 'xt') | %p | qa!
EOF
)

It outputs ".

Expected behavior

It outputs r.

Environment

• Vim version: 8.2 Included patches: 1-1101
• OS: Ubuntu 16.04.6 LTS
• Terminal: XTerm(356)

Additional context

It seems inconsistent.

We can use a builtin operator (like d) or a custom one (via g@).
We can use a builtin text-object (like iw) or a custom one.

Therefore, a change can be performed by 4 different types of commands:

1. builtin operator + builtin text-object
2. builtin operator + custom text-object
3. custom operator + builtin text-object
4. custom operator + custom text-object

All of them correctly handle a register without any special code, except the fourth one.

Test 1:

vim -Nu NONE -i NONE +"pu='word'"

" press:  "rdaw
:reg r
Type Name Content
  c  "r   word

Notice how word was correctly written inside the r register, meaning that daw correctly handled "r.

Test 2:

vim -Nu NONE -i NONE -S <(cat <<'EOF'
    pu='word'
    xno io iw
    ono io :norm vio<cr>
EOF
)

" press:  "rdio
:reg r
Type Name Content
  c  "r   word

Again, notice how word was correctly written inside the r register, meaning that dio correctly handled "r.

Test 3:

vim -Nu NONE -i NONE -S <(cat <<'EOF'
    pu='word'
    fu Opfunc(...)
        if !a:0
            let &opfunc = 'Opfunc'
            return 'g@'
        endif
        pu=v:register
    endfu
    nno <expr> <c-b> Opfunc()
EOF
)

" press:  "r C-b iw

Notice that Vim puts the text r in the buffer, meaning that "r correctly passed the r register to the opfunc.

If Vim is able to correctly handle a register in the first 3 cases (in particular 2.), I would expect it to correctly handle case 4..

[lacygoill]

One workaround is to pass v:register manually.

When not passing it:

xno io iw
ono io :normal vio<cr>

When passing it:

xno io iw
ono io :normal vio"<c-r>=v:register<cr><cr>
                  ^-------------------^

Test:

vim -es -Nu NONE -S <(cat <<'EOF'
    fu Opfunc(...)
        if !a:0
            let &opfunc = 'Opfunc'
            return 'g@'
        endif
        pu=v:register
    endfu
    nno <expr> <c-b> Opfunc()
    xno io iw
    ono io :normal vio"<c-r>=v:register<cr><cr>
    call feedkeys('"r'.."\<c-b>"..'io', 'xt') | %p | qa!
EOF
)

This correctly outputs r.

It works but it's one more pitfall to be aware of, and fixing this could make existing text-objects provided by third-party plugins more reliable.

[andymass]

Relevant question; https://vi.stackexchange.com/questions/20322/how-to-pass-vregister-to-custom-operator-when-working-on-custom-text-object/