:terminal output completes pending op (d, y, ...)

[benwr]

I started using neovim last week, and one of my favorite features is the built-in terminal. It's extremely convenient. I'm coming from Emacs + Evil, and one of my longtime gripes was that eterm is terrible. Somehow neovim's terminal is exactly right, except for a few minor issues. In this case, if I have a big terminal window, output in the terminal can screw up input into text buffers.

NVIM v0.1.5
Build type: Debug
Compilation: /usr/lib/ccache/cc -Wconversion -g -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-prototypes -std=gnu99 -Wvla -fstack-protector --param ssp-buffer-size=4 -DINCLUDE_GENERATED_DECLARATIONS -DHAVE_CONFIG_H -D_GNU_SOURCE -I/home/ben/sources/neovim/build/config -I/home/ben/sources/neovim/src -I/home/ben/sources/neovim/.deps/usr/include -I/home/ben/sources/neovim/.deps/usr/include -I/home/ben/sources/neovim/.deps/usr/include -I/home/ben/sources/neovim/.deps/usr/include -I/home/ben/sources/neovim/.deps/usr/include -I/home/ben/sources/neovim/.deps/usr/include -I/usr/include -I/home/ben/sources/neovim/build/src/nvim/auto -I/home/ben/sources/neovim/build/include
Compiled by ben@[redacted]

Optional features included (+) or not (-): +acl   +iconv    +jemalloc +tui
For differences from Vim, see :help vim-differences

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/usr/local/share/nvim"

• Vim: N/A (doesn't have built-in terminal)
• Operating system/version: Ubuntu 14.04
• Terminal name/version: st 0.7, urxvt 9.19
• $TERM: xterm-256color

Actual behaviour

When a program prints lots of things in TERMINAL mode, typing d in text buffers immediately deletes a line, as though you had typed dd. With really high volume output, other weird things seem to happen, but they're harder to reproduce without spamming so hard that my computer freezes.

Expected behaviour

d should wait for a text object as an argument, as it does in normal situations.

Steps to reproduce using nvim -u NORC

nvim -u NORC
i
some text 1
some text 2
some text 3
some text 4
<Esc>
<C-w>s
:term
while true; do yes | head -n 50; sleep 0.01; done # maybe tweak this to be more intense (shorter sleep, more lines of yes), depending on your system
<C-\><C-n>
<C-w>j
d

[fwalch]

Alternative reproduction steps in #5417.

[justinmk]

Possibly the same root cause as #6166.