Dispatch output broken, requires clicking Enter twice

Is this the normal behavior? It's a bit ugly :/ If I use the default dispatcher, nothing shows up in the QuickFix.

NVIM v0.3.1
Build type: Release
LuaJIT 2.0.5
Compilation: /usr/local/Homebrew/Library/Homebrew/shims/mac/super/clang -Wconversion -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -DNDEBUG -DMIN_LOG_LEVEL=3 -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-prototypes -std=gnu99 -Wimplicit-fallthrough -Wvla -fstack-protector-strong -fdiagnostics-color=auto -DINCLUDE_GENERATED_DECLARATIONS -D_GNU_SOURCE -DNVIM_MSGPACK_HAS_FLOAT32 -DNVIM_UNIBI_HAS_VAR_FROM -I/tmp/neovim-20180831-45030-1c6df1y/neovim-0.3.1/build/config -I/tmp/neovim-20180831-45030-1c6df1y/neovim-0.3.1/src -I/usr/local/include -I/usr/local/opt/gettext/include -I/Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include -I/tmp/neovim-20180831-45030-1c6df1y/neovim-0.3.1/build/src/nvim/auto -I/tmp/neovim-20180831-45030-1c6df1y/neovim-0.3.1/build/include
Compiled by brew@Mojave.local

Features: +acl +iconv +jemalloc +tui 
See ":help feature-compile"

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/usr/local/Cellar/neovim/0.3.1/share/nvim"

Run :checkhealth for more info

Reproduce issue #332 with the default dispatcher on Neovim v0.3.1, following the attached screencast and checking the QuickFix output after each Enter press. Trace the dispatch entry point and related test-runner behavior; done means output appears after one Enter and the default dispatcher populates QuickFix correctly.