Remote parts don't seem to work in snapcraft 3.0

[Alan Pope 🍺🐧🐱 🦄]

I've got a yaml which has after: [desktop-gtk2], and an apps stanza which has "desktop-launch foo". When building snapcraft errors with.

Failed to generate snap metadata: The specified command 'desktop-launch' defined in the app 'snes9x-gtk' does not exist or is not executable.
Ensure that 'desktop-launch' is relative to the prime directory.

I'm doing this inside multipass if that matters, and it's a core18 based snap.

name: snes9x
version: '1.56.2' # just for humans, typically '1.2+git' or '1.3.2'
summary: Super NES Emulator
description: |
  Snes9x is a portable, freeware Super Nintendo Entertainment System (SNES)
  emulator. It basically allows you to play most games designed for the SNES
  and Super Famicom Nintendo game systems on your PC or Workstation; they
  include some real gems that were only ever released in Japan.

base: core18

grade: stable
confinement: strict

apps:
  snes9x-gtk:
    environment:
      "LD_LIBRARY_PATH": "$LD_LIBRARY_PATH:$SNAP/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/pulseaudio"
    command: desktop-launch $SNAP/bin/snes9x-gtk
    plugs:
      - x11
      - network
      - network-bind
      - joystick
      - home
      - pulseaudio
      - removable-media
parts:
  snes9x:
    after: [desktop-gtk2]
    source: https://github.com/snes9xgit/snes9x.git
    plugin: autotools
    source-tag: '1.56.2'
    build-packages:
      - libsdl1.2-dev
      - libboost-thread-dev
      - libboost-system-dev
      - libsdl-ttf2.0-dev
      - libasound2-dev
      - zlib1g-dev
      - libpng-dev
      - xorg-dev
      - libpulse-dev
      - libx11-dev
      - libxml2-dev
      - portaudio19-dev
      - intltool
      - libgtk-3-dev
      - libminizip-dev
      - libsdl2-dev
    stage-packages:
      - pulseaudio-utils
      - libpulse0
    override-build: |
      cd gtk
      autoreconf --install
      intltoolize --force
      ./configure
      make
      cp -a snes9x-gtk $SNAPCRAFT_PART_INSTALL/bin

[Lucy Llewellyn (lucyllewy)]

It's because you've set a `base:`. When you do so, snapcraft thinks you want the "new world order" which doesn't include remote parts. There are two solutions depending on requirements:

1. If the application works against libraries in xenial then remove `base: core18`.
2. Otherwise, you need to add the remote part definition into the `snapcraft.yaml`:

```yaml
  desktop-gtk2:
    source: https://github.com/ubuntu/snapcraft-desktop-helpers.git
    source-subdir: gtk
    plugin: make
    make-parameters: ["FLAVOR=gtk2"]
    build-packages:
      - build-essential
      - libgtk2.0-dev
    stage-packages:
      - libxkbcommon0 # XKB_CONFIG_ROOT
      - ttf-ubuntu-font-family
      - dmz-cursor-theme
      - light-themes
      - adwaita-icon-theme
      - gnome-themes-standard
      - shared-mime-info
      - libgtk2.0-0
      - libgdk-pixbuf2.0-0
      - libglib2.0-bin
      - libgtk2.0-bin
      - unity-gtk2-module
      - locales-all
      - libappindicator1
      - xdg-user-dirs
      - ibus-gtk
      - libibus-1.0-5
```

[Sergio Schvezov (sergiusens)]

This is by design, extensions or adding the part into the snapcraft.yaml at hand are the migration path.