Adding manually

You can add this alsa-lib configuration to your project manually. This method is limited to the Ubuntu-distributed version of ALSA only, because the changes required for compiling ALSA from source are too extensive to detail succinctly here. Such complex changes are the reason that sc-jsonnet was created.

Howto

To use Ubuntu’s ALSA, copy the following part into your snapcraft.yaml:

parts:
    alsa-mixin:
        source: https://github.com/diddledan/snapcraft-alsa.git
        plugin: nil
        override-pull: |
            cat > asound.conf <<EOF
            pcm.!default {
                type pulse
                fallback "sysdefault"
                hint {
                    show on
                    description \"Default ALSA Output (currently PulseAudio Sound Server)\"
                }
            }
            ctl.!default {
                type pulse
                fallback "sysdefault"
            }
            EOF
        override-build: "install -m644 -D -t $SNAPCRAFT_PART_INSTALL/etc asound.conf"
        build-packages:
        - libasound2-dev
        stage-packages:
        - libasound2
        - libasound2-plugins
        after:
        - alsa-lib-mixin
        - alsa-plugins-mixin

Now add this layout definition:

layout:
    "/etc/asound.conf":
        symlink: "$SNAP/etc/asound.conf"
    "/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/alsa-lib":
        symlink: "$SNAP/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/alsa-lib"

Finally, add after: [alsa-mixin] to any parts that require ALSA.

See also

Adding snapcraft-alsa to your snapcraft.yaml with jsonnet