Tau - add env var flag to disable MIDI subsystems completely

Use this to bypass loading MIDI subsystems on linux CI tests (which currently fail due to MIDI/hardward issues). Given that the tests don't currently cover any MIDI behaviour, it's ok to simply not load the MIDI subsystems in this case.

Author: samaaron

.github/workflows/build.yml

@@ -183,10 +183,17 @@ jobs:
       run: mix test
       if: matrix.os == 'windows-latest'
 
-    - name: BEAM Tests (Mac/Linux)
+    - name: BEAM Tests (Linux)
       working-directory: ${{github.workspace}}/app/server/beam/tau
       run: mix test
-      if: matrix.os == 'ubuntu-latest' || matrix.os == 'macos-latest'
+      if: matrix.os == 'ubuntu-latest'
+      env:
+        TAU_DISABLE_MIDI: true
+
+    - name: BEAM Tests (macOS)
+      working-directory: ${{github.workspace}}/app/server/beam/tau
+      run: mix test
+      if: matrix.os == 'macos-latest'
 
     - name: Ruby Tests (Mac/Linux)
       working-directory: ${{github.workspace}}/app/server/ruby

app/server/beam/tau/src/tau_server/tau_server_sup.erl

@@ -68,9 +68,6 @@ init(_Args) ->
                   #{id => tau_server_cue,
                     start => {tau_server_cue, start_link, []}
                    },
-                  #{id => tau_server_midi,
-                    start => {tau_server_midi, start_link, [CueServer]}
-                   },
                   #{id => tau_server_link,
                     start => {tau_server_link, start_link, [CueServer]}
                    },
@@ -80,4 +77,18 @@ init(_Args) ->
 
                  ],
 
+    ENV = os:getenv("TAU_DISABLE_MIDI", "false"),
+    MIDIChildSpecs = if
+                         ENV == "true" ->
+                             ChildSpecs;
+
+                         true ->
+                             [ChildSpecs | #{id    => tau_server_midi,
+                                             start => {tau_server_midi,
+                                                       start_link,
+                                                       [CueServer]}}]
+
+
+                     end,
+
     {ok, {SupFlags, ChildSpecs}}.