meson.build: always enable Wave encoder for Snapcast

Even if the "wave_encoder" option is disabled (and no other encoder
plugins are enabled), forcefully enable the Wave encoder (if Snapcast
is enabled).

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1500

src/encoder/meson.build

@@ -3,6 +3,22 @@ encoder_features = configuration_data()
 encoder_features.set('ENABLE_ENCODER', need_encoder)
 
 if not need_encoder
+  if need_wave_encoder
+    # Special case for the Snapcast output plugin which only needs the
+    # PCM wave encoder encoder plugin
+    encoder_glue = static_library(
+      'encoder_glue',
+      'plugins/WaveEncoderPlugin.cxx',
+      include_directories: inc,
+    )
+
+    encoder_glue_dep = declare_dependency(
+      link_with: encoder_glue,
+    )
+
+    subdir_done()
+  endif
+
   encoder_glue_dep = dependency('', required: false)
   configure_file(output: 'Features.h', configuration: encoder_features)
   subdir_done()

src/encoder/plugins/meson.build

@@ -35,7 +35,7 @@ if libshine_dep.found()
 endif
 
 encoder_features.set('ENABLE_WAVE_ENCODER', get_option('wave_encoder'))
-if get_option('wave_encoder')
+if get_option('wave_encoder') or need_wave_encoder
   encoder_plugins_sources += 'WaveEncoderPlugin.cxx'
 endif
 

src/output/plugins/meson.build

@@ -10,6 +10,7 @@ output_plugins_deps = [
 ]
 
 need_encoder = false
+need_wave_encoder = false
 
 if alsa_dep.found()
   output_plugins_sources += 'AlsaOutputPlugin.cxx'
@@ -127,9 +128,7 @@ if get_option('snapcast')
 
   output_features.set('HAVE_YAJL', yajl_dep.found())
 
-  # TODO: the Snapcast plugin needs just the "wave" encoder, but this
-  # enables all available encoders
-  need_encoder = true
+  need_wave_encoder = true
 endif
 
 enable_solaris_output = get_option('solaris_output')

test/meson.build

@@ -572,7 +572,7 @@ executable(
 # Encoder
 #
 
-if encoder_glue_dep.found()
+if need_encoder
   executable(
     'run_encoder',
     'run_encoder.cxx',