Meson: Set unity builds by default

BUILDING.md

@@ -64,10 +64,10 @@ Although it is recommended to use `meson-setup.sh`, you can completely ignore
 its flags and invoke meson manually.
 
 ### Unity builds in Meson
-Unity builds can't be set by default without disrupting developer workflow. The
-`meson-setup.sh` script uses unity builds for release build style (which is the
-default). This is also the recommended setup in
-[README.md](README.md#build-requirements).
+Unity builds are fully configurable in Meson. They are enabled by default.
+The `meson-setup.sh` script disables unity builds for `debug` and `sanitize`
+build styles. You can use Meson's `--unity=off` flag to turn off unity builds
+when configuring the project manually.
 
 ## Support
 J4-dmenu-desktop has been tested on glibc and musl, cross compilation has been

meson-setup.sh

@@ -52,14 +52,14 @@ fi
 
 case $build_type in
 release)
-    exec $DRYRUN meson setup --buildtype=release -Db_lto=true --unity on --unity-size 9999 "$1"
+    exec $DRYRUN meson setup --buildtype=release -Db_lto=true "$1"
     ;;
 debug)
-    exec $DRYRUN meson setup -Dsplit-source=true "$1"
+    exec $DRYRUN meson setup -Dsplit-source=true --unity=off "$1"
     ;;
 sanitize)
     # See https://github.com/catchorg/Catch2/issues/2811 for explanation of forcefallback
-    exec $DRYRUN meson setup -Dsplit-source=true -Db_sanitize=address,undefined -Dcpp_debugstl=true -Db_lundef=false --wrap-mode forcefallback "$1"
+    exec $DRYRUN meson setup -Dsplit-source=true -Db_sanitize=address,undefined -Dcpp_debugstl=true -Db_lundef=false --wrap-mode forcefallback --unity=off "$1"
     ;;
 *)
     echo "Unknown build style $build_type!" 1>&2

meson.build

@@ -5,6 +5,8 @@ project(
   default_options: [
     'warning_level=3',
     'cpp_std=c++17',
+    'unity=on',
+    'unity_size=9999'
   ],
   license: 'GPL-3.0-or-later',
   license_files: 'LICENSE',