[meld] Update meson build to byte-compile Python source by default

[Kai Willadsen <kaiw src gnome org>]

commit 3b682e168be3f3becd8bc5d1745618d151fac83c
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 25 11:12:09 2020 +1000

    Update meson build to byte-compile Python source by default
    
    This includes the option to disable byte compilation for the benefit of
    distributions.

 meson.build           | 6 +++++-
 meson_options.txt     | 6 ++++++
 meson_post_install.py | 8 ++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 378c9ea9..90612a0a 100644
--- a/meson.build
+++ b/meson.build
@@ -59,4 +59,8 @@ subdir('po')
 
 install_data('bin/meld', install_dir: bindir)
 
-meson.add_install_script('meson_post_install.py')
+if get_option('byte-compile')
+    meson.add_install_script('meson_post_install.py', python3.get_install_dir())
+else
+    meson.add_install_script('meson_post_install.py')
+endif
diff --git a/meson_options.txt b/meson_options.txt
index fa5966ae..9c545a9c 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -4,3 +4,9 @@ option(
   value: '',
   description: 'Build with specified application ID',
 )
+option(
+  'byte-compile',
+  type: 'boolean',
+  value: true,
+  description: 'Byte-compile installed Python source files',
+)
diff --git a/meson_post_install.py b/meson_post_install.py
index 682633a3..79bc1ac5 100644
--- a/meson_post_install.py
+++ b/meson_post_install.py
@@ -1,5 +1,7 @@
 #!/usr/bin/env python3
 
+import sys
+from compileall import compile_dir
 from os import environ, path
 from subprocess import call
 
@@ -12,3 +14,9 @@ if not environ.get('DESTDIR', ''):
     call(["glib-compile-schemas", path.join(DATA_DIR, 'glib-2.0', 'schemas')])
     print("Updating desktop database")
     call(["update-desktop-database", path.join(DATA_DIR, 'applications')])
+
+# Byte-compilation is enabled by passing the site-packages path to this script
+if len(sys.argv) > 1:
+    print('Byte-compiling Python module...')
+    python_source_install_path = sys.argv[1]
+    compile_dir(path.join(python_source_install_path, 'meld'), optimize=1)