meson.build: check for missing python modules

Check those modules that aren't part of the python installation and bail out
of meson where they're missing. This is technically wrong because we don't
need them at build-time and only at run-time but pragmatically sensible
because we waste too much time dealing with those bugs.

Fixes #200

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

.circleci/config.yml

@@ -7,7 +7,7 @@ jobs:
     steps:
       - run:
           command: |
-            dnf install -y meson gettext python3-devel pygobject3-devel python3-flake8 desktop-file-utils libappstream-glib python3-pytest python3-pyxdg python3-pyyaml
+            dnf install -y meson gettext python3-devel pygobject3-devel python3-flake8 desktop-file-utils libappstream-glib python3-pytest python3-pyxdg python3-pyyaml python3-svgwrite
       - checkout
       - run:
           command: |

meson.build

@@ -28,9 +28,26 @@ i18n = import('i18n')
 subdir('po')
 subdir('data')
 
-# Find the directory to install our Python code
 pymod = import('python')
-py3 = pymod.find_installation()
+
+# external python modules that are required for running Tuhi
+python_modules = [
+    'svgwrite',
+    'xdg',
+    'gi',
+    'yaml',
+]
+if meson.version().version_compare('>=0.51')
+    py3 = pymod.find_installation(modules: python_modules)
+else
+    py3 = pymod.find_installation()
+
+    foreach module: python_modules
+        if run_command(py3, '-c', 'import @0@'.format(module)).returncode() != 0
+            error('Failed to find required python module \'@0@\'.'.format(module))
+        endif
+    endforeach
+endif
 python_dir = py3.get_install_dir()
 install_subdir('tuhi',
                install_dir: python_dir,