Module filter: make libidn2 and libpcre2 optional. If they are missing

filter module will not be built

meson.build

@@ -27,8 +27,6 @@ lmdb = dependency('lmdb', required: false)
 if not lmdb.found()  # darwin workaround: missing pkgconfig
   lmdb = meson.get_compiler('c').find_library('lmdb')
 endif
-libidn2 = dependency('libidn2', version: '>=2.0.0')
-libpcre2 = dependency('libpcre2-8', version: '>=10.00')
 gnutls = dependency('gnutls', version: '>=3.4')
 luajit = dependency('luajit')
 # https://mesonbuild.com/howtox.html#add-math-library-lm-portably
@@ -166,6 +164,9 @@ malloc = meson.get_compiler('c').find_library(
   # Fortunately it seems unlikely that dynamic wouldn't be found and static would be.
 )
 
+### filter module
+libidn2 = dependency('libidn2', version: '>=2.0.0', required: false)
+libpcre2 = dependency('libpcre2-8', version: '>=10.00', required: false)
 message('---------------------------')
 
 ## Compiler args

modules/filter/filter.test.lua

@@ -1,9 +1,13 @@
 -- SPDX-License-Identifier: GPL-3.0-or-later
+-- try loading the module
+local has_filter = pcall(modules.load, 'filter')
+if not has_filter then
+	os.exit(77) -- SKIP filter tests
+end
+
 local kres = require('kres')
 local condition = require('cqueues.condition')
 
-modules = { 'filter' }
-
 -- helper to wait for query resolution
 local function wait_resolve(qname)
 	local waiting, done, cond = false, false, condition.new()

modules/filter/meson.build

@@ -10,16 +10,18 @@ config_tests += [
   ['filter', files('filter.test.lua')],
 ]
 
-filter_mod = shared_module(
-  'filter',
-  filter_src,
-  dependencies: mod_deps + [
-    libidn2,
-    libpcre2
-  ],
-  include_directories: mod_inc_dir,
-  name_prefix: '',
-  install: true,
-  install_dir: modules_dir,
-  link_with: kresd,
-)
+if libidn2.found() and libpcre2.found()
+  filter_mod = shared_module(
+    'filter',
+    filter_src,
+    dependencies: mod_deps + [
+      libidn2,
+      libpcre2,
+    ],
+    include_directories: mod_inc_dir,
+    name_prefix: '',
+    install: true,
+    install_dir: modules_dir,
+    link_with: kresd,
+  )
+endif