libdnf5: Turn the Appstream data installation code into a plugin

This allows to split out the appstream library dependency into a separate
package, not adding it and its dependencies into the core part of the libdnf5.

dnf5.spec

@@ -609,6 +609,23 @@ Libdnf5 plugin that allows to run actions (external executables) on hooks.
 %{_mandir}/man8/libdnf5-actions.8.*
 %endif
 
+# ========== libdnf5-plugin-appstream ==========
+
+%if %{with appstream}
+
+%package -n libdnf5-plugin-appstream
+Summary:        Libdnf5 plugin to install repo Appstream data
+License:        LGPL-2.1-or-later
+Requires:       libdnf5%{?_isa} = %{version}-%{release}
+
+%description -n libdnf5-plugin-appstream
+Libdnf5 plugin that installs repository's Appstream data, for repositories which provide them.
+
+%files -n libdnf5-plugin-appstream
+%{_libdir}/libdnf5/plugins/appstream.so
+%config %{_sysconfdir}/dnf/libdnf5-plugins/appstream.conf
+
+%endif
 
 # ========== libdnf5-plugin-plugin_rhsm ==========
 

include/libdnf5/repo/repo.hpp

@@ -144,10 +144,6 @@ class LIBDNF_API Repo {
     // @replaces libdnf:repo/Repo.hpp:method:Repo.loadCache(bool throwExcept)
     void read_metadata_cache();
 
-    /// Installs downloaded Appstream data for the repo, if available and
-    /// if built with the Appstream support.
-    void install_appstream();
-
     /// Checks whether the locally downloaded metadata are in sync with the origin.
     /// @return `true` if metadata are in sync with the origin, `false` otherwise.
     bool is_in_sync();
@@ -318,6 +314,9 @@ class LIBDNF_API Repo {
     // @replaces libdnf:repo/Repo.hpp:method:Repo.downloadMetadata(const std::string & destdir)
     void download_metadata(const std::string & destdir);
 
+    /// Returns a list of pairs of the rpmmd type and filename of the Appstream data of the repo
+    std::vector<std::pair<std::string, std::string>> get_appstream_metadata() const;
+
 private:
     class LIBDNF_LOCAL Impl;
     friend class RepoSack;

libdnf5-plugins/CMakeLists.txt

@@ -4,3 +4,7 @@ set(CMAKE_C_VISIBILITY_PRESET hidden)
 add_subdirectory("actions")
 add_subdirectory("python_plugins_loader")
 add_subdirectory("rhsm")
+
+if(WITH_APPSTREAM)
+    add_subdirectory("appstream")
+endif()

libdnf5-plugins/appstream/CMakeLists.txt

@@ -0,0 +1,13 @@
+add_library(appstream_plugin MODULE appstream.cpp)
+
+# disable the 'lib' prefix in order to create appstream.so
+set_target_properties(appstream_plugin PROPERTIES PREFIX "")
+set_target_properties(appstream_plugin PROPERTIES OUTPUT_NAME "appstream")
+
+pkg_check_modules(APPSTREAM REQUIRED appstream>=0.16)
+include_directories(${APPSTREAM_INCLUDE_DIRS})
+target_link_libraries(appstream_plugin PRIVATE ${APPSTREAM_LIBRARIES})
+target_link_libraries(appstream_plugin PRIVATE libdnf5)
+
+install(TARGETS appstream_plugin LIBRARY DESTINATION "${CMAKE_INSTALL_FULL_LIBDIR}/libdnf5/plugins/")
+install(FILES "appstream.conf" DESTINATION "${CMAKE_INSTALL_FULL_SYSCONFDIR}/dnf/libdnf5-plugins")

libdnf5-plugins/appstream/appstream.conf

@@ -0,0 +1,3 @@
+[main]
+name = appstream
+enabled = 1

libdnf5-plugins/appstream/appstream.cpp

@@ -0,0 +1,131 @@
+/*
+Copyright Contributors to the libdnf project.
+
+This file is part of libdnf: https://github.com/rpm-software-management/libdnf/
+
+Libdnf is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+Libdnf is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include <appstream.h>
+#include <libdnf5/base/base.hpp>
+#include <libdnf5/conf/const.hpp>
+#include <libdnf5/plugin/iplugin.hpp>
+#include <libdnf5/repo/repo.hpp>
+#include <libdnf5/repo/repo_query.hpp>
+
+#include <iostream>
+
+using namespace libdnf5;
+
+namespace {
+
+constexpr const char * PLUGIN_NAME{"appstream"};
+constexpr libdnf5::plugin::Version PLUGIN_VERSION{.major = 1, .minor = 0, .micro = 0};
+
+constexpr const char * attrs[]{"author.name", "author.email", "description", nullptr};
+constexpr const char * attrs_value[]{"Milan Crha", "[email protected]", "install repo Appstream data."};
+
+class AppstreamPlugin : public plugin::IPlugin {
+public:
+    AppstreamPlugin(libdnf5::plugin::IPluginData & data, libdnf5::ConfigParser &) : IPlugin(data) {}
+    virtual ~AppstreamPlugin() = default;
+
+    PluginAPIVersion get_api_version() const noexcept override { return PLUGIN_API_VERSION; }
+
+    const char * get_name() const noexcept override { return PLUGIN_NAME; }
+
+    plugin::Version get_version() const noexcept override { return PLUGIN_VERSION; }
+
+    const char * const * get_attributes() const noexcept override { return attrs; }
+
+    const char * get_attribute(const char * attribute) const noexcept override {
+        for (size_t i = 0; attrs[i]; ++i) {
+            if (std::strcmp(attribute, attrs[i]) == 0) {
+                return attrs_value[i];
+            }
+        }
+        return nullptr;
+    }
+
+    void repos_loaded() override {
+        Base & base = get_base();
+        repo::RepoQuery repos(base);
+        repos.filter_enabled(true);
+        for (const auto & repo : repos) {
+            switch (repo->get_type()) {
+                case repo::Repo::Type::AVAILABLE:
+                case repo::Repo::Type::SYSTEM:
+                    install_appstream(repo.get());
+                    break;
+                case repo::Repo::Type::COMMANDLINE:;
+            }
+        }
+    }
+
+private:
+    void install_appstream(libdnf5::repo::Repo * repo);
+};
+
+void AppstreamPlugin::install_appstream(libdnf5::repo::Repo * repo) {
+    libdnf5::Base & base = get_base();
+    if (!repo->get_config().get_main_config().get_optional_metadata_types_option().get_value().contains(
+            libdnf5::METADATA_TYPE_APPSTREAM))
+        return;
+
+    std::string repo_id = repo->get_config().get_id();
+    auto appstream_metadata = repo->get_appstream_metadata();
+    for (auto & item : appstream_metadata) {
+        const std::string path = item.second;
+        GError * local_error = NULL;
+
+        if (!as_utils_install_metadata_file(
+                AS_METADATA_LOCATION_CACHE, path.c_str(), repo_id.c_str(), NULL, &local_error)) {
+            base.get_logger()->debug(
+                "Failed to install Appstream metadata file '{}' for repo '{}': {}",
+                path,
+                repo_id,
+                local_error ? local_error->message : "Unknown error");
+        }
+
+        g_clear_error(&local_error);
+    }
+}
+
+}  // namespace
+
+
+PluginAPIVersion libdnf_plugin_get_api_version(void) {
+    return PLUGIN_API_VERSION;
+}
+
+const char * libdnf_plugin_get_name(void) {
+    return PLUGIN_NAME;
+}
+
+plugin::Version libdnf_plugin_get_version(void) {
+    return PLUGIN_VERSION;
+}
+
+plugin::IPlugin * libdnf_plugin_new_instance(
+    [[maybe_unused]] LibraryVersion library_version,
+    libdnf5::plugin::IPluginData & data,
+    libdnf5::ConfigParser & parser) try {
+    return new AppstreamPlugin(data, parser);
+} catch (...) {
+    return nullptr;
+}
+
+void libdnf_plugin_delete_instance(plugin::IPlugin * plugin_object) {
+    delete plugin_object;
+}

libdnf5/CMakeLists.txt

@@ -81,13 +81,6 @@ if (WITH_MODULEMD)
     target_link_libraries(libdnf5_static PRIVATE ${LIBMODULEMD_LIBRARIES})
 endif()
 
-if (WITH_APPSTREAM)
-    pkg_check_modules(APPSTREAM REQUIRED appstream>=0.16)
-    include_directories(${APPSTREAM_INCLUDE_DIRS})
-    target_link_libraries(libdnf5 PRIVATE ${APPSTREAM_LIBRARIES})
-    target_link_libraries(libdnf5_static PRIVATE ${APPSTREAM_LIBRARIES})
-endif()
-
 if (ENABLE_SOLV_FOCUSNEW)
     pkg_check_modules(LIBSOLV REQUIRED libsolv>=0.7.30)
 else()

libdnf5/repo/repo.cpp

@@ -52,10 +52,6 @@ extern "C" {
 #include <filesystem>
 #include <set>
 
-#ifdef WITH_APPSTREAM
-#include <appstream.h>
-#endif
-
 namespace libdnf5::repo {
 
 static void is_readable_rpm(const std::string & fn) {
@@ -206,30 +202,8 @@ void Repo::read_metadata_cache() {
     p_impl->downloader->load_local();
 }
 
-void Repo::install_appstream() {
-#ifdef WITH_APPSTREAM
-    if (!p_impl->config.get_main_config().get_optional_metadata_types_option().get_value().contains(
-            libdnf5::METADATA_TYPE_APPSTREAM))
-        return;
-
-    std::string repo_id = p_impl->config.get_id();
-    auto appstream_metadata = p_impl->downloader->get_appstream_metadata();
-    for (auto & item : appstream_metadata) {
-        const std::string path = item.second;
-        GError * local_error = NULL;
-
-        if (!as_utils_install_metadata_file(
-                AS_METADATA_LOCATION_CACHE, path.c_str(), repo_id.c_str(), NULL, &local_error)) {
-            p_impl->base->get_logger()->debug(
-                "Failed to install Appstream metadata file '{}' for repo '{}': {}",
-                path,
-                repo_id,
-                local_error ? local_error->message : "Unknown error");
-        }
-
-        g_clear_error(&local_error);
-    }
-#endif
+std::vector<std::pair<std::string, std::string>> Repo::get_appstream_metadata() const {
+    return get_downloader().get_appstream_metadata();
 }
 
 bool Repo::is_in_sync() {

libdnf5/repo/repo_sack.cpp

@@ -575,7 +575,6 @@ void RepoSack::Impl::update_and_load_repos(libdnf5::repo::RepoQuery & repos, boo
                 RepoCache(base, cache_dir).remove_attribute(RepoCache::ATTRIBUTE_EXPIRED);
                 repo->mark_fresh();
                 repo->read_metadata_cache();
-                repo->install_appstream();
 
                 repos_for_processing.erase(repos_for_processing.begin() + static_cast<ssize_t>(idx));
                 send_to_sack_loader(repo);