Support for AppRun hooks installed by plugins, mk. 1

src/core/appdir_root_setup.cpp

@@ -15,6 +15,9 @@ namespace linuxdeploy {
 
 
         class AppDirRootSetup::Private {
+        public:
+            static constexpr auto APPRUN_HOOKS_DIRNAME = "apprun-hooks";
+
         public:
             const AppDir& appDir;
 
@@ -137,6 +140,94 @@ namespace linuxdeploy {
                     }
                 }
             }
+
+            bool deployAppRunWrapperIfNecessary() const {
+                const bf::path appRunPath(appDir.path() / "AppRun");
+                const bf::path wrappedAppRunPath(appRunPath.string() + ".wrapped");
+
+                const bf::path appRunHooksPath(appDir.path() / APPRUN_HOOKS_DIRNAME);
+
+                // first, we check whether there's that special directory containing hooks
+                if (!bf::is_directory(appRunHooksPath)) {
+                    ldLog() << LD_DEBUG << "Could not find apprun-hooks dir, no need to deploy the AppRun wrapper" << std::endl;
+                    return true;
+                }
+
+                // if there's no files in there we don't have to do anything
+                bf::directory_iterator firstRegularFile = std::find_if(
+                    bf::directory_iterator(appRunHooksPath),
+                    bf::directory_iterator{},
+                    [](const bf::path& p) {
+                        return bf::is_regular_file(p);
+                    }
+                );
+                if (firstRegularFile == bf::directory_iterator{}) {
+                    ldLog() << LD_WARNING << "Found an empty apprun-hooks directory, assuming there is no need to deploy the AppRun wrapper" << std::endl;
+                    return true;
+                }
+
+                // any file within that directory is considered to be a script
+                // we can't perform any validity checks, that would be way too much complexity and even tools which
+                // claim they can, like e.g., shellcheck, aren't perfect, they only aid in avoiding bugs but cannot
+                // prevent them completely
+
+                // let's put together the wrapper script's contents
+                std::ostringstream oss;
+
+                oss << "#! /usr/bin/env bash" << std::endl
+                    << std::endl
+                    << "# autogenerated by linuxdeploy" << std::endl
+                    << std::endl
+                    << "export APPDIR=${APPDIR:-$(readlink -f $(dirname \"$0\"))}" << std::endl
+                    << std::endl;
+
+                std::for_each(bf::directory_iterator(appRunHooksPath), bf::directory_iterator{}, [&oss](const bf::path& p) {
+                    if (!bf::is_regular_file(p))
+                        return;
+
+                    oss << "source \"$APPDIR\"/" << APPRUN_HOOKS_DIRNAME << "/" << p.filename();
+                });
+
+                oss << std::endl
+                    << "exec \"$APPDIR\"/AppRun.wrapped" << std::endl;
+
+                // first we need to make sure we're not running this more than once
+                // this might cause more harm than good
+                // we require the user to clean up the mess at first
+                // FIXME: try to find a way how to rewrap AppRun on subsequent runs or, even better, become idempotent
+                if (bf::exists(wrappedAppRunPath)) {
+                    ldLog() << LD_WARNING << "Already found wrapped AppRun, using existing file/symlink" << std::endl;
+                }
+
+                // in case the above check triggered a warning, it's possible that there is another AppRun in the AppDir
+                // this one has to be cleaned up in that case
+                if (bf::exists(appRunPath)) {
+                    ldLog() << LD_WARNING << "Found an AppRun file/symlink, possibly due to re-run of linuxdeploy, "
+                                            "overwriting" << std::endl;
+                    bf::remove(appRunPath);
+                }
+
+                // backup original AppRun
+                bf::rename(appRunPath, wrappedAppRunPath);
+
+
+                // install new script
+                std::ofstream ofs(appRunPath.string());
+                ofs << oss.str();
+
+                // make sure data is written to disk
+                ofs.flush();
+                ofs.close();
+
+                // make new file executable
+                bf::permissions(appRunPath,
+                    bf::perms::owner_all | bf::perms::group_read | bf::perms::others_read |
+                    bf::perms::group_exe | bf::perms::others_exe
+                );
+
+                // we're done!
+                return true;
+            }
         };
 
         AppDirRootSetup::AppDirRootSetup(const AppDir& appDir) : d(new Private(appDir)) {}
@@ -160,6 +251,15 @@ namespace linuxdeploy {
                     return false;
             }
 
+            // plugins might need to run some initializing code to make certain features work
+            // these involve setting environment variables because libraries or frameworks don't support any other
+            // way of pointing them to resources inside the AppDir instead of looking into config files in locations
+            // inside the AppImage, etc.
+            // the linuxdeploy plugin specification states that if plugins put files into a specified directory in
+            // the AppImage, linuxdeploy will make sure they're run before running the regular AppRun
+            if (!d->deployAppRunWrapperIfNecessary())
+                return false;
+
             return true;
         }
     }