HackStudio: Detection of externally deleted files

HackStudio can now detect that files that have been opened in it were
deleted. When this occurs, it will update the list of open files and
reasign a file to the editors that showed the deleted file before the
deletion. The new file is either another file that was opened or the
default editor is no other open file is available

Closes SerenityOS#6632

Userland/DevTools/HackStudio/HackStudioWidget.cpp

@@ -33,6 +33,7 @@
 #include <LibCore/Event.h>
 #include <LibCore/EventLoop.h>
 #include <LibCore/File.h>
+#include <LibCore/FileWatcher.h>
 #include <LibDebug/DebugSession.h>
 #include <LibGUI/Action.h>
 #include <LibGUI/ActionGroup.h>
@@ -69,6 +70,7 @@
 #include <fcntl.h>
 #include <spawn.h>
 #include <stdio.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -231,6 +233,20 @@ bool HackStudioWidget::open_file(const String& full_filename)
         new_project_file = m_project->get_file(filename);
         m_open_files.set(filename, *new_project_file);
         m_open_files_vector.append(filename);
+        auto watcher_or_error = Core::FileWatcher::watch(filename);
+        if (!watcher_or_error.is_error()) {
+            auto& watcher = watcher_or_error.value();
+            watcher->on_change = [this, filename]() {
+                struct stat st;
+                if (lstat(filename.characters(), &st) < 0) {
+                    if (errno == ENOENT) {
+                        handle_external_file_deletion(filename);
+                    }
+                }
+            };
+            m_file_watchers.set(filename, watcher_or_error.release_value());
+        }
+
         m_open_files_view->model()->update();
     }
 
@@ -1074,6 +1090,36 @@ void HackStudioWidget::initialize_menubar(GUI::Menubar& menubar)
     create_help_menubar(menubar);
 }
 
+void HackStudioWidget::handle_external_file_deletion(const String& filepath)
+{
+    m_open_files.remove(filepath);
+    m_open_files_vector.remove_all_matching(
+        [&filepath](const String& element) { return element == filepath; });
+
+    for (auto& editor_wrapper : m_all_editor_wrappers) {
+        Editor& editor = editor_wrapper.editor();
+        String editor_file_path = editor.code_document().file_path();
+        String relative_editor_file_path = LexicalPath::relative_path(editor_file_path, project().root_path());
+
+        if (relative_editor_file_path == filepath) {
+            if (m_open_files_vector.is_empty()) {
+                editor.set_document(CodeDocument::create());
+                editor_wrapper.filename_label().set_text(String { "Undefined" });
+                m_currently_open_file = "";
+            } else {
+                auto& first_path = m_open_files_vector[0];
+                auto& document = m_open_files.get(first_path).value()->code_document();
+                editor.set_document(document);
+                editor_wrapper.filename_label().set_text(first_path);
+                m_currently_open_file = first_path;
+            }
+        }
+    }
+
+    m_file_watchers.remove(filepath);
+    m_open_files_view->model()->update();
+}
+
 HackStudioWidget::~HackStudioWidget()
 {
     if (!m_debugger_thread.is_null()) {

Userland/DevTools/HackStudio/HackStudioWidget.h

@@ -93,6 +93,8 @@ private:
     void reveal_action_tab(GUI::Widget&);
     void initialize_debugger();
 
+    void handle_external_file_deletion(const String& filepath);
+
     void create_open_files_view(GUI::Widget& parent);
     void create_form_editor(GUI::Widget& parent);
     void create_toolbar(GUI::Widget& parent);
@@ -118,7 +120,8 @@ private:
     String m_currently_open_file;
 
     HashMap<String, NonnullRefPtr<ProjectFile>> m_open_files;
-    Vector<String> m_open_files_vector; // NOTE: This contains the keys from m_open_files
+    HashMap<String, NonnullRefPtr<Core::FileWatcher>> m_file_watchers;
+    Vector<String> m_open_files_vector; // NOTE: This contains the keys from m_open_files and m_file_watchers
 
     OwnPtr<Project> m_project;