Improve Lua error reporting

Display Lua errors in a dedicated window/file. A typo or missing
dependency (e.g. lpeg) in visrc.lua will no longer silently fail
without any indication.

The Lua integration in view.h is not yet converted.

ui-curses.c

@@ -988,6 +988,11 @@ static void ui_info_hide(Ui *ui) {
 static bool ui_init(Ui *ui, Vis *vis) {
 	UiCurses *uic = (UiCurses*)ui;
 	uic->vis = vis;
+	return true;
+}
+
+static bool ui_start(Ui *ui) {
+	Vis *vis = ((UiCurses*)ui)->vis;
 	const char *theme = getenv("VIS_THEME");
 	if (theme && theme[0]) {
 		if (!vis_theme_load(vis, theme))
@@ -1087,6 +1092,7 @@ Ui *ui_curses_new(void) {
 
 	*ui = (Ui) {
 		.init = ui_init,
+		.start = ui_start,
 		.free = ui_curses_free,
 		.termkey_get = ui_termkey_get,
 		.suspend = ui_suspend,

ui.h

@@ -44,6 +44,7 @@ enum UiStyles {
 
 struct Ui {
 	bool (*init)(Ui*, Vis*);
+	bool (*start)(Ui*);
 	void (*free)(Ui*);
 	void (*resize)(Ui*);
 	UiWin* (*window_new)(Ui*, View*, File*, enum UiOption);

vis-core.h

@@ -132,6 +132,7 @@ struct Vis {
 	File *search_file;                   /* special internal file used to store /,? search prompt */
 	Win *windows;                        /* all windows currently managed by this editor instance */
 	Win *win;                            /* currently active/focused window */
+	Win *message_window;                 /* special window to display multi line messages */
 	Register registers[VIS_REG_INVALID]; /* registers used for yank and put */
 	Macro macros[VIS_MACRO_INVALID];     /* recorded macros */
 	Macro *recording, *last_recording;   /* currently (if non NULL) and least recently recorded macro */

vis-lua.c

@@ -78,6 +78,28 @@ static void stack_dump(lua_State *L, const char *format, ...) {
 
 #endif
 
+static int error_function(lua_State *L) {
+	Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
+	size_t len;
+	const char *msg = lua_tostring(L, 1);
+	if (msg)
+		luaL_traceback(L, L, msg, 1);
+	msg = lua_tolstring(L, 1, &len);
+	vis_message_show(vis, msg);
+	return 1;
+}
+
+static int pcall(Vis *vis, lua_State *L, int nargs, int nresults) {
+	/* insert a custom error function below all arguments */
+	int msgh = lua_gettop(L) - nargs;
+	lua_pushlightuserdata(L, vis);
+	lua_pushcclosure(L, error_function, 1);
+	lua_insert(L, msgh);
+	int ret = lua_pcall(L, nargs, nresults, msgh);
+	lua_remove(L, msgh);
+	return ret;
+}
+
 static void *obj_new(lua_State *L, size_t size, const char *type) {
 	void *obj = lua_newuserdata(L, size);
 	luaL_getmetatable(L, type);
@@ -586,10 +608,10 @@ void vis_lua_start(Vis *vis) {
 
 	lua_getglobal(L, "require");
 	lua_pushstring(L, "visrc");
-	lua_pcall(L, 1, 0, 0);
+	pcall(vis, L, 1, 0);
 	vis_lua_event(vis, "start");
 	if (lua_isfunction(L, -1))
-		lua_pcall(L, 0, 0, 0);
+		pcall(vis, L, 0, 0);
 	lua_pop(L, 1);
 }
 
@@ -599,7 +621,7 @@ void vis_lua_quit(Vis *vis) {
 		return;
 	vis_lua_event(vis, "quit");
 	if (lua_isfunction(L, -1))
-		lua_pcall(L, 0, 0, 0);
+		pcall(vis, L, 0, 0);
 	lua_pop(L, 1);
 	lua_close(L);
 }
@@ -617,7 +639,7 @@ void vis_lua_file_close(Vis *vis, File *file) {
 	vis_lua_event(vis, "file_close");
 	if (lua_isfunction(L, -1)) {
 		obj_ref_new(L, file, "vis.file");
-		lua_pcall(L, 1, 0, 0);
+		pcall(vis, L, 1, 0);
 	}
 	obj_ref_free(L, file->text);
 	obj_ref_free(L, file);
@@ -629,7 +651,7 @@ void vis_lua_win_open(Vis *vis, Win *win) {
 	vis_lua_event(vis, "win_open");
 	if (lua_isfunction(L, -1)) {
 		obj_ref_new(L, win, "vis.window");
-		lua_pcall(L, 1, 0, 0);
+		pcall(vis, L, 1, 0);
 	}
 	lua_pop(L, 1);
 }
@@ -639,7 +661,7 @@ void vis_lua_win_close(Vis *vis, Win *win) {
 	vis_lua_event(vis, "win_close");
 	if (lua_isfunction(L, -1)) {
 		obj_ref_new(L, win, "vis.window");
-		lua_pcall(L, 1, 0, 0);
+		pcall(vis, L, 1, 0);
 	}
 	obj_ref_free(L, win->view);
 	obj_ref_free(L, win);
@@ -663,7 +685,7 @@ bool vis_theme_load(Vis *vis, const char *name) {
 	lua_pop(L, 2);
 	lua_getglobal(L, "require");
 	lua_pushvalue(L, -2);
-	if (lua_pcall(L, 1, 0, 0))
+	if (pcall(vis, L, 1, 0))
 		return false;
 	for (Win *win = vis->windows; win; win = win->next)
 		view_syntax_set(win->view, view_syntax_get(win->view));

vis-prompt.c

@@ -187,3 +187,26 @@ void vis_info_hide(Vis *vis) {
 	vis->ui->info_hide(vis->ui);
 }
 
+void vis_message_show(Vis *vis, const char *msg) {
+	if (!msg)
+		return;
+	if (!vis->message_window) {
+		if (!vis_window_new(vis, NULL))
+			return;
+		vis->message_window = vis->win;
+	}
+
+	Win *win = vis->message_window;
+	Text *txt = win->file->text;
+	size_t pos = text_size(txt);
+	text_appendf(txt, "%s\n", msg);
+	text_save(txt, NULL);
+	view_cursor_to(win->view, pos);
+}
+
+void vis_message_hide(Vis *vis) {
+	if (!vis->message_window)
+		return;
+	vis_window_close(vis->message_window);
+	vis->message_window = NULL;
+}

vis.c

@@ -297,6 +297,8 @@ void vis_window_close(Win *win) {
 		vis->windows = win->next;
 	if (vis->win == win)
 		vis->win = win->next ? win->next : win->prev;
+	if (win == vis->message_window)
+		vis->message_window = NULL;
 	window_free(win);
 	if (vis->win)
 		vis->ui->window_focus(vis->win->ui);
@@ -309,8 +311,6 @@ Vis *vis_new(Ui *ui, VisEvent *event) {
 	Vis *vis = calloc(1, sizeof(Vis));
 	if (!vis)
 		return NULL;
-	if (event && event->vis_start)
-		event->vis_start(vis);
 	vis->ui = ui;
 	vis->ui->init(vis->ui, vis);
 	vis->tabwidth = 8;
@@ -324,6 +324,9 @@ Vis *vis_new(Ui *ui, VisEvent *event) {
 		goto err;
 	vis->mode_prev = vis->mode = &vis_modes[VIS_MODE_NORMAL];
 	vis->event = event;
+	if (event && event->vis_start)
+		event->vis_start(vis);
+	vis->ui->start(vis->ui);
 	return vis;
 err:
 	vis_free(vis);

vis.h

@@ -81,10 +81,14 @@ void vis_window_prev(Vis*);
 /* display a user prompt with a certain title and default text */
 void vis_prompt_show(Vis*, const char *title);
 
-/* display a message to the user */
+/* display a one line message to the user, will be hidden upon keypress */
 void vis_info_show(Vis*, const char *msg, ...);
 void vis_info_hide(Vis*);
 
+/* display an arbitrary long message in a special window/file */
+void vis_message_show(Vis*, const char *msg);
+void vis_message_hide(Vis*);
+
 /* these function operate on the currently focused window but make sure
  * that all windows which show the affected region are redrawn too. */
 void vis_insert(Vis*, size_t pos, const char *data, size_t len);