[tarantool-patches] [PATCH v2 1/2] lua: new function luaT_return_error()

[imeevma@tarantool.org]

Currently, if we have to return errors using the format
'return nil, error', we must do it manually. Since this error
return method is described in our Lua coding style, it makes sense
to create a function that will return an error in this format.
This patch creates a function.

Needed for #4390
---
 src/box/lua/session.c | 12 +++------
 src/lua/error.c       | 10 +++++++
 src/lua/error.h       |  9 +++++++
 src/lua/fio.c         | 74 +++++++++++++--------------------------------------
 src/lua/swim.c        |  7 +++--
 5 files changed, 45 insertions(+), 67 deletions(-)

diff --git a/src/box/lua/session.c b/src/box/lua/session.c
index c0ac491..b6b2c07 100644
--- a/src/box/lua/session.c
+++ b/src/box/lua/session.c
@@ -395,14 +395,10 @@ lbox_session_push(struct lua_State *L)
 	}
 	struct port port;
 	port_lua_create(&port, L);
-	if (session_push(session, sync, &port) != 0) {
-		lua_pushnil(L);
-		luaT_pusherror(L, box_error_last());
-		return 2;
-	} else {
-		lua_pushboolean(L, true);
-		return 1;
-	}
+	if (session_push(session, sync, &port) != 0)
+		return luaT_return_error(L);
+	lua_pushboolean(L, true);
+	return 1;
 }
 
 /**
diff --git a/src/lua/error.c b/src/lua/error.c
index fca87f9..8cb7ca0 100644
--- a/src/lua/error.c
+++ b/src/lua/error.c
@@ -104,6 +104,16 @@ luaT_error(lua_State *L)
 	return 0;
 }
 
+int
+luaT_return_error(lua_State *L)
+{
+	struct error *e = diag_last_error(&fiber()->diag);
+	assert(e != NULL);
+	lua_pushnil(L);
+	luaT_pusherror(L, e);
+	return 2;
+}
+
 void
 tarantool_lua_error_init(struct lua_State *L)
 {
diff --git a/src/lua/error.h b/src/lua/error.h
index 67a43da..2d622d3 100644
--- a/src/lua/error.h
+++ b/src/lua/error.h
@@ -49,6 +49,15 @@ struct error;
 LUA_API int
 luaT_error(lua_State *L);
 
+/**
+ * Return nil as the first return value and an error as the
+ * second. The error is received using box_error_last().
+ *
+ * @param L Lua stack.
+ */
+LUA_API int
+luaT_return_error(lua_State *L);
+
 void
 luaT_pusherror(struct lua_State *L, struct error *e);
 /** \endcond public */
diff --git a/src/lua/fio.c b/src/lua/fio.c
index 55fa667..cb7e31e 100644
--- a/src/lua/fio.c
+++ b/src/lua/fio.c
@@ -47,11 +47,9 @@
 #include "lua/utils.h"
 #include "coio_file.h"
 
-static inline void
-lbox_fio_pushsyserror(struct lua_State *L)
-{
-	diag_set(SystemError, "fio: %s", strerror(errno));
-	luaT_pusherror(L, diag_get()->last);
+#define lbox_fio_pushsyserror(L) {				\
+	diag_set(SystemError, "fio: %s", strerror(errno));	\
+	return luaT_return_error(L);				\
 }
 
 static int
@@ -69,11 +67,8 @@ usage:
 	int mode = lua_tointeger(L, 3);
 
 	int fh = coio_file_open(pathname, flags, mode);
-	if (fh < 0) {
-		lua_pushnil(L);
+	if (fh < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushinteger(L, fh);
 	return 1;
 }
@@ -90,11 +85,8 @@ lbox_fio_pwrite(struct lua_State *L)
 	size_t offset = lua_tonumber(L, 4);
 
 	int res = coio_pwrite(fh, buf, len, offset);
-	if (res < 0) {
-		lua_pushnil(L);
+	if (res < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushinteger(L, res);
 	return 1;
 }
@@ -115,11 +107,8 @@ lbox_fio_pread(struct lua_State *L)
 
 	int res = coio_pread(fh, buf, len, offset);
 
-	if (res < 0) {
-		lua_pushnil(L);
+	if (res < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushinteger(L, res);
 	return 1;
 }
@@ -129,7 +118,10 @@ lbox_fio_pushbool(struct lua_State *L, bool res)
 {
 	lua_pushboolean(L, res);
 	if (!res) {
-		lbox_fio_pushsyserror(L);
+		diag_set(SystemError, "fio: %s", strerror(errno));
+		struct error *e = diag_last_error(diag_get());
+		assert(e != NULL);
+		luaT_pusherror(L, e);
 		return 2;
 	}
 	return 1;
@@ -211,11 +203,8 @@ lbox_fio_write(struct lua_State *L)
 	size_t len = lua_tonumber(L, 3);
 
 	int res = coio_write(fh, buf, len);
-	if (res < 0) {
-		lua_pushnil(L);
+	if (res < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushinteger(L, res);
 	return 1;
 }
@@ -298,11 +287,8 @@ lbox_fio_read(struct lua_State *L)
 
 	int res = coio_read(fh, buf, len);
 
-	if (res < 0) {
-		lua_pushnil(L);
+	if (res < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushinteger(L, res);
 	return 1;
 }
@@ -371,11 +357,8 @@ DEF_STAT_METHOD(is_sock, S_ISSOCK);
 static int
 lbox_fio_pushstat(struct lua_State *L, int res, const struct stat *stat)
 {
-	if (res < 0) {
-		lua_pushnil(L);
+	if (res < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_newtable(L);
 
 	PUSHTABLE("dev", lua_pushinteger, stat->st_dev);
@@ -518,11 +501,8 @@ lbox_fio_listdir(struct lua_State *L)
 	}
 	pathname = lua_tostring(L, 1);
 	char *buf;
-	if (coio_readdir(pathname, &buf) < 0) {
-		lua_pushnil(L);
+	if (coio_readdir(pathname, &buf) < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushstring(L, buf);
 	free(buf);
 	return 1;
@@ -613,11 +593,8 @@ usage:
 		goto usage;
 	char *path = (char *)lua_newuserdata(L, PATH_MAX);
 	int res = coio_readlink(pathname, path, PATH_MAX);
-	if (res < 0) {
-		lua_pushnil(L);
+	if (res < 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushlstring(L, path, res);
 	lua_remove(L, -2);
 	return 1;
@@ -629,16 +606,11 @@ lbox_fio_tempdir(struct lua_State *L)
 	char *buf = (char *)lua_newuserdata(L, PATH_MAX);
 	if (!buf) {
 		errno = ENOMEM;
-		lua_pushnil(L);
 		lbox_fio_pushsyserror(L);
-		return 2;
 	}
 
-	if (coio_tempdir(buf, PATH_MAX) != 0) {
-		lua_pushnil(L);
+	if (coio_tempdir(buf, PATH_MAX) != 0)
 		lbox_fio_pushsyserror(L);
-		return 2;
-	}
 	lua_pushstring(L, buf);
 	lua_remove(L, -2);
 	return 1;
@@ -650,20 +622,12 @@ lbox_fio_cwd(struct lua_State *L)
 	char *buf = (char *)lua_newuserdata(L, PATH_MAX);
 	if (!buf) {
 		errno = ENOMEM;
-		lua_pushnil(L);
 		lbox_fio_pushsyserror(L);
-		return 2;
 	}
-
-
-	if (getcwd(buf, PATH_MAX)) {
-		lua_pushstring(L, buf);
-		lua_remove(L, -2);
-	} else {
+	if (getcwd(buf, PATH_MAX) == NULL)
 		lbox_fio_pushsyserror(L);
-		lua_pushnil(L);
-		return 2;
-	}
+	lua_pushstring(L, buf);
+	lua_remove(L, -2);
 	return 1;
 }
 
diff --git a/src/lua/swim.c b/src/lua/swim.c
index 26646f4..6c35f9f 100644
--- a/src/lua/swim.c
+++ b/src/lua/swim.c
@@ -69,11 +69,10 @@ lua_swim_new(struct lua_State *L)
 {
 	uint64_t generation = luaL_checkuint64(L, 1);
 	struct swim *s = swim_new(generation);
+	if (s == NULL)
+		return luaT_return_error(L);
 	*(struct swim **) luaL_pushcdata(L, ctid_swim_ptr) = s;
-	if (s != NULL)
-		return 1;
-	luaT_pusherror(L, diag_last_error(diag_get()));
-	return 2;
+	return 1;
 }
 
 /**
-- 
2.7.4