Make pushString and pushStringZ always return a string

In Lua 5.1, LuaJIT, and Luau, pushlstring does not return the pushed
string. I think it is better to make this consistent with the later
versions of Lua in the Zig wrapper, so we can use toString to get the
most recently pushed string.

Though this makes an additional API call for the above mentioned
versions, I think the added consistency is worth it.

Going forward I want to remove as much switch (lang) as possible.

Author: natecraddock

src/lib.zig

@@ -1530,15 +1530,13 @@ pub const Lua = struct {
 
     /// Pushes the string onto the stack. Returns a slice pointing to Lua's internal copy of the string
     /// See https://www.lua.org/manual/5.4/manual.html#lua_pushlstring
-    pub fn pushString(lua: *Lua, str: []const u8) switch (lang) {
-        .lua51, .luajit, .luau => void,
-        else => []const u8,
-    } {
+    pub fn pushString(lua: *Lua, str: []const u8) [:0]const u8 {
         switch (lang) {
             .lua51, .luajit, .luau => {
                 c.lua_pushlstring(lua.state, str.ptr, str.len);
+                return lua.toString(-1) catch unreachable;
             },
-            else => return c.lua_pushlstring(lua.state, str.ptr, str.len)[0..str.len],
+            else => return c.lua_pushlstring(lua.state, str.ptr, str.len)[0..str.len :0],
         }
     }
 
@@ -1558,13 +1556,11 @@ pub const Lua = struct {
     /// Lua makes a copy of the string so `str` may be freed immediately after return
     /// Returns a pointer to the internal Lua string
     /// See https://www.lua.org/manual/5.4/manual.html#lua_pushstring
-    pub fn pushStringZ(lua: *Lua, str: [:0]const u8) switch (lang) {
-        .lua51, .luajit, .luau => void,
-        else => [:0]const u8,
-    } {
+    pub fn pushStringZ(lua: *Lua, str: [:0]const u8) [:0]const u8 {
         switch (lang) {
             .lua51, .luajit, .luau => {
                 c.lua_pushstring(lua.state, str.ptr);
+                return lua.toString(-1) catch unreachable;
             },
             else => return c.lua_pushstring(lua.state, str.ptr)[0..str.len :0],
         }

src/tests.zig

@@ -320,7 +320,7 @@ test "type of and getting values" {
     try expect(lua.isThread(-1));
     try expectEqual(lua.state, (try lua.toThread(-1)).state);
 
-    _ = lua.pushStringZ("all your codebase are belong to us");
+    try expectEqualStrings("all your codebase are belong to us", lua.pushStringZ("all your codebase are belong to us"));
     try expectEqual(.string, lua.typeOf(-1));
     try expect(lua.isString(-1));
 
@@ -330,7 +330,7 @@ test "type of and getting values" {
     try expect(lua.isFunction(-1));
     try expectEqual(ziglua.wrap(add), try lua.toCFunction(-1));
 
-    _ = lua.pushString("hello world");
+    try expectEqualStrings("hello world", lua.pushString("hello world"));
     try expectEqual(.string, lua.typeOf(-1));
     try expect(lua.isString(-1));
 
@@ -1572,7 +1572,7 @@ test "ref luau" {
 
     // In luau lua.ref does not pop the item from the stack
     // and the data is stored in the registry_index by default
-    lua.pushString("Hello there");
+    _ = lua.pushString("Hello there");
     const ref = try lua.ref(2);
 
     _ = lua.rawGetIndex(ziglua.registry_index, ref);
@@ -1846,7 +1846,7 @@ test "objectLen" {
     var lua = try Lua.init(&testing.allocator);
     defer lua.deinit();
 
-    lua.pushStringZ("lua");
+    _ = lua.pushStringZ("lua");
     try testing.expectEqual(3, lua.objectLen(-1));
 }
 
@@ -2346,7 +2346,7 @@ test "namecall" {
     lua.pushVector(0, 0, 0);
 
     try lua.newMetatable("vector");
-    lua.pushStringZ("__namecall");
+    _ = lua.pushStringZ("__namecall");
     lua.pushFunctionNamed(ziglua.wrap(funcs.vectorNamecall), "vector_namecall");
     lua.setTable(-3);