feat(lua): store "nvim -l" scriptname in _G.arg[0]

runtime/doc/starting.txt

@@ -218,15 +218,13 @@ argument.
 -l {script} [args]
 		Executes Lua {script} non-interactively (no UI) with optional
 		[args] after processing any preceding Nvim |cli-arguments|,
-		then exits. See |-S| to run multiple Lua scripts without args,
-		or in an interactive session.
+		then exits. Exits 1 on Lua error. See |-S| to run multiple Lua
+		scripts without args, with a UI.
 								    *lua-args*
-		All [args] are treated as {script} arguments and passed
-		literally to Lua (in the conventional `_G.arg` global table),
-		thus "-l" ends processing of Nvim arguments.
+		All [args] are treated as {script} arguments and stored in the
+		Lua `_G.arg` global table, thus "-l" ends processing of Nvim
+		arguments. The {script} name is stored at `_G.arg[0]`.
 		
-		Exits with code 1 on Lua error.
-
 		Sets 'verbose' to 1 (like "-V1"), so Lua `print()` writes to
 		output.
 

src/nvim/lua/executor.c

@@ -323,13 +323,12 @@ static int nlua_thr_api_nvim__get_runtime(lua_State *lstate)
   return 1;
 }
 
-/// Copies args starting at `lua_arg0` into the Lua `arg` global.
+/// Copies args starting at `lua_arg0` to Lua `_G.arg`, and sets `_G.arg[0]` to the scriptname.
 ///
-/// Example (`lua_arg0` points to "--arg1"):
+/// Example (arg[0] => "foo.lua", arg[1] => "--arg1", …):
 ///     nvim -l foo.lua --arg1 --arg2
 ///
-/// @note Lua CLI sets arguments upto "-e" as _negative_ `_G.arg` indices, but we currently don't
-/// follow that convention.
+/// @note Lua CLI sets args before "-e" as _negative_ `_G.arg` indices, but we currently don't.
 ///
 /// @see https://www.lua.org/pil/1.4.html
 /// @see https://github.com/premake/premake-core/blob/1c1304637f4f5e50ba8c57aae8d1d80ec3b7aaf2/src/host/premake.c#L563-L594
@@ -337,12 +336,19 @@ static int nlua_thr_api_nvim__get_runtime(lua_State *lstate)
 /// @returns number of args
 static int nlua_init_argv(lua_State *const L, char **argv, int argc, int lua_arg0)
 {
-  lua_newtable(L);  // _G.arg
   int i = 0;
-  for (; lua_arg0 >= 0 && i + lua_arg0 < argc; i++) {
-    lua_pushstring(L, argv[i + lua_arg0]);
-    lua_rawseti(L, -2, i + 1);  // _G.arg[i+1] = "arg1"
+  lua_newtable(L);  // _G.arg
+
+  if (lua_arg0 > 0) {
+    lua_pushstring(L, argv[lua_arg0 - 1]);
+    lua_rawseti(L, -2, 0);  // _G.arg[0] = "foo.lua"
+
+    for (; lua_arg0 >= 0 && i + lua_arg0 < argc; i++) {
+      lua_pushstring(L, argv[i + lua_arg0]);
+      lua_rawseti(L, -2, i + 1);  // _G.arg[i+1] = "--foo"
+    }
   }
+
   lua_setglobal(L, "arg");
   return i;
 }

test/functional/core/startup_spec.lua

@@ -108,7 +108,9 @@ describe('startup', function()
       assert_l_out([[
           bufs:
           nvim args: 7
-          lua args: { "-arg1", "--exitcode", "73", "--arg2" }]],
+          lua args: { "-arg1", "--exitcode", "73", "--arg2",
+            [0] = "test/functional/fixtures/startup.lua"
+          }]],
         {},
         { '-arg1', "--exitcode", "73", '--arg2' }
       )
@@ -126,11 +128,11 @@ describe('startup', function()
     end)
 
     it('executes stdin "-"', function()
-      assert_l_out('args=2 whoa',
+      assert_l_out('arg0=- args=2 whoa',
         nil,
         { 'arg1', 'arg 2' },
         '-',
-        "print(('args=%d %s'):format(#_G.arg, 'whoa'))")
+        "print(('arg0=%s args=%d %s'):format(_G.arg[0], #_G.arg, 'whoa'))")
       assert_l_out('biiig input: 1000042',
         nil,
         nil,
@@ -140,23 +142,15 @@ describe('startup', function()
     end)
 
     it('sets _G.arg', function()
-      -- nvim -l foo.lua -arg1 -- a b c
+      -- nvim -l foo.lua [args]
       assert_l_out([[
           bufs:
-          nvim args: 6
-          lua args: { "-arg1", "--arg2", "arg3" }]],
+          nvim args: 7
+          lua args: { "-arg1", "--arg2", "--", "arg3",
+            [0] = "test/functional/fixtures/startup.lua"
+          }]],
         {},
-        { '-arg1', '--arg2', 'arg3' }
-      )
-      eq(0, eval('v:shell_error'))
-
-      -- nvim -l foo.lua --
-      assert_l_out([[
-          bufs:
-          nvim args: 4
-          lua args: { "--" }]],
-        {},
-        { '--' }
+        { '-arg1', '--arg2', '--', 'arg3' }
       )
       eq(0, eval('v:shell_error'))
 
@@ -164,27 +158,21 @@ describe('startup', function()
       assert_l_out([[
           bufs: file1 file2
           nvim args: 10
-          lua args: { "-arg1", "arg 2", "--", "file3", "file4" }]],
+          lua args: { "-arg1", "arg 2", "--", "file3", "file4",
+            [0] = "test/functional/fixtures/startup.lua"
+          }]],
         { 'file1', 'file2', },
         { '-arg1', 'arg 2', '--', 'file3', 'file4' }
       )
       eq(0, eval('v:shell_error'))
 
-      -- nvim file1 file2 -l foo.lua -arg1 --
-      assert_l_out([[
-          bufs: file1 file2
-          nvim args: 7
-          lua args: { "-arg1", "--" }]],
-        { 'file1', 'file2', },
-        { '-arg1', '--' }
-      )
-      eq(0, eval('v:shell_error'))
-
       -- nvim -l foo.lua <vim args>
       assert_l_out([[
           bufs:
           nvim args: 5
-          lua args: { "-c", "set wrap?" }]],
+          lua args: { "-c", "set wrap?",
+            [0] = "test/functional/fixtures/startup.lua"
+          }]],
         {},
         { '-c', 'set wrap?' }
       )
@@ -198,7 +186,9 @@ describe('startup', function()
           
           bufs:
           nvim args: 7
-          lua args: { "-c", "set wrap?" }]],
+          lua args: { "-c", "set wrap?",
+            [0] = "test/functional/fixtures/startup.lua"
+          }]],
         { '-c', 'set wrap?' },
         { '-c', 'set wrap?' }
       )