vim-patch:8.1.0493: argv() and argc() only work on the current argument list

Problem:    argv() and argc() only work on the current argument list.
Solution:   Add a window ID argument. (Yegappan Lakshmanan, closes vim/vim#832)

https://github.com/vim/vim/commit/e6e3989c1b3f18907a0c305712b867e9a3821369

3 files changed, 127 insertions, 30 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index db278b2fb0..f5817279df 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1970,11 +1970,11 @@ and({expr}, {expr})		Number  bitwise AND
 api_info()			Dict	api metadata
 append({lnum}, {string})	Number	append {string} below line {lnum}
 append({lnum}, {list})		Number	append lines {list} below line {lnum}
-argc()				Number	number of files in the argument list
+argc([{winid}])			Number	number of files in the argument list
 argidx()			Number	current index in the argument list
 arglistid([{winnr} [, {tabnr}]]) Number	argument list id
-argv({nr})			String	{nr} entry of the argument list
-argv()				List	the argument list
+argv({nr} [, {winid}])		String	{nr} entry of the argument list
+argv([-1, {winid}])		List	the argument list
 assert_equal({exp}, {act} [, {msg}])
 				none	assert {exp} is equal to {act}
 assert_exception({error} [, {msg}])
@@ -2446,8 +2446,15 @@ append({lnum}, {text})					*append()*
 			:let failed = append(0, ["Chapter 1", "the beginning"])
 <
 							*argc()*
-argc()		The result is the number of files in the argument list of the
-		current window.  See |arglist|.
+argc([{winid}])
+		The result is the number of files in the argument list.  See
+		|arglist|.
+		If {winid} is not supplied, the argument list of the current
+		window is used.
+		If {winid} is -1, the global argument list is used.
+		Otherwise {winid} specifies the window of which the argument
+		list is used: either the window number or the window ID.
+		Returns -1 if the {winid} argument is invalid.
 
 							*argidx()*
 argidx()	The result is the current index in the argument list.  0 is
@@ -2458,7 +2465,7 @@ arglistid([{winnr} [, {tabnr}]])
 		Return the argument list ID.  This is a number which
 		identifies the argument list being used.  Zero is used for the
 		global argument list.  See |arglist|.
-		Return -1 if the arguments are invalid.
+		Returns -1 if the arguments are invalid.
 
 		Without arguments use the current window.
 		With {winnr} only use this window in the current tab page.
@@ -2467,17 +2474,19 @@ arglistid([{winnr} [, {tabnr}]])
 		{winnr} can be the window number or the |window-ID|.
 
 							*argv()*
-argv([{nr}])	The result is the {nr}th file in the argument list of the
-		current window.  See |arglist|.  "argv(0)" is the first one.
-		Example: >
+argv([{nr} [, {winid}])
+		The result is the {nr}th file in the argument list.  See
+		|arglist|.  "argv(0)" is the first one.  Example: >
 	:let i = 0
 	:while i < argc()
 	:  let f = escape(fnameescape(argv(i)), '.')
 	:  exe 'amenu Arg.' . f . ' :e ' . f . '<CR>'
 	:  let i = i + 1
 	:endwhile
-<		Without the {nr} argument a |List| with the whole |arglist| is
-		returned.
+<		Without the {nr} argument, or when {nr} is -1, a |List| with
+		the whole |arglist| is returned.
+
+		The {winid} argument specifies the window ID, see |argc()|.
 
 							*assert_equal()*
 assert_equal({expected}, {actual}, [, {msg}])
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 68a0c86583..833a5073c4 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -6662,12 +6662,24 @@ static void f_append(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     rettv->vval.v_number = 1;           /* Failed */
 }
 
-/*
- * "argc()" function
- */
 static void f_argc(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
-  rettv->vval.v_number = ARGCOUNT;
+  if (argvars[0].v_type == VAR_UNKNOWN) {
+    // use the current window
+    rettv->vval.v_number = ARGCOUNT;
+  } else if (argvars[0].v_type == VAR_NUMBER
+             && tv_get_number(&argvars[0]) == -1) {
+    // use the global argument list
+    rettv->vval.v_number = GARGCOUNT;
+  } else {
+    // use the argument list of the specified window
+    win_T *wp = find_win_by_nr_or_id(&argvars[0]);
+    if (wp != NULL) {
+      rettv->vval.v_number = WARGCOUNT(wp);
+    } else {
+      rettv->vval.v_number = -1;
+    }
+  }
 }
 
 /*
@@ -6688,28 +6700,54 @@ static void f_arglistid(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
+/// Get the argument list for a given window
+static void get_arglist_as_rettv(aentry_T *arglist, int argcount,
+                                 typval_T *rettv)
+{
+  tv_list_alloc_ret(rettv, argcount);
+  if (arglist != NULL) {
+    for (int idx = 0; idx < argcount; idx++) {
+      tv_list_append_string(rettv->vval.v_list,
+                            (const char *)alist_name(&arglist[idx]), -1);
+    }
+  }
+}
+
 /*
  * "argv(nr)" function
  */
 static void f_argv(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
-  int idx;
+  aentry_T *arglist = NULL;
+  int argcount = -1;
 
   if (argvars[0].v_type != VAR_UNKNOWN) {
-    idx = (int)tv_get_number_chk(&argvars[0], NULL);
-    if (idx >= 0 && idx < ARGCOUNT) {
-      rettv->vval.v_string = (char_u *)xstrdup(
-          (const char *)alist_name(&ARGLIST[idx]));
+    if (argvars[1].v_type == VAR_UNKNOWN) {
+      arglist = ARGLIST;
+      argcount = ARGCOUNT;
+    } else if (argvars[1].v_type == VAR_NUMBER
+               && tv_get_number(&argvars[1]) == -1) {
+      arglist = GARGLIST;
+      argcount = GARGCOUNT;
     } else {
-      rettv->vval.v_string = NULL;
+      win_T *wp = find_win_by_nr_or_id(&argvars[1]);
+      if (wp != NULL) {
+        // Use the argument list of the specified window
+        arglist = WARGLIST(wp);
+        argcount = WARGCOUNT(wp);
+      }
     }
     rettv->v_type = VAR_STRING;
-  } else {
-    tv_list_alloc_ret(rettv, ARGCOUNT);
-    for (idx = 0; idx < ARGCOUNT; idx++) {
-      tv_list_append_string(rettv->vval.v_list,
-                            (const char *)alist_name(&ARGLIST[idx]), -1);
+    rettv->vval.v_string = NULL;
+    int idx = tv_get_number_chk(&argvars[0], NULL);
+    if (arglist != NULL && idx >= 0 && idx < argcount) {
+      rettv->vval.v_string = (char_u *)xstrdup(
+          (const char *)alist_name(&arglist[idx]));
+    } else if (idx == -1) {
+      get_arglist_as_rettv(arglist, argcount, rettv);
     }
+  } else {
+    get_arglist_as_rettv(ARGLIST, ARGCOUNT, rettv);
   }
 }
 
@@ -8219,6 +8257,19 @@ static void f_exepath(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   rettv->vval.v_string = path;
 }
 
+/// Find a window: When using a Window ID in any tab page, when using a number
+/// in the current tab page.
+win_T * find_win_by_nr_or_id(typval_T *vp)
+{
+  int nr = (int)tv_get_number_chk(vp, NULL);
+
+  if (nr >= LOWEST_WIN_ID) {
+    return win_id2wp(vp);
+  }
+
+  return find_win_by_nr(vp, NULL);
+}
+
 /*
  * "exists()" function
  */
@@ -11205,7 +11256,6 @@ static void f_index(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
 static int inputsecret_flag = 0;
 
-
 /*
  * This function is used by f_input() and f_inputdialog() functions. The third
  * argument to f_input() specifies the type of completion to use at the
@@ -16667,7 +16717,6 @@ static void f_tabpagebuflist(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
-
 /*
  * "tabpagenr()" function
  */
@@ -16748,7 +16797,6 @@ static void f_tabpagewinnr(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   rettv->vval.v_number = nr;
 }
 
-
 /*
  * "tagfiles()" function
  */
diff --git a/src/nvim/testdir/test_arglist.vim b/src/nvim/testdir/test_arglist.vim
index 368fc9810d..ae975fe137 100644
--- a/src/nvim/testdir/test_arglist.vim
+++ b/src/nvim/testdir/test_arglist.vim
@@ -240,13 +240,53 @@ func Test_arglistid()
   call assert_equal(0, arglistid())
 endfunc
 
-" Test for argv()
+" Tests for argv() and argc()
 func Test_argv()
   call Reset_arglist()
   call assert_equal([], argv())
   call assert_equal("", argv(2))
+  call assert_equal(0, argc())
   argadd a b c d
+  call assert_equal(4, argc())
   call assert_equal('c', argv(2))
+
+  let w1_id = win_getid()
+  split
+  let w2_id = win_getid()
+  arglocal
+  args e f g
+  tabnew
+  let w3_id = win_getid()
+  split
+  let w4_id = win_getid()
+  argglobal
+  tabfirst
+  call assert_equal(4, argc(w1_id))
+  call assert_equal('b', argv(1, w1_id))
+  call assert_equal(['a', 'b', 'c', 'd'], argv(-1, w1_id))
+
+  call assert_equal(3, argc(w2_id))
+  call assert_equal('f', argv(1, w2_id))
+  call assert_equal(['e', 'f', 'g'], argv(-1, w2_id))
+
+  call assert_equal(3, argc(w3_id))
+  call assert_equal('e', argv(0, w3_id))
+  call assert_equal(['e', 'f', 'g'], argv(-1, w3_id))
+
+  call assert_equal(4, argc(w4_id))
+  call assert_equal('c', argv(2, w4_id))
+  call assert_equal(['a', 'b', 'c', 'd'], argv(-1, w4_id))
+
+  call assert_equal(4, argc(-1))
+  call assert_equal(3, argc())
+  call assert_equal('d', argv(3, -1))
+  call assert_equal(['a', 'b', 'c', 'd'], argv(-1, -1))
+  tabonly | only | enew!
+  " Negative test cases
+  call assert_equal(-1, argc(100))
+  call assert_equal('', argv(1, 100))
+  call assert_equal([], argv(-1, 100))
+  call assert_equal('', argv(10, -1))
 endfunc
 
 " Test for the :argedit command