vim-patch:8.0.1514: getting the list of changes is not easy

Problem:    Getting the list of changes is not easy.
Solution:   Add the getchangelist() function. (Yegappan Lakshmanan,
            closes vim/vim#2634)
07ad816525

runtime/doc/eval.txt

@@ -2081,6 +2081,7 @@ getbufline({expr}, {lnum} [, {end}])
 				List	lines {lnum} to {end} of buffer {expr}
 getbufvar({expr}, {varname} [, {def}])
 				any	variable {varname} in buffer {expr}
+getchangelist({expr})		List	list of change list items
 getchar([expr])		Number	get one character from the user
 getcharmod()			Number	modifiers for the last typed character
 getcharsearch()			Dict	last character search
@@ -4013,6 +4014,22 @@ getbufvar({expr}, {varname} [, {def}])				*getbufvar()*
 			:let bufmodified = getbufvar(1, "&mod")
 			:echo "todo myvar = " . getbufvar("todo", "myvar")
 <
+getchangelist({expr})					*getchangelist()*
+		Returns the |changelist| for the buffer {expr}. For the use
+		of {expr}, see |bufname()| above. If buffer {expr} doesn't
+		exist, an empty list is returned.
+
+		The returned list contains two entries: a list with the change
+		locations and the current position in the list.  Each
+		entry in the change list is a dictionary with the following
+		entries:
+			col		column number
+			coladd		column offset for 'virtualedit'
+			lnum		line number
+		If buffer {expr} is the current buffer, then the current
+		position refers to the position in the list. For other
+		buffers, it is set to the length of the list.
+
 getchar([expr])						*getchar()*
 		Get a single character from the user or input stream.
 		If [expr] is omitted, wait until a character is available.

runtime/doc/usr_41.txt

@@ -806,6 +806,7 @@ Buffers, windows and the argument list:
 	getbufinfo()		get a list with buffer information
 	gettabinfo()		get a list with tab page information
 	getwininfo()		get a list with window information
+	getchangelist()		get a list of change list entries
 	getjumplist()		get a list of jump list entries
 
 Command line:					*command-line-functions*

src/nvim/eval.c

@@ -9547,6 +9547,37 @@ f_getbufvar_end:
   }
 }
 
+// "getchangelist()" function
+static void f_getchangelist(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  tv_list_alloc_ret(rettv, 2);
+  const buf_T *const buf = find_buffer(&argvars[0]);
+  if (buf == NULL) {
+    return;
+  }
+
+  list_T *const l = tv_list_alloc(buf->b_changelistlen);
+  tv_list_append_list(rettv->vval.v_list, l);
+  // The current window change list index tracks only the position in the
+  // current buffer change list. For other buffers, use the change list
+  // length as the current index.
+  tv_list_append_number(rettv->vval.v_list,
+                        (buf == curwin->w_buffer)
+                        ? curwin->w_changelistidx
+                        : buf->b_changelistlen);
+
+  for (int i = 0; i < buf->b_changelistlen; i++) {
+    if (buf->b_changelist[i].mark.lnum == 0) {
+      continue;
+    }
+    dict_T *const d = tv_dict_alloc();
+    tv_list_append_dict(l, d);
+    tv_dict_add_nr(d, S_LEN("lnum"), buf->b_changelist[i].mark.lnum);
+    tv_dict_add_nr(d, S_LEN("col"), buf->b_changelist[i].mark.col);
+    tv_dict_add_nr(d, S_LEN("coladd"), buf->b_changelist[i].mark.coladd);
+  }
+}
+
 /*
  * "getchar()" function
  */

src/nvim/eval.lua

@@ -116,6 +116,7 @@ return {
     getbufinfo={args={0, 1}},
     getbufline={args={2, 3}},
     getbufvar={args={2, 3}},
+    getchangelist={args={1, 1}},
     getchar={args={0, 1}},
     getcharmod={},
     getcharsearch={},

src/nvim/testdir/test_changelist.vim

@@ -0,0 +1,48 @@
+" Tests for the changelist functionality
+
+" Tests for the getchangelist() function
+func Test_getchangelist()
+  if !has("jumplist")
+    return
+  endif
+
+  bwipe!
+  enew
+  call assert_equal([], getchangelist(10))
+  call assert_equal([[], 0], getchangelist(bufnr('%')))
+
+  call writefile(['line1', 'line2', 'line3'], 'Xfile1.txt')
+  call writefile(['line1', 'line2', 'line3'], 'Xfile2.txt')
+
+  edit Xfile1.txt
+  exe "normal 1Goline\<C-G>u1.1"
+  exe "normal 3Goline\<C-G>u2.1"
+  exe "normal 5Goline\<C-G>u3.1"
+  normal g;
+  call assert_equal([[
+	      \ {'lnum' : 2, 'col' : 4, 'coladd' : 0},
+	      \ {'lnum' : 4, 'col' : 4, 'coladd' : 0},
+	      \ {'lnum' : 6, 'col' : 4, 'coladd' : 0}], 2],
+	      \ getchangelist(bufnr('%')))
+
+  hide edit Xfile2.txt
+  exe "normal 1GOline\<C-G>u1.0"
+  exe "normal 2Goline\<C-G>u2.0"
+  call assert_equal([[
+	      \ {'lnum' : 1, 'col' : 6, 'coladd' : 0},
+	      \ {'lnum' : 3, 'col' : 6, 'coladd' : 0}], 2],
+	      \ getchangelist(bufnr('%')))
+  hide enew
+
+  call assert_equal([[
+	      \ {'lnum' : 2, 'col' : 4, 'coladd' : 0},
+	      \ {'lnum' : 4, 'col' : 4, 'coladd' : 0},
+	      \ {'lnum' : 6, 'col' : 4, 'coladd' : 0}], 3], getchangelist(2))
+  call assert_equal([[
+	      \ {'lnum' : 1, 'col' : 6, 'coladd' : 0},
+	      \ {'lnum' : 3, 'col' : 6, 'coladd' : 0}], 2], getchangelist(3))
+
+  bwipe!
+  call delete('Xfile1.txt')
+  call delete('Xfile2.txt')
+endfunc