vim-patch:8.2.1347: cannot easily get the script ID

Problem:    Cannot easily get the script ID.
Solution:   Support expand('<SID>').
909443028b

runtime/doc/map.txt

@@ -1078,6 +1078,10 @@ When executing an autocommand or a user command, it will run in the context of
 the script it was defined in.  This makes it possible that the command calls a
 local function or uses a local mapping.
 
+In case the value is used in a context where <SID> cannot be correctly
+expanded, use the expand() function: >
+	let &includexpr = expand('<SID>') .. 'My_includeexpr()'
+
 Otherwise, using "<SID>" outside of a script context is an error.
 
 If you need to get the script number to use in a complicated script, you can

src/nvim/ex_docmd.c

@@ -8617,14 +8617,20 @@ ssize_t find_cmdline_var(const char_u *src, size_t *usedlen)
 #define SPEC_SFILE  (SPEC_CFILE + 1)
     "<slnum>",                          // ":so" file line number
 #define SPEC_SLNUM  (SPEC_SFILE + 1)
+    "<stack>",                          // call stack
+#define SPEC_STACK  (SPEC_SLNUM + 1)
     "<afile>",                          // autocommand file name
-#define SPEC_AFILE  (SPEC_SLNUM + 1)
+#define SPEC_AFILE  (SPEC_STACK + 1)
     "<abuf>",                           // autocommand buffer number
 #define SPEC_ABUF   (SPEC_AFILE + 1)
     "<amatch>",                         // autocommand match name
 #define SPEC_AMATCH (SPEC_ABUF + 1)
     "<sflnum>",                         // script file line number
 #define SPEC_SFLNUM (SPEC_AMATCH + 1)
+    "<SID>",                            // script ID: <SNR>123_
+#define SPEC_SID  (SPEC_SFLNUM + 1)
+    "<client>"
+#define SPEC_CLIENT (SPEC_SID + 1)
   };
 
   for (size_t i = 0; i < ARRAY_SIZE(spec_str); ++i) {
@@ -8871,6 +8877,16 @@ eval_vars (
       result = (char_u *)strbuf;
       break;
 
+    case SPEC_SID:
+      if (current_sctx.sc_sid <= 0) {
+        *errormsg = (char_u *)_(e_usingsid);
+        return NULL;
+      }
+      snprintf(strbuf, sizeof(strbuf), "<SNR>%" PRIdSCID "_",
+               current_sctx.sc_sid);
+      result = (char_u *)strbuf;
+      break;
+
     default:
       // should not happen
       *errormsg = (char_u *)"";

src/nvim/testdir/test_expand_func.vim

@@ -1,5 +1,7 @@
 " Tests for expand()
 
+source shared.vim
+
 let s:sfile = expand('<sfile>')
 let s:slnum = str2nr(expand('<slnum>'))
 let s:sflnum = str2nr(expand('<sflnum>'))
@@ -16,6 +18,25 @@ func s:expand_sflnum()
   return str2nr(expand('<sflnum>'))  
 endfunc
 
+" This test depends on the location in the test file, put it first.
+func Test_expand_sflnum()
+  call assert_equal(7, s:sflnum)
+  call assert_equal(24, str2nr(expand('<sflnum>')))
+
+  " Line-continuation
+  call assert_equal(
+        \ 27,
+        \ str2nr(expand('<sflnum>')))
+
+  " Call in script-local function
+  call assert_equal(18, s:expand_sflnum())
+
+  " Call in command
+  command Flnum echo expand('<sflnum>')
+  call assert_equal(36, str2nr(trim(execute('Flnum'))))
+  delcommand Flnum
+endfunc
+
 func Test_expand_sfile()
   call assert_match('test_expand_func\.vim$', s:sfile)
   call assert_match('^function .*\.\.Test_expand_sfile$', expand('<sfile>'))
@@ -30,7 +51,7 @@ func Test_expand_sfile()
 endfunc
 
 func Test_expand_slnum()
-  call assert_equal(4, s:slnum)
+  call assert_equal(6, s:slnum)
   call assert_equal(2, str2nr(expand('<slnum>')))
 
   " Line-continuation
@@ -47,20 +68,14 @@ func Test_expand_slnum()
   delcommand Slnum
 endfunc
 
-func Test_expand_sflnum()
+func s:sid_test()
-  call assert_equal(5, s:sflnum)
+  return 'works'
-  call assert_equal(52, str2nr(expand('<sflnum>')))
-
-  " Line-continuation
-  call assert_equal(
-        \ 55,
-        \ str2nr(expand('<sflnum>')))
-
-  " Call in script-local function
-  call assert_equal(16, s:expand_sflnum())
-
-  " Call in command
-  command Flnum echo expand('<sflnum>')
-  call assert_equal(64, str2nr(trim(execute('Flnum'))))
-  delcommand Flnum
 endfunc
+
+func Test_expand_SID()
+  let sid = expand('<SID>')
+  execute 'let g:sid_result = ' .. sid .. 'sid_test()'
+  call assert_equal('works', g:sid_result)
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab