vim-patch:8.2.0920: writing viminfo fails with a circular reference

Problem:    Writing viminfo fails with a circular reference.
Solution:   Use copyID to detect the cycle. (closes vim/vim#6217)
5b157fe2ed

src/nvim/shada.c

@@ -2679,7 +2679,30 @@ static ShaDaWriteResult shada_write(ShaDaWriteDef *const sd_writer,
       switch (vartv.v_type) {
         case VAR_FUNC:
         case VAR_PARTIAL:
+          tv_clear(&vartv);
           continue;
+        case VAR_DICT:
+          {
+            dict_T *di = vartv.vval.v_dict;
+            int copyID = get_copyID();
+            if (!set_ref_in_ht(&di->dv_hashtab, copyID, NULL)
+                && copyID == di->dv_copyID) {
+              tv_clear(&vartv);
+              continue;
+            }
+            break;
+          }
+        case VAR_LIST:
+          {
+            list_T *l = vartv.vval.v_list;
+            int copyID = get_copyID();
+            if (!set_ref_in_list(l, copyID, NULL)
+                && copyID == l->lv_copyID) {
+              tv_clear(&vartv);
+              continue;
+            }
+            break;
+          }
         default:
           break;
       }

test/functional/shada/errors_spec.lua

@@ -1,7 +1,7 @@
 -- ShaDa errors handling support
 local helpers = require('test.functional.helpers')(after_each)
-local nvim_command, eq, exc_exec, redir_exec =
+local nvim_command, eq, exc_exec =
-  helpers.command, helpers.eq, helpers.exc_exec, helpers.redir_exec
+  helpers.command, helpers.eq, helpers.exc_exec
 
 local shada_helpers = require('test.functional.shada.helpers')
 local reset, clear, get_shada_rw =
@@ -494,15 +494,6 @@ $
     eq(0, exc_exec('wshada! ' .. shada_fname))
   end)
 
-  it('errors when a self-referencing list is stored in a variable', function()
-    nvim_command('let L = []')
-    nvim_command('call add(L, L)')
-    nvim_command('set shada+=!')
-    eq('\nE5005: Unable to dump variable g:L: container references itself in index 0'
-       .. '\nE574: Failed to write variable L',
-       redir_exec('wshada'))
-  end)
-
   it('errors with too large items', function()
     wshada({
         1, 206,  70,  90,  31, 179,  86, 133, 169, 103, 101, 110, 101, 114,  97,

test/functional/shada/variables_spec.lua

@@ -1,7 +1,7 @@
 -- ShaDa variables saving/reading support
 local helpers = require('test.functional.helpers')(after_each)
-local meths, funcs, nvim_command, eq, exc_exec =
+local meths, funcs, nvim_command, eq =
-  helpers.meths, helpers.funcs, helpers.command, helpers.eq, helpers.exc_exec
+  helpers.meths, helpers.funcs, helpers.command, helpers.eq
 
 local shada_helpers = require('test.functional.shada.helpers')
 local reset, clear = shada_helpers.reset, shada_helpers.clear
@@ -145,16 +145,15 @@ describe('ShaDa support code', function()
     eq('10', meths.get_var('U'))
   end)
 
-  it('errors and writes when a self-referencing list is stored in a variable',
+  it('ignore when a self-referencing list is stored in a variable',
   function()
     meths.set_var('L', {})
     nvim_command('call add(L, L)')
     meths.set_var('U', '10')
     nvim_command('set shada+=!')
-    eq('Vim(wshada):E5005: Unable to dump variable g:L: container references itself in index 0',
+    nvim_command('wshada')
-       exc_exec('wshada'))
+    reset()
-    meths.set_option('shada', '')
+    nvim_command('rshada')
-    reset('set shada+=!')
     eq('10', meths.get_var('U'))
   end)
 end)