vim-patch:9.1.0335: String interpolation fails for List type (#28364)

Problem:  String interpolation fails for List type
Solution: use implicit string(list) for string interpolation and :put =
          (Yegappan Lakshmanan)

related: vim/vim#14529
closes: vim/vim#14556

bce51d9005

Cherry-pick eval_to_string_eap() from patch 8.2.1914.

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/nvim/eval.c

@@ -969,13 +969,12 @@ int skip_expr(char **pp, evalarg_T *const evalarg)
 
 /// Convert "tv" to a string.
 ///
-/// @param convert  when true convert a List into a sequence of lines
+/// @param join_list  when true convert a List into a sequence of lines.
-///                 and a Dict into a textual representation of the Dict.
 ///
 /// @return  an allocated string.
-static char *typval2string(typval_T *tv, bool convert)
+static char *typval2string(typval_T *tv, bool join_list)
 {
-  if (convert && tv->v_type == VAR_LIST) {
+  if (join_list && tv->v_type == VAR_LIST) {
     garray_T ga;
     ga_init(&ga, (int)sizeof(char), 80);
     if (tv->vval.v_list != NULL) {
@@ -986,7 +985,7 @@ static char *typval2string(typval_T *tv, bool convert)
     }
     ga_append(&ga, NUL);
     return (char *)ga.ga_data;
-  } else if (convert && tv->v_type == VAR_DICT) {
+  } else if (tv->v_type == VAR_LIST || tv->v_type == VAR_DICT) {
     return encode_tv2string(tv, NULL);
   }
   return xstrdup(tv_get_string(tv));
@@ -994,18 +993,20 @@ static char *typval2string(typval_T *tv, bool convert)
 
 /// Top level evaluation function, returning a string.
 ///
-/// @param convert  when true convert a List into a sequence of lines.
+/// @param join_list  when true convert a List into a sequence of lines.
 ///
 /// @return  pointer to allocated memory, or NULL for failure.
-char *eval_to_string(char *arg, bool convert)
+char *eval_to_string_eap(char *arg, bool join_list, exarg_T *eap)
 {
   typval_T tv;
   char *retval;
 
-  if (eval0(arg, &tv, NULL, &EVALARG_EVALUATE) == FAIL) {
+  evalarg_T evalarg;
+  fill_evalarg_from_eap(&evalarg, eap, eap != NULL && eap->skip);
+  if (eval0(arg, &tv, NULL, &evalarg) == FAIL) {
     retval = NULL;
   } else {
-    retval = typval2string(&tv, convert);
+    retval = typval2string(&tv, join_list);
     tv_clear(&tv);
   }
   clear_evalarg(&EVALARG_EVALUATE, NULL);
@@ -1013,6 +1014,11 @@ char *eval_to_string(char *arg, bool convert)
   return retval;
 }
 
+char *eval_to_string(char *arg, bool join_list)
+{
+  return eval_to_string_eap(arg, join_list, NULL);
+}
+
 /// Call eval_to_string() without using current local variables and using
 /// textlock.
 ///

src/nvim/eval/vars.c

@@ -88,7 +88,7 @@ char *eval_one_expr_in_str(char *p, garray_T *gap, bool evaluate)
   }
   if (evaluate) {
     *block_end = NUL;
-    char *expr_val = eval_to_string(block_start, true);
+    char *expr_val = eval_to_string(block_start, false);
     *block_end = '}';
     if (expr_val == NULL) {
       return NULL;

test/old/testdir/test_expr.vim

@@ -907,6 +907,18 @@ func Test_string_interp()
     #" Dict interpolation
     VAR d = {'a': 10, 'b': [1, 2]}
     call assert_equal("{'a': 10, 'b': [1, 2]}", $'{d}')
+    VAR emptydict = {}
+    call assert_equal("a{}b", $'a{emptydict}b')
+    VAR nulldict = v:_null_dict
+    call assert_equal("a{}b", $'a{nulldict}b')
+
+    #" List interpolation
+    VAR l = ['a', 'b', 'c']
+    call assert_equal("['a', 'b', 'c']", $'{l}')
+    VAR emptylist = []
+    call assert_equal("a[]b", $'a{emptylist}b')
+    VAR nulllist = v:_null_list
+    call assert_equal("a[]b", $'a{nulllist}b')
 
     #" Stray closing brace.
     call assert_fails('echo $"moo}"', 'E1278:')

test/old/testdir/test_let.vim

@@ -694,6 +694,41 @@ END
   END
   call assert_equal(["let d2 = {'a': 10, 'b': 'ss', 'c': {}}"], code)
 
+  " Empty dictionary
+  let d1 = {}
+  let code =<< eval trim END
+    let d2 = {d1}
+  END
+  call assert_equal(["let d2 = {}"], code)
+
+  " null dictionary
+  let d1 = v:_null_dict
+  let code =<< eval trim END
+    let d2 = {d1}
+  END
+  call assert_equal(["let d2 = {}"], code)
+
+  " Evaluate a List
+  let l1 = ['a', 'b', 'c']
+  let code =<< eval trim END
+    let l2 = {l1}
+  END
+  call assert_equal(["let l2 = ['a', 'b', 'c']"], code)
+
+  " Empty List
+  let l1 = []
+  let code =<< eval trim END
+    let l2 = {l1}
+  END
+  call assert_equal(["let l2 = []"], code)
+
+  " Null List
+  let l1 = v:_null_list
+  let code =<< eval trim END
+    let l2 = {l1}
+  END
+  call assert_equal(["let l2 = []"], code)
+
   let code = 'xxx'
   let code =<< eval trim END
     let n = {5 +

test/old/testdir/test_put.vim

@@ -332,4 +332,12 @@ func Test_put_dict()
   call assert_equal(["{'a': {'b': 'abc'}, 'c': [1, 2], 'd': 0z10}", ''],
         \ getline(1, '$'))
   bw!
+endfunc
+
+func Test_put_list()
+  new
+  let l = ['a', 'b', 'c']
+  put! =l
+  call assert_equal(['a', 'b', 'c', ''], getline(1, '$'))
+  bw!
 endfunc