patch 9.1.0360: Vim9: does not handle autoloaded variables well

Problem:  Vim9: does not handle autoloaded variables well
Solution: Better handle script-level exported variable references from
          autoload files (Ernie Rael).

fixes: #14591
closes: #14607

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/evalvars.c

@@ -3340,12 +3340,31 @@ find_var(char_u *name, hashtab_T **htp, int no_autoload)
 	}
     }
 
+    // and finally try
+    return find_var_autoload_prefix(name, 0, htp, NULL);
+}
+
+/*
+ * Find variable "name" with sn_autoload_prefix.
+ * Return a pointer to it if found, NULL if not found.
+ * When "sid" > 0, use it otherwise use "current_sctx.sc_sid".
+ * When "htp" is not NULL  set "htp" to the hashtab_T used.
+ * When "namep" is not NULL set "namep" to the generated name, and
+ * then the caller gets ownership and is responsible for freeing the name.
+ */
+    dictitem_T *
+find_var_autoload_prefix(char_u *name, int sid, hashtab_T **htp,
+							    char_u **namep)
+{
+    hashtab_T	*ht;
+    dictitem_T	*ret = NULL;
     // When using "vim9script autoload" script-local items are prefixed but can
     // be used with s:name.
-    if (SCRIPT_ID_VALID(current_sctx.sc_sid)
+    int check_sid = sid > 0 ? sid : current_sctx.sc_sid;
+    if (SCRIPT_ID_VALID(check_sid)
 		   && (in_vim9script() || (name[0] == 's' && name[1] == ':')))
     {
-	scriptitem_T *si = SCRIPT_ITEM(current_sctx.sc_sid);
+	scriptitem_T *si = SCRIPT_ITEM(check_sid);
 
 	if (si->sn_autoload_prefix != NULL)
 	{
@@ -3355,20 +3374,26 @@ find_var(char_u *name, hashtab_T **htp, int no_autoload)
 
 	    if (auto_name != NULL)
 	    {
+		int free_auto_name = TRUE;
 		ht = &globvarht;
 		ret = find_var_in_ht(ht, 'g', auto_name, TRUE);
-		vim_free(auto_name);
 		if (ret != NULL)
 		{
 		    if (htp != NULL)
 			*htp = ht;
-		    return ret;
+		    if (namep != NULL)
+		    {
+			free_auto_name = FALSE;
+			*namep = auto_name;
+		    }
 		}
+		if (free_auto_name)
+		    vim_free(auto_name);
 	    }
 	}
     }
 
-    return NULL;
+    return ret;
 }
 
 /*
@@ -3508,7 +3533,11 @@ lookup_scriptitem(
     hi = hash_find(ht, p);
     res = HASHITEM_EMPTY(hi) ? FAIL : OK;
 
-    // if not script-local, then perhaps imported
+    // if not script-local, then perhaps autoload-exported
+    if (res == FAIL && find_var_autoload_prefix(p, 0, NULL, NULL) != NULL)
+	res = OK;
+
+    // if not script-local or autoload, then perhaps imported
     if (res == FAIL && find_imported(p, 0, FALSE) != NULL)
 	res = OK;
     if (p != buffer)
@@ -3904,23 +3933,40 @@ set_var_const(
 
     if (sid != 0)
     {
+	varname = NULL;
 	if (SCRIPT_ID_VALID(sid))
-	    ht = &SCRIPT_VARS(sid);
-	varname = name;
+	{
+	    char_u	*auto_name = NULL;
+	    if (find_var_autoload_prefix(name, sid, &ht, &auto_name) != NULL)
+	    {
+		var_in_autoload = TRUE;
+		varname = auto_name;
+		name_tofree = varname;
+	    }
+	    else
+		ht = &SCRIPT_VARS(sid);
+	}
+	if (varname == NULL)
+	    varname = name;
     }
     else
     {
-	scriptitem_T *si;
+	scriptitem_T	*si;
+	char_u		*auto_name = NULL;
 
-	if (in_vim9script() && is_export
-		&& SCRIPT_ID_VALID(current_sctx.sc_sid)
-		&& (si = SCRIPT_ITEM(current_sctx.sc_sid))
-						  ->sn_autoload_prefix != NULL)
+	if (in_vim9script()
+	    && SCRIPT_ID_VALID(current_sctx.sc_sid)
+	    && (si = SCRIPT_ITEM(current_sctx.sc_sid))
+					      ->sn_autoload_prefix != NULL
+	    && (is_export
+		|| find_var_autoload_prefix(name, 0, NULL, &auto_name)
+								    != NULL))
 	{
 	    // In a vim9 autoload script an exported variable is put in the
 	    // global namespace with the autoload prefix.
 	    var_in_autoload = TRUE;
-	    varname = concat_str(si->sn_autoload_prefix, name);
+	    varname = auto_name != NULL ? auto_name
+		      : concat_str(si->sn_autoload_prefix, name);
 	    if (varname == NULL)
 		goto failed;
 	    name_tofree = varname;

src/proto/evalvars.pro

@@ -63,6 +63,7 @@ int eval_variable(char_u *name, int len, scid_T sid, typval_T *rettv, dictitem_T
 int eval_variable_import(char_u *name, typval_T *rettv);
 void check_vars(char_u *name, int len);
 dictitem_T *find_var(char_u *name, hashtab_T **htp, int no_autoload);
+dictitem_T *find_var_autoload_prefix(char_u *name, int sid, hashtab_T **htp, char_u **namep);
 dictitem_T *find_var_also_in_script(char_u *name, hashtab_T **htp, int no_autoload);
 dictitem_T *find_var_in_ht(hashtab_T *ht, int htname, char_u *varname, int no_autoload);
 hashtab_T *get_script_local_ht(void);

src/testdir/test_vim9_import.vim

@@ -1201,6 +1201,71 @@ def Test_autoload_import_relative_from_buffer_in_dir()
   :bw!
 enddef
 
+" Test modifying exported autoload variable. Github issue: #14591
+def Test_autoload_export_variables()
+  mkdir('Xautoload_vars/autoload', 'pR')
+  var lines =<< trim END
+    vim9script
+    export var val = 11
+    val = 42
+  END
+
+  # Test that the imported script, above, can modify the exported variable;
+  # and test that the importing script, below, can modify the variable.
+  writefile(lines, 'Xautoload_vars/autoload/Xauto_vars_f2.vim', 'D')
+  lines =<< trim END
+    vim9script
+
+    import autoload './Xautoload_vars/autoload/Xauto_vars_f2.vim' as f2
+
+    def F(): number
+      return f2.val
+    enddef
+    assert_equal(42, F())
+    assert_equal(42, f2.val)
+    f2.val = 17
+    assert_equal(17, f2.val)
+
+    def G()
+      f2.val = 19
+    enddef
+    G()
+    assert_equal(19, f2.val)
+  END
+  v9.CheckScriptSuccess(lines)
+
+  # Test const var is not modifiable.
+  lines =<< trim END
+    vim9script
+    export const val = 11
+    val = 42
+  END
+  writefile(lines, 'Xautoload_vars/autoload/Xauto_vars_f3.vim', 'D')
+  lines =<< trim END
+    vim9script
+
+    import autoload './Xautoload_vars/autoload/Xauto_vars_f3.vim' as f3
+
+    var x = f3.val
+  END
+  v9.CheckScriptFailure(lines, 'E46:')
+
+  # Test const var is not modifiable from importing script.
+  lines =<< trim END
+    vim9script
+    export const val = 11
+  END
+  writefile(lines, 'Xautoload_vars/autoload/Xauto_vars_f4.vim', 'D')
+  lines =<< trim END
+    vim9script
+
+    import autoload './Xautoload_vars/autoload/Xauto_vars_f4.vim' as f4
+
+    f4.val = 13
+  END
+  v9.CheckScriptFailure(lines, 'E46:')
+enddef
+
 def Test_autoload_import_relative_autoload_dir()
   mkdir('autoload', 'pR')
   var lines =<< trim END

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    360,
 /**/
     359,
 /**/