vim-patch:8.1.0211: expanding a file name "~" results in $HOME

Problem:    Expanding a file name "~" results in $HOME. (Aidan Shafran)
Solution:   Change "~" to "./~" before expanding. (closes vim/vim#3072)
00136dc321

src/nvim/eval.c

@@ -8868,8 +8868,8 @@ static void f_fnamemodify(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   } else {
     len = strlen(fname);
     size_t usedlen = 0;
-    (void)modify_fname((char_u *)mods, &usedlen, (char_u **)&fname, &fbuf,
-                       &len);
+    (void)modify_fname((char_u *)mods, false, &usedlen,
+                       (char_u **)&fname, &fbuf, &len);
   }
 
   rettv->v_type = VAR_STRING;
@@ -22623,6 +22623,7 @@ void reset_v_option_vars(void)
 int
 modify_fname(
     char_u *src,              // string with modifiers
+    bool tilde_file,          // "~" is a file name, not $HOME
     size_t *usedlen,          // characters after src that are used
     char_u **fnamep,          // file name so far
     char_u **bufp,            // buffer for allocated file name or NULL
@@ -22652,8 +22653,8 @@ repeat:
             || (*fnamep)[1] == '\\'
 # endif
             || (*fnamep)[1] == NUL)
-
 #endif
+        && !(tilde_file && (*fnamep)[1] == NUL)
         ) {
       *fnamep = expand_env_save(*fnamep);
       xfree(*bufp);          /* free any allocated file name */

src/nvim/ex_docmd.c

@@ -8552,6 +8552,7 @@ eval_vars (
   size_t resultlen;
   buf_T       *buf;
   int valid = VALID_HEAD | VALID_PATH;  // Assume valid result.
+  bool tilde_file = false;
   int skip_mod = false;
   char strbuf[30];
 
@@ -8609,8 +8610,10 @@ eval_vars (
       if (curbuf->b_fname == NULL) {
         result = (char_u *)"";
         valid = 0;                  /* Must have ":p:h" to be valid */
-      } else
+      } else {
         result = curbuf->b_fname;
+        tilde_file = STRCMP(result, "~") == 0;
+      }
       break;
 
     case SPEC_HASH:             /* '#' or "#99": alternate file */
@@ -8660,8 +8663,10 @@ eval_vars (
         if (buf->b_fname == NULL) {
           result = (char_u *)"";
           valid = 0;                        /* Must have ":p:h" to be valid */
-        } else
+        } else {
           result = buf->b_fname;
+          tilde_file = STRCMP(result, "~") == 0;
+        }
       }
       break;
 
@@ -8746,7 +8751,8 @@ eval_vars (
         resultlen = (size_t)(s - result);
       }
     } else if (!skip_mod) {
-      valid |= modify_fname(src, usedlen, &result, &resultbuf, &resultlen);
+      valid |= modify_fname(src, tilde_file, usedlen, &result,
+                            &resultbuf, &resultlen);
       if (result == NULL) {
         *errormsg = (char_u *)"";
         return NULL;

src/nvim/if_cscope.c

@@ -425,7 +425,8 @@ cs_add_common(
   expand_env((char_u *)arg1, (char_u *)fname, MAXPATHL);
   size_t len = STRLEN(fname);
   fbuf = (char_u *)fname;
-  (void)modify_fname((char_u *)":p", &usedlen, (char_u **)&fname, &fbuf, &len);
+  (void)modify_fname((char_u *)":p", false, &usedlen,
+                     (char_u **)&fname, &fbuf, &len);
   if (fname == NULL)
     goto add_err;
   fname = (char *)vim_strnsave((char_u *)fname, len);

src/nvim/os/env.c

@@ -870,8 +870,8 @@ size_t home_replace(const buf_T *const buf, const char_u *src,
     size_t usedlen = 0;
     size_t flen = strlen(homedir_env_mod);
     char_u *fbuf = NULL;
-    (void)modify_fname((char_u *)":p", &usedlen, (char_u **)&homedir_env_mod,
-                       &fbuf, &flen);
+    (void)modify_fname((char_u *)":p", false, &usedlen,
+                       (char_u **)&homedir_env_mod, &fbuf, &flen);
     flen = strlen(homedir_env_mod);
     assert(homedir_env_mod != homedir_env);
     if (vim_ispathsep(homedir_env_mod[flen - 1])) {

test/functional/legacy/expand_spec.lua

@@ -62,6 +62,14 @@ describe('expand file name', function()
         call delete('Xdir ~ dir', 'd')
         call assert_false(isdirectory('Xdir ~ dir'))
       endfunc
+
+      func Test_expand_tilde_filename()
+        split ~
+        call assert_equal('~', expand('%'))
+        call assert_notequal(expand('%:p'), expand('~/'))
+        call assert_match('\~', expand('%:p'))
+        bwipe!
+      endfunc
     ]])
   end)
 
@@ -74,4 +82,9 @@ describe('expand file name', function()
     call('Test_with_tilde')
     expected_empty()
   end)
+
+  it('does not expand tilde if it is a filename', function()
+    call('Test_expand_tilde_filename')
+    expected_empty()
+  end)
 end)