:recover : Fix crash on non-existent *.swp #9504

Reverts d2944e6a29. mf_open() _can_ fail if the file does not exist.

closes #9503
closes #9504

src/nvim/memfile.c

@@ -76,7 +76,8 @@
 
 /// @param flags  Flags for open() call.
 ///
-/// @return The open memory file.
+/// @return - The open memory file, on success.
+///         - NULL, on failure (e.g. file does not exist).
 memfile_T *mf_open(char_u *fname, int flags)
 {
   memfile_T *mfp = xmalloc(sizeof(memfile_T));

src/nvim/memline.c

@@ -277,6 +277,9 @@ int ml_open(buf_T *buf)
 
   // Open the memfile.  No swap file is created yet.
   memfile_T *mfp = mf_open(NULL, 0);
+  if (mfp == NULL) {
+    goto error;
+  }
 
   buf->b_ml.ml_mfp = mfp;
   buf->b_ml.ml_flags = ML_EMPTY;
@@ -360,10 +363,12 @@ int ml_open(buf_T *buf)
   return OK;
 
 error:
-  if (hp) {
-    mf_put(mfp, hp, false, false);
+  if (mfp != NULL) {
+    if (hp) {
+      mf_put(mfp, hp, false, false);
+    }
+    mf_close(mfp, true);  // will also xfree(mfp->mf_fname)
   }
-  mf_close(mfp, true);  // will also xfree(mfp->mf_fname)
   buf->b_ml.ml_mfp = NULL;
   return FAIL;
 }
@@ -839,7 +844,7 @@ void ml_recover(void)
                                     mf_open() will consume "fname_used"! */
   mfp = mf_open(fname_used, O_RDONLY);
   fname_used = p;
-  if (mfp->mf_fd < 0) {
+  if (mfp == NULL || mfp->mf_fd < 0) {
     EMSG2(_("E306: Cannot open %s"), fname_used);
     goto theend;
   }

src/nvim/spell.c

@@ -2510,7 +2510,7 @@ buf_T *open_spellbuf(void)
   buf->b_spell = true;
   buf->b_p_swf = true;        // may create a swap file
   if (ml_open(buf) == FAIL) {
-    abort();
+    ELOG("Error opening a new memline");
   }
   ml_open_file(buf);          // create swap file now
 

test/functional/ex_cmds/swapfile_preserve_recover_spec.lua

@@ -1,10 +1,11 @@
 local Screen = require('test.functional.ui.screen')
 local helpers = require('test.functional.helpers')(after_each)
 local lfs = require('lfs')
-local feed_command, eq, eval, expect, source =
-  helpers.feed_command, helpers.eq, helpers.eval, helpers.expect, helpers.source
+local eq, eval, expect, source =
+  helpers.eq, helpers.eval, helpers.expect, helpers.source
 local clear = helpers.clear
 local command = helpers.command
+local expect_err = helpers.expect_err
 local feed = helpers.feed
 local nvim_prog = helpers.nvim_prog
 local ok = helpers.ok
@@ -17,9 +18,14 @@ describe(':recover', function()
   before_each(clear)
 
   it('fails if given a non-existent swapfile', function()
-    local swapname = 'bogus-swapfile'
-    feed_command('recover '..swapname) -- This should not segfault. #2117
-    eq('E305: No swap file found for '..swapname, eval('v:errmsg'))
+    local swapname = 'bogus_swapfile'
+    local swapname2 = 'bogus_swapfile.swp'
+    expect_err('E305: No swap file found for '..swapname,
+               command, 'recover '..swapname)  -- Should not segfault. #2117
+    -- Also check filename ending with ".swp". #9504
+    expect_err('Vim%(recover%):E306: Cannot open '..swapname2,
+               command, 'recover '..swapname2)  -- Should not segfault. #2117
+    eq(2, eval('1+1'))  -- Still alive?
   end)
 
 end)