vim-patch:8.1.0313: information about a swap file is unavailable

Problem:    Information about a swap file is unavailable.
Solution:   Add swapinfo(). (Enzo Ferber)
00f123a565

runtime/doc/eval.txt

@@ -2321,6 +2321,7 @@ submatch({nr} [, {list}])	String or List
 					specific match in ":s" or substitute()
 substitute({expr}, {pat}, {sub}, {flags})
 				String	all {pat} in {expr} replaced with {sub}
+swapinfo({fname})		Dict	information about swap file {fname}
 synID({lnum}, {col}, {trans})	Number	syntax ID at {lnum} and {col}
 synIDattr({synID}, {what} [, {mode}])
 				String	attribute {what} of syntax ID {synID}
@@ -7758,6 +7759,22 @@ substitute({expr}, {pat}, {sub}, {flags})		*substitute()*
 		|submatch()| returns. Example: >
 		   :echo substitute(s, '\(\x\x\)', {m -> '0x' . m[1]}, 'g')
 
+swapinfo({fname})					swapinfo()
+		The result is a dictionary, which holds information about the
+		swapfile {fname}. The available fields are:
+			version VIM version
+			user	user name
+			host	host name
+			fname	original file name
+			pid	PID of the VIM process that created the swap
+				file
+			mtime	last modification time in seconds
+			inode	Optional: INODE number of the file
+		In case of failure an "error" item is added with the reason:
+			Cannot open file: file not found or in accessible
+			Cannot read file: cannot read first block
+			magic number mismatch: info in first block is invalid
+
 synID({lnum}, {col}, {trans})				*synID()*
 		The result is a Number, which is the syntax ID at the position
 		{lnum} and {col} in the current window.

src/nvim/eval.c

@@ -16423,6 +16423,13 @@ static void f_substitute(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
+/// "swapinfo(swap_filename)" function
+static void f_swapinfo(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  tv_dict_alloc_ret(rettv);
+  get_b0_dict(tv_get_string(argvars), rettv->vval.v_dict);
+}
+
 /// "synID(lnum, col, trans)" function
 static void f_synID(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {

src/nvim/eval.lua

@@ -301,6 +301,7 @@ return {
     strwidth={args=1},
     submatch={args={1, 2}},
     substitute={args=4},
+    swapinfo={args={1}},
     synID={args=3},
     synIDattr={args={2, 3}},
     synIDtrans={args=1},

src/nvim/memline.c

@@ -1457,10 +1457,41 @@ static char *make_percent_swname(const char *dir, char *name)
 static bool process_still_running;
 #endif
 
-/*
- * Give information about an existing swap file.
- * Returns timestamp (0 when unknown).
- */
+/// Return information found in swapfile "fname" in dictionary "d".
+/// This is used by the swapinfo() function.
+void get_b0_dict(const char *fname, dict_T *d)
+{
+  int fd;
+  struct block0 b0;
+
+  if ((fd = os_open(fname, O_RDONLY, 0)) >= 0) {
+    if (read_eintr(fd, &b0, sizeof(b0)) == sizeof(b0)) {
+      if (b0_magic_wrong(&b0)) {
+        tv_dict_add_str(d, S_LEN("error"), xstrdup("magic number mismatch"));
+      } else {
+        // We have swap information.
+        tv_dict_add_str(d, S_LEN("version"), xstrdup((char *)b0.b0_version));
+        tv_dict_add_str(d, S_LEN("user"), xstrdup((char *)b0.b0_uname));
+        tv_dict_add_str(d, S_LEN("host"), xstrdup((char *)b0.b0_hname));
+        tv_dict_add_str(d, S_LEN("fname"), xstrdup((char *)b0.b0_fname));
+
+        tv_dict_add_nr(d, S_LEN("pid"), char_to_long(b0.b0_pid));
+        tv_dict_add_nr(d, S_LEN("mtime"), char_to_long(b0.b0_mtime));
+#ifdef CHECK_INODE
+        tv_dict_add_nr(d, S_LEN("inode"), char_to_long(b0.b0_ino));
+#endif
+      }
+    } else {
+      tv_dict_add_str(d, S_LEN("error"), xstrdup("Cannot read file"));
+    }
+    close(fd);
+  } else {
+    tv_dict_add_str(d, S_LEN("error"), xstrdup("Cannot open file"));
+  }
+}
+
+/// Give information about an existing swap file.
+/// Returns timestamp (0 when unknown).
 static time_t swapfile_info(char_u *fname)
 {
   assert(fname != NULL);

src/nvim/testdir/test_swap.vim

@@ -61,3 +61,37 @@ func Test_missing_dir()
   set directory&
   call delete('Xswapdir', 'rf')
 endfunc
+
+func Test_swapinfo()
+  new Xswapinfo
+  call setline(1, ['one', 'two', 'three'])
+  w
+  let fname = trim(execute('swapname'))
+  call assert_match('Xswapinfo', fname)
+  let info = swapinfo(fname)
+  call assert_match('8\.', info.version)
+  call assert_match('\w', info.user)
+  call assert_equal(hostname(), info.host)
+  call assert_match('Xswapinfo', info.fname)
+  call assert_equal(getpid(), info.pid)
+  call assert_match('^\d*$', info.mtime)
+  if has_key(info, 'inode')
+    call assert_match('\d', info.inode)
+  endif
+  bwipe!
+  call delete(fname)
+  call delete('Xswapinfo')
+
+  let info = swapinfo('doesnotexist')
+  call assert_equal('Cannot open file', info.error)
+
+  call writefile(['burp'], 'Xnotaswapfile')
+  let info = swapinfo('Xnotaswapfile')
+  call assert_equal('Cannot read file', info.error)
+  call delete('Xnotaswapfile')
+
+  call writefile([repeat('x', 10000)], 'Xnotaswapfile')
+  let info = swapinfo('Xnotaswapfile')
+  call assert_equal('magic number mismatch', info.error)
+  call delete('Xnotaswapfile')
+endfunc