Merge pull request #13973 from chentau/on_bytes_undofile

New versions of neovim will not read undofiles written by nvim before this merge (there will be an error message about incopmatible version). Nvim 0.4 (or an master up to bda12927be84f0e0e05e885f9acb40a7ac2c5524 ) can be used to recover older undofiles, so if you worried about unsaved changes lurking around in undofiles it would make sense to keep such version around somewhere to recover them.

This is a necessary change to keep tree-sitter and plugins dependent on byte-level buffer change events fully working with undo states from a undofile. If there is a clear demand we might implement reading of the old format. Such recovered buffers will not be be fully functional with plugins relying on buffer updates or tree-sitter, however.

1 files changed, 108 insertions, 6 deletions

diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index 8c2ae3bc35..f52850f6f3 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -594,13 +594,20 @@ int u_savecommon(linenr_T top, linenr_T bot, linenr_T newbot, int reload)
 }
 
 
-# define UF_START_MAGIC     "Vim\237UnDo\345"  /* magic at start of undofile */
+// magic at start of undofile
+# define UF_START_MAGIC     "Vim\237UnDo\345"
 # define UF_START_MAGIC_LEN     9
-# define UF_HEADER_MAGIC        0x5fd0  /* magic at start of header */
-# define UF_HEADER_END_MAGIC    0xe7aa  /* magic after last header */
-# define UF_ENTRY_MAGIC         0xf518  /* magic at start of entry */
-# define UF_ENTRY_END_MAGIC     0x3581  /* magic after last entry */
-# define UF_VERSION             2       /* 2-byte undofile version number */
+// magic at start of header
+# define UF_HEADER_MAGIC        0x5fd0
+// magic after last header
+# define UF_HEADER_END_MAGIC    0xe7aa
+// magic at start of entry
+# define UF_ENTRY_MAGIC         0xf518
+// magic after last entry
+# define UF_ENTRY_END_MAGIC     0x3581
+
+// 2-byte undofile version number
+# define UF_VERSION             3
 
 /* extra fields for header */
 # define UF_LAST_SAVE_NR        1
@@ -847,6 +854,15 @@ static bool serialize_uhp(bufinfo_T *bi, u_header_T *uhp)
     }
   }
   undo_write_bytes(bi, (uintmax_t)UF_ENTRY_END_MAGIC, 2);
+
+  // Write all extmark undo objects
+  for (size_t i = 0; i < kv_size(uhp->uh_extmark); i++) {
+    if (!serialize_extmark(bi, kv_A(uhp->uh_extmark, i))) {
+      return false;
+    }
+  }
+  undo_write_bytes(bi, (uintmax_t)UF_ENTRY_END_MAGIC, 2);
+
   return true;
 }
 
@@ -928,9 +944,95 @@ static u_header_T *unserialize_uhp(bufinfo_T *bi,
     return NULL;
   }
 
+  // Unserialize all extmark undo information
+  ExtmarkUndoObject *extup;
+  kv_init(uhp->uh_extmark);
+
+  while ((c = undo_read_2c(bi)) == UF_ENTRY_MAGIC) {
+    bool error = false;
+    extup = unserialize_extmark(bi, &error, file_name);
+    if (error) {
+      kv_destroy(uhp->uh_extmark);
+      xfree(extup);
+      return NULL;
+    }
+    kv_push(uhp->uh_extmark, *extup);
+    xfree(extup);
+  }
+  if (c != UF_ENTRY_END_MAGIC) {
+    corruption_error("entry end", file_name);
+    u_free_uhp(uhp);
+    return NULL;
+  }
+
   return uhp;
 }
 
+static bool serialize_extmark(bufinfo_T *bi, ExtmarkUndoObject extup)
+{
+  if (extup.type == kExtmarkSplice) {
+    undo_write_bytes(bi, (uintmax_t)UF_ENTRY_MAGIC, 2);
+    undo_write_bytes(bi, (uintmax_t)extup.type, 4);
+    if (!undo_write(bi, (uint8_t *)&(extup.data.splice),
+                    sizeof(ExtmarkSplice))) {
+        return false;
+    }
+  } else if (extup.type == kExtmarkMove) {
+    undo_write_bytes(bi, (uintmax_t)UF_ENTRY_MAGIC, 2);
+    undo_write_bytes(bi, (uintmax_t)extup.type, 4);
+    if (!undo_write(bi, (uint8_t *)&(extup.data.move), sizeof(ExtmarkMove))) {
+      return false;
+    }
+  }
+  // Note: We do not serialize ExtmarkSavePos information, since
+  // buffer marktrees are not retained when closing/reopening a file
+  return true;
+}
+
+static ExtmarkUndoObject *unserialize_extmark(bufinfo_T *bi, bool *error,
+                                              const char *filename)
+{
+  UndoObjectType type;
+  uint8_t *buf = NULL;
+  size_t n_elems;
+
+  ExtmarkUndoObject *extup = xmalloc(sizeof(ExtmarkUndoObject));
+
+  type = (UndoObjectType)undo_read_4c(bi);
+  extup->type = type;
+  if (type == kExtmarkSplice) {
+    n_elems = (size_t)sizeof(ExtmarkSplice) / sizeof(uint8_t);
+    buf = xcalloc(sizeof(uint8_t), n_elems);
+    if (!undo_read(bi, buf, n_elems)) {
+      goto error;
+    }
+    extup->data.splice = *(ExtmarkSplice *)buf;
+  } else if (type == kExtmarkMove) {
+    n_elems = (size_t)sizeof(ExtmarkMove) / sizeof(uint8_t);
+    buf = xcalloc(sizeof(uint8_t), n_elems);
+    if (!undo_read(bi, buf, n_elems)) {
+      goto error;
+    }
+    extup->data.move = *(ExtmarkMove *)buf;
+  } else {
+      goto error;
+  }
+
+  if (buf) {
+    xfree(buf);
+  }
+
+  return extup;
+
+error:
+  xfree(extup);
+  if (buf) {
+    xfree(buf);
+  }
+  *error = true;
+  return NULL;
+}
+
 /// Serializes "uep".
 ///
 /// @param bi  The buffer information