Keep register changes the user makes while a snippet is active

ChangeLog

@@ -126,6 +126,10 @@ next:
 	  carry the full trace and the "please report" preamble.
 	  (#1676)
 	- Work around a globbing performance issue in Python 3.12 (#1696, #1694)
+	- Register changes the user makes while a snippet is still active but no
+	  placeholder is being replaced are no longer reverted to the pre-snippet
+	  registers when insert mode is left or the snippet is torn down. (#1697,
+	  #1695)
 
 version 4.0 (10-May-2026):
 	New features:

pythonx/UltiSnips/vim_state.py

@@ -55,7 +55,14 @@ def __init__(self):
         self._poss = deque(maxlen=5)
         self._lvb = None
 
-        self._text_to_expect = ""
+        # Texts of the placeholders the snippet has selected since the
+        # register cache below was taken. Typing over a select-mode
+        # placeholder deletes it into @" (and @- or @1), so @" holding one
+        # of these means the snippet clobbered the registers and the cache
+        # must be restored. Anything else in @" was put there by the user,
+        # e.g. a `dd` after leaving the snippet with <Esc>, and must win
+        # over the cache (#1695).
+        self._placeholder_texts = []
 
         # Cache reginfo dicts for each preserved register in a Vim variable
         # so binary register contents (which can't always cross the
@@ -64,26 +71,37 @@ def __init__(self):
         # snippet, cleared at teardown.
         vim.command("let g:_ultisnips_reg_cache = {}")
 
-    def remember_unnamed_register(self, text_to_expect):
-        """Cache the snippet-clobberable registers if @" doesn't already
-        match the previously-expected text.
-
-        'text_to_expect' is text we expect to be in @" on the next call
-        (typically the placeholder text the snippet just put there). When
-        @" still matches the previous expectation we know we put it there
-        ourselves, so we don't overwrite the original cached state.
-
-        """
-        escaped_text = self._text_to_expect.replace("'", "''")
-        res = int(vim_helper.eval('@" != ' + "'" + escaped_text + "'"))
-        if res:
+    def _unnamed_register_holds_placeholder_text(self):
+        """Whether @" holds the text of a placeholder the snippet selected
+        since the cache was taken, i.e. whether the snippet is what last
+        wrote @". Compared inside Vim so binary register contents never
+        have to cross the Python boundary."""
+        if not self._placeholder_texts:
+            return False
+        texts = ",".join(_vim_str(text) for text in self._placeholder_texts)
+        return vim_helper.eval(f'index([{texts}], @") >= 0') == "1"
+
+    def remember_unnamed_register(self, placeholder_text):
+        """Cache the snippet-clobberable registers unless @" still holds
+        text we put there ourselves, then note 'placeholder_text' (the text
+        of the placeholder the snippet just selected) as text a select-mode
+        replacement may push into @" before the next call."""
+        if not self._unnamed_register_holds_placeholder_text():
             for reg in self._PRESERVED_REGISTERS:
                 lit = _vim_str(reg)
                 vim.command(f"let g:_ultisnips_reg_cache[{lit}] = getreginfo({lit})")
-        self._text_to_expect = text_to_expect
+            self._placeholder_texts = []
+        if placeholder_text not in self._placeholder_texts:
+            self._placeholder_texts.append(placeholder_text)
 
     def restore_unnamed_register(self):
-        """Restore the cached registers, if we have any cached.
+        """Restore the cached registers, if we have any cached and the
+        snippet is what last wrote @".
+
+        When @" holds none of the placeholder texts the snippet selected,
+        the user changed the registers themselves while the snippet was
+        still active (a `dd` after leaving it with <Esc>, say) and restoring
+        the cache would throw their change away (#1695).
 
         Iteration order matters because `setreg('0', …)` and
         `setreg('"', dict)` both update the unnamed-register pointer.
@@ -102,6 +120,8 @@ def restore_unnamed_register(self):
         """
         if int(vim_helper.eval("empty(g:_ultisnips_reg_cache)")):
             return
+        if not self._unnamed_register_holds_placeholder_text():
+            return
         for reg in self._PRESERVED_REGISTERS:
             lit = _vim_str(reg)
             vim.command(
@@ -114,7 +134,7 @@ def reset_register_cache(self):
         """Drop the cached register state. Called when the snippet
         finishes so the next one starts from a clean slate."""
         vim.command("let g:_ultisnips_reg_cache = {}")
-        self._text_to_expect = ""
+        self._placeholder_texts = []
 
     def remember_position(self):
         """Remember the current position as a previous pose."""

test/test_Fixes.py

@@ -149,6 +149,32 @@ class PreservesNumberedRegisterAcrossSnippet(_VimTest):
     wanted = "\n[X]\n\nLINE1"
 
 
+# Tests for https://github.com/SirVer/ultisnips/issues/1695 —
+# The register cache taken at expansion time is restored when the snippet
+# is torn down and whenever insert mode is left. Register changes the user
+# makes in between, while the snippet is still active but no placeholder is
+# being replaced, must survive that restore instead of being reverted to
+# the pre-snippet state.
+
+
+class RetainsUserRegisterChange_AfterLeavingSnippet(_VimTest):
+    # `yy`, expand, `<Esc>`, `dd` the snippet line, move away (teardown),
+    # `p`: the `dd`'d line must be pasted, not the yank from before the
+    # snippet.
+    snippets = ("test", "${1:hello} ${2:world} $0")
+    keys = "yank" + ESC + "yy" + "otest" + EX + ESC + "dd" + "k" + "p"
+    wanted = "yank\nhello world "
+
+
+class RetainsUserRegisterChange_OnInsertLeave(_VimTest):
+    # `yy`, expand, `<Esc>`, `x` inside the snippet (`@"` = "o"), re-enter
+    # and leave insert mode (InsertLeave restore), `p`: the `x`'d character
+    # must be pasted, not the yank from before the snippet.
+    snippets = ("test", "${1:hello} ${2:world} $0")
+    keys = "yank" + ESC + "yy" + "otest" + EX + ESC + "x" + "a" + ESC + "p"
+    wanted = "yank\nhell oworld "
+
+
 # End: Github Pull Request # 134
 
 # Test to ensure that shiftwidth follows tabstop when it's set to zero post