Update config/vis/visrc.lua

config/vis/visrc.lua

@@ -78,3 +78,31 @@ if vis.ftdetect then
     end
 end
 
+-- ---------------------------------------------------------------------------
+-- On save: strip trailing spaces/tabs and extra blank lines at the end of
+-- the file. Skips files where trailing whitespace means something.
+-- ---------------------------------------------------------------------------
+local keep_whitespace = { md = true, markdown = true, diff = true, patch = true }
+
+vis.events.subscribe(vis.events.FILE_SAVE_PRE, function(file, path)
+    local ext = path and path:match('%.(%w+)$')
+    if ext and keep_whitespace[ext:lower()] then return true end
+
+    -- trailing spaces/tabs (not \r, so CRLF files stay CRLF);
+    -- read every line first, then rewrite only the ones that changed
+    local trimmed, n = {}, 0
+    for line in file:lines_iterator() do
+        n = n + 1
+        local s = line:find('[ \t]+$')
+        if s then trimmed[n] = line:sub(1, s - 1) end
+    end
+    for i, line in pairs(trimmed) do file.lines[i] = line end
+
+    -- blank lines at the end: keep exactly one final newline
+    local size = file.size
+    local tail = file:content(math.max(0, size - 256), math.min(size, 256))
+    local extra = tail:match('\n(\n+)$')
+    if extra then file:delete(size - #extra, #extra) end
+
+    return true
+end)