fix(lsp): handle using array as open_floating_preview title (#33016)

runtime/doc/lsp.txt

@@ -2101,7 +2101,7 @@ Lua module: vim.lsp.util                                            *lsp-util*
       • {border}?        (`string|(string|[string,string])[]`) override
                          `border`
       • {zindex}?        (`integer`) override `zindex`, defaults to 50
-      • {title}?         (`string`)
+      • {title}?         (`string|[string,string][]`)
       • {title_pos}?     (`'left'|'center'|'right'`)
       • {relative}?      (`'mouse'|'cursor'|'editor'`) (default: `'cursor'`)
       • {anchor_bias}?   (`'auto'|'above'|'below'`, default: `'auto'`) Adjusts

runtime/lua/vim/lsp/util.lua

@@ -1411,10 +1411,16 @@ function M._make_floating_popup_size(contents, opts)
   width = math.min(width, screen_width - border_width)
 
   -- Make sure that the width is large enough to fit the title.
-  if opts.title then
-    width = math.max(width, vim.fn.strdisplaywidth(opts.title))
+  local title_length = 0
+  local chunks = type(opts.title) == 'string' and { { opts.title } } or opts.title or {}
+  for _, chunk in
+    ipairs(chunks --[=[@as [string, string][]]=])
+  do
+    title_length = title_length + vim.fn.strdisplaywidth(chunk[1])
   end
 
+  width = math.max(width, title_length)
+
   if wrap_at then
     wrap_at = math.min(wrap_at, width)
   end
@@ -1490,7 +1496,7 @@ end
 --- @field offset_y? integer
 --- @field border? string|(string|[string,string])[] override `border`
 --- @field zindex? integer override `zindex`, defaults to 50
---- @field title? string
+--- @field title? string|[string,string][]
 --- @field title_pos? 'left'|'center'|'right'
 ---
 --- (default: `'cursor'`)

test/functional/plugin/lsp_spec.lua

@@ -3529,7 +3529,7 @@ describe('LSP', function()
       )
     end)
 
-    it('considers title when computing width', function()
+    it('considers string title when computing width', function()
       eq(
         { 17, 2 },
         exec_lua(function()
@@ -3542,6 +3542,20 @@ describe('LSP', function()
         end)
       )
     end)
+
+    it('considers [string,string][] title when computing width', function()
+      eq(
+        { 17, 2 },
+        exec_lua(function()
+          return {
+            vim.lsp.util._make_floating_popup_size(
+              { 'foo', 'bar' },
+              { title = { { 'A very ', 'Normal' }, { 'long title', 'Normal' } } }
+            ),
+          }
+        end)
+      )
+    end)
   end)
 
   describe('lsp.util.trim.trim_empty_lines', function()