fix(floatwin): don't always use winheight

src/nvim/window.c

@@ -4608,11 +4608,12 @@ static void win_enter_ext(win_T *wp, bool undo_sync, int curwin_invalid,
     redraw_all_later(NOT_VALID);
   }
 
-  /* set window height to desired minimal value */
+  // set window height to desired minimal value
-  if (curwin->w_height < p_wh && !curwin->w_p_wfh)
+  if (curwin->w_height < p_wh && !curwin->w_p_wfh && !curwin->w_floating) {
     win_setheight((int)p_wh);
-  else if (curwin->w_height == 0)
+  } else if (curwin->w_height == 0) {
     win_setheight(1);
+  }
 
   // set window width to desired minimal value
   if (curwin->w_width < p_wiw && !curwin->w_p_wfw && !wp->w_floating) {

test/functional/ui/float_spec.lua

@@ -83,6 +83,50 @@ describe('floatwin', function()
     assert_alive()
   end)
 
+  it('opened with correct height', function()
+    local height = exec_lua([[
+      vim.api.nvim_set_option("winheight", 20)
+      local bufnr = vim.api.nvim_create_buf(false, true)
+
+      local opts = {
+        height = 10,
+        col = 5,
+        row = 1,
+        relative = 'editor',
+        style = 'minimal',
+        width = 15
+      }
+
+      local win_id = vim.api.nvim_open_win(bufnr, true, opts)
+
+      return vim.api.nvim_win_get_height(win_id)
+    ]])
+
+    eq(10, height)
+  end)
+
+  it('opened with correct width', function()
+    local width = exec_lua([[
+      vim.api.nvim_set_option("winwidth", 20)
+      local bufnr = vim.api.nvim_create_buf(false, true)
+
+      local opts = {
+        height = 10,
+        col = 5,
+        row = 1,
+        relative = 'editor',
+        style = 'minimal',
+        width = 10
+      }
+
+      local win_id = vim.api.nvim_open_win(bufnr, true, opts)
+
+      return vim.api.nvim_win_get_width(win_id)
+    ]])
+
+    eq(10, width)
+  end)
+
   local function with_ext_multigrid(multigrid)
     local screen
     before_each(function()