test: add a test for input highlighting

test/manual/highlight.lua

@@ -0,0 +1,30 @@
+-- Run this test with :source %
+
+vim.cmd([[
+  highlight RBP1 guibg=Red ctermbg=red
+  highlight RBP2 guibg=Yellow ctermbg=yellow
+  highlight RBP3 guibg=Green ctermbg=green
+  highlight RBP4 guibg=Blue ctermbg=blue
+]])
+local rainbow_levels = 4
+local function rainbow_hl(cmdline)
+  local ret = {}
+  local lvl = 0
+  for i = 1, string.len(cmdline) do
+    local char = string.sub(cmdline, i, i)
+    if char == "(" then
+      table.insert(ret, { i - 1, i, string.format("RBP%d", (lvl % rainbow_levels) + 1) })
+      lvl = lvl + 1
+    elseif char == ")" then
+      lvl = lvl - 1
+      table.insert(ret, { i - 1, i, string.format("RBP%d", (lvl % rainbow_levels) + 1) })
+    end
+  end
+  return ret
+end
+
+vim.ui.input({
+  prompt = "Rainbow: ",
+  default = "((()(())))",
+  highlight = rainbow_hl,
+}, function() end)