refactor(keymap): own mappings through a slot registry

VERSION

@@ -1 +1 @@
-2.62.2
+2.63.0

lua/codediff/keymap/init.lua

@@ -0,0 +1,35 @@
+-- Keymap registry facade.
+--
+-- Every codediff mapping is installed through a per-session registry, which
+-- records exactly what it installed and what was there before, so teardown can
+-- hand the key back to its previous owner instead of deleting it.
+--
+-- See codediff.keymap.slots for the ownership rules.
+
+local M = {}
+
+local registry = require("codediff.keymap.registry")
+local slots = require("codediff.keymap.slots")
+local normalize = require("codediff.keymap.normalize")
+
+--- Create a registry for one session.
+--- @param name string Diagnostic label
+--- @return table
+function M.new(name)
+  return registry.new(name)
+end
+
+--- Forget every slot for a wiped buffer without touching Neovim.
+--- @param bufnr number
+function M.forget_buffer(bufnr)
+  slots.forget_buffer(bufnr)
+end
+
+M.canonical = normalize.canonical
+M.resolve = normalize.resolve
+
+--- Live slot count. Test/diagnostic helper.
+M.slot_count = slots.count
+M.inspect_slot = slots.inspect
+
+return M

lua/codediff/keymap/normalize.lua

@@ -0,0 +1,46 @@
+-- Key-sequence normalization for the keymap registry.
+--
+-- Mapping identity must be canonical: `<Tab>` and `<C-i>` are the same key to
+-- Neovim, and `<leader>x` depends on the value of `mapleader` at the moment
+-- the mapping is created. Slots are therefore keyed by the fully expanded
+-- byte sequence, computed once at claim time and stored, never recomputed.
+
+local M = {}
+
+--- Expand a key sequence to its canonical byte form.
+--- @param lhs string
+--- @return string|nil canonical nil when lhs is not a usable key sequence
+function M.canonical(lhs)
+  if type(lhs) ~= "string" or lhs == "" then
+    return nil
+  end
+  local ok, expanded = pcall(vim.api.nvim_replace_termcodes, lhs, true, true, true)
+  if not ok or expanded == "" then
+    return nil
+  end
+  return expanded
+end
+
+--- Resolve a configured binding value to a key sequence.
+--- Preserves the existing contract: a string binds, `false` (or nil, or an
+--- empty string) silently disables. No other shape is accepted.
+--- @param value string|false|nil
+--- @return string|nil lhs
+function M.resolve(value)
+  if type(value) ~= "string" or value == "" then
+    return nil
+  end
+  return value
+end
+
+--- Normalize a mode argument to a list of single-character modes.
+--- @param modes string|string[]
+--- @return string[]
+function M.modes(modes)
+  if type(modes) == "table" then
+    return modes
+  end
+  return { modes }
+end
+
+return M