refactor(options): remove `.indir`, redesign option scopes #31066

Problem:
The way option scopes currently work is inflexible and does not allow for nested
option scopes or easily finding the value of an option at any arbitrary scope
without having to do long handwritten switch-case statements like in
`get_varp()`. `.indir` is also confusing and redundant since option indices for
each scope can be autogenerated.

Solution:
Expand option scopes in such a way that an option can support any amount of
scopes using a set of scope flags, similarly to how it's already done for option
types. Also make options contain information about its index at each scope it
supports. This allows for massively simplifying `get_varp()` and
`get_varp_scope()` in the future by just using a struct for options at each
scope. This would be done by creating a table that stores the offset of an
option's variable at a scope by using the option's index at that scope as a key.
This PR also autogenerates enums for option indices at each scope to remove the
need for `.indir` entirely, and also to allow easily iterating over options all
options that support any scope.

Ref: #29314

1 files changed, 174 insertions, 45 deletions

diff --git a/src/nvim/generators/gen_options.lua b/src/nvim/generators/gen_options.lua
index 92349b5298..02f3ac3257 100644
--- a/src/nvim/generators/gen_options.lua
+++ b/src/nvim/generators/gen_options.lua
@@ -1,6 +1,10 @@
 local options_file = arg[1]
+local options_enum_file = arg[2]
+local options_map_file = arg[3]
 
 local opt_fd = assert(io.open(options_file, 'w'))
+local opt_enum_fd = assert(io.open(options_enum_file, 'w'))
+local opt_map_fd = assert(io.open(options_map_file, 'w'))
 
 local w = function(s)
   if s:match('^    %.') then
@@ -10,10 +14,129 @@ local w = function(s)
   end
 end
 
+--- @param s string
+local function enum_w(s)
+  opt_enum_fd:write(s .. '\n')
+end
+
+--- @param s string
+local function map_w(s)
+  opt_map_fd:write(s .. '\n')
+end
+
 --- @module 'nvim.options'
 local options = require('options')
+local options_meta = options.options
 
 local cstr = options.cstr
+local valid_scopes = options.valid_scopes
+
+--- Options for each scope.
+--- @type table<string, vim.option_meta[]>
+local scope_options = {}
+for _, scope in ipairs(valid_scopes) do
+  scope_options[scope] = {}
+end
+
+--- @param s string
+--- @return string
+local lowercase_to_titlecase = function(s)
+  return s:sub(1, 1):upper() .. s:sub(2)
+end
+
+-- Generate options enum file
+enum_w('// IWYU pragma: private, include "nvim/option_defs.h"')
+enum_w('')
+
+--- Map of option name to option index
+--- @type table<string, string>
+local option_index = {}
+
+-- Generate option index enum and populate the `option_index` and `scope_option` dicts.
+enum_w('typedef enum {')
+enum_w('  kOptInvalid = -1,')
+
+for i, o in ipairs(options_meta) do
+  local enum_val_name = 'kOpt' .. lowercase_to_titlecase(o.full_name)
+  enum_w(('  %s = %u,'):format(enum_val_name, i - 1))
+
+  option_index[o.full_name] = enum_val_name
+
+  if o.abbreviation then
+    option_index[o.abbreviation] = enum_val_name
+  end
+
+  if o.alias then
+    o.alias = type(o.alias) == 'string' and { o.alias } or o.alias
+
+    for _, v in ipairs(o.alias) do
+      option_index[v] = enum_val_name
+    end
+  end
+
+  for _, scope in ipairs(o.scope) do
+    table.insert(scope_options[scope], o)
+  end
+end
+
+enum_w('  // Option count')
+enum_w('#define kOptCount ' .. tostring(#options_meta))
+enum_w('} OptIndex;')
+
+--- @param scope string
+--- @param option_name string
+--- @return string
+local get_scope_option = function(scope, option_name)
+  return ('k%sOpt%s'):format(lowercase_to_titlecase(scope), lowercase_to_titlecase(option_name))
+end
+
+-- Generate option index enum for each scope
+for _, scope in ipairs(valid_scopes) do
+  enum_w('')
+
+  local scope_name = lowercase_to_titlecase(scope)
+  enum_w('typedef enum {')
+  enum_w(('  %s = -1,'):format(get_scope_option(scope, 'Invalid')))
+
+  for idx, option in ipairs(scope_options[scope]) do
+    enum_w(('  %s = %u,'):format(get_scope_option(scope, option.full_name), idx - 1))
+  end
+
+  enum_w(('  // %s option count'):format(scope_name))
+  enum_w(('#define %s %d'):format(get_scope_option(scope, 'Count'), #scope_options[scope]))
+  enum_w(('} %sOptIndex;'):format(scope_name))
+end
+
+-- Generate reverse lookup from option scope index to option index for each scope.
+for _, scope in ipairs(valid_scopes) do
+  enum_w('')
+  enum_w(('EXTERN const OptIndex %s_opt_idx[] INIT( = {'):format(scope))
+  for _, option in ipairs(scope_options[scope]) do
+    local idx = option_index[option.full_name]
+    enum_w(('  [%s] = %s,'):format(get_scope_option(scope, option.full_name), idx))
+  end
+  enum_w('});')
+end
+
+opt_enum_fd:close()
+
+-- Generate option index map.
+local hashy = require('generators.hashy')
+local neworder, hashfun = hashy.hashy_hash('find_option', vim.tbl_keys(option_index), function(idx)
+  return ('option_hash_elems[%s].name'):format(idx)
+end)
+
+map_w('static const struct { const char *name; OptIndex opt_idx; } option_hash_elems[] = {')
+
+for _, name in ipairs(neworder) do
+  assert(option_index[name] ~= nil)
+  map_w(('  { .name = "%s", .opt_idx = %s },'):format(name, option_index[name]))
+end
+
+map_w('};\n')
+map_w('static ' .. hashfun)
+
+opt_map_fd:close()
 
 local redraw_flags = {
   ui_option = 'kOptFlagUIOption',
@@ -35,12 +158,6 @@ local list_flags = {
   flagscomma = 'kOptFlagComma|kOptFlagFlagList',
 }
 
---- @param s string
---- @return string
-local lowercase_to_titlecase = function(s)
-  return s:sub(1, 1):upper() .. s:sub(2)
-end
-
 --- @param o vim.option_meta
 --- @return string
 local function get_flags(o)
@@ -95,6 +212,12 @@ local function opt_type_enum(opt_type)
   return ('kOptValType%s'):format(lowercase_to_titlecase(opt_type))
 end
 
+--- @param scope vim.option_scope
+--- @return string
+local function opt_scope_enum(scope)
+  return ('kOptScope%s'):format(lowercase_to_titlecase(scope))
+end
+
 --- @param o vim.option_meta
 --- @return string
 local function get_type_flags(o)
@@ -110,6 +233,35 @@ local function get_type_flags(o)
   return type_flags
 end
 
+--- @param o vim.option_meta
+--- @return string
+local function get_scope_flags(o)
+  local scope_flags = '0'
+
+  for _, scope in ipairs(o.scope) do
+    scope_flags = ('%s | (1 << %s)'):format(scope_flags, opt_scope_enum(scope))
+  end
+
+  return scope_flags
+end
+
+--- @param o vim.option_meta
+--- @return string
+local function get_scope_idx(o)
+  --- @type string[]
+  local strs = {}
+
+  for _, scope in pairs(valid_scopes) do
+    local has_scope = vim.tbl_contains(o.scope, scope)
+    strs[#strs + 1] = ('      [%s] = %s'):format(
+      opt_scope_enum(scope),
+      get_scope_option(scope, has_scope and o.full_name or 'Invalid')
+    )
+  end
+
+  return ('{\n%s\n    }'):format(table.concat(strs, ',\n'))
+end
+
 --- @param c string|string[]
 --- @param base_string? string
 --- @return string
@@ -166,7 +318,6 @@ end
 --- @param d vim.option_value|function
 --- @param n string
 --- @return string
-
 local get_defaults = function(d, n)
   if d == nil then
     error("option '" .. n .. "' should have a default value")
@@ -174,9 +325,6 @@ local get_defaults = function(d, n)
   return get_opt_val(d)
 end
 
---- @type [string,string][]
-local defines = {}
-
 --- @param i integer
 --- @param o vim.option_meta
 local function dump_option(i, o)
@@ -187,42 +335,28 @@ local function dump_option(i, o)
   end
   w('    .flags=' .. get_flags(o))
   w('    .type_flags=' .. get_type_flags(o))
+  w('    .scope_flags=' .. get_scope_flags(o))
+  w('    .scope_idx=' .. get_scope_idx(o))
   if o.enable_if then
     w(get_cond(o.enable_if))
   end
 
-  if o.varname then
-    w('    .var=&' .. o.varname)
-  elseif o.immutable then
-    -- Immutable options can directly point to the default value.
-    w(('    .var=&options[%u].def_val.data'):format(i - 1))
-  elseif #o.scope == 1 and o.scope[1] == 'window' then
-    w('    .var=VAR_WIN')
+  local is_window_local = #o.scope == 1 and o.scope[1] == 'win'
+
+  if not is_window_local then
+    if o.varname then
+      w('    .var=&' .. o.varname)
+    elseif o.immutable then
+      -- Immutable options can directly point to the default value.
+      w(('    .var=&options[%u].def_val.data'):format(i - 1))
+    else
+      -- Option must be immutable or have a variable.
+      assert(false)
+    end
   else
-    -- Option must be immutable or have a variable.
-    assert(false)
+    w('    .var=NULL')
   end
   w('    .immutable=' .. (o.immutable and 'true' or 'false'))
-  if #o.scope == 1 and o.scope[1] == 'global' then
-    w('    .indir=PV_NONE')
-  else
-    assert(#o.scope == 1 or #o.scope == 2)
-    assert(#o.scope == 1 or o.scope[1] == 'global')
-    local min_scope = o.scope[#o.scope]
-    local varname = o.pv_name or o.varname or ('p_' .. (o.abbreviation or o.full_name))
-    local pv_name = (
-      'OPT_'
-      .. min_scope:sub(1, 3):upper()
-      .. '('
-      .. (min_scope:sub(1, 1):upper() .. 'V_' .. varname:sub(3):upper())
-      .. ')'
-    )
-    if #o.scope == 2 then
-      pv_name = 'OPT_BOTH(' .. pv_name .. ')'
-    end
-    table.insert(defines, { 'PV_' .. varname:sub(3):upper(), pv_name })
-    w('    .indir=' .. pv_name)
-  end
   if o.cb then
     w('    .opt_did_set_cb=' .. o.cb)
   end
@@ -235,7 +369,6 @@ local function dump_option(i, o)
     w(('    .var=&options[%u].def_val.data'):format(i - 1))
     -- Option is always immutable on the false branch of `enable_if`.
     w('    .immutable=true')
-    w('    .indir=PV_NONE')
     w('#endif')
   end
   if o.defaults then
@@ -256,6 +389,7 @@ local function dump_option(i, o)
   w('  },')
 end
 
+-- Generate options[] array.
 w([[
 #include "nvim/ex_docmd.h"
 #include "nvim/ex_getln.h"
@@ -274,8 +408,3 @@ for i, o in ipairs(options.options) do
   dump_option(i, o)
 end
 w('};')
-w('')
-
-for _, v in ipairs(defines) do
-  w('#define ' .. v[1] .. ' ' .. v[2])
-end