feat(api): autocmd `group` can be either name or id (#17559)

* feat(api): `group` can be either string or int

This affects the following API functions:
- `vim.api.nvim_create_autocmd`
- `vim.api.nvim_get_autocmds`
- `vim.api.nvim_do_autocmd`

closes #17552

* refactor: add two maps for fast lookups

* fix: delete augroup info from id->name map

When in "stupid_legacy_mode", the value in name->id map would be updated
to `AUGROUP_DELETED`, but the entry would still remain in id->name. This
would create a problem in `augroup_name` function which would return the
name of the augroup instead of `--DELETED--`.

The id->name map is only used for fast loopup in `augroup_name` function
so there's no point in keeping the entry of deleted augroup in it.

Co-authored-by: TJ DeVries <devries.timothyj@gmail.com>

1 files changed, 37 insertions, 22 deletions

diff --git a/src/nvim/autocmd.c b/src/nvim/autocmd.c
index 7cb493f57d..a850e5c1a0 100644
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -105,15 +105,24 @@ static char_u *old_termresponse = NULL;
 #define FOR_ALL_AUPATS_IN_EVENT(event, ap) \
   for (AutoPat *ap = first_autopat[event]; ap != NULL; ap = ap->next)  // NOLINT
 
-// Map of autocmd group names.
+// Map of autocmd group names and ids.
 //  name -> ID
-static Map(String, int) augroup_map = MAP_INIT;
+//  ID -> name
+static Map(String, int) map_augroup_name_to_id = MAP_INIT;
+static Map(int, String) map_augroup_id_to_name = MAP_INIT;
 
-static void augroup_map_del(char *name)
+static void augroup_map_del(int id, char *name)
 {
-  String key = map_key(String, int)(&augroup_map, cstr_as_string(name));
-  map_del(String, int)(&augroup_map, key);
-  api_free_string(key);
+  if (name != NULL) {
+    String key = map_key(String, int)(&map_augroup_name_to_id, cstr_as_string(name));
+    map_del(String, int)(&map_augroup_name_to_id, key);
+    api_free_string(key);
+  }
+  if (id > 0) {
+    String mapped = map_get(int, String)(&map_augroup_id_to_name, id);
+    api_free_string(mapped);
+    map_del(int, String)(&map_augroup_id_to_name, id);
+  }
 }
 
 
@@ -382,12 +391,14 @@ int augroup_add(char *name)
   }
 
   if (existing_id == AUGROUP_DELETED) {
-    augroup_map_del(name);
+    augroup_map_del(existing_id, name);
   }
 
   int next_id = next_augroup_id++;
-  String name_copy = cstr_to_string(name);
-  map_put(String, int)(&augroup_map, name_copy, next_id);
+  String name_key = cstr_to_string(name);
+  String name_val = cstr_to_string(name);
+  map_put(String, int)(&map_augroup_name_to_id, name_key, next_id);
+  map_put(int, String)(&map_augroup_id_to_name, next_id, name_val);
 
   return next_id;
 }
@@ -416,7 +427,8 @@ void augroup_del(char *name, bool stupid_legacy_mode)
         FOR_ALL_AUPATS_IN_EVENT(event, ap) {
           if (ap->group == i && ap->pat != NULL) {
             give_warning((char_u *)_("W19: Deleting augroup that is still in use"), true);
-            map_put(String, int)(&augroup_map, cstr_as_string(name), AUGROUP_DELETED);
+            map_put(String, int)(&map_augroup_name_to_id, cstr_as_string(name), AUGROUP_DELETED);
+            augroup_map_del(ap->group, NULL);
             return;
           }
         }
@@ -432,7 +444,7 @@ void augroup_del(char *name, bool stupid_legacy_mode)
     }
 
     // Remove the group because it's not currently in use.
-    augroup_map_del(name);
+    augroup_map_del(i, name);
     au_cleanup();
   }
 }
@@ -445,7 +457,7 @@ void augroup_del(char *name, bool stupid_legacy_mode)
 int augroup_find(const char *name)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  int existing_id = map_get(String, int)(&augroup_map, cstr_as_string((char *)name));
+  int existing_id = map_get(String, int)(&map_augroup_name_to_id, cstr_as_string((char *)name));
   if (existing_id == AUGROUP_DELETED) {
     return existing_id;
   }
@@ -487,13 +499,10 @@ char *augroup_name(int group)
     return NULL;
   }
 
-  String key;
-  int value;
-  map_foreach(&augroup_map, key, value, {
-    if (value == group) {
-      return key.data;
-    }
-  });
+  String key = map_get(int, String)(&map_augroup_id_to_name, group);
+  if (key.data != NULL) {
+    return key.data;
+  }
 
   // If it's not in the map anymore, then it must have been deleted.
   return (char *)get_deleted_augroup();
@@ -526,7 +535,7 @@ void do_augroup(char_u *arg, int del_group)
 
     String name;
     int value;
-    map_foreach(&augroup_map, name, value, {
+    map_foreach(&map_augroup_name_to_id, name, value, {
       if (value > 0) {
         msg_puts(name.data);
       } else {
@@ -556,11 +565,17 @@ void free_all_autocmds(void)
   // Delete the augroup_map, including free the data
   String name;
   int id;
-  map_foreach(&augroup_map, name, id, {
+  map_foreach(&map_augroup_name_to_id, name, id, {
+    (void)id;
+    api_free_string(name);
+  })
+  map_destroy(String, int)(&map_augroup_name_to_id);
+
+  map_foreach(&map_augroup_id_to_name, id, name, {
     (void)id;
     api_free_string(name);
   })
-  map_destroy(String, int)(&augroup_map);
+  map_destroy(int, String)(&map_augroup_id_to_name);
 }
 #endif