refactor(shada): rework msgpack decoding without msgpack-c

This also makes shada reading slightly faster due to avoiding
some copying and allocation.

Use keysets to drive decoding of msgpack maps for shada entries.

src/nvim/api/command.c

@@ -515,7 +515,7 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Arena
 
   if (HAS_KEY(cmd, cmd, magic)) {
     Dict(cmd_magic) magic[1] = KEYDICT_INIT;
-    if (!api_dict_to_keydict(magic, KeyDict_cmd_magic_get_field, cmd->magic, err)) {
+    if (!api_dict_to_keydict(magic, DictHash(cmd_magic), cmd->magic, err)) {
       goto end;
     }
 
@@ -533,14 +533,14 @@ String nvim_cmd(uint64_t channel_id, Dict(cmd) *cmd, Dict(cmd_opts) *opts, Arena
 
   if (HAS_KEY(cmd, cmd, mods)) {
     Dict(cmd_mods) mods[1] = KEYDICT_INIT;
-    if (!api_dict_to_keydict(mods, KeyDict_cmd_mods_get_field, cmd->mods, err)) {
+    if (!api_dict_to_keydict(mods, DictHash(cmd_mods), cmd->mods, err)) {
       goto end;
     }
 
     if (HAS_KEY(mods, cmd_mods, filter)) {
       Dict(cmd_mods_filter) filter[1] = KEYDICT_INIT;
 
-      if (!api_dict_to_keydict(&filter, KeyDict_cmd_mods_filter_get_field,
+      if (!api_dict_to_keydict(&filter, DictHash(cmd_mods_filter),
                                mods->filter, err)) {
         goto end;
       }

src/nvim/api/keysets_defs.h

@@ -103,7 +103,7 @@ typedef struct {
   Object nargs;
   Object preview;
   Object range;
-  Boolean register_;
+  Boolean register_ DictKey(register);
 } Dict(user_command);
 
 typedef struct {
@@ -170,7 +170,7 @@ typedef struct {
   Boolean reverse;
   Boolean altfont;
   Boolean nocombine;
-  Boolean default_;
+  Boolean default_ DictKey(default);
   Object cterm;
   Object foreground;
   Object fg;
@@ -392,3 +392,41 @@ typedef struct {
   OptionalKeys is_set__ns_opts_;
   Array wins;
 } Dict(ns_opts);
+
+typedef struct {
+  OptionalKeys is_set___shada_search_pat_;
+  Boolean magic DictKey(sm);
+  Boolean smartcase DictKey(sc);
+  Boolean has_line_offset DictKey(sl);
+  Boolean place_cursor_at_end DictKey(se);
+  Boolean is_last_used DictKey(su);
+  Boolean is_substitute_pattern DictKey(ss);
+  Boolean highlighted DictKey(sh);
+  Boolean search_backward DictKey(sb);
+  Integer offset DictKey(so);
+  String pat DictKey(sp);
+} Dict(_shada_search_pat);
+
+typedef struct {
+  OptionalKeys is_set___shada_mark_;
+  Integer n;
+  Integer l;
+  Integer c;
+  String f;
+} Dict(_shada_mark);
+
+typedef struct {
+  OptionalKeys is_set___shada_register_;
+  StringArray rc;
+  Boolean ru;
+  Integer rt;
+  Integer n;
+  Integer rw;
+} Dict(_shada_register);
+
+typedef struct {
+  OptionalKeys is_set___shada_buflist_item_;
+  Integer l;
+  Integer c;
+  String f;
+} Dict(_shada_buflist_item);

src/nvim/api/private/defs.h

@@ -19,6 +19,8 @@
 # define ArrayOf(...) Array
 # define DictionaryOf(...) Dictionary
 # define Dict(name) KeyDict_##name
+# define DictHash(name) KeyDict_##name##_get_field
+# define DictKey(name)
 # include "api/private/defs.h.inline.generated.h"
 #endif
 
@@ -88,6 +90,8 @@ typedef kvec_t(Object) Array;
 typedef struct key_value_pair KeyValuePair;
 typedef kvec_t(KeyValuePair) Dictionary;
 
+typedef kvec_t(String) StringArray;
+
 typedef enum {
   kObjectTypeNil = 0,
   kObjectTypeBoolean,
@@ -103,6 +107,10 @@ typedef enum {
   kObjectTypeTabpage,
 } ObjectType;
 
+typedef enum {
+  kUnpackTypeStringArray = -1,
+} UnpackType;
+
 /// Value by which objects represented as EXT type are shifted
 ///
 /// Subtracted when packing, added when unpacking. Used to allow moving
@@ -140,7 +148,7 @@ typedef struct {
 typedef struct {
   char *str;
   size_t ptr_off;
-  ObjectType type;  // kObjectTypeNil == untyped
+  int type;  // ObjectType or UnpackType. kObjectTypeNil == untyped
   int opt_index;
   bool is_hlgroup;
 } KeySetLink;

src/nvim/api/private/helpers.c

@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <limits.h>
-#include <msgpack/unpack.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -922,15 +921,17 @@ bool api_dict_to_keydict(void *retval, FieldHashfn hashy, Dictionary dict, Error
       } else if (value->type == kObjectTypeDictionary) {
         *val = value->data.dictionary;
       } else {
-        api_err_exp(err, field->str, api_typename(field->type), api_typename(value->type));
+        api_err_exp(err, field->str, api_typename((ObjectType)field->type),
+                    api_typename(value->type));
         return false;
       }
     } else if (field->type == kObjectTypeBuffer || field->type == kObjectTypeWindow
                || field->type == kObjectTypeTabpage) {
-      if (value->type == kObjectTypeInteger || value->type == field->type) {
+      if (value->type == kObjectTypeInteger || value->type == (ObjectType)field->type) {
         *(handle_T *)mem = (handle_T)value->data.integer;
       } else {
-        api_err_exp(err, field->str, api_typename(field->type), api_typename(value->type));
+        api_err_exp(err, field->str, api_typename((ObjectType)field->type),
+                    api_typename(value->type));
         return false;
       }
     } else if (field->type == kObjectTypeLuaRef) {
@@ -980,7 +981,7 @@ Dictionary api_keydict_to_dict(void *value, KeySetLink *table, size_t max_size,
     } else if (field->type == kObjectTypeBuffer || field->type == kObjectTypeWindow
                || field->type == kObjectTypeTabpage) {
       val.data.integer = *(handle_T *)mem;
-      val.type = field->type;
+      val.type = (ObjectType)field->type;
     } else if (field->type == kObjectTypeLuaRef) {
       // do nothing
     } else {

src/nvim/api/ui.c

@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <inttypes.h>
-#include <msgpack/pack.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>