eval: Implement dictionary change notifications

src/nvim/eval.c

@@ -98,6 +98,7 @@
 #include "nvim/os/input.h"
 #include "nvim/event/loop.h"
 #include "nvim/lib/kvec.h"
+#include "nvim/lib/queue.h"
 
 #define DICT_MAXNEST 100        /* maximum nesting of lists and dicts */
 
@@ -459,6 +460,13 @@ typedef struct {
   Queue *events;
 } TerminalJobData;
 
+typedef struct dict_watcher {
+  ufunc_T *callback;
+  char *key_pattern;
+  QUEUE node;
+  bool busy;  // prevent recursion if the dict is changed in the callback
+} DictWatcher;
+
 /// Structure representing current VimL to messagepack conversion state
 typedef struct {
   enum {
@@ -2376,6 +2384,14 @@ static void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv, int copy, ch
              : lp->ll_n1 != lp->ll_n2)
       EMSG(_("E711: List value has not enough items"));
   } else {
+    typval_T oldtv;
+    dict_T *dict = lp->ll_dict;
+    bool watched = is_watched(dict);
+
+    if (watched) {
+      init_tv(&oldtv);
+    }
+
     /*
      * Assign to a List or Dictionary item.
      */
@@ -2392,22 +2408,38 @@ static void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv, int copy, ch
         return;
       }
       lp->ll_tv = &di->di_tv;
-    } else if (op != NULL && *op != '=') {
-      tv_op(lp->ll_tv, rettv, op);
-      return;
-    } else
-      clear_tv(lp->ll_tv);
+    } else {
+      if (watched) {
+        copy_tv(lp->ll_tv, &oldtv);
+      }
 
-    /*
-     * Assign the value to the variable or list item.
-     */
-    if (copy)
+      if (op != NULL && *op != '=') {
+        tv_op(lp->ll_tv, rettv, op);
+        goto notify;
+      } else {
+        clear_tv(lp->ll_tv);
+      }
+    }
+
+    // Assign the value to the variable or list item.
+    if (copy) {
       copy_tv(rettv, lp->ll_tv);
-    else {
+    } else {
       *lp->ll_tv = *rettv;
       lp->ll_tv->v_lock = 0;
       init_tv(rettv);
     }
+
+notify:
+    if (watched) {
+      if (oldtv.v_type == VAR_UNKNOWN) {
+        dictwatcher_notify(dict, (char *)lp->ll_newkey, lp->ll_tv, NULL);
+      } else {
+        dictitem_T *di = lp->ll_di;
+        dictwatcher_notify(dict, (char *)di->di_key, lp->ll_tv, &oldtv);
+        clear_tv(&oldtv);
+      }
+    }
   }
 }
 
@@ -2932,12 +2964,31 @@ static int do_unlet_var(lval_T *lp, char_u *name_end, int forceit)
       ++lp->ll_n1;
     }
   } else {
-    if (lp->ll_list != NULL)
-      /* unlet a List item. */
+    if (lp->ll_list != NULL) {
+      // unlet a List item.
       listitem_remove(lp->ll_list, lp->ll_li);
-    else
-      /* unlet a Dictionary item. */
-      dictitem_remove(lp->ll_dict, lp->ll_di);
+    } else {
+      // unlet a Dictionary item.
+      dict_T *d = lp->ll_dict;
+      dictitem_T *di = lp->ll_di;
+      bool watched = is_watched(d);
+      char *key = NULL;
+      typval_T oldtv;
+
+      if (watched) {
+        copy_tv(&di->di_tv, &oldtv);
+        // need to save key because dictitem_remove will free it
+        key = xstrdup((char *)di->di_key);
+      }
+
+      dictitem_remove(d, di);
+
+      if (watched) {
+        dictwatcher_notify(d, key, NULL, &oldtv);
+        clear_tv(&oldtv);
+        xfree(key);
+      }
+    }
   }
 
   return ret;
@@ -2953,8 +3004,9 @@ int do_unlet(char_u *name, int forceit)
   hashitem_T  *hi;
   char_u      *varname;
   dictitem_T  *di;
+  dict_T *dict;
+  ht = find_var_ht_dict(name, &varname, &dict);
 
-  ht = find_var_ht(name, &varname);
   if (ht != NULL && *varname != NUL) {
     hi = hash_find(ht, varname);
     if (!HASHITEM_EMPTY(hi)) {
@@ -2962,7 +3014,19 @@ int do_unlet(char_u *name, int forceit)
       if (var_check_fixed(di->di_flags, name)
           || var_check_ro(di->di_flags, name))
         return FAIL;
+      typval_T oldtv;
+      bool watched = is_watched(dict);
+
+      if (watched) {
+        copy_tv(&di->di_tv, &oldtv);
+      }
+
       delete_var(ht, hi);
+
+      if (watched) {
+        dictwatcher_notify(dict, (char *)varname, NULL, &oldtv);
+        clear_tv(&oldtv);
+      }
       return OK;
     }
   }
@@ -5959,6 +6023,7 @@ dict_T *dict_alloc(void) FUNC_ATTR_NONNULL_RET
   d->dv_refcount = 0;
   d->dv_copyID = 0;
   d->internal_refcount = 0;
+  QUEUE_INIT(&d->watchers);
 
   return d;
 }
@@ -6025,6 +6090,14 @@ dict_free (
       --todo;
     }
   }
+
+  while (!QUEUE_EMPTY(&d->watchers)) {
+    QUEUE *w = QUEUE_HEAD(&d->watchers);
+    DictWatcher *watcher = dictwatcher_node_data(w);
+    dictwatcher_free(watcher);
+    QUEUE_REMOVE(w);
+  }
+
   hash_clear(&d->dv_hashtab);
   xfree(d);
 }
@@ -6066,10 +6139,11 @@ static void dictitem_remove(dict_T *dict, dictitem_T *item)
   hashitem_T  *hi;
 
   hi = hash_find(&dict->dv_hashtab, item->di_key);
-  if (HASHITEM_EMPTY(hi))
+  if (HASHITEM_EMPTY(hi)) {
     EMSG2(_(e_intern2), "dictitem_remove()");
-  else
+  } else {
     hash_remove(&dict->dv_hashtab, hi);
+  }
   dictitem_free(item);
 }
 
@@ -6285,6 +6359,12 @@ static ufunc_T *find_ufunc(uint8_t *name)
     // dict function, name is already translated
     rv = find_func(n);
   }
+
+  if (!rv) {
+    EMSG2(_("Function %s doesn't exist"), name);
+    return NULL;
+  }
+
   return rv;
 }
 
@@ -7098,6 +7178,8 @@ static struct fst {
   {"cursor",          1, 3, f_cursor},
   {"deepcopy",        1, 2, f_deepcopy},
   {"delete",          1, 1, f_delete},
+  {"dictwatcheradd",  3, 3, f_dictwatcheradd},
+  {"dictwatcherdel",  3, 3, f_dictwatcherdel},
   {"did_filetype",    0, 0, f_did_filetype},
   {"diff_filler",     1, 1, f_diff_filler},
   {"diff_hlID",       2, 2, f_diff_hlID},
@@ -8666,6 +8748,110 @@ static void f_delete(typval_T *argvars, typval_T *rettv)
     rettv->vval.v_number = os_remove((char *)get_tv_string(&argvars[0]));
 }
 
+// dictwatcheradd(dict, key, funcref) function
+static void f_dictwatcheradd(typval_T *argvars, typval_T *rettv)
+{
+  if (check_restricted() || check_secure()) {
+    return;
+  }
+
+  if (argvars[0].v_type != VAR_DICT) {
+    EMSG2(e_invarg2, "dict");
+    return;
+  }
+
+  if (argvars[1].v_type != VAR_STRING && argvars[1].v_type != VAR_NUMBER) {
+    EMSG2(e_invarg2, "key");
+    return;
+  }
+
+  if (argvars[2].v_type != VAR_FUNC && argvars[2].v_type != VAR_STRING) {
+    EMSG2(e_invarg2, "funcref");
+    return;
+  }
+
+  char *key_pattern = (char *)get_tv_string_chk(argvars + 1);
+  assert(key_pattern);
+  const size_t key_len = STRLEN(argvars[1].vval.v_string);
+
+  if (key_len == 0) {
+    EMSG(_(e_emptykey));
+    return;
+  }
+
+  ufunc_T *func = find_ufunc(argvars[2].vval.v_string);
+  if (!func) {
+    // Invalid function name. Error already reported by `find_ufunc`.
+    return;
+  }
+
+  func->uf_refcount++;
+  DictWatcher *watcher = xmalloc(sizeof(DictWatcher));
+  watcher->key_pattern = xmemdupz(key_pattern, key_len);
+  watcher->callback = func;
+  watcher->busy = false;
+  QUEUE_INSERT_TAIL(&argvars[0].vval.v_dict->watchers, &watcher->node);
+}
+
+// dictwatcherdel(dict, key, funcref) function
+static void f_dictwatcherdel(typval_T *argvars, typval_T *rettv)
+{
+  if (check_restricted() || check_secure()) {
+    return;
+  }
+
+  if (argvars[0].v_type != VAR_DICT) {
+    EMSG2(e_invarg2, "dict");
+    return;
+  }
+
+  if (argvars[1].v_type != VAR_STRING && argvars[1].v_type != VAR_NUMBER) {
+    EMSG2(e_invarg2, "key");
+    return;
+  }
+
+  if (argvars[2].v_type != VAR_FUNC && argvars[2].v_type != VAR_STRING) {
+    EMSG2(e_invarg2, "funcref");
+    return;
+  }
+
+  char *key_pattern = (char *)get_tv_string_chk(argvars + 1);
+  assert(key_pattern);
+  const size_t key_len = STRLEN(argvars[1].vval.v_string);
+
+  if (key_len == 0) {
+    EMSG(_(e_emptykey));
+    return;
+  }
+
+  ufunc_T *func = find_ufunc(argvars[2].vval.v_string);
+  if (!func) {
+    // Invalid function name. Error already reported by `find_ufunc`.
+    return;
+  }
+
+  dict_T *dict = argvars[0].vval.v_dict;
+  QUEUE *w = NULL;
+  DictWatcher *watcher = NULL;
+  bool matched = false;
+  QUEUE_FOREACH(w, &dict->watchers) {
+    watcher = dictwatcher_node_data(w);
+    if (func == watcher->callback
+        && !strcmp(watcher->key_pattern, key_pattern)) {
+      matched = true;
+      break;
+    }
+  }
+
+  if (!matched) {
+    EMSG("Couldn't find a watcher matching key and callback");
+    return;
+  }
+
+  QUEUE_REMOVE(w);
+  dictwatcher_free(watcher);
+}
+
 /*
  * "did_filetype()" function
  */
@@ -8972,6 +9158,7 @@ void dict_extend(dict_T *d1, dict_T *d2, char_u *action)
   dictitem_T  *di1;
   hashitem_T  *hi2;
   int todo;
+  bool watched = is_watched(d1);
 
   todo = (int)d2->dv_hashtab.ht_used;
   for (hi2 = d2->dv_hashtab.ht_array; todo > 0; ++hi2) {
@@ -8992,14 +9179,30 @@ void dict_extend(dict_T *d1, dict_T *d2, char_u *action)
       }
       if (di1 == NULL) {
         di1 = dictitem_copy(HI2DI(hi2));
-        if (dict_add(d1, di1) == FAIL)
+        if (dict_add(d1, di1) == FAIL) {
           dictitem_free(di1);
+        }
+
+        if (watched) {
+          dictwatcher_notify(d1, (char *)di1->di_key, &di1->di_tv, NULL);
+        }
       } else if (*action == 'e') {
         EMSG2(_("E737: Key already exists: %s"), hi2->hi_key);
         break;
       } else if (*action == 'f' && HI2DI(hi2) != di1) {
+        typval_T oldtv;
+
+        if (watched) {
+          copy_tv(&di1->di_tv, &oldtv);
+        }
+
         clear_tv(&di1->di_tv);
         copy_tv(&HI2DI(hi2)->di_tv, &di1->di_tv);
+
+        if (watched) {
+          dictwatcher_notify(d1, (char *)di1->di_key, &di1->di_tv, &oldtv);
+          clear_tv(&oldtv);
+        }
       }
     }
   }
@@ -13517,6 +13720,9 @@ static void f_remove(typval_T *argvars, typval_T *rettv)
           *rettv = di->di_tv;
           init_tv(&di->di_tv);
           dictitem_remove(d, di);
+          if (is_watched(d)) {
+            dictwatcher_notify(d, (char *)key, NULL, rettv);
+          }
         }
       }
     }
@@ -18233,6 +18439,7 @@ void init_var_dict(dict_T *dict, dictitem_T *dict_var, int scope)
   dict_var->di_tv.v_lock = VAR_FIXED;
   dict_var->di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
   dict_var->di_key[0] = NUL;
+  QUEUE_INIT(&dict->watchers);
 }
 
 /*
@@ -18365,8 +18572,16 @@ set_var (
   dictitem_T  *v;
   char_u      *varname;
   hashtab_T   *ht;
+  typval_T oldtv;
+  dict_T *dict;
+
+  ht = find_var_ht_dict(name, &varname, &dict);
+  bool watched = is_watched(dict);
+
+  if (watched) {
+    init_tv(&oldtv);
+  }
 
-  ht = find_var_ht(name, &varname);
   if (ht == NULL || *varname == NUL) {
     EMSG2(_(e_illvar), name);
     return;
@@ -18423,6 +18638,9 @@ set_var (
       return;
     }
 
+    if (watched) {
+      copy_tv(&v->di_tv, &oldtv);
+    }
     clear_tv(&v->di_tv);
   } else {                /* add a new variable */
     /* Can't add "v:" variable. */
@@ -18444,13 +18662,22 @@ set_var (
     v->di_flags = 0;
   }
 
-  if (copy || tv->v_type == VAR_NUMBER || tv->v_type == VAR_FLOAT)
+  if (copy || tv->v_type == VAR_NUMBER || tv->v_type == VAR_FLOAT) {
     copy_tv(tv, &v->di_tv);
-  else {
+  } else {
     v->di_tv = *tv;
     v->di_tv.v_lock = 0;
     init_tv(tv);
   }
+
+  if (watched) {
+    if (oldtv.v_type == VAR_UNKNOWN) {
+      dictwatcher_notify(dict, (char *)v->di_key, &v->di_tv, NULL);
+    } else {
+      dictwatcher_notify(dict, (char *)v->di_key, &v->di_tv, &oldtv);
+      clear_tv(&oldtv);
+    }
+  }
 }
 
 /*
@@ -21771,3 +21998,94 @@ bool eval_has_provider(char *name)
 
   return false;
 }
+
+// Compute the `DictWatcher` address from a QUEUE node. This only exists because
+// ASAN doesn't handle `QUEUE_DATA` pointer arithmetic, and we blacklist this
+// function on .asan-blacklist.
+static DictWatcher *dictwatcher_node_data(QUEUE *q)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_NONNULL_RET
+{
+  return QUEUE_DATA(q, DictWatcher, node);
+}
+
+// Send a change notification to all `dict` watchers that match `key`.
+static void dictwatcher_notify(dict_T *dict, const char *key, typval_T *newtv,
+    typval_T *oldtv)
+  FUNC_ATTR_NONNULL_ARG(1) FUNC_ATTR_NONNULL_ARG(2)
+{
+  typval_T argv[3];
+  for (size_t i = 0; i < ARRAY_SIZE(argv); i++) {
+    init_tv(argv + i);
+  }
+
+  argv[0].v_type = VAR_DICT;
+  argv[0].vval.v_dict = dict;
+  argv[1].v_type = VAR_STRING;
+  argv[1].vval.v_string = (char_u *)xstrdup(key);
+  argv[2].v_type = VAR_DICT;
+  argv[2].vval.v_dict = dict_alloc();
+  argv[2].vval.v_dict->dv_refcount++;
+
+  if (newtv) {
+    dictitem_T *v = dictitem_alloc((char_u *)"new");
+    copy_tv(newtv, &v->di_tv);
+    dict_add(argv[2].vval.v_dict, v);
+  }
+
+  if (oldtv) {
+    dictitem_T *v = dictitem_alloc((char_u *)"old");
+    copy_tv(oldtv, &v->di_tv);
+    dict_add(argv[2].vval.v_dict, v);
+  }
+
+  typval_T rettv;
+
+  QUEUE *w;
+  QUEUE_FOREACH(w, &dict->watchers) {
+    DictWatcher *watcher = dictwatcher_node_data(w);
+    if (!watcher->busy && dictwatcher_matches(watcher, key)) {
+      init_tv(&rettv);
+      watcher->busy = true;
+      call_user_func(watcher->callback, ARRAY_SIZE(argv), argv, &rettv,
+          curwin->w_cursor.lnum, curwin->w_cursor.lnum, NULL);
+      watcher->busy = false;
+      clear_tv(&rettv);
+    }
+  }
+
+  for (size_t i = 1; i < ARRAY_SIZE(argv); i++) {
+    clear_tv(argv + i);
+  }
+}
+
+// Test if `key` matches with with `watcher->key_pattern`
+static bool dictwatcher_matches(DictWatcher *watcher, const char *key)
+  FUNC_ATTR_NONNULL_ALL
+{
+  // For now only allow very simple globbing in key patterns: a '*' at the end
+  // of the string means it should match everything up to the '*' instead of the
+  // whole string.
+  char *nul = strchr(watcher->key_pattern, NUL);
+  size_t len = nul - watcher->key_pattern;
+  if (*(nul - 1) == '*') {
+    return !strncmp(key, watcher->key_pattern, len - 1);
+  } else {
+    return !strcmp(key, watcher->key_pattern);
+  }
+}
+
+// Perform all necessary cleanup for a `DictWatcher` instance.
+static void dictwatcher_free(DictWatcher *watcher)
+  FUNC_ATTR_NONNULL_ALL
+{
+  user_func_unref(watcher->callback);
+  xfree(watcher->key_pattern);
+  xfree(watcher);
+}
+
+// Check if `d` has at least one watcher.
+static bool is_watched(dict_T *d)
+{
+  return d && !QUEUE_EMPTY(&d->watchers);
+}
+