Merge #6569 from justinmk/apierror

api: Do not truncate errors <1 MB

22 files changed, 243 insertions, 184 deletions

diff --git a/scripts/gendispatch.lua b/scripts/gendispatch.lua
index 45a4f4a4de..0ee3ae6475 100644
--- a/scripts/gendispatch.lua
+++ b/scripts/gendispatch.lua
@@ -225,8 +225,7 @@ for i = 1, #functions do
     end
     output:write('\n')
     output:write('\n  if (args.size != '..#fn.parameters..') {')
-    output:write('\n    snprintf(error->msg, sizeof(error->msg), "Wrong number of arguments: expecting '..#fn.parameters..' but got %zu", args.size);')
-    output:write('\n    error->set = true;')
+    output:write('\n    api_set_error(error, kErrorTypeException, "Wrong number of arguments: expecting '..#fn.parameters..' but got %zu", args.size);')
     output:write('\n    goto cleanup;')
     output:write('\n  }\n')
 
@@ -251,8 +250,7 @@ for i = 1, #functions do
           output:write('\n    '..converted..' = (handle_T)args.items['..(j - 1)..'].data.integer;')
         end
         output:write('\n  } else {')
-        output:write('\n    snprintf(error->msg, sizeof(error->msg), "Wrong type for argument '..j..', expecting '..param[1]..'");')
-        output:write('\n    error->set = true;')
+        output:write('\n    api_set_error(error, kErrorTypeException, "Wrong type for argument '..j..', expecting '..param[1]..'");')
         output:write('\n    goto cleanup;')
         output:write('\n  }\n')
       else
@@ -292,7 +290,7 @@ for i = 1, #functions do
         output:write('error);\n')
       end
       -- and check for the error
-      output:write('\n  if (error->set) {')
+      output:write('\n  if (ERROR_SET(error)) {')
       output:write('\n    goto cleanup;')
       output:write('\n  }\n')
     else
diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 1b3592679b..ae5728ee21 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -65,7 +65,7 @@ String buffer_get_line(Buffer buffer, Integer index, Error *err)
   index = convert_index(index);
   Array slice = nvim_buf_get_lines(0, buffer, index, index+1, true, err);
 
-  if (!err->set && slice.size) {
+  if (!ERROR_SET(err) && slice.size) {
     rv = slice.items[0].data.string;
   }
 
@@ -171,7 +171,7 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
   end = normalize_index(buf, end, &oob);
 
   if (strict_indexing && oob) {
-    api_set_error(err, Validation, _("Index out of bounds"));
+    api_set_error(err, kErrorTypeValidation, "Index out of bounds");
     return rv;
   }
 
@@ -187,7 +187,7 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
     int64_t lnum = start + (int64_t)i;
 
     if (lnum > LONG_MAX) {
-      api_set_error(err, Validation, _("Line index is too high"));
+      api_set_error(err, kErrorTypeValidation, "Line index is too high");
       goto end;
     }
 
@@ -203,7 +203,7 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
   }
 
 end:
-  if (err->set) {
+  if (ERROR_SET(err)) {
     for (size_t i = 0; i < rv.size; i++) {
       xfree(rv.items[i].data.string.data);
     }
@@ -283,15 +283,15 @@ void nvim_buf_set_lines(uint64_t channel_id,
   end = normalize_index(buf, end, &oob);
 
   if (strict_indexing && oob) {
-    api_set_error(err, Validation, _("Index out of bounds"));
+    api_set_error(err, kErrorTypeValidation, "Index out of bounds");
     return;
   }
 
 
   if (start > end) {
     api_set_error(err,
-                  Validation,
-                  _("Argument \"start\" is higher than \"end\""));
+                  kErrorTypeValidation,
+                  "Argument \"start\" is higher than \"end\"");
     return;
   }
 
@@ -305,8 +305,8 @@ void nvim_buf_set_lines(uint64_t channel_id,
   for (size_t i = 0; i < new_len; i++) {
     if (replacement.items[i].type != kObjectTypeString) {
       api_set_error(err,
-                    Validation,
-                    _("All items in the replacement array must be strings"));
+                    kErrorTypeValidation,
+                    "All items in the replacement array must be strings");
       goto end;
     }
 
@@ -317,7 +317,8 @@ void nvim_buf_set_lines(uint64_t channel_id,
     lines[i] = xmallocz(l.size);
     for (size_t j = 0; j < l.size; j++) {
       if (l.data[j] == '\n' && channel_id != INTERNAL_CALL) {
-        api_set_error(err, Exception, _("string cannot contain newlines"));
+        api_set_error(err, kErrorTypeException,
+                      "String cannot contain newlines");
         new_len = i + 1;
         goto end;
       }
@@ -330,7 +331,7 @@ void nvim_buf_set_lines(uint64_t channel_id,
   switch_to_win_for_buf(buf, &save_curwin, &save_curtab, &save_curbuf);
 
   if (u_save((linenr_T)(start - 1), (linenr_T)end) == FAIL) {
-    api_set_error(err, Exception, _("Failed to save undo information"));
+    api_set_error(err, kErrorTypeException, "Failed to save undo information");
     goto end;
   }
 
@@ -340,7 +341,7 @@ void nvim_buf_set_lines(uint64_t channel_id,
   size_t to_delete = (new_len < old_len) ? (size_t)(old_len - new_len) : 0;
   for (size_t i = 0; i < to_delete; i++) {
     if (ml_delete((linenr_T)start, false) == FAIL) {
-      api_set_error(err, Exception, _("Failed to delete line"));
+      api_set_error(err, kErrorTypeException, "Failed to delete line");
       goto end;
     }
   }
@@ -357,12 +358,12 @@ void nvim_buf_set_lines(uint64_t channel_id,
     int64_t lnum = start + (int64_t)i;
 
     if (lnum > LONG_MAX) {
-      api_set_error(err, Validation, _("Index value is too high"));
+      api_set_error(err, kErrorTypeValidation, "Index value is too high");
       goto end;
     }
 
     if (ml_replace((linenr_T)lnum, (char_u *)lines[i], false) == FAIL) {
-      api_set_error(err, Exception, _("Failed to replace line"));
+      api_set_error(err, kErrorTypeException, "Failed to replace line");
       goto end;
     }
     // Mark lines that haven't been passed to the buffer as they need
@@ -375,12 +376,12 @@ void nvim_buf_set_lines(uint64_t channel_id,
     int64_t lnum = start + (int64_t)i - 1;
 
     if (lnum > LONG_MAX) {
-      api_set_error(err, Validation, _("Index value is too high"));
+      api_set_error(err, kErrorTypeValidation, "Index value is too high");
       goto end;
     }
 
     if (ml_append((linenr_T)lnum, (char_u *)lines[i], 0, false) == FAIL) {
-      api_set_error(err, Exception, _("Failed to insert line"));
+      api_set_error(err, kErrorTypeException, "Failed to insert line");
       goto end;
     }
 
@@ -627,7 +628,7 @@ void nvim_buf_set_name(Buffer buffer, String name, Error *err)
   }
 
   if (ren_ret == FAIL) {
-    api_set_error(err, Exception, _("Failed to rename buffer"));
+    api_set_error(err, kErrorTypeException, "Failed to rename buffer");
   }
 }
 
@@ -639,7 +640,9 @@ Boolean nvim_buf_is_valid(Buffer buffer)
     FUNC_API_SINCE(1)
 {
   Error stub = ERROR_INIT;
-  return find_buffer_by_handle(buffer, &stub) != NULL;
+  Boolean ret = find_buffer_by_handle(buffer, &stub) != NULL;
+  api_clear_error(&stub);
+  return ret;
 }
 
 /// Inserts a sequence of lines to a buffer at a certain index
@@ -678,7 +681,8 @@ ArrayOf(Integer, 2) nvim_buf_get_mark(Buffer buffer, String name, Error *err)
   }
 
   if (name.size != 1) {
-    api_set_error(err, Validation, _("Mark name must be a single character"));
+    api_set_error(err, kErrorTypeValidation,
+                  "Mark name must be a single character");
     return rv;
   }
 
@@ -696,7 +700,7 @@ ArrayOf(Integer, 2) nvim_buf_get_mark(Buffer buffer, String name, Error *err)
   }
 
   if (posp == NULL) {
-    api_set_error(err, Validation, _("Invalid mark name"));
+    api_set_error(err, kErrorTypeValidation, "Invalid mark name");
     return rv;
   }
 
@@ -751,11 +755,11 @@ Integer nvim_buf_add_highlight(Buffer buffer,
   }
 
   if (line < 0 || line >= MAXLNUM) {
-    api_set_error(err, Validation, _("Line number outside range"));
+    api_set_error(err, kErrorTypeValidation, "Line number outside range");
     return 0;
   }
   if (col_start < 0 || col_start > MAXCOL) {
-    api_set_error(err, Validation, _("Column value outside range"));
+    api_set_error(err, kErrorTypeValidation, "Column value outside range");
     return 0;
   }
   if (col_end < 0 || col_end > MAXCOL) {
@@ -792,7 +796,7 @@ void nvim_buf_clear_highlight(Buffer buffer,
   }
 
   if (line_start < 0 || line_start >= MAXLNUM) {
-    api_set_error(err, Validation, _("Line number outside range"));
+    api_set_error(err, kErrorTypeValidation, "Line number outside range");
     return;
   }
   if (line_end < 0 || line_end > MAXLNUM) {
diff --git a/src/nvim/api/private/defs.h b/src/nvim/api/private/defs.h
index 223aab09dc..60bf38265f 100644
--- a/src/nvim/api/private/defs.h
+++ b/src/nvim/api/private/defs.h
@@ -8,9 +8,11 @@
 #define ARRAY_DICT_INIT {.size = 0, .capacity = 0, .items = NULL}
 #define STRING_INIT {.data = NULL, .size = 0}
 #define OBJECT_INIT { .type = kObjectTypeNil }
-#define ERROR_INIT { .set = false }
+#define ERROR_INIT { .type = kErrorTypeNone, .msg = NULL }
 #define REMOTE_TYPE(type) typedef handle_T type
 
+#define ERROR_SET(e) ((e)->type != kErrorTypeNone)
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # define ArrayOf(...) Array
 # define DictionaryOf(...) Dictionary
@@ -20,6 +22,7 @@ typedef int handle_T;
 
 // Basic types
 typedef enum {
+  kErrorTypeNone = -1,
   kErrorTypeException,
   kErrorTypeValidation
 } ErrorType;
@@ -38,8 +41,7 @@ typedef enum {
 
 typedef struct {
   ErrorType type;
-  char msg[1024];
-  bool set;
+  char *msg;
 } Error;
 
 typedef bool Boolean;
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index 5877b848fc..69cb19c14f 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -61,7 +61,7 @@ bool try_end(Error *err)
       discard_current_exception();
     }
 
-    api_set_error(err, Exception, _("Keyboard interrupt"));
+    api_set_error(err, kErrorTypeException, "Keyboard interrupt");
     got_int = false;
   } else if (msg_list != NULL && *msg_list != NULL) {
     int should_free;
@@ -69,19 +69,18 @@ bool try_end(Error *err)
                                              ET_ERROR,
                                              NULL,
                                              &should_free);
-    xstrlcpy(err->msg, msg, sizeof(err->msg));
-    err->set = true;
+    api_set_error(err, kErrorTypeException, "%s", msg);
     free_global_msglist();
 
     if (should_free) {
       xfree(msg);
     }
   } else if (did_throw) {
-    api_set_error(err, Exception, "%s", current_exception->value);
+    api_set_error(err, kErrorTypeException, "%s", current_exception->value);
     discard_current_exception();
   }
 
-  return err->set;
+  return ERROR_SET(err);
 }
 
 /// Recursively expands a vimscript value in a dict
@@ -94,8 +93,8 @@ Object dict_get_value(dict_T *dict, String key, Error *err)
   dictitem_T *const di = tv_dict_find(dict, key.data, (ptrdiff_t)key.size);
 
   if (di == NULL) {
-    api_set_error(err, Validation, _("Key not found"));
-    return (Object) OBJECT_INIT;
+    api_set_error(err, kErrorTypeValidation, "Key not found");
+    return (Object)OBJECT_INIT;
   }
 
   return vim_to_object(&di->di_tv);
@@ -118,17 +117,18 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del,
   Object rv = OBJECT_INIT;
 
   if (dict->dv_lock) {
-    api_set_error(err, Exception, _("Dictionary is locked"));
+    api_set_error(err, kErrorTypeException, "Dictionary is locked");
     return rv;
   }
 
   if (key.size == 0) {
-    api_set_error(err, Validation, _("Empty variable names aren't allowed"));
+    api_set_error(err, kErrorTypeValidation,
+                  "Empty variable names aren't allowed");
     return rv;
   }
 
   if (key.size > INT_MAX) {
-    api_set_error(err, Validation, _("Key length is too high"));
+    api_set_error(err, kErrorTypeValidation, "Key length is too high");
     return rv;
   }
 
@@ -136,13 +136,13 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del,
 
   if (di != NULL) {
     if (di->di_flags & DI_FLAGS_RO) {
-      api_set_error(err, Exception, _("Key is read-only: %s"), key.data);
+      api_set_error(err, kErrorTypeException, "Key is read-only: %s", key.data);
       return rv;
     } else if (di->di_flags & DI_FLAGS_FIX) {
-      api_set_error(err, Exception, _("Key is fixed: %s"), key.data);
+      api_set_error(err, kErrorTypeException, "Key is fixed: %s", key.data);
       return rv;
     } else if (di->di_flags & DI_FLAGS_LOCK) {
-      api_set_error(err, Exception, _("Key is locked: %s"), key.data);
+      api_set_error(err, kErrorTypeException, "Key is locked: %s", key.data);
       return rv;
     }
   }
@@ -151,7 +151,8 @@ Object dict_set_var(dict_T *dict, String key, Object value, bool del,
     // Delete the key
     if (di == NULL) {
       // Doesn't exist, fail
-      api_set_error(err, Validation, _("Key \"%s\" doesn't exist"), key.data);
+      api_set_error(err, kErrorTypeValidation, "Key does not exist: %s",
+                    key.data);
     } else {
       // Return the old value
       if (retval) {
@@ -203,7 +204,7 @@ Object get_option_from(void *from, int type, String name, Error *err)
   Object rv = OBJECT_INIT;
 
   if (name.size == 0) {
-    api_set_error(err, Validation, _("Empty option name"));
+    api_set_error(err, kErrorTypeValidation, "Empty option name");
     return rv;
   }
 
@@ -215,8 +216,8 @@ Object get_option_from(void *from, int type, String name, Error *err)
 
   if (!flags) {
     api_set_error(err,
-                  Validation,
-                  _("Invalid option name \"%s\""),
+                  kErrorTypeValidation,
+                  "Invalid option name \"%s\"",
                   name.data);
     return rv;
   }
@@ -234,14 +235,14 @@ Object get_option_from(void *from, int type, String name, Error *err)
       rv.data.string.size = strlen(stringval);
     } else {
       api_set_error(err,
-                    Exception,
-                    _("Unable to get value for option \"%s\""),
+                    kErrorTypeException,
+                    "Unable to get value for option \"%s\"",
                     name.data);
     }
   } else {
     api_set_error(err,
-                  Exception,
-                  _("Unknown type for option \"%s\""),
+                  kErrorTypeException,
+                  "Unknown type for option \"%s\"",
                   name.data);
   }
 
@@ -258,7 +259,7 @@ Object get_option_from(void *from, int type, String name, Error *err)
 void set_option_to(void *to, int type, String name, Object value, Error *err)
 {
   if (name.size == 0) {
-    api_set_error(err, Validation, _("Empty option name"));
+    api_set_error(err, kErrorTypeValidation, "Empty option name");
     return;
   }
 
@@ -266,8 +267,8 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
 
   if (flags == 0) {
     api_set_error(err,
-                  Validation,
-                  _("Invalid option name \"%s\""),
+                  kErrorTypeValidation,
+                  "Invalid option name \"%s\"",
                   name.data);
     return;
   }
@@ -275,15 +276,15 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
   if (value.type == kObjectTypeNil) {
     if (type == SREQ_GLOBAL) {
       api_set_error(err,
-                    Exception,
-                    _("Unable to unset option \"%s\""),
+                    kErrorTypeException,
+                    "Unable to unset option \"%s\"",
                     name.data);
       return;
     } else if (!(flags & SOPT_GLOBAL)) {
       api_set_error(err,
-                    Exception,
-                    _("Cannot unset option \"%s\" "
-                      "because it doesn't have a global value"),
+                    kErrorTypeException,
+                    "Cannot unset option \"%s\" "
+                    "because it doesn't have a global value",
                     name.data);
       return;
     } else {
@@ -297,8 +298,8 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
   if (flags & SOPT_BOOL) {
     if (value.type != kObjectTypeBoolean) {
       api_set_error(err,
-                    Validation,
-                    _("Option \"%s\" requires a boolean value"),
+                    kErrorTypeValidation,
+                    "Option \"%s\" requires a boolean value",
                     name.data);
       return;
     }
@@ -308,16 +309,16 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
   } else if (flags & SOPT_NUM) {
     if (value.type != kObjectTypeInteger) {
       api_set_error(err,
-                    Validation,
-                    _("Option \"%s\" requires an integer value"),
+                    kErrorTypeValidation,
+                    "Option \"%s\" requires an integer value",
                     name.data);
       return;
     }
 
     if (value.data.integer > INT_MAX || value.data.integer < INT_MIN) {
       api_set_error(err,
-                    Validation,
-                    _("Value for option \"%s\" is outside range"),
+                    kErrorTypeValidation,
+                    "Value for option \"%s\" is outside range",
                     name.data);
       return;
     }
@@ -327,8 +328,8 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
   } else {
     if (value.type != kObjectTypeString) {
       api_set_error(err,
-                    Validation,
-                    _("Option \"%s\" requires a string value"),
+                    kErrorTypeValidation,
+                    "Option \"%s\" requires a string value",
                     name.data);
       return;
     }
@@ -561,13 +562,13 @@ buf_T *find_buffer_by_handle(Buffer buffer, Error *err)
   buf_T *rv = handle_get_buffer(buffer);
 
   if (!rv) {
-    api_set_error(err, Validation, _("Invalid buffer id"));
+    api_set_error(err, kErrorTypeValidation, "Invalid buffer id");
   }
 
   return rv;
 }
 
-win_T * find_window_by_handle(Window window, Error *err)
+win_T *find_window_by_handle(Window window, Error *err)
 {
   if (window == 0) {
     return curwin;
@@ -576,13 +577,13 @@ win_T * find_window_by_handle(Window window, Error *err)
   win_T *rv = handle_get_window(window);
 
   if (!rv) {
-    api_set_error(err, Validation, _("Invalid window id"));
+    api_set_error(err, kErrorTypeValidation, "Invalid window id");
   }
 
   return rv;
 }
 
-tabpage_T * find_tab_by_handle(Tabpage tabpage, Error *err)
+tabpage_T *find_tab_by_handle(Tabpage tabpage, Error *err)
 {
   if (tabpage == 0) {
     return curtab;
@@ -591,7 +592,7 @@ tabpage_T * find_tab_by_handle(Tabpage tabpage, Error *err)
   tabpage_T *rv = handle_get_tabpage(tabpage);
 
   if (!rv) {
-    api_set_error(err, Validation, _("Invalid tabpage id"));
+    api_set_error(err, kErrorTypeValidation, "Invalid tabpage id");
   }
 
   return rv;
@@ -659,7 +660,7 @@ bool object_to_vim(Object obj, typval_T *tv, Error *err)
     case kObjectTypeInteger:
       if (obj.data.integer > VARNUMBER_MAX
           || obj.data.integer < VARNUMBER_MIN) {
-        api_set_error(err, Validation, _("Integer value outside range"));
+        api_set_error(err, kErrorTypeValidation, "Integer value outside range");
         return false;
       }
 
@@ -713,8 +714,8 @@ bool object_to_vim(Object obj, typval_T *tv, Error *err)
         String key = item.key;
 
         if (key.size == 0) {
-          api_set_error(err, Validation,
-                        _("Empty dictionary keys aren't allowed"));
+          api_set_error(err, kErrorTypeValidation,
+                        "Empty dictionary keys aren't allowed");
           // cleanup
           tv_dict_free(dict);
           return false;
@@ -801,6 +802,17 @@ void api_free_dictionary(Dictionary value)
   xfree(value.items);
 }
 
+void api_clear_error(Error *value)
+  FUNC_ATTR_NONNULL_ALL
+{
+  if (!ERROR_SET(value)) {
+    return;
+  }
+  xfree(value->msg);
+  value->msg = NULL;
+  value->type = kErrorTypeNone;
+}
+
 Dictionary api_metadata(void)
 {
   static Dictionary metadata = ARRAY_DICT_INIT;
@@ -927,8 +939,8 @@ static void set_option_value_for(char *key,
           return;
         }
         api_set_error(err,
-                      Exception,
-                      _("Problem while switching windows"));
+                      kErrorTypeException,
+                      "Problem while switching windows");
         return;
       }
       set_option_value_err(key, numval, stringval, opt_flags, err);
@@ -944,7 +956,7 @@ static void set_option_value_for(char *key,
       break;
   }
 
-  if (err->set) {
+  if (ERROR_SET(err)) {
     return;
   }
 
@@ -965,6 +977,26 @@ static void set_option_value_err(char *key,
       return;
     }
 
-    api_set_error(err, Exception, "%s", errmsg);
+    api_set_error(err, kErrorTypeException, "%s", errmsg);
   }
 }
+
+void api_set_error(Error *err, ErrorType errType, const char *format, ...)
+  FUNC_ATTR_NONNULL_ALL
+{
+  assert(kErrorTypeNone != errType);
+  va_list args1;
+  va_list args2;
+  va_start(args1, format);
+  va_copy(args2, args1);
+  int len = vsnprintf(NULL, 0, format, args1);
+  va_end(args1);
+  assert(len >= 0);
+  // Limit error message to 1 MB.
+  size_t bufsize = MIN((size_t)len + 1, 1024 * 1024);
+  err->msg = xmalloc(bufsize);
+  vsnprintf(err->msg, bufsize, format, args2);
+  va_end(args2);
+
+  err->type = errType;
+}
diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index 20b4015fb5..681945ac9c 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -8,16 +8,6 @@
 #include "nvim/memory.h"
 #include "nvim/lib/kvec.h"
 
-// -V:api_set_error:618
-#define api_set_error(err, errtype, ...) \
-  do { \
-    snprintf((err)->msg, \
-             sizeof((err)->msg), \
-             __VA_ARGS__); \
-    (err)->set = true; \
-    (err)->type = kErrorType##errtype; \
-  } while (0)
-
 #define OBJECT_OBJ(o) o
 
 #define BOOLEAN_OBJ(b) ((Object) { \
diff --git a/src/nvim/api/tabpage.c b/src/nvim/api/tabpage.c
index 29592408fc..6f2f9e1d2a 100644
--- a/src/nvim/api/tabpage.c
+++ b/src/nvim/api/tabpage.c
@@ -193,6 +193,8 @@ Boolean nvim_tabpage_is_valid(Tabpage tabpage)
     FUNC_API_SINCE(1)
 {
   Error stub = ERROR_INIT;
-  return find_tab_by_handle(tabpage, &stub) != NULL;
+  Boolean ret = find_tab_by_handle(tabpage, &stub) != NULL;
+  api_clear_error(&stub);
+  return ret;
 }
 
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 2a33d2ad72..f0da0d1812 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -55,13 +55,13 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height,
     FUNC_API_SINCE(1) FUNC_API_NOEVAL
 {
   if (pmap_has(uint64_t)(connected_uis, channel_id)) {
-    api_set_error(err, Exception, _("UI already attached for channel"));
+    api_set_error(err, kErrorTypeException, "UI already attached for channel");
     return;
   }
 
   if (width <= 0 || height <= 0) {
-    api_set_error(err, Validation,
-                  _("Expected width > 0 and height > 0"));
+    api_set_error(err, kErrorTypeValidation,
+                  "Expected width > 0 and height > 0");
     return;
   }
   UI *ui = xcalloc(1, sizeof(UI));
@@ -97,7 +97,7 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height,
 
   for (size_t i = 0; i < options.size; i++) {
     ui_set_option(ui, options.items[i].key, options.items[i].value, err);
-    if (err->set) {
+    if (ERROR_SET(err)) {
       xfree(ui);
       return;
     }
@@ -126,7 +126,7 @@ void nvim_ui_detach(uint64_t channel_id, Error *err)
     FUNC_API_SINCE(1) FUNC_API_NOEVAL
 {
   if (!pmap_has(uint64_t)(connected_uis, channel_id)) {
-    api_set_error(err, Exception, _("UI is not attached for channel"));
+    api_set_error(err, kErrorTypeException, "UI is not attached for channel");
     return;
   }
   remote_ui_disconnect(channel_id);
@@ -138,13 +138,13 @@ void nvim_ui_try_resize(uint64_t channel_id, Integer width,
     FUNC_API_SINCE(1) FUNC_API_NOEVAL
 {
   if (!pmap_has(uint64_t)(connected_uis, channel_id)) {
-    api_set_error(err, Exception, _("UI is not attached for channel"));
+    api_set_error(err, kErrorTypeException, "UI is not attached for channel");
     return;
   }
 
   if (width <= 0 || height <= 0) {
-    api_set_error(err, Validation,
-                  _("Expected width > 0 and height > 0"));
+    api_set_error(err, kErrorTypeValidation,
+                  "Expected width > 0 and height > 0");
     return;
   }
 
@@ -159,13 +159,13 @@ void nvim_ui_set_option(uint64_t channel_id, String name,
     FUNC_API_SINCE(1) FUNC_API_NOEVAL
 {
   if (!pmap_has(uint64_t)(connected_uis, channel_id)) {
-    api_set_error(error, Exception, _("UI is not attached for channel"));
+    api_set_error(error, kErrorTypeException, "UI is not attached for channel");
     return;
   }
   UI *ui = pmap_get(uint64_t)(connected_uis, channel_id);
 
   ui_set_option(ui, name, value, error);
-  if (!error->set) {
+  if (!ERROR_SET(error)) {
     ui_refresh();
   }
 }
@@ -173,19 +173,19 @@ void nvim_ui_set_option(uint64_t channel_id, String name,
 static void ui_set_option(UI *ui, String name, Object value, Error *error) {
   if (strcmp(name.data, "rgb") == 0) {
     if (value.type != kObjectTypeBoolean) {
-      api_set_error(error, Validation, _("rgb must be a Boolean"));
+      api_set_error(error, kErrorTypeValidation, "rgb must be a Boolean");
       return;
     }
     ui->rgb = value.data.boolean;
   } else if (strcmp(name.data, "popupmenu_external") == 0) {
     if (value.type != kObjectTypeBoolean) {
-      api_set_error(error, Validation,
-                    _("popupmenu_external must be a Boolean"));
+      api_set_error(error, kErrorTypeValidation,
+                    "popupmenu_external must be a Boolean");
       return;
     }
     ui->pum_external = value.data.boolean;
   } else {
-    api_set_error(error, Validation, _("No such ui option"));
+    api_set_error(error, kErrorTypeValidation, "No such ui option");
   }
 }
 
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index e5ef4a35c1..da00fbc6e3 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -165,8 +165,8 @@ String nvim_command_output(String str, Error *err)
   nvim_command(str, err);
   do_cmdline_cmd("redir END");
 
-  if (err->set) {
-    return (String) STRING_INIT;
+  if (ERROR_SET(err)) {
+    return (String)STRING_INIT;
   }
 
   return cstr_to_string((char *)get_vim_var_str(VV_COMMAND_OUTPUT));
@@ -188,7 +188,7 @@ Object nvim_eval(String expr, Error *err)
 
   typval_T rettv;
   if (eval0((char_u *)expr.data, &rettv, NULL, true) == FAIL) {
-    api_set_error(err, Exception, "Failed to evaluate expression");
+    api_set_error(err, kErrorTypeException, "Failed to evaluate expression");
   }
 
   if (!try_end(err)) {
@@ -214,8 +214,8 @@ Object nvim_call_function(String fname, Array args, Error *err)
 {
   Object rv = OBJECT_INIT;
   if (args.size > MAX_FUNC_ARGS) {
-    api_set_error(err, Validation,
-      _("Function called with too many arguments."));
+    api_set_error(err, kErrorTypeValidation,
+                  "Function called with too many arguments.");
     return rv;
   }
 
@@ -237,7 +237,7 @@ Object nvim_call_function(String fname, Array args, Error *err)
                     curwin->w_cursor.lnum, curwin->w_cursor.lnum, &dummy,
                     true, NULL, NULL);
   if (r == FAIL) {
-    api_set_error(err, Exception, _("Error calling function."));
+    api_set_error(err, kErrorTypeException, "Error calling function.");
   }
   if (!try_end(err)) {
     rv = vim_to_object(&rettv);
@@ -262,7 +262,7 @@ Integer nvim_strwidth(String str, Error *err)
     FUNC_API_SINCE(1)
 {
   if (str.size > INT_MAX) {
-    api_set_error(err, Validation, _("String length is too high"));
+    api_set_error(err, kErrorTypeValidation, "String length is too high");
     return 0;
   }
 
@@ -318,7 +318,7 @@ void nvim_set_current_dir(String dir, Error *err)
     FUNC_API_SINCE(1)
 {
   if (dir.size >= MAXPATHL) {
-    api_set_error(err, Validation, _("Directory string is too long"));
+    api_set_error(err, kErrorTypeValidation, "Directory string is too long");
     return;
   }
 
@@ -330,7 +330,7 @@ void nvim_set_current_dir(String dir, Error *err)
 
   if (vim_chdir((char_u *)string, kCdScopeGlobal)) {
     if (!try_end(err)) {
-      api_set_error(err, Exception, _("Failed to change directory"));
+      api_set_error(err, kErrorTypeException, "Failed to change directory");
     }
     return;
   }
@@ -539,8 +539,8 @@ void nvim_set_current_buf(Buffer buffer, Error *err)
   int result = do_buffer(DOBUF_GOTO, DOBUF_FIRST, FORWARD, buf->b_fnum, 0);
   if (!try_end(err) && result == FAIL) {
     api_set_error(err,
-                  Exception,
-                  _("Failed to switch to buffer %d"),
+                  kErrorTypeException,
+                  "Failed to switch to buffer %d",
                   buffer);
   }
 }
@@ -592,8 +592,8 @@ void nvim_set_current_win(Window window, Error *err)
   goto_tabpage_win(win_find_tabpage(win), win);
   if (!try_end(err) && win != curwin) {
     api_set_error(err,
-                  Exception,
-                  _("Failed to switch to window %d"),
+                  kErrorTypeException,
+                  "Failed to switch to window %d",
                   window);
   }
 }
@@ -646,8 +646,8 @@ void nvim_set_current_tabpage(Tabpage tabpage, Error *err)
   goto_tabpage_tp(tp, true, true);
   if (!try_end(err) && tp != curtab) {
     api_set_error(err,
-                  Exception,
-                  _("Failed to switch to tabpage %d"),
+                  kErrorTypeException,
+                  "Failed to switch to tabpage %d",
                   tabpage);
   }
 }
@@ -745,30 +745,30 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
   for (i = 0; i < calls.size; i++) {
     if (calls.items[i].type != kObjectTypeArray) {
       api_set_error(err,
-                    Validation,
-                    _("All items in calls array must be arrays"));
+                    kErrorTypeValidation,
+                    "All items in calls array must be arrays");
       goto validation_error;
     }
     Array call = calls.items[i].data.array;
     if (call.size != 2) {
       api_set_error(err,
-                    Validation,
-                    _("All items in calls array must be arrays of size 2"));
+                    kErrorTypeValidation,
+                    "All items in calls array must be arrays of size 2");
       goto validation_error;
     }
 
     if (call.items[0].type != kObjectTypeString) {
       api_set_error(err,
-                    Validation,
-                    _("name must be String"));
+                    kErrorTypeValidation,
+                    "Name must be String");
       goto validation_error;
     }
     String name = call.items[0].data.string;
 
     if (call.items[1].type != kObjectTypeArray) {
       api_set_error(err,
-                    Validation,
-                    _("args must be Array"));
+                    kErrorTypeValidation,
+                    "Args must be Array");
       goto validation_error;
     }
     Array args = call.items[1].data.array;
@@ -776,7 +776,7 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
     MsgpackRpcRequestHandler handler = msgpack_rpc_get_handler_for(name.data,
                                                                    name.size);
     Object result = handler.fn(channel_id, args, &nested_error);
-    if (nested_error.set) {
+    if (ERROR_SET(&nested_error)) {
       // error handled after loop
       break;
     }
@@ -785,7 +785,7 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
   }
 
   ADD(rv, ARRAY_OBJ(results));
-  if (nested_error.set) {
+  if (ERROR_SET(&nested_error)) {
     Array errval = ARRAY_DICT_INIT;
     ADD(errval, INTEGER_OBJ((Integer)i));
     ADD(errval, INTEGER_OBJ(nested_error.type));
@@ -794,10 +794,12 @@ Array nvim_call_atomic(uint64_t channel_id, Array calls, Error *err)
   } else {
     ADD(rv, NIL);
   }
-  return rv;
+  goto theend;
 
 validation_error:
   api_free_array(results);
+theend:
+  api_clear_error(&nested_error);
   return rv;
 }
 
diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index e1bb70ee0d..859bf88398 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -65,8 +65,8 @@ void nvim_win_set_cursor(Window window, ArrayOf(Integer, 2) pos, Error *err)
   if (pos.size != 2 || pos.items[0].type != kObjectTypeInteger
       || pos.items[1].type != kObjectTypeInteger) {
     api_set_error(err,
-                  Validation,
-                  _("Argument \"pos\" must be a [row, col] array"));
+                  kErrorTypeValidation,
+                  "Argument \"pos\" must be a [row, col] array");
     return;
   }
 
@@ -78,12 +78,12 @@ void nvim_win_set_cursor(Window window, ArrayOf(Integer, 2) pos, Error *err)
   int64_t col = pos.items[1].data.integer;
 
   if (row <= 0 || row > win->w_buffer->b_ml.ml_line_count) {
-    api_set_error(err, Validation, _("Cursor position outside buffer"));
+    api_set_error(err, kErrorTypeValidation, "Cursor position outside buffer");
     return;
   }
 
   if (col > MAXCOL || col < 0) {
-    api_set_error(err, Validation, _("Column value outside range"));
+    api_set_error(err, kErrorTypeValidation, "Column value outside range");
     return;
   }
 
@@ -132,7 +132,7 @@ void nvim_win_set_height(Window window, Integer height, Error *err)
   }
 
   if (height > INT_MAX || height < INT_MIN) {
-    api_set_error(err, Validation, _("Height value outside range"));
+    api_set_error(err, kErrorTypeValidation, "Height value outside range");
     return;
   }
 
@@ -177,7 +177,7 @@ void nvim_win_set_width(Window window, Integer width, Error *err)
   }
 
   if (width > INT_MAX || width < INT_MIN) {
-    api_set_error(err, Validation, _("Width value outside range"));
+    api_set_error(err, kErrorTypeValidation, "Width value outside range");
     return;
   }
 
@@ -387,6 +387,8 @@ Boolean nvim_win_is_valid(Window window)
     FUNC_API_SINCE(1)
 {
   Error stub = ERROR_INIT;
-  return find_window_by_handle(window, &stub) != NULL;
+  Boolean ret = find_window_by_handle(window, &stub) != NULL;
+  api_clear_error(&stub);
+  return ret;
 }
 
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 7cef0d81ed..d7feed8bfd 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -6512,7 +6512,7 @@ static void api_wrapper(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   Error err = ERROR_INIT;
   Object result = fn(INTERNAL_CALL, args, &err);
 
-  if (err.set) {
+  if (ERROR_SET(&err)) {
     nvim_err_writeln(cstr_as_string(err.msg));
     goto end;
   }
@@ -6524,6 +6524,7 @@ static void api_wrapper(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 end:
   api_free_array(args);
   api_free_object(result);
+  api_clear_error(&err);
 }
 
 /*
@@ -13783,7 +13784,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     restore_funccal(save_funccalp);
   }
 
-  if (err.set) {
+  if (ERROR_SET(&err)) {
     nvim_err_writeln(cstr_as_string(err.msg));
     goto end;
   }
@@ -13794,6 +13795,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
 end:
   api_free_object(result);
+  api_clear_error(&err);
 }
 
 // "rpcstart()" function (DEPRECATED)
@@ -16523,11 +16525,13 @@ static void f_termopen(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   curbuf->b_p_swf = false;
   (void)setfname(curbuf, (char_u *)buf, NULL, true);
   // Save the job id and pid in b:terminal_job_{id,pid}
-  Error err;
+  Error err = ERROR_INIT;
   dict_set_var(curbuf->b_vars, cstr_as_string("terminal_job_id"),
                INTEGER_OBJ(rettv->vval.v_number), false, false, &err);
+  api_clear_error(&err);
   dict_set_var(curbuf->b_vars, cstr_as_string("terminal_job_pid"),
                INTEGER_OBJ(pid), false, false, &err);
+  api_clear_error(&err);
 
   Terminal *term = terminal_open(topts);
   data->term = term;
diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index b2c6ef852c..59594357de 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -192,7 +192,7 @@ Object channel_send_call(uint64_t id,
   Channel *channel = NULL;
 
   if (!(channel = pmap_get(uint64_t)(channels, id)) || channel->closed) {
-    api_set_error(err, Exception, _("Invalid channel \"%" PRIu64 "\""), id);
+    api_set_error(err, kErrorTypeException, "Invalid channel: %" PRIu64, id);
     api_free_array(args);
     return NIL;
   }
@@ -212,7 +212,8 @@ Object channel_send_call(uint64_t id,
 
   if (frame.errored) {
     if (frame.result.type == kObjectTypeString) {
-      api_set_error(err, Exception, "%s", frame.result.data.string.data);
+      api_set_error(err, kErrorTypeException, "%s",
+                    frame.result.data.string.data);
     } else if (frame.result.type == kObjectTypeArray) {
       // Should be an error in the form [type, message]
       Array array = frame.result.data.array;
@@ -220,14 +221,13 @@ Object channel_send_call(uint64_t id,
           && (array.items[0].data.integer == kErrorTypeException
               || array.items[0].data.integer == kErrorTypeValidation)
           && array.items[1].type == kObjectTypeString) {
-        err->type = (ErrorType) array.items[0].data.integer;
-        xstrlcpy(err->msg, array.items[1].data.string.data, sizeof(err->msg));
-        err->set = true;
+        api_set_error(err, (ErrorType)array.items[0].data.integer, "%s",
+                      array.items[1].data.string.data);
       } else {
-        api_set_error(err, Exception, "%s", "unknown error");
+        api_set_error(err, kErrorTypeException, "%s", "unknown error");
       }
     } else {
-      api_set_error(err, Exception, "%s", "unknown error");
+      api_set_error(err, kErrorTypeException, "%s", "unknown error");
     }
 
     api_free_object(frame.result);
@@ -398,7 +398,7 @@ static void handle_request(Channel *channel, msgpack_object *request)
   Error error = ERROR_INIT;
   msgpack_rpc_validate(&request_id, request, &error);
 
-  if (error.set) {
+  if (ERROR_SET(&error)) {
     // Validation failed, send response with error
     if (channel_write(channel,
                       serialize_response(channel->id,
@@ -412,9 +412,9 @@ static void handle_request(Channel *channel, msgpack_object *request)
                channel->id);
       call_set_error(channel, buf);
     }
+    api_clear_error(&error);
     return;
   }
-
   // Retrieve the request handler
   MsgpackRpcRequestHandler handler;
   msgpack_object *method = msgpack_rpc_method(request);
@@ -470,6 +470,7 @@ static void on_request_event(void **argv)
   api_free_array(args);
   decref(channel);
   xfree(e);
+  api_clear_error(&error);
 }
 
 static bool channel_write(Channel *channel, WBuffer *buffer)
@@ -512,12 +513,13 @@ static bool channel_write(Channel *channel, WBuffer *buffer)
 static void send_error(Channel *channel, uint64_t id, char *err)
 {
   Error e = ERROR_INIT;
-  api_set_error(&e, Exception, "%s", err);
+  api_set_error(&e, kErrorTypeException, "%s", err);
   channel_write(channel, serialize_response(channel->id,
                                             id,
                                             &e,
                                             NIL,
                                             &out_buffer));
+  api_clear_error(&e);
 }
 
 static void send_request(Channel *channel,
diff --git a/src/nvim/msgpack_rpc/helpers.c b/src/nvim/msgpack_rpc/helpers.c
index 967ce31c1b..0228582d37 100644
--- a/src/nvim/msgpack_rpc/helpers.c
+++ b/src/nvim/msgpack_rpc/helpers.c
@@ -475,8 +475,7 @@ Object msgpack_rpc_handle_missing_method(uint64_t channel_id,
                                          Array args,
                                          Error *error)
 {
-  snprintf(error->msg, sizeof(error->msg), "Invalid method name");
-  error->set = true;
+  api_set_error(error, kErrorTypeException, "Invalid method name");
   return NIL;
 }
 
@@ -485,8 +484,7 @@ Object msgpack_rpc_handle_invalid_arguments(uint64_t channel_id,
                                             Array args,
                                             Error *error)
 {
-  snprintf(error->msg, sizeof(error->msg), "Invalid method arguments");
-  error->set = true;
+  api_set_error(error, kErrorTypeException, "Invalid method arguments");
   return NIL;
 }
 
@@ -519,7 +517,7 @@ void msgpack_rpc_serialize_response(uint64_t response_id,
   msgpack_pack_int(pac, 1);
   msgpack_pack_uint64(pac, response_id);
 
-  if (err->set) {
+  if (ERROR_SET(err)) {
     // error represented by a [type, message] array
     msgpack_pack_array(pac, 2);
     msgpack_rpc_from_integer(err->type, pac);
@@ -572,49 +570,49 @@ void msgpack_rpc_validate(uint64_t *response_id,
   *response_id = NO_RESPONSE;
   // Validate the basic structure of the msgpack-rpc payload
   if (req->type != MSGPACK_OBJECT_ARRAY) {
-    api_set_error(err, Validation, _("Message is not an array"));
+    api_set_error(err, kErrorTypeValidation, "Message is not an array");
     return;
   }
 
   if (req->via.array.size == 0) {
-    api_set_error(err, Validation, _("Message is empty"));
+    api_set_error(err, kErrorTypeValidation, "Message is empty");
     return;
   }
 
   if (req->via.array.ptr[0].type != MSGPACK_OBJECT_POSITIVE_INTEGER) {
-    api_set_error(err, Validation, _("Message type must be an integer"));
+    api_set_error(err, kErrorTypeValidation, "Message type must be an integer");
     return;
   }
 
   uint64_t type = req->via.array.ptr[0].via.u64;
   if (type != kMessageTypeRequest && type != kMessageTypeNotification) {
-    api_set_error(err, Validation, _("Unknown message type"));
+    api_set_error(err, kErrorTypeValidation, "Unknown message type");
     return;
   }
 
   if ((type == kMessageTypeRequest && req->via.array.size != 4)
       || (type == kMessageTypeNotification && req->via.array.size != 3)) {
-    api_set_error(err, Validation, _("Request array size should be 4 (request) "
-                                     "or 3 (notification)"));
+    api_set_error(err, kErrorTypeValidation,
+                  "Request array size must be 4 (request) or 3 (notification)");
     return;
   }
 
   if (type == kMessageTypeRequest) {
     msgpack_object *id_obj = msgpack_rpc_msg_id(req);
     if (!id_obj) {
-      api_set_error(err, Validation, _("ID must be a positive integer"));
+      api_set_error(err, kErrorTypeValidation, "ID must be a positive integer");
       return;
     }
     *response_id = id_obj->via.u64;
   }
 
   if (!msgpack_rpc_method(req)) {
-    api_set_error(err, Validation, _("Method must be a string"));
+    api_set_error(err, kErrorTypeValidation, "Method must be a string");
     return;
   }
 
   if (!msgpack_rpc_args(req)) {
-    api_set_error(err, Validation, _("Parameters must be an array"));
+    api_set_error(err, kErrorTypeValidation, "Parameters must be an array");
     return;
   }
 }
diff --git a/src/nvim/po/fi.po b/src/nvim/po/fi.po
index d817144151..3551c07ff2 100644
--- a/src/nvim/po/fi.po
+++ b/src/nvim/po/fi.po
@@ -116,7 +116,7 @@ msgstr "merkkijono ei saa sisältää rivinvaihtoja"
 
 #. Doesn't exist, fail
 #, fuzzy, c-format
-#~ msgid "Key \"%s\" doesn't exist"
+#~ msgid "Key does not exist: %s"
 #~ msgstr "Tiedostoa %s ei ole"
 
 #, fuzzy
@@ -3986,7 +3986,7 @@ msgid "Calling shell to execute: \"%s\""
 msgstr "Kutsutaan kuorta suorittamaan: %s"
 
 #, c-format
-#~ msgid "Invalid channel \"%<PRIu64>\""
+#~ msgid "Invalid channel: %<PRIu64>"
 #~ msgstr ""
 
 #~ msgid "Message is not an array"
@@ -4003,7 +4003,7 @@ msgstr "Kutsutaan kuorta suorittamaan: %s"
 #~ msgid "Unknown message type"
 #~ msgstr "E574: Tuntematon rekisterityyppi %d"
 
-#~ msgid "Request array size should be 4 (request) or 3 (notification)"
+#~ msgid "Request array size must be 4 (request) or 3 (notification)"
 #~ msgstr ""
 
 #~ msgid "ID must be a positive integer"
diff --git a/src/nvim/po/uk.po b/src/nvim/po/uk.po
index cff140508b..2c203f808f 100644
--- a/src/nvim/po/uk.po
+++ b/src/nvim/po/uk.po
@@ -82,7 +82,7 @@ msgid "Key length is too high"
 msgstr "Довжина ключа завелика"
 
 #, c-format
-msgid "Key \"%s\" doesn't exist"
+msgid "Key does not exist: %s"
 msgstr "Ключ «%s» не існує"
 
 msgid "Empty option name"
@@ -3719,7 +3719,7 @@ msgid "Calling shell to execute: \"%s\""
 msgstr "Викликається оболонка щоб виконати: «%s»"
 
 #, c-format
-msgid "Invalid channel \"%<PRIu64>\""
+msgid "Invalid channel: %<PRIu64>"
 msgstr "Некоректний канал «%<PRIu64>»"
 
 msgid "Message is not an array"
@@ -3734,7 +3734,7 @@ msgstr "Повідомлення має бути цілим числом"
 msgid "Unknown message type"
 msgstr "Невідомий тип повідомлення"
 
-msgid "Request array size should be 4 (request) or 3 (notification)"
+msgid "Request array size must be 4 (request) or 3 (notification)"
 msgstr "Розмір масиву запиту має бути 4 (запит) чи 3 (повідомлення)"
 
 msgid "ID must be a positive integer"
diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index 19b9bdc19f..c44fe15be5 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -633,13 +633,14 @@ static int term_movecursor(VTermPos new, VTermPos old, int visible,
 static void buf_set_term_title(buf_T *buf, char *title)
     FUNC_ATTR_NONNULL_ALL
 {
-  Error err;
+  Error err = ERROR_INIT;
   dict_set_var(buf->b_vars,
                STATIC_CSTR_AS_STRING("term_title"),
                STRING_OBJ(cstr_as_string(title)),
                false,
                false,
                &err);
+  api_clear_error(&err);
 }
 
 static int term_settermprop(VTermProp prop, VTermValue *val, void *data)
@@ -1220,12 +1221,14 @@ static bool is_focused(Terminal *term)
 
 #define GET_CONFIG_VALUE(k, o) \
   do { \
-    Error err; \
+    Error err = ERROR_INIT; \
     /* Only called from terminal_open where curbuf->terminal is the */ \
     /* context  */ \
     o = dict_get_value(curbuf->b_vars, cstr_as_string(k), &err); \
+    api_clear_error(&err); \
     if (o.type == kObjectTypeNil) { \
       o = dict_get_value(&globvardict, cstr_as_string(k), &err); \
+      api_clear_error(&err); \
     } \
   } while (0)
 
diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index 3f2ccd4746..b86ab8cf2f 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -223,12 +223,14 @@ static int get_key_code_timeout(void)
 {
   Integer ms = -1;
   // Check 'ttimeout' to determine if we should send ESC after 'ttimeoutlen'.
-  // See :help 'ttimeout' for more information
   Error err = ERROR_INIT;
   if (nvim_get_option(cstr_as_string("ttimeout"), &err).data.boolean) {
-    ms = nvim_get_option(cstr_as_string("ttimeoutlen"), &err).data.integer;
+    Object rv = nvim_get_option(cstr_as_string("ttimeoutlen"), &err);
+    if (!ERROR_SET(&err)) {
+      ms = rv.data.integer;
+    }
   }
-
+  api_clear_error(&err);
   return (int)ms;
 }
 
diff --git a/test/functional/api/buffer_spec.lua b/test/functional/api/buffer_spec.lua
index c3002618b0..9699ea8f85 100644
--- a/test/functional/api/buffer_spec.lua
+++ b/test/functional/api/buffer_spec.lua
@@ -271,7 +271,7 @@ describe('api/buf', function()
       eq(1, funcs.exists('b:lua'))
       curbufmeths.del_var('lua')
       eq(0, funcs.exists('b:lua'))
-      eq({false, 'Key "lua" doesn\'t exist'}, meth_pcall(curbufmeths.del_var, 'lua'))
+      eq({false, 'Key does not exist: lua'}, meth_pcall(curbufmeths.del_var, 'lua'))
       curbufmeths.set_var('lua', 1)
       command('lockvar b:lua')
       eq({false, 'Key is locked: lua'}, meth_pcall(curbufmeths.del_var, 'lua'))
diff --git a/test/functional/api/tabpage_spec.lua b/test/functional/api/tabpage_spec.lua
index d7ef53a88f..260a91a80c 100644
--- a/test/functional/api/tabpage_spec.lua
+++ b/test/functional/api/tabpage_spec.lua
@@ -34,7 +34,7 @@ describe('api/tabpage', function()
       eq(1, funcs.exists('t:lua'))
       curtabmeths.del_var('lua')
       eq(0, funcs.exists('t:lua'))
-      eq({false, 'Key "lua" doesn\'t exist'}, meth_pcall(curtabmeths.del_var, 'lua'))
+      eq({false, 'Key does not exist: lua'}, meth_pcall(curtabmeths.del_var, 'lua'))
       curtabmeths.set_var('lua', 1)
       command('lockvar t:lua')
       eq({false, 'Key is locked: lua'}, meth_pcall(curtabmeths.del_var, 'lua'))
diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index 8f9f155110..5b173f3196 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -119,7 +119,7 @@ describe('api', function()
       eq(1, funcs.exists('g:lua'))
       meths.del_var('lua')
       eq(0, funcs.exists('g:lua'))
-      eq({false, 'Key "lua" doesn\'t exist'}, meth_pcall(meths.del_var, 'lua'))
+      eq({false, 'Key does not exist: lua'}, meth_pcall(meths.del_var, 'lua'))
       meths.set_var('lua', 1)
       command('lockvar lua')
       eq({false, 'Key is locked: lua'}, meth_pcall(meths.del_var, 'lua'))
@@ -412,7 +412,7 @@ describe('api', function()
       eq(5, meths.get_var('avar'))
     end)
 
-    it('throws error on malformated arguments', function()
+    it('throws error on malformed arguments', function()
       local req = {
         {'nvim_set_var', {'avar', 1}},
         {'nvim_set_var'},
@@ -439,7 +439,7 @@ describe('api', function()
       }
       status, err = pcall(meths.call_atomic, req)
       eq(false, status)
-      ok(err:match('args must be Array') ~= nil)
+      ok(err:match('Args must be Array') ~= nil)
       -- call before was done, but not after
       eq(1, meths.get_var('avar'))
       eq({''}, meths.buf_get_lines(0, 0, -1, true))
@@ -452,6 +452,13 @@ describe('api', function()
     ok(err:match('Invalid option name') ~= nil)
   end)
 
+  it('does not truncate error message <1 MB #5984', function()
+    local very_long_name = 'A'..('x'):rep(10000)..'Z'
+    local status, err = pcall(nvim, 'get_option', very_long_name)
+    eq(false, status)
+    eq(very_long_name, err:match('Ax+Z?'))
+  end)
+
   it("doesn't leak memory on incorrect argument types", function()
     local status, err = pcall(nvim, 'set_current_dir',{'not', 'a', 'dir'})
     eq(false, status)
diff --git a/test/functional/api/window_spec.lua b/test/functional/api/window_spec.lua
index deffc68994..6882f50a3e 100644
--- a/test/functional/api/window_spec.lua
+++ b/test/functional/api/window_spec.lua
@@ -139,7 +139,7 @@ describe('api/win', function()
       eq(1, funcs.exists('w:lua'))
       curwinmeths.del_var('lua')
       eq(0, funcs.exists('w:lua'))
-      eq({false, 'Key "lua" doesn\'t exist'}, meth_pcall(curwinmeths.del_var, 'lua'))
+      eq({false, 'Key does not exist: lua'}, meth_pcall(curwinmeths.del_var, 'lua'))
       curwinmeths.set_var('lua', 1)
       command('lockvar w:lua')
       eq({false, 'Key is locked: lua'}, meth_pcall(curwinmeths.del_var, 'lua'))
diff --git a/test/functional/provider/python3_spec.lua b/test/functional/provider/python3_spec.lua
index a4e9a49c8a..89a546675f 100644
--- a/test/functional/provider/python3_spec.lua
+++ b/test/functional/provider/python3_spec.lua
@@ -2,6 +2,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local eval, command, feed = helpers.eval, helpers.command, helpers.feed
 local eq, clear, insert = helpers.eq, helpers.clear, helpers.insert
 local expect, write_file = helpers.expect, helpers.write_file
+local feed_command = helpers.feed_command
 
 do
   clear()
@@ -30,6 +31,15 @@ describe('python3 commands and functions', function()
     eq({100, 0}, eval('g:set_by_python3'))
   end)
 
+  it('does not truncate error message <1 MB', function()
+    -- XXX: Python limits the error name to 200 chars, so this test is
+    -- mostly bogus.
+    local very_long_symbol = string.rep('a', 1200)
+    feed_command(':silent! py3 print('..very_long_symbol..' b)')
+    -- Truncated error message would not contain this (last) line.
+    eq('SyntaxError: invalid syntax', eval('v:errmsg'))
+  end)
+
   it('python3_execute with nested commands', function()
     command([[python3 vim.command('python3 vim.command("python3 vim.command(\'let set_by_nested_python3 = 555\')")')]])
     eq(555, eval('g:set_by_nested_python3'))
diff --git a/test/functional/ui/screen.lua b/test/functional/ui/screen.lua
index bcf2a2e3d6..7d9cd6c026 100644
--- a/test/functional/ui/screen.lua
+++ b/test/functional/ui/screen.lua
@@ -312,12 +312,13 @@ function Screen:_redraw(updates)
     -- print(require('inspect')(update))
     local method = update[1]
     for i = 2, #update do
-      local handler = self['_handle_'..method]
+      local handler_name = '_handle_'..method
+      local handler = self[handler_name]
       if handler ~= nil then
         handler(self, unpack(update[i]))
       else
         assert(self._on_event,
-          "Add Screen:_handle_XXX method or call Screen:set_on_event_handler")
+          "Add Screen:"..handler_name.." or call Screen:set_on_event_handler")
         self._on_event(method, update[i])
       end
     end