5 files changed, 95 insertions, 15 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 26f9a6f592..611f29f1f2 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -192,7 +192,7 @@ ArrayOf(String) nvim_buf_get_lines(uint64_t channel_id,
     Object str = STRING_OBJ(cstr_to_string(bufstr));
 
     // Vim represents NULs as NLs, but this may confuse clients.
-    if (channel_id != INTERNAL_CALL) {
+    if (channel_id != VIML_INTERNAL_CALL) {
       strchrsub(str.data.string.data, '\n', '\0');
     }
 
@@ -313,7 +313,7 @@ void nvim_buf_set_lines(uint64_t channel_id,
     // line and convert NULs to newlines to avoid truncation.
     lines[i] = xmallocz(l.size);
     for (size_t j = 0; j < l.size; j++) {
-      if (l.data[j] == '\n' && channel_id != INTERNAL_CALL) {
+      if (l.data[j] == '\n' && channel_id != VIML_INTERNAL_CALL) {
         api_set_error(err, Exception, _("string cannot contain newlines"));
         new_len = i + 1;
         goto end;
diff --git a/src/nvim/api/private/defs.h b/src/nvim/api/private/defs.h
index 223aab09dc..8bd1dd5085 100644
--- a/src/nvim/api/private/defs.h
+++ b/src/nvim/api/private/defs.h
@@ -5,6 +5,8 @@
 #include <stdbool.h>
 #include <string.h>
 
+#include "nvim/func_attr.h"
+
 #define ARRAY_DICT_INIT {.size = 0, .capacity = 0, .items = NULL}
 #define STRING_INIT {.data = NULL, .size = 0}
 #define OBJECT_INIT { .type = kObjectTypeNil }
@@ -33,8 +35,27 @@ typedef enum {
 /// Used as the message ID of notifications.
 #define NO_RESPONSE UINT64_MAX
 
-/// Used as channel_id when the call is local.
-#define INTERNAL_CALL UINT64_MAX
+/// Mask for all internal calls
+#define INTERNAL_CALL_MASK (((uint64_t)1) << (sizeof(uint64_t) * 8 - 1))
+
+/// Internal call from VimL code
+#define VIML_INTERNAL_CALL INTERNAL_CALL_MASK
+
+/// Internal call from lua code
+#define LUA_INTERNAL_CALL (VIML_INTERNAL_CALL + 1)
+
+static inline bool is_internal_call(uint64_t channel_id)
+  REAL_FATTR_ALWAYS_INLINE REAL_FATTR_CONST;
+
+/// Check whether call is internal
+///
+/// @param[in]  channel_id  Channel id.
+///
+/// @return true if channel_id refers to internal channel.
+static inline bool is_internal_call(const uint64_t channel_id)
+{
+  return !!(channel_id & INTERNAL_CALL_MASK);
+}
 
 typedef struct {
   ErrorType type;
@@ -76,16 +97,17 @@ typedef struct {
 } Dictionary;
 
 typedef enum {
-  kObjectTypeBuffer,
-  kObjectTypeWindow,
-  kObjectTypeTabpage,
-  kObjectTypeNil,
+  kObjectTypeNil = 0,
   kObjectTypeBoolean,
   kObjectTypeInteger,
   kObjectTypeFloat,
   kObjectTypeString,
   kObjectTypeArray,
   kObjectTypeDictionary,
+  // EXT types, cannot be split or reordered, see #EXT_OBJECT_TYPE_SHIFT
+  kObjectTypeBuffer,
+  kObjectTypeWindow,
+  kObjectTypeTabpage,
 } ObjectType;
 
 struct object {
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index fe15b28041..7b898bc044 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -349,7 +349,7 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
 #define TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER TYPVAL_ENCODE_CONV_NUMBER
 
 #define TYPVAL_ENCODE_CONV_FLOAT(tv, flt) \
-    kv_push(edata->stack, FLOATING_OBJ((Float)(flt)))
+    kv_push(edata->stack, FLOAT_OBJ((Float)(flt)))
 
 #define TYPVAL_ENCODE_CONV_STRING(tv, str, len) \
     do { \
@@ -849,15 +849,18 @@ static void init_type_metadata(Dictionary *metadata)
   Dictionary types = ARRAY_DICT_INIT;
 
   Dictionary buffer_metadata = ARRAY_DICT_INIT;
-  PUT(buffer_metadata, "id", INTEGER_OBJ(kObjectTypeBuffer));
+  PUT(buffer_metadata, "id",
+      INTEGER_OBJ(kObjectTypeBuffer - EXT_OBJECT_TYPE_SHIFT));
   PUT(buffer_metadata, "prefix", STRING_OBJ(cstr_to_string("nvim_buf_")));
 
   Dictionary window_metadata = ARRAY_DICT_INIT;
-  PUT(window_metadata, "id", INTEGER_OBJ(kObjectTypeWindow));
+  PUT(window_metadata, "id",
+      INTEGER_OBJ(kObjectTypeWindow - EXT_OBJECT_TYPE_SHIFT));
   PUT(window_metadata, "prefix", STRING_OBJ(cstr_to_string("nvim_win_")));
 
   Dictionary tabpage_metadata = ARRAY_DICT_INIT;
-  PUT(tabpage_metadata, "id", INTEGER_OBJ(kObjectTypeTabpage));
+  PUT(tabpage_metadata, "id",
+      INTEGER_OBJ(kObjectTypeTabpage - EXT_OBJECT_TYPE_SHIFT));
   PUT(tabpage_metadata, "prefix", STRING_OBJ(cstr_to_string("nvim_tabpage_")));
 
   PUT(types, "Buffer", DICTIONARY_OBJ(buffer_metadata));
diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index 9fe8c351cf..640e901fa1 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -27,7 +27,7 @@
     .type = kObjectTypeInteger, \
     .data.integer = i })
 
-#define FLOATING_OBJ(f) ((Object) { \
+#define FLOAT_OBJ(f) ((Object) { \
     .type = kObjectTypeFloat, \
     .data.floating = f })
 
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 6926436d2f..511c87f408 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -140,7 +140,7 @@ String nvim_replace_termcodes(String str, Boolean from_part, Boolean do_lt,
 {
   if (str.size == 0) {
     // Empty string
-    return str;
+    return (String) { .data = NULL, .size = 0 };
   }
 
   char *ptr = NULL;
@@ -199,7 +199,8 @@ Object nvim_eval(String expr, Error *err)
   return rv;
 }
 
-/// Calls a VimL function with the given arguments.
+/// Calls a VimL function with the given arguments
+///
 /// On VimL error: Returns a generic error; v:errmsg is not updated.
 ///
 /// @param fname    Function to call
@@ -831,3 +832,57 @@ static void write_msg(String message, bool to_err)
   --no_wait_return;
   msg_end();
 }
+
+// Functions used for testing purposes
+
+/// Returns object given as argument
+///
+/// This API function is used for testing. One should not rely on its presence
+/// in plugins.
+///
+/// @param[in]  obj  Object to return.
+///
+/// @return its argument.
+Object _vim_id(Object obj)
+{
+  return copy_object(obj);
+}
+
+/// Returns array given as argument
+///
+/// This API function is used for testing. One should not rely on its presence
+/// in plugins.
+///
+/// @param[in]  arr  Array to return.
+///
+/// @return its argument.
+Array _vim_id_array(Array arr)
+{
+  return copy_object(ARRAY_OBJ(arr)).data.array;
+}
+
+/// Returns dictionary given as argument
+///
+/// This API function is used for testing. One should not rely on its presence
+/// in plugins.
+///
+/// @param[in]  dct  Dictionary to return.
+///
+/// @return its argument.
+Dictionary _vim_id_dictionary(Dictionary dct)
+{
+  return copy_object(DICTIONARY_OBJ(dct)).data.dictionary;
+}
+
+/// Returns floating-point value given as argument
+///
+/// This API function is used for testing. One should not rely on its presence
+/// in plugins.
+///
+/// @param[in]  flt  Value to return.
+///
+/// @return its argument.
+Float _vim_id_float(Float flt)
+{
+  return flt;
+}