break: streamlining of some function returns in the c library (#58)

breaking changes for c ABI. unrelated for lua users.

- `get_positions` can now return NULL for an empty pattern input
- `get_score` will now return 1 for an empty pattern input. previously handled in the telescope lua part of the code. Now its moved to c

lua/fzf_lib.lua

@@ -49,6 +49,10 @@ end
 
 fzf.get_pos = function(input, pattern_struct, slab)
   local pos = native.fzf_get_positions(input, pattern_struct, slab)
+  if pos == nil then
+    return
+  end
+
   local res = {}
   for i = 1, tonumber(pos.size) do
     res[i] = pos.data[i - 1] + 1

lua/telescope/_extensions/fzf.lua

@@ -90,10 +90,6 @@ local get_fzf_sorter = function(opts)
     discard = true,
     scoring_function = function(self, prompt, line)
       local obj = get_struct(self, prompt)
-      if obj.size == 0 then
-        return 1
-      end
-
       local score = fzf.get_score(line, obj, self.state.slab)
       if score == 0 then
         return -1

src/fzf.c

@@ -1200,6 +1200,12 @@ void fzf_free_pattern(fzf_pattern_t *pattern) {
 
 int32_t fzf_get_score(const char *text, fzf_pattern_t *pattern,
                       fzf_slab_t *slab) {
+  // If the pattern is an empty string then pattern->ptr will be NULL and we
+  // basically don't want to filter. Return 1 for telescope
+  if (pattern->ptr == NULL) {
+    return 1;
+  }
+
   fzf_string_t input = {.data = text, .size = strlen(text)};
 
   if (pattern->only_inv) {
@@ -1244,6 +1250,12 @@ int32_t fzf_get_score(const char *text, fzf_pattern_t *pattern,
 
 fzf_position_t *fzf_get_positions(const char *text, fzf_pattern_t *pattern,
                                   fzf_slab_t *slab) {
+  // If the pattern is an empty string then pattern->ptr will be NULL and we
+  // basically don't want to filter. Return 1 for telescope
+  if (pattern->ptr == NULL) {
+    return NULL;
+  }
+
   fzf_string_t input = {.data = text, .size = strlen(text)};
 
   fzf_position_t *all_pos = pos_array(true, 1);