path: add helper for checking a file extension

src/nvim/path.c

@@ -1704,6 +1704,13 @@ int path_with_url(const char *fname)
   return path_is_url(p);
 }
 
+bool path_with_extension(const char *path, const char *extension)
+{
+  const char *last_dot = strrchr(path, '.');
+  if (!last_dot) { return false; }
+  return strcmp(last_dot + 1, extension) == 0;
+}
+
 /*
  * Return TRUE if "name" is a full (absolute) path name or URL.
  */

test/unit/path_spec.lua

@@ -603,4 +603,21 @@ describe('path.c', function()
       eq(FAIL, path_is_absolute('not/in/my/home~/directory'))
     end)
   end)
+
+  describe('path_with_extension', function()
+    local function path_with_extension(filename, extension)
+      local c_filename = to_cstr(filename)
+      local c_extension = to_cstr(extension)
+      return cimp.path_with_extension(c_filename, c_extension)
+    end
+
+    itp('returns true if filename includes a provided extension', function()
+      eq(true, path_with_extension('/some/path/file.lua', 'lua'))
+    end)
+
+    itp('returns false if filename does not include a provided extension', function()
+      eq(false, path_with_extension('/some/path/file.vim', 'lua'))
+      eq(false, path_with_extension('/some/path/file', 'lua'))
+    end)
+  end)
 end)