fix formatting log lines causing errors

lua/dep/ui/format.lua

@@ -20,16 +20,29 @@ end
 ---@param log_line string log line
 ---@return chunk[] chunks
 function format.log_line(log_line)
-  local log_time = string.sub( log_line, string.find(log_line, "%[") + 1,
-    string.find(log_line, "%]") - 1)
-  local colon = string.find(log_line, ":", 11)
-  local log_path = string.sub(log_line, string.find(log_line, "%]") + 2,
-    colon - 1)
-  local log_path_ln = string.sub(log_line, colon + 1,
-    string.find(log_line, ":", colon + 1) - 1)
-  local level = string.sub(log_line, string.find(log_line, "%(") + 1,
-    string.find(log_line, "%)") - 1)
-  local rest = string.sub(log_line, string.find(log_line, "%)") + 2)
+  -- make sure we don't do operations on nil values
+  if not log_line or log_line == "" then
+    return {}
+  end
+
+  -- error on any nil values, this should prevent us from parsing an incorrectly
+  -- formatted log line
+  local log_time, colon, log_path, log_path_ln, level, rest
+  local ok = pcall(function()
+    log_time = string.sub(log_line, string.find(log_line, "%[") + 1,
+      string.find(log_line, "%]") - 1)
+    colon = string.find(log_line, ":", 11)
+    log_path = string.sub(log_line, string.find(log_line, "%]") + 2,
+      colon - 1)
+    log_path_ln = string.sub(log_line, colon + 1,
+      string.find(log_line, ":", colon + 1) - 1)
+    level = string.sub(log_line, string.find(log_line, "%(") + 1,
+      string.find(log_line, "%)") - 1)
+    rest = string.sub(log_line, string.find(log_line, "%)") + 2)
+  end)
+  if not ok then
+    return {}
+  end
 
   return {
     { "[", "" },

tests/dep_spec.lua

@@ -17,6 +17,14 @@ describe("ui log formatting", function()
       },
       dep_ui_format.log_line("[11:22:33] file.lua:1:(vim) some fancy message")
     )
+
+    -- malformed log line
+    assert.same({},
+      dep_ui_format.log_line("11:22:33] file.lua:1:(vim) some fancy message"))
+
+    -- test nil values
+    assert.same({}, dep_ui_format.log_line(""))
+    assert.same({}, dep_ui_format.log_line(nil))
   end)
 end)