Introduce const for the zero value that denotes an empty cell

src/functions/functions.js

@@ -1,16 +1,17 @@
 const COMPLETION_ENTITY_KIND = 'openai-excel-formulas:chat-completion';
+const EMPTY_OR_ZERO = 0;
 
 CustomFunctions.associate('CHAT_COMPLETE', chatComplete);
 async function chatComplete(messages, params) {
  const {
  API_KEY: apiKey,
  API_BASE: apiBase = 'https://api.openai.com/',
  messages: _,
- 0: __, // Empty key cell in range
+ [EMPTY_OR_ZERO]: __,
  ...userParams
  } = Object.fromEntries(params);
 
- if (apiKey == null || apiKey === 0) {
+ if (apiKey == null || apiKey === EMPTY_OR_ZERO) {
  throw new CustomFunctions.Error(
  CustomFunctions.ErrorCode.invalidValue,
  'API_KEY is required',
@@ -28,7 +29,7 @@ async function chatComplete(messages, params) {
  const requestBody = {
  ...userParams,
  messages: messages
- .filter(([role]) => role !== 0)
+ .filter(([role]) => role !== EMPTY_OR_ZERO)
  .map(([role, content]) => ({ role, content })),
  };
 
@@ -86,9 +87,9 @@ async function chatComplete(messages, params) {
 // Terminology note: our _cost_ is driven by usage and OpenAI's _prices_.
 CustomFunctions.associate('COST', cost);
 function cost(completionsMatrix, pricesMatrix) {
- const completions = completionsMatrix.flat().filter(
- (value) => value !== 0, // Empty value in range
- );
+ const completions = completionsMatrix
+ .flat()
+  .filter((value) => value !== EMPTY_OR_ZERO);
  completions.forEach(validateIsCompletion);
  const allPrices = Object.fromEntries(
  pricesMatrix.map((row) => [row[0], { input: row[1], output: row[2] }]),