Error: "Reference does not exist" when using a custom function - google-apps-script

Question

I'm trying to scrape a webpage & to put the value in cache in order to not hit the daily urlFetch limit.
This is the code I'm using, it works without the Cache & Properties service but not when I try to add that element.
function scrapercache(url) {
var url = "https://www.gurufocus.com/term/fscore/nyse:ABBV/Piotroski-F-Score";
var result = [];
var description;
var options = {
'muteHttpExceptions': true,
'followRedirects': false,
};
Logger.log('line 16 OK');
var cache = CacheService.getScriptCache();
var properties = PropertiesService.getScriptProperties();
Logger.log('line 21 OK');
let res = cache.get(url);
// if(res){
// return JSON.parse(res)
//}
Logger.log(res);
Logger.log('line 24 OK');
if (res) {
// trim url to prevent (rare) errors
url.toString().trim();
var r = UrlFetchApp.fetch(url, options);
Logger.log(r);
Logger.log('line 34 OK');
var c = r.getResponseCode();
Logger.log(c);
Logger.log('line 38 OK');
// check for meta refresh if 200 ok
if (c == 200) {
var html = r.getContentText();
cache.put(url, "cached", 21600);
properties.setProperty(url, html);
Logger.log('line 46 OK');
var $ = Cheerio.load(html); // make sure this lib is added to your project!
Logger.log('line 49 OK');
// meta description
if ($('meta[name=description]').attr("content")) {
description = $('meta[name=description]').attr("content").trim();
var trim_des = description.substr(0, 40);
Logger.log('line 55 OK');
}
}
result.push([trim_des]);
Logger.log('line 60 OK');
}
return result;
Logger.log('line 64 OK');
}
I call the function like that:
=scrapercache("https://www.gurufocus.com/term/fscore/nyse:ABBV/Piotroski-F-Score")
& I get the following error message
Error: Reference does not exist
EDIT: I added log lines to see if the script was processing correctly & it looks like it's ok only until like 28

Answer 1

You're not putting the results in the cache, you're putting the string "cached" there. Consider:
let cached = cache.get(url)
if(cached){
return JSON.parse(cached)
}
let results = ["blah","blah"] // stuff we got with cheerio
cache.put(url, JSON.stringify(results), 120)
return results

Answer 2

Error: “Reference does not exist”
This error message is usually returned by calling a custom function in a spreadsheet cell that does not return a value. It is explicitly mentioned by the official docs, but the error message is not provided, so the confusion is understandable.
An empty array is not a valid return value (since there are no elements to return). The error is easily reproducible with the following custom function:
/**
* #customfunction
*/
function testReferenceError() {
const list = [];
return list;
}
Which, when called in a cell, resulting in the "desired" error:
Applied to your case
In your situation, when there is a cached data in cache, the if statement clause evaluates to false (truthy value when negated evaluates to false). When it does, nothing gets pushed to the result, and an empty array is returned in finally (see above for the explanation of consequences). Consider this mock:
const cache = {
get() {
return "cached";
}
};
let res = cache.get("mock_url");
//ternary operator here acts the same as "if...else":
console.log( !res ? "will enter if block" : "will enter else block" );
Note on return in finally: If you put a return statement into a finally block, expect it to override the return statements in try or catch. Consider this example close to how your program is structured:
const final = (add = false) => {
const list = [];
try {
add && list.push(1);
return [1,2]; //this return is skipped
}
catch(error) {
list.push(error);
}
finally {
return list;
}
};
console.log( final() );
Also, the question already has an answer here