I've been able to sort out the middle bit (the API seems to be called to just fine) along with the submenu displaying. Originally I thought that just the end part wasn't working but I'm now thinking that the selection part isn't either.
What am I doing wrong with the getSelection() and what do I need to do to insert a link into said selection? (to clarify, not to replace the text with a link, but to insert a link into the text)

//Open trigger to get menu
function onOpen(e) {
 DocumentApp.getUi().createAddonMenu()
  .addItem('Scry', 'serumVisions')
  .addToUi();
}

//Installation trigger
function onInstall(e) {
 onOpen(e);
}

//I'm not sure if I need to do this but in case; declare var elements first

var elements

// Get selected text (not working)
function getSelectedText() {
const selection = DocumentApp.getActiveDocument().getSelection();
 if (selection) {
  var elements = selection.getRangeElements();
  Logger.log(elements);
 } else {
  var elements = "Lack of selection"
  Logger.log("Lack of selection");
 }
}

//Test run
// insert here

// Search Function
function searchFunction(nameTag) {
 // API call   inserted Value
 let URL = "https://api.scryfall.com/cards/named?exact="   nameTag;
 // Grabbing response
 let response = UrlFetchApp.fetch(URL, {muteHttpExceptions: true});
 let json = response.getContentText();
 // Translation
 let data = JSON.parse(json);
 // Jackpot
 let link = data.scryfall_uri;
 // Output
 Logger.log(link);
}

// Test run
searchFunction("Lightning Bolt");

//Let's hope this works how I think it works
function serumVisions() {
 const hostText = getSelectedText();
 const linkage = searchFunction(hostText);
 // Unsure what class I'm supposed to use, this doesn't
 const insertLink = DocumentApp.getActiveDocument().getSelection().newRichTextValue()
 .setLinkUrl(linkage);
 Logger.log(linkage);
}

For the first part, I tried the getSelection() and getCursor() examples from the Google documentation but they don't seem to work, they all just keep returning null.

For the inserting link bit, I read all those classes from the Spreadsheet section of the documentation, at the time I was unaware but now knowing, I haven't been able to find a version of the same task for Google Docs. Maybe it works but I'm writing it wrong as well, idk.

CodePudding user response：

Modification points:

• In your script, the functions of getSelectedText() and searchFunction(nameTag) return no values. I think that this might be the reason for your current issue of they all just keep returning null..
• elements of var elements = selection.getRangeElements(); is not text data.
• DocumentApp.getActiveDocument().getSelection() has no method of newRichTextValue().
• In the case of searchFunction("Lightning Bolt");, when the script is run, this function is always run. Please be careful about this.

When these points are reflected in your script, how about the following modification?

Modified script:

Please remove searchFunction("Lightning Bolt");. And, in this case, var elements is not used. Please be careful about this.

From your script, I guessed that in your situation, you might have wanted to run serumVisions(). And also, I thought that you might have wanted to run the individual function. So, I modified your script as follows.

function getSelectedText() {
  const selection = DocumentApp.getActiveDocument().getSelection();
  var text = "";
  if (selection) {
    text = selection.getRangeElements()[0].getElement().asText().getText().trim();
    Logger.log(text);
  } else {
    text = "Lack of selection"
    Logger.log("Lack of selection");
  }
  return text;
}

function searchFunction(nameTag) {
  let URL = "https://api.scryfall.com/cards/named?exact="   encodeURIComponent(nameTag);
  let response = UrlFetchApp.fetch(URL, { muteHttpExceptions: true });
  let json = response.getContentText();
  let data = JSON.parse(json);
  let link = data.scryfall_uri;
  Logger.log(link);
  return link;
}

// Please run this function.
function serumVisions() {
  const hostText = getSelectedText();
  const linkage = searchFunction(hostText);
  if (linkage) {
    Logger.log(linkage);
    DocumentApp.getActiveDocument().getSelection().getRangeElements()[0].getElement().asText().editAsText().setLinkUrl(linkage);
  }
}

• When you select the text of "Lightning Bolt" in the Google Document and run the function serumVisions(), the text of Lightning Bolt is retrieved, and the URL like https://scryfall.com/card/2x2/117/lightning-bolt?utm_source=api is retrieved. And, this link is set to the selected text of "Lightning Bolt".

Reference:

• getSelection()