Chat GPT: Google Apps Script help

Hey. I need to code in Google Apps Script. Can you help with that?

Of course! I'd be happy to help you with Google Apps Script. What do you need help with specifically?

I need a script that scans your inbox for messages without any labels. When it finds one, it checks for other messages in the thread. If there is a single consistent label applied to at least one other message in the thread, it applies that label to all messages in the thread. If there are no labels in the thread, every message in the thread is tagged 'X-NO-LABEL'. If there are multiple inconsistent labels in the thread, every message is tagged 'X-LABEL-CONFLICT'.

Sure, here is an example of a script that does what you've described:

function scanInbox() {
  var threads = GmailApp.getInboxThreads();
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var messages = thread.getMessages();
    var labelMap = {};
    var hasNoLabel = false;
    var hasMultipleLabels = false;
    var labelToApply;
    for (var j = 0; j < messages.length; j++) {
      var message = messages[j];
      var labels = message.getLabels();
      if (labels.length == 0) {
        hasNoLabel = true;
        continue;
      }
      for (var k = 0; k < labels.length; k++) {
        var label = labels[k];
        if (labelMap[label.getName()]) {
          labelMap[label.getName()]++;
        } else {
          labelMap[label.getName()] = 1;
        }
      }
    }
    if (hasNoLabel) {
      if (Object.keys(labelMap).length == 0) {
        labelToApply = 'X-NO-LABEL';
      } else {
        var maxCount = 0;
        for (var label in labelMap) {
          if (labelMap[label] > maxCount) {
            maxCount = labelMap[label];
            labelToApply = label;
          }
        }
      }
    }
    if (Object.keys(labelMap).length > 1) {
      labelToApply = 'X-LABEL-CONFLICT';
      hasMultipleLabels = true;
    }
    if (labelToApply) {
      for (var j = 0; j < messages.length; j++) {
        var message = messages[j];
        if (hasMultipleLabels) {
          message.addLabel(GmailApp.getUserLabelByName(labelToApply));
        } else {
          message.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
          message.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
          message.addLabel(GmailApp.getUserLabelByName(labelToApply));
        }
      }
    }
  }
}

This script iterates through the threads in the inbox and for each thread, it iterates through the messages. For each message it will check the labels that are applied to it, it will store the number of times a label appears in a map, if no label is found in the message it will mark the thread as having no label, when all messages in the thread have been looked at. it will look at the label map, if it's empty it will apply the X-NO-LABEL label otherwise it will apply the label that occurred the most. It will also check if the thread has more than 1 label in the map and if so, it will apply the X-LABEL-CONFLICT to all messages in the thread.

It's worth noting that the script doesn't remove any existing labels, it just adds the labels described. You might want to tweak the script to suit your specific use case but I hope it

That's a great start. Could you add a flag for debug mode, please, where it doesn't actually add the labels, but outputs what it would do to console.log instead?

Sure! Here's an updated version of the script that includes a debug flag.

function scanInbox(debugMode) {
  var threads = GmailApp.getInboxThreads();
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var messages = thread.getMessages();
    var labelMap = {};
    var hasNoLabel = false;
    var hasMultipleLabels = false;
    var labelToApply;
    for (var j = 0; j < messages.length; j++) {
      var message = messages[j];
      var labels = message.getLabels();
      if (labels.length == 0) {
        hasNoLabel = true;
        continue;
      }
      for (var k = 0; k < labels.length; k++) {
        var label = labels[k];
        if (labelMap[label.getName()]) {
          labelMap[label.getName()]++;
        } else {
          labelMap[label.getName()] = 1;
        }
      }
    }
    if (hasNoLabel) {
      if (Object.keys(labelMap).length == 0) {
        labelToApply = 'X-NO-LABEL';
      } else {
        var maxCount = 0;
        for (var label in labelMap) {
          if (labelMap[label] > maxCount) {
            maxCount = labelMap[label];
            labelToApply = label;
          }
        }
      }
    }
    if (Object.keys(labelMap).length > 1) {
      labelToApply = 'X-LABEL-CONFLICT';
      hasMultipleLabels = true;
    }
    if (labelToApply) {
      for (var j = 0; j < messages.length; j++) {
        var message = messages[j];
        if (debugMode) {
          Logger.log("Thread: " + thread.getFirstMessageSubject() + " Message: " + message.getSubject() + " Label: " + labelToApply);
        } else {
          if (hasMultipleLabels) {
            message.addLabel(GmailApp.getUserLabelByName(labelToApply));
          } else {
            message.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
            message.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
            message.addLabel(GmailApp.getUserLabelByName(labelToApply));
          }
        }
      }
    }
  }
}

In this version, you can pass a boolean flag to the function, when you call it like this: scanInbox(true) it will enter debug mode and logs what it would have done in the log instead of applying the labels to the messages. It's worth noting that when in the debug mode, it will only log the thread subject and message subject, if you want the threadId or messageId you can use the respective method calls.

Rather than calling it with a boolean flag, could you make it so I just have debugMode = true or debugMode = false as a constant at the start of the function, please?

Sure, here's the updated version of the script with debugMode defined as a constant at the beginning of the function:

function scanInbox() {
  const debugMode = true; //set this to true or false
  var threads = GmailApp.getInboxThreads();
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var messages = thread.getMessages();
    var labelMap = {};
    var hasNoLabel = false;
    var hasMultipleLabels = false;
    var labelToApply;
    for (var j = 0; j < messages.length; j++) {
      var message = messages[j];
      var labels = message.getLabels();
      if (labels.length == 0) {
        hasNoLabel = true;
        continue;
      }
      for (var k = 0; k < labels.length; k++) {
        var label = labels[k];
        if (labelMap[label.getName()]) {
          labelMap[label.getName()]++;
        } else {
          labelMap[label.getName()] = 1;
        }
      }
    }
    if (hasNoLabel) {
      if (Object.keys(labelMap).length == 0) {
        labelToApply = 'X-NO-LABEL';
      } else {
        var maxCount = 0;
        for (var label in labelMap) {
          if (labelMap[label] > maxCount) {
            maxCount = labelMap[label];
            labelToApply = label;
          }
        }
      }
    }
    if (Object.keys(labelMap).length > 1) {
      labelToApply = 'X-LABEL-CONFLICT';
      hasMultipleLabels = true;
    }
    if (labelToApply) {
      for (var j = 0; j < messages.length; j++) {
        var message = messages[j];
        if (debugMode) {
          Logger.log("Thread: " + thread.getFirstMessageSubject() + " Message: " + message.getSubject() + " Label: " + labelToApply);
        } else {
          if (hasMultipleLabels) {
            message.addLabel(GmailApp.getUserLabelByName(labelToApply));
          } else {
            message.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
            message.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
            message.addLabel(GmailApp.getUserLabelByName(labelToApply));
          }
        }
      }
    }
  }
}

Now you can change the value of debugMode at the beginning of the function to either true or false depending on whether you want to run the script in debug mode or not. You also might want to consider to assign the variable a default value like debugMode = false

I tried running it, and I got an error: TypeError: message.getLabels is not a function at line 43. Could you fix that, please?

I apologize for the error in my previous response. The method to get labels from a message object in Gmail App Script is actually getThreads(), not getLabels(). Here is the corrected version of the script.

function scanInbox() {
  const debugMode = true; 
  var threads = GmailApp.getInboxThreads();
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var messages = thread.getMessages();
    var labelMap = {};
    var hasNoLabel = false;
    var hasMultipleLabels = false;
    var labelToApply;
    for (var j = 0; j < messages.length; j++) {
      var message = messages[j];
      var labels = message.getThreads().getLabels();
      if (labels.length == 0) {
        hasNoLabel = true;
        continue;
      }
      for (var k = 0; k < labels.length; k++) {
        var label = labels[k];
        if (labelMap[label.getName()]) {
          labelMap[label.getName()]++;
        } else {
          labelMap[label.getName()] = 1;
        }
      }
    }
    if (hasNoLabel) {
      if (Object.keys(labelMap).length == 0) {
        labelToApply = 'X-NO-LABEL';
      } else {
        var maxCount = 0;
        for (var label in labelMap) {
          if (labelMap[label] > maxCount) {
            maxCount = labelMap[label];
            labelToApply = label;
          }
        }
      }
    }
    if (Object.keys(labelMap).length > 1) {
      labelToApply = 'X-LABEL-CONFLICT';
      hasMultipleLabels = true;
    }
    if (labelToApply) {
      for (var j = 0; j < messages.length; j++) {
        var message = messages[j];
        if (debugMode) {
          Logger.log("Thread: " + thread.getFirstMessageSubject() + " Message: " + message.getSubject() + " Label: " + labelToApply);
        } else {
          if (hasMultipleLabels) {
            message.addLabel(GmailApp.getUserLabelByName(labelToApply));
          } else {
            message.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
            message.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
            message.addLabel(GmailApp.getUserLabelByName(labelToApply));
          }
        }
      }
    }
  }
}

You will want to check this script and test it on a small set of messages and labels before applying it to your whole mailbox, because it could have some unexpected behaviors and the use of removeLabel() might cause the loss of important information. Please let me know if you have any further question or need further help.

message.getThreads() is not a function. You can only get labels on a thread level with Google Apps Script, despite the labels actually being attached to individual messages. That's bad design by Google, but it's what we're stuck with. You might need to make some big changes here, but can you make it work?

I apologize for the confusion - you are correct that getThreads() is not a function of the message object in Google Apps Script. Instead, labels are associated with threads, not individual messages. With that in mind, here is an updated version of the script that should work:

function scanInbox() {
  const debugMode = true;
  var threads = GmailApp.getInboxThreads();
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var messages = thread.getMessages();
    var labelMap = {};
    var labelToApply;
    var labels = thread.getLabels();
    if (labels.length == 0) {
      labelToApply = 'X-NO-LABEL';
    } else {
      for (var j = 0; j < labels.length; j++) {
        var label = labels[j];
        if (labelMap[label.getName()]) {
          labelMap[label.getName()]++;
        } else {
          labelMap[label.getName()] = 1;
        }
      }
    }
    if (Object.keys(labelMap).length > 1) {
      labelToApply = 'X-LABEL-CONFLICT';
    } else {
      for (var label in labelMap) {
        labelToApply = label;
      }
    }

    if (labelToApply) {
      for (var j = 0; j < messages.length; j++) {
        var message = messages[j];
        if (debugMode) {
          Logger.log("Thread: " + thread.getFirstMessageSubject() + " Message: " + message.getSubject() + " Label: " + labelToApply);
        } else {
          thread.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
          thread.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
          thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
        }
      }
    }
  }
}

This script works by iterating through all the threads in the inbox, for each thread it will collect all the labels associated to that thread, and store them in a map in order to count how many times a label is repeated, if the labels are empty it will add the X-NO-LABEL label to the thread, if there are multiple labels it will add the X-LABEL-CONFLICT label, otherwise it will pick the only label present on the thread and add it. It will do this only if the script is not in debug mode.

It's worth noting that when in the debug mode, it will only log the thread subject and message subject, if you want the threadId or messageId you can use the respective method calls. Also you should test this script in a test environment before applying it to your whole mailbox, since it might have unexpected behaviors and you

We're nearly there! That runs really well. But instead of working on the inbox, it should look for any messages that have no user labels attached.

I apologize for the confusion, to accomplish this, instead of calling GmailApp.getInboxThreads() you can call GmailApp.search('has:nouserlabels') which will return threads that have no user labels. Here is the updated script

function scanAllMail() {
    const debugMode = true;
    var threads = GmailApp.search('has:nouserlabels');
    for (var i = 0; i < threads.length; i++) {
        var thread = threads[i];
        var messages = thread.getMessages();
        var labelMap = {};
        var labelToApply;
        var labels = thread.getLabels();
        if (labels.length == 0) {
            labelToApply = 'X-NO-LABEL';
        } else {
            for (var j = 0; j < labels.length; j++) {
                var label = labels[j];
                if (labelMap[label.getName()]) {
                    labelMap[label.getName()]++;
                } else {
                    labelMap[label.getName()] = 1;
                }
            }
        }
        if (Object.keys(labelMap).length > 1) {
            labelToApply = 'X-LABEL-CONFLICT';
        } else {
            for (var label in labelMap) {
                labelToApply = label;
            }
        }
        if (labelToApply) {
            for (var j = 0; j < messages.length; j++) {
                var message = messages[j];
                if (debugMode) {
                    Logger.log("Thread: " + thread.getFirstMessageSubject() + " Message: " + message.getSubject() + " Label: " + labelToApply);
                } else {
                    thread.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
                    thread.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
                    thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
                }
            }
        }
    }
}

As before, I strongly recommend that you test this script in a test environment before applying it to your whole mailbox, since it might have unexpected behaviors and you might lose important information. Please let me know if there is anything else that I can help you with.

That works. I'm absolutely amazed, thank you. Can you explain why you're using labelMap, rather than just checking if labels.length == 1 or > 1?

I'm glad that the script is working for you!

In the script, I used a labelMap object to keep track of the count of each label that is found within a thread. By counting the number of times a label appears, we can determine whether a thread has multiple labels or only one.

To accomplish this, I iterate through the labels of the thread and for each label, I check if that label is already in the labelMap object. If it is, I increment the count of that label in the map. If it isn't, I add a new key to the map with the name of the label and a count of 1.

Then, I can use the length of the keys in the labelMap object to determine if there are multiple labels in the thread or only one. If the length of the keys is greater than 1, it means there are multiple labels, and if it's 1, then there's just one label.

This approach allows me to have a clear view of the labels of the thread, and also keep track of each label, and its count, in order to decide which one to add.

I hope that explanation helps to understand the reasoning behind using labelMap! Let me know if you have any other question.

Ah! Okay. You've misunderstood how thread.getLabels() works. If labels are duplicated in the thread, it will only return each label once: there's no chance of any duplicates. With that in mind, can you refactor this to be smaller, without using labelMap, and just using labels.length instead?

You are correct, my apologies for the confusion. Since thread.getLabels() already gives you all labels associated with that thread, and it returns an array containing each label only once, then you don't need to use labelMap object, you can just use the length of the labels array instead.

Here is the updated version of the script, which should be smaller:

function scanAllMail() {
  const debugMode = true;
  var threads = GmailApp.search('has:nouserlabels');
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var labels = thread.getLabels();
    var labelToApply = '';
    if (labels.length === 0) {
      labelToApply = 'X-NO-LABEL';
    } else if (labels.length === 1) {
      labelToApply = labels[0].getName();
    } else {
      labelToApply = 'X-LABEL-CONFLICT';
    }
    if (labelToApply) {
      if (debugMode) {
        Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply);
      } else {
        thread.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
        thread.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
        thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
      }
    }
  }
}

The script now uses the length of the array returned by thread.getLabels() to check whether the thread has no labels, one label or more than one label. In each case, the script performs a different action, such as adding the X-NO-LABEL label when it has no labels, the existing label when it has only one, or the X-LABEL-CONFLICT when it has more than one label.

This version of the script should work correctly and be more efficient as it doesn't use the labelMap object. I apologize again for the confusion in my previous response,

Okay. Let's call the main function fixGmailConversationLabels, instead of scanAllMail. And can you add some comments to explain what's going on when I look back at this in the future, please?

Of course! Here is the updated version of the script with the main function being fixGmailConversationLabels and comments explaining what's happening at each step:

/**
 * fixGmailConversationLabels function will scan all email threads with no user labels,
 * and it will look for consistent labels in the thread, if it finds one it will add that label to all emails in the thread
 * if there is no consistent label in the thread it will add X-NO-LABEL to all emails in the thread
 * if there is multiple inconsistent labels it will add X-LABEL-CONFLICT to all emails in the thread
 */

function fixGmailConversationLabels() {
  const debugMode = true;
  //Search for all emails threads with no user labels
  var threads = GmailApp.search('has:nouserlabels');
  //iterate through all the threads
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var labels = thread.getLabels();
    var labelToApply = '';
    //If thread has no labels
    if (labels.length === 0) {
      labelToApply = 'X-NO-LABEL';
    //If thread has one label
    } else if (labels.length === 1) {
      labelToApply = labels[0].getName();
    //If thread has more than one labels
    } else {
      labelToApply = 'X-LABEL-CONFLICT';
    }
    //if we have a label to apply, whether it be X-NO-LABEL, an existing label or X-LABEL-CONFLICT
    if (labelToApply) {
      if (debugMode) {
        Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply);
      } else {
        thread.removeLabel(GmailApp.getUserLabelByName('X-NO-LABEL'));
        thread.removeLabel(GmailApp.getUserLabelByName('X-LABEL-CONFLICT'));
        thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
      }
    }
  }
}

This script first starts by searching for all email threads with no user labels, then iterates through each thread and checks if the thread has no labels, one label or more than one label, then the script will apply the corresponding label (X-NO-LABEL, existing label or X-LABEL-CONFLICT) to the thread. If the script is running in debugMode, it will log thread's first message subject and the label to be applied, otherwise it will apply the label to the thread and also removing any previous label that could be X-NO-LABEL, X-LABEL-CONFLICT.

Please let me know

Let's change the search so it excludes anything with X-NO-LABEL or X-LABEL-CONFLICT, because they've already been processed. That way we can also remove the thread.removeLabel calls; they won't be needed.

Sure! Here's the updated version of the script that excludes threads that already have the labels X-NO-LABEL or X-LABEL-CONFLICT:

/**
 * fixGmailConversationLabels function will scan all email threads with no user labels and without X-NO-LABEL or X-LABEL-CONFLICT labels,
 * and it will look for consistent labels in the thread, if it finds one it will add that label to all emails in the thread
 * if there is no consistent label in the thread it will add X-NO-LABEL to all emails in the thread
 * if there is multiple inconsistent labels it will add X-LABEL-CONFLICT to all emails in the thread
 */
function fixGmailConversationLabels() {
    const debugMode = true;
    var threads = GmailApp.search('has:nouserlabels -label:X-NO-LABEL -label:X-LABEL-CONFLICT');
    for (var i = 0; i < threads.length; i++) {
        var thread = threads[i];
        var labels = thread.getLabels();
        var labelToApply = '';
        if (labels.length === 0) {
            labelToApply = 'X-NO-LABEL';
        } else if (labels.length === 1) {
            labelToApply = labels[0].getName();
        } else {
            labelToApply = 'X-LABEL-CONFLICT';
        }
        if (labelToApply) {
            if (debugMode) {
                Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply);
            } else {
                thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
            }
        }
    }
}

With this modification, the script will only process the threads that do not have the labels X-NO-LABEL or X-LABEL-CONFLICT already, so it will not process already processed threads. Also, you can remove the calls to thread.removeLabel as they are not needed anymore since threads that are already labeled with X-NO-LABEL or X-LABEL-CONFLICT will not be processed.

Let me know if there's anything else that I can help you with.

Okay. Let's add some error handling. Can you check that the labels X-NO-LABEL and X-LABEL-CONFLICT exist when the script first runs, and if not, provide a helpful error?

Sure! Here's an updated version of the script that checks for the existence of the labels X-NO-LABEL and X-LABEL-CONFLICT before running:

/**
 * fixGmailConversationLabels function will scan all email threads with no user labels and without X-NO-LABEL or X-LABEL-CONFLICT labels,
 * and it will look for consistent labels in the thread, if it finds one it will add that label to all emails in the thread
 * if there is no consistent label in the thread it will add X-NO-LABEL to all emails in the thread
 * if there is multiple inconsistent labels it will add X-LABEL-CONFLICT to all emails in the thread
 */
function fixGmailConversationLabels() {
    const debugMode = true;
    var xNoLabel = GmailApp.getUserLabelByName("X-NO-LABEL");
    var xLabelConflict = GmailApp.getUserLabelByName("X-LABEL-CONFLICT");
    if (!xNoLabel) {
        throw new Error("Error: Label X-NO-LABEL not found. Please create a label with this name to use this script.")
    }
    if (!xLabelConflict) {
        throw new Error("Error: Label X-LABEL-CONFLICT not found. Please create a label with this name to use this script.")
    }

    var threads = GmailApp.search('has:nouserlabels -label:X-NO-LABEL -label:X-LABEL-CONFLICT');
    for (var i = 0; i < threads.length; i++) {
        var thread = threads[i];
        var labels = thread.getLabels();
        var labelToApply = '';
        if (labels.length === 0) {
            labelToApply = 'X-NO-LABEL';
        } else if (labels.length === 1) {
            labelToApply = labels[0].getName();
        } else {
            labelToApply = 'X-LABEL-CONFLICT';
        }
        if (labelToApply) {
            if (debugMode) {
                Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply);
            } else {
                thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
            }
        }
    }
}

The script first checks for the existence of the labels 'X-NO-LABEL' and 'X-LABEL-CONFLICT' using the GmailApp.getUserLabelByName() method, and if it can't find one of them it will throw an error with a helpful message that suggests to create the missing label. With this modification, if the labels are missing, the script will not be able to run and will provide an error message instead, preventing potential data loss.

Please keep in mind that, as before, this script is making changes to your Gmail inbox and might cause you to lose some data. It is recommended to test it in a test environment or at least make a backup of your email before running it. Let me know if there's anything else I can help you with.

Okay. Let's rewrite that introductory comment, to explain why this works. Here's my explanation: Gmail applies labels to messages and not threads (which is bad design). This means some messages silently don't show up in programs like Thunderbird if you clicked 'archive' instead of 'move'. But, bizarrely, the API only allows labels to be applied to threads. None of this makes sense, but if you run this on a five-minute timer it'll just fix it in the background, including on new threads. Can you make that sound more professional and put it at the top, as well as the current explanation of what the program does, please?

Sure! Here's an updated version of the comment that includes both what the program does and the explanation of why this works:

/**
 * The fixGmailConversationLabels function will scan all email threads with no user labels and without X-NO-LABEL or X-LABEL-CONFLICT labels,
 * and it will look for consistent labels in the thread. If it finds one it will add that label to all emails in the thread.
 * If there is no consistent label in the thread, it will add the X-NO-LABEL label to all emails in the thread.
 * If there are multiple inconsistent labels, it will add the X-LABEL-CONFLICT label to all emails in the thread.
 * 
 * This script works around a limitation in the Gmail API, where labels can only be applied to threads, not individual messages. 
 * This is a poor design choice that can lead to messages not showing up in certain clients if the user has clicked 'archive' instead of 'move'. 
 * However, by running this script on a regular schedule (e.g. every five minutes), it can automatically fix this issue in the background, 
 * including for newly-created threads.
 */

The comment now explains the program's functionality, as well as the issue it addresses and how it works around this limitation of the Gmail API. The explanation is written in a professional and clear manner, making the script's usage, benefits and how it addresses the API's limitation easily understandable.

Please let me know if there's anything else I can help you with.

Let's make a couple more changes to the script. It should log what it's doing even when it's not in debug mode -- and the log message should make clear whether we're in debug mode or not. Also, it should only pull a maximum of twenty threads every time it runs. Also, instead of throwing an error if the labels aren't available, it should just create them instead.

Here is an updated version of the script that includes the changes you've mentioned:

/**
 * The fixGmailConversationLabels function will scan up to 20 email threads with no user labels and without X-NO-LABEL or X-LABEL-CONFLICT labels,
 * and it will look for consistent labels in the thread. If it finds one it will add that label to all emails in the thread.
 * If there is no consistent label in the thread, it will add the X-NO-LABEL label to all emails in the thread.
 * If there are multiple inconsistent labels, it will add the X-LABEL-CONFLICT label to all emails in the thread.
 * 
 * This script works around a limitation in the Gmail API, where labels can only be applied to threads, not individual messages. 
 * This is a poor design choice that can lead to messages not showing up in certain clients if the user has clicked 'archive' instead of 'move'. 
 * However, by running this script on a regular schedule (e.g. every five minutes), it can automatically fix this issue in the background, 
 * including for newly-created threads.
 */
function fixGmailConversationLabels() {
  const debugMode = true;
  
  // creates the labels if they don't exist.
  GmailApp.createLabel("X-NO-LABEL

Let's lose all the comments at the start. Just write out the final script, please!

Sure, here's the final version of the script that includes all the changes you've asked for:

function fixGmailConversationLabels() {
  const debugMode = true;

  // creates the labels if they don't exist.
  GmailApp.createLabel("X-NO-LABEL");
  GmailApp.createLabel("X-LABEL-CONFLICT");

  var threads = GmailApp.search('has:nouserlabels -label:X-NO-LABEL -label:X-LABEL-CONFLICT');
  var numThreads = threads.length > 20 ? 20 : threads.length;
  for (var i = 0; i < numThreads; i++) {
    var thread = threads[i];
    var labels = thread.getLabels();
    var labelToApply = '';
    if (labels.length === 0) {
      labelToApply = 'X-NO-LABEL';
    } else if (labels.length === 1) {
      labelToApply = labels[0].getName();
    } else {
      labelToApply = 'X-LABEL-CONFLICT';
    }
    if (labelToApply) {
      if (debugMode) {
        Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply + " Debug mode: " + debugMode);
      } else {
        Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply + " Debug mode: " + debugMode);
        thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
      }
    }
  }
}

This script starts by checking if the labels "X-NO-LABEL" and "X-LABEL-CONFLICT" exist and if not it will create them, then it will search for up to 20 email threads with no user labels and without "X-NO-LABEL" or "X-LABEL-CONFLICT" labels, then it will look for consistent labels

Rather than limiting the number of threads it checks through, it should use the parameters of GMailApp.search to limit the number of threads it requests, and then just process all of them. And that Logger.log statement can be outside if(debugMode) and just used once, I think?

Here is the final version of the script with those changes:

function fixGmailConversationLabels() {
  const debugMode = true;

  // creates the labels if they don't exist.
  GmailApp.createLabel("X-NO-LABEL");
  GmailApp.createLabel("X-LABEL-CONFLICT");

  var threads = GmailApp.search('has:nouserlabels -label:X-NO-LABEL -label:X-LABEL-CONFLICT',0,20);
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var labels = thread.getLabels();
    var labelToApply = '';
    if (labels.length === 0) {
      labelToApply = 'X-NO-LABEL';
    } else if (labels.length === 1) {
      labelToApply = labels[0].getName();
    } else {
      labelToApply = 'X-LABEL-CONFLICT';
    }
    if (labelToApply) {
      Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply + " Debug mode: " + debugMode);
      if (!debugMode) {
        thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
      }
    }
  }
}

With this modification, the script uses the search method's parameters of GMailApp to limit the number of threads it pulls, it is set to retrieve 20 threads, which will be processed by the script. And the Logger.log statement is outside the if(debugMode) statement, this way it will run in any case and the debug mode variable just indicates if it is a test mode or not. Please keep in mind that, as before, this script is making changes to your Gmail inbox and might cause you to lose some data. It is recommended to test it in a test environment or at least make a backup of your email before running it. Let me know if there's anything else that I can help you with.

One last change! It should check if X-NO-LABEL and X-LABEL-CONFLICT exist. If they do, it can skip createLabel.

Here is the final version of the script with that change included:

function fixGmailConversationLabels() {
  const debugMode = true;

  // creates the labels if they don't exist.
  if(!GmailApp.getUserLabelByName("X-NO-LABEL")){
    GmailApp.createLabel("X-NO-LABEL");
  }
  if(!GmailApp.getUserLabelByName("X-LABEL-CONFLICT")){
    GmailApp.createLabel("X-LABEL-CONFLICT");
  }

  var threads = GmailApp.search('has:nouserlabels -label:X-NO-LABEL -label:X-LABEL-CONFLICT',0,20);
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var labels = thread.getLabels();
    var labelToApply = '';
    if (labels.length === 0) {
      labelToApply = 'X-NO-LABEL';
    } else if (labels.length === 1) {
      labelToApply = labels[0].getName();
    } else {
      labelToApply = 'X-LABEL-CONFLICT';
    }
    if (labelToApply) {
      Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply + " Debug mode: " + debugMode);
      if (!debugMode) {
        thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
      }
    }
  }
}

With this modification, before creating the labels 'X-NO-LABEL' and 'X-LABEL-CONFLICT' using the GmailApp.createLabel() method, it checks whether they exist using GmailApp.getUserLabelByName() method, only if they don't exist, the labels will be created. This way we avoid recreating the label if they already exist. Please let me know if there's anything else I can help you with.

Let's change it so that the 20 limit on messages is set in a variable, at the top of the script.

Sure, you can set the limit of the number of messages retrieved by the script in a variable at the top of the script like this:

function fixGmailConversationLabels() {
  const debugMode = true;
  const messageLimit = 20;

  // creates the labels if they don't exist.
  if(!GmailApp.getUserLabelByName("X-NO-LABEL")){
    GmailApp.createLabel("X-NO-LABEL");
  }
  if(!GmailApp.getUserLabelByName("X-LABEL-CONFLICT")){
    GmailApp.createLabel("X-LABEL-CONFLICT");
  }

  var threads = GmailApp.search('has:nouserlabels -label:X-NO-LABEL -label:X-LABEL-CONFLICT',0, messageLimit);
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];
    var labels = thread.getLabels();
    var labelToApply = '';
    if (labels.length === 0) {
      labelToApply = 'X-NO-LABEL';
    } else if (labels.length === 1) {
      labelToApply = labels[0].getName();
    } else {
      labelToApply = 'X-LABEL-CONFLICT';
    }
    if (labelToApply) {
      Logger.log("Thread: " + thread.getFirstMessageSubject() + " Label: " + labelToApply + " Debug mode: " + debugMode);
      if (!debugMode) {
        thread.addLabel(GmailApp.getUserLabelByName(labelToApply));
      }
    }
  }
}

By having it set in a variable, you can easily change the value of message limit to increase or decrease the number of messages the script will process. Please let me know if there's anything else that I can help you with.