AWS CDK "Stack with id null does not exist"

We host in AWS at work, which allows us to use the AWS CDK for IaC and CI/CD Pipelines (so many acronyms). Our DevOps team crafted the original CDK pipeline files for us and handed them over to live in our repository, but when it came time to change the architecture of our application I figured I could use what we already had combined with a little help from Copilot and/or ChatGPT and fix it up to do what I need. I was eventually able to do that, but not without a major challenge in the form of a cryptic error message that took me nearly two weeks to figure out and resolve.

TL;DR: AWS caps the length of the handler of a Lambda's build to 128 characters. I had 129 characters so it failed, but didn't give me a useful error message. I had to pull the template from the pipeline and try to manually create it via the UI to get to the error message.

The architecture change was to go from one single Lambda to two Lambdas and an S3 bucket where the first Lambda accepts a file upload request and generates a pre-signed URL to upload the file to the S3 bucket. The client uploads the file using the pre-signed URL and the second Lambda is notified to process the file. It's a fairly straightforward design and all the pieces to implement it exist directly in AWS. It should have been easy.

I added everything and ran the pipeline and it failed with the message in the title: "Stack with id null does not exist". There was another error with the message "ChangeSet [arn:aws:cloudformation:{region}:{target account}:changeSet/PipelineChange/{guid}] does not exist", but no additional information. So the pipeline was running, which should have generated a stack and a changeset on that stack, but neither was being created. Why not? That's where my two weeks went. describe-events didn't tell me anything. Logs didn't tell me anything. I was getting nowhere so I started over and just created the S3 bucket: success. No issues whatsoever. I was able to generate a pre-signed URL and upload a file to it. So I added the second Lambda back in. More failures.

I don't remember all the troubleshooting steps, but at various points I found the bucket creation failed because it already exists and learned that bucket names are globally unique. Not per account or region or customer/subscription. Globally unique. Solved that and still had the same error. ChatGPT or Copilot thought there must be a circular reference so I revamped all the new CDK files to make sure there wasn't. Same failure. So I started over again. This time I just added the second Lambda and did nothing with the bucket and immediately got the same failure again. Obviously, the problem was in the definition of the new Lambda, right? Yes, but no.

The AWS CLI allowed me to generate the template that would be used by the pipeline to create the stack, and then validate that template. Everything was fine. Validation passed, but when I ran the actual pipeline, it failed. Then ChatGPT suggested pulling the template that was generated during the pipeline build (using `aws cloudformation get-template --change-set-name PipelineChange --stack-name {stack name} --region {region} --query 'TemplateBody' --output json > {filename}.json`) and using the template to manually create the Lambda via the AWS UI. That finally led me to an error message that indicated my resource value was too long. My handler was 129 characters and the limit is 128 characters. One too many characters cost me two weeks because AWS wasn't giving me a useful error message.

Extension Methods in C#

I was explaining extension methods in C# to somebody and realized it was a good topic for a blog post, so here we are.

Extension methods are a way to enhance (or extend) an existing object. If you've done any significant coding with C# I can virtually guarantee you've already used extension methods that were built-in to the framework. Things like " banana ".Trim(), which removes leading and trailing whitespace from the string. But you can also create your own extension methods and it's actually pretty easy to do.

First you need to identify what you're trying to extend. For example, if you always want to safely convert a string to an integer and return -1 when the string is not an integer, would you be extending strings or ints? The answer is strings.

 

I actually wrote a separate post with some examples of string extensions that I use pretty frequently. Basically, we're extending (hence the name) the framework's built-in capabilities so we can manipulate an object (type) more easily. Extension methods are a great way to avoid littering your application with helper methods like "GetTrimmedString(string toTrim)". But you want to be aware of unnecessarily polluting your code base with extension methods that are only used in one place.

Fuzzy Matching in C#

I've been working on a project where we allow users to provide us a .csv file and tell us about it, like what kind of data is in which column. Think of it like this: we have a fixed list of data points that we need to have mapped and the user is going to give us a file that contains all the data, but we don't know which column will have which piece of information so the user has to tell us. If we need First Name, Last Name, and Age, the user just has to tell us which column in their file has which value. We want to make that as easy as possible so we check the header in their file to see if we can deduce that information so the user doesn't have to. It's easy if the columns are named First Name, Last Name, and Age, but it gets a little trickier when they're named FName, LName, and AgeInYears. That's where fuzzy matching comes in.

We decided to use a library called Fuzzy Sharp (there are several with that name so be cautious when choosing one) to do the heavy lifting for us. It's pretty simple to use, but there are lots of options and the "documentation" isn't super clear. Fortunately in 2025 we have AI to help us make sense of the nonsensical!

In our first attempt we checked for an exact match manually, then stripped off special characters from both sets for comparison and checked for another "exact" match, then finally relented and used the FuzzySharp library to check for a match:

 

private int FindSourceColumnNumber(string destinationName, IEnumerable<string> columnNames)
{
    var exactMatch = columnNames.Select((name, index) => new { Name = name, Position = index })
        .FirstOrDefault(a => a.Name.Equals(destinationName, StringComparison.OrdinalIgnoreCase));
 
    if (exactMatch is not null)
    {
        return exactMatch.Position;
    }
 
    var strippedColumnNames = columnNames
        .Select((name, index) => new {
            Name = name,
            Position = index,
            StrippedName = SpecialCharacterReplacementRegex().Replace(name, "")
        });
    var strippedDestinationName = SpecialCharacterReplacementRegex().Replace(destinationName, "");
 
    var strippedMatch = strippedColumnNames
        .FirstOrDefault(name => string.Equals(name, strippedDestinationName, StringComparison.InvariantCultureIgnoreCase));
 
    if (strippedMatch is not null)
    {
        return strippedMatch.Position;
    }
 
    var fuzzyMatch = strippedColumnNames
        .Select((name, index) => new { Name = name, Position = index, Score = Fuzz.Ratio(strippedDestinationName, name) })
        .Where(x => x.Score >= 70)
        .OrderByDescendinx(x => x.Score)
        .FirstOrDefault();
 
    return fuzzyMatch is not null ? fuzzyMatch.Position : -1;
}

That was fine, but it turned out there was a much better way to do this by taking advantage of the FuzzySharp library. We were able to simplify our code to just this:

private int? FindSourceColumnNumber(string destinationName, IEnumerable<string> columnNames)
{
    var exactMatch = columnNames.Select((name, index) => new { Name = name, Position = index })
        .FirstOrDefault(a => a.Name.Equals(destinationName, StringComparison.OrdinalIgnoreCase));
 
    if (exactMatch is not null)
    {
        return exactMatch.Position;
    }
 
    // Step 2: Fuzzy match (slower, but more flexible)
    var fuzzyMatch = columnNames
        .Select((name, index) => new { Name = name, Position = index, Score = Fuzz.Ratio(destinationName, name, PreprocessMode.Full) })
        .Where(x => x.Score >= 70)
        .OrderByDescending(x => x.Score)
        .FirstOrDefault();
 
    return fuzzyMatch is not null ? fuzzyMatch.Position : null;
}

Adding the PreprocessMode.Full parameter tells FuzzySharp to strip out non-alphanumeric characters on its own. Since the authors of that library focused on speed and efficiency we've basically decided to trust that they're doing a better job with it than we were when we were using the Regex match capability. There's a ton more that FuzzySharp can do, but this is the extent of what we needed so I didn't delve too deep into its other features.

Distinct Array Values in JavaScript

Sometimes when you're working with collections (in any language) you find yourself needing to get just the distinct list of items in the collection. JavaScript has an object called a Set that makes doing this with arrays really, really easy.

Start with an array of primitives:

let arr = [1, 2, 3, 4, 5, 5, 4, 3, 2, 1, 1, 1, 1, 3, 4, 5, 6]

From that array, create a Set: 

let set = new Set(arr)

Convert it back to an array (this step is optional because you may find working with the Set directly meets your needs):

let result = Array.from(set);

That's it. Now you have an array of distinct primitive values. If you have an array of complex objects, you can use this same trick, but it's a little... trickier.

let arr = [{id:1,name:'Frodo',relatives:[{id:2,name:'Bilbo'}]},{id:1,name:'Frodo',relatives:[{id:2,name:'Bilbo'}]}];
let set = new Set(arr.map(JSON.stringify));
let result = Array.from(set);

Setting Up esLint for an Angular 19 Project

The angular-eslint package makes setting up linting in an Angular project pretty easy, but due to some recent changes there are a few new steps I had to work out to get it working so I figured I'd put them here for next time.

1. Install the angular-eslint package: ng add angular-eslint
2. Rename the generated eslint.config.js to eslint.config.mjs
3. Change the 3 require statements at the top of the config file to import statements
1. const eslint = require("@eslint/js"); => import esLint from '@eslint/js';
2. const tseslint = require("typescript-eslint"); => import tsEsLint from 'typescript-eslint';
3. const angular = require("angular-eslint"); => import angular from 'angular-eslint';
4. Change the module.exports to export default
1. module.exports = tseslint.config( => export default tsEsLint.config(
5. In package.json, add a "type" setting with a value of "module"

At this point, esLint should be all setup. It actually works before any of this, but I wanted to use a plugin (more on that in a moment) and that required me to make these changes.

So, about that plugin. esLint made the decision in 8.53 to stop including stylistic rules as part of the linting process. I understand the decision, but I don't like it. Fortunately, there's a plugin for stylistic linting that you can add and it's pretty easy now that the above changes have been implemented.

1. Install @stylistic/eslint-plugin-ts package: npm install @stylistic/eslint-plugin-ts
2. Import the plugin in eslint.config.mjs
1. import stylisticPlugin from '@stylistic/eslint-plugin-ts'
3. In eslint.config.mjs, add a node as a sibling to the "files" node for plugins:
   plugins: {
         stylistic: stylisticPlugin
       },
4.  Add the individual style rules to the rules node of eslint.config.mjs
1. For example, to enfore the 1 true brace style rule, add "stylistic/brace-style": ["error", "1tbs"],
   

That's it! esLint should be all good to go. If you install a live linter extension in your working environment (like the esLint plugin for VS Code) you should see all your lint rules - including stylistic ones - applied.

JavaScript Boolean Object

It has been a looooooong time since I posted. Not because I haven't had a ton to post about, but because at my core I'm super lazy. Anyway, here's a quick hitter on how to check if every property on an object is true using the Boolean function in JavaScript.

return Object.values(this.data.modal.validation).every(Boolean);

You do need to watch out for a couple of things if you want to use this. First, because of type coercion in JavaScript, an object that has pretty much any kind of data on a property will count as true. So if you had an object with a name property that had a value of "Mickey", that's true in this scenario. Second (and related), if you have a property with a value of 0 it will count as false, again due to type coercion.

I'm using this to check an object that only has boolean properties and it works very well.

Azure DevOps Unable to Edit Wiki

I recently discovered project-wide repository policies in Azure DevOps so naturally I took advantage of them. The next time I tried to update the wiki in that project I was met with an error that read "Pushes to this branch is not permitted. Please continue with 'Edit in Repos' and use a pull request to update this branch. Click on 'Learn More' to find out how to edit in Repos."

A quick Google search lead me to a Microsoft "answer" that at least explained what was happening, but didn't give me any insight on how to fix it. Fortunately, the next search result did. Since that's just someone's blog and I have no guarantee they'll keep it up forever, I'm just going to reproduce their information here.

Instead, you can apply a security exception.  To do this you go to the Wiki home page and edit the "Wiki security", accessed through the menu for the wiki.

Here you have the same permissions dialogue you'd find against a repository.  Find an appropriate group (Contributors makes sense, but you might want to allow other users too), and then grant "Bypass policies when pushing" flag for that group.