Debug tools for M Code

[RT8]

Are there any debugging tools for M Code? Sometimes M Code can get complicated with function calls within function and some of them can be recursive etc.

[johnbasha33]

@RT8 
Yeah, debugging M code (Power Query language) can be a real pain sometimes.
Unlike normal programming languages where you have fancy debuggers, breakpoints, and step-by-step tools, M code doesn’t really give you much.

👉 Break big stuff into smaller steps.
👉 Add little "peek" columns when things get confusing.
👉 Use Diagnostics.Trace if you really need behind-the-scenes info.
👉 Stay calm — M code is weird but predictable once you slice it into pieces.

Did I answer your question? Mark my post as a solution! Appreciate your Kudos !!

[RT8]

Thannks very much for your suggestions @johnbasha33 for your suggestions. I gsest 1 & 4.

Can you please elaborate 2 & 3

[v-karpurapud · Accepted solution]

Hi @RT8 

Thank you for reaching out to the Microsoft Fabric Community Forum.
 

Power Query (M) does not have a traditional debugger, but it provides powerful built-in tools and techniques to debug effectively.
 

To troubleshoot complex M code:

1. Use intermediate steps in the Advanced Editor to inspect outputs step-by-step.
2. Apply the try...otherwise expression to catch and isolate errors.
3. Use Diagnostics.Trace to log values during execution, especially in recursive or nested functions.

When working with complex or recursive logic:

1. Consider using List.Accumulate as a more efficient and readable alternative to recursion, especially for large datasets.
2. As suggested by @lbendlin , List.Generate can also be a powerful approach for building iterative logic in a controlled manner.
   
   

If this response resolves your query, please mark it as the Accepted Solution to assist other community members. A Kudos is also appreciated if you found the response helpful.

Thank You!

[RT8]

Where this does not solve  my problem these are good suggestions and I will take them up. Thanks for your time in responding to my question

[v-karpurapud]

Hi @RT8 

If Debug tools for M Code important for your use case, it’s recommended to submit feedback via Microsoft Fabric Ideas so that it can be considered for future updates. If many customers demand this feature, Microsoft will prioritize it and work on rolling it out soon. I hope your issue gets resolved quickly. 

 Thank You!

[RT8]

That is a great idea. Thanks for the suggestion. I have submitted this idea.

[v-karpurapud]

Hi @RT8 

Thank you for the response.

[lbendlin]

Interesting question.  I think when you get to that point you need to take a step back and simplify your code.  Avoid recursions - use List.Generate instead.  Avoid functions inside functions inside functions - inline your code instead.

For better code readability you can use powerqueryformatter.com

[RT8]

Thanks for your response. While this does not solve my problem I will take up your advice and try the tool you recommended.