Not my own words, but copied verbatim from Chris Schmidt on the OpenLayers Mailing List. Change the name, and they are mostly applicable to any package, not just OpenLayers. Having been guilty of not following these instructions myself, I’d advocate that all new mailing list subscribers should read it before signing up…

Many times, users have come to me, or asked questions in IRC, related to getting help with a particular behavior. Whether that behavior is a bug or user error, there is one thing that you can do to make it more likely that a developer will be able to quickly help you with your problem. (In some cases, this is the difference between getting help at all, and simply not receiving any.) I have never seen any situation where this rule does not apply, and so I want to share it publicly with the users and dev communities so that we can all learn from it, and learn how to help each other more quickly and easily.

(Throughout this post, I use the terms ‘developers’ and ‘users’. By these terms, I mean “persons who have knowledge of the code inside of the OpenLayers library” and “persons who have knowledge of using the OpenLayers library, but not what is inside the library itself.“)

Minimizing Test Cases

In order for developers to help fix a problem, they first have to understand it. In order to do that, they need to understand everything thati s going on in a situation where the problem is reproducible. Oftentimes, the particular behavior is only existing in a certain type of situation, or in a limited case that is not exploited by the commonly used code. (In addition, some problems are the result of user error in some way.)

In order to help developers help you, the best thing to do is to minimize the error to the smallest amount of code that can cause it to happen. Additionally, when attempting to reproduce, any developer will need to set up the code so that it is possible to run in the developer’s test environment. This means that it is ideal to remove external references to other Javascript files, and external files at all, where possible. (Clearly, this is not always possible: WFS server bugs can’t typically be demonstrated inside of a single page, for example – but you should minimize external dependancies as much as possible.)

Once you’ve done this, you should remove all non-neccesary lines of code from your example. Does the problem require the ScaleBar control in order to manifest itself? If not, toss it. Does it need multiple layers? If not, toss them. In short, any line of code that is not directly related to reproducing the problem should be removed, as each line will need to be read by the developer – and in the case of multiple developers working on a problem, read by each developer – in order to determine whether the problem is related to that.

This minimization step should include removing any unneccesary Javascript, unneccesary CSS files, unneccesary HTML, etc. until the resulting code is as small as possible.

Many times, in doing this, you will come across a particular minimization step that causes the problem to go away. This is a good sign, because it means you have narrowed the problem down to that particular aspect of code. Put it back, and keep minimizing.

Additionally, many times in doing this, you find a particular construct in your code that can help you understand how to work around the problem.

If not, then continue onto the next section.

OpenLayers Library References

There are multiple hosted versions of the OpenLayers library.

This will always represent the most recent released ‘stable’ version of the OpenLayers API.

This is always a 10-minute delayed build of OpenLayers trunk.

To simplify allowing developers to set up the code on their own testing environments, it is often beneficial to point directly to one of these library URLs. In addition, this also ensures that the problem is not something specific to your build of OpenLayers.

Publishing your Problem

Once you have minimized your test case, you need to publish it. In general, it is easiest if you publish an HTML page on a web accessible URL. Even if your project is not yet public, you can likely put a page up on another server which demonstrates the problem. Doing this is much more likely to have a developer actually follow the link and explore your problem. This is especially true for things like WFS which require a proxy to work correctly:  Downloading the page, setting up a proxy, and testing locally is a lot of work for a developer simply to confirm that a problem exists.

If you do not have any place to publish webpages, you can attempt to paste your code to a public site like ‘’. However, be aware that doing so means that a developer has to perform more steps to reproduce your problem – and every step is one that makes the problem less likely to be solved quickly and easily.

Communicating about your Problem

The best way to communicate your problem is to send an email to the users list demonstrating the problem. Oftentimes other users will be able to point out a particular flaw in your code that is causing the error, or explain that the behavior is a known lack of functionality in OpenLayers.

Be clear on steps for reproduction. Users who don’t know what they’re supposed to do to cause the bug will not be able to see it, and if they can’t see it, they can’t help you.

If you have determined the particular change in the OpenLayers source code which is required to change the behavior, then it is more likely that the Developers list is the best place to go. Any discussion which involves code from OpenLayers itself is probably better suited for the dev list.


By following the steps: * Simplify/Minimize * Publish * Communicate

(If you’d like, you can toss a “???, Profit!” at the end of this.)

You can ensure that it is as easy as possible for a developer to determine whether the problem you’re having is with the library. You also make it easier for develpoers and users to find potential problems in your usage of the library and suggest solutions. Finally, you may find in the process that you find the bug yourself, thus saving yourself and everyone else time in trying to debug.

The end result is a more workable system for everyone. The easier it is to understand the problem you’re having, the faster, and more easily, you will be able to get help.

Best Regards,

Christopher Schmidt MetaCarta