Recently, we got tons of feedback about the need for a debugger in Julia: [image] List of most desired features for Julia v1.x Community In this thread I’d like to share my list of most desired features for Julia v1.x: The ability to manipulate types in a parametric type as discussed here (see also #18466) Interfaces or traits: #6975 Default field values: #10146 With these features I should be near 100% happy with the language, what about you? I wonder how people rely on debuggers for day-to-day coding. I was trained to reason through code with my brain, and it typically works very well! The only time I really felt the necessity to use a debugger in my years as a programmer was when I was playing with heavy parallel programming on a cluster. My impression is that people are overusing debuggers, but I may be wrong… Today I saw a comment on the forum: “I cannot upgrade to Julia v0.6 because it doesn’t have a debugger.” I never used this criterion myself to choose a programming language! What is the rationale?

Hi All, I am a novice Julia developer. I have 2 projects actively been developed : A PDF parser Sample code solution for AI a modern approach I definitely need a debugger for 1. Without single stepping debugging a parser is almost impossible. In a handwritten parser with direct and indirect recursions after a few tokens it becomes very hard to track progress without a debugger. Sample code example is a very scientific computation kind of problem. I can write special testcases for misuse cases and ensure the algorithm is working as intended. A single stepping debugger should be given priority for native Julia ASAP. It can save lots of time and efforts. regards, Sambit

[image] tamasgal: I use them [debuggers] when they feel comfortable/natural to use, i.e. are easily accessible. While I agree that debuggers are not absolutely necessary, they certainly can be quite useful. I spent about 8 years coding mainly in C++ (and some Fortran) and then the last two years coding mainly in Julia (and some Python). My first experience with debuggers was with Visual Studio and I have to say that setup was really amazing (it says really bad things about Microsoft that I nevertheless find that not to be worth it). Even so, back then I was using the debugger for its intended purpose: to debug (this was C++ mind you). Therefore, debugging didn’t seem like much more than a convenient curiosity to me at the time. When I started using Python I made much more extensive use of the debugger. I dare say that it seems likely that the ease and power of debuggers in interpreted languages is a major reason for the success of Python. In Python I used the debugger as a user interface: I would write command line tools that launched me into the Python debugger. While other people were using excel to view data, I was using my command datacat which quickly loaded a dataset into a pandas dataframe. I would write scripts that were part interactive (via the debugger), part static. Granted, much of this was to overcome what I found to be the shortcomings of Python, but me the debugger eliminated many uses of GUI’s. I also became somewhat accustomed to reasoning about code by inserting lots of break points, going in and messing around, and seeing what result I got. When I was using it, it still seemed like a fun new toy, so I have to imagine that as time passed I would have used it much less. I have said many times before on this forum that the debugger is the one and only thing I miss about Python. Granted, Julia has a much better REPL than Python, and it also has pretty much the best stack traces I’ve ever seen (though sometimes tracebacks through macros are still ugly) so I think the situation we have right now is just about as good as it could be without a debugger. I still think we should have a really good one though.

Minor but kind of related improvement in 0.6: after a stack trace, number + Ctrl-Q in the REPL takes you to the right function. Together with Revise.jl, and #265 fixed, I experienced large increases in productivity when debugging (so now I generate more subtle and insidious bugs).

Is there any timelines when the debugger will support 0.6 or 0.7? As much we think we are 100% sure of the system we build there is one thing or the other in the wild that proves our limitation of knowledge. So debugger definitely helps than introducing debug prints all over the place and then remove them. Please consider this as a high priority requirement. regards, Sambit

I have seen some comments to the effect that work on updating the debugger is ‘ongoing’, but it’s not so easy to see what’s going on. https://github.com/Keno/Gallium.jl doesn’t show any activity, though sometimes people work on ‘private branches’. My uneducated, ill-informed guess is that the update may not come until after version 1.0 is out, since there is a tremendous amount of other work that is getting higher priority, breaking changes, etc. I don’t know this, but I’m getting that sense from lack of ‘chatter’, no mention of timelines, and that the most active contributors don’t seem to need a debugger that desperately.

The work on the new version of ASTInterpreter is in GitHub - JuliaDebug/ASTInterpreter2.jl: Re-write of ASTInterpreter for julia 0.6+. It mostly works, but there’s a few things to take care of before I formally announce it. It doesn’t have breakingpointing, which is a pretty difficult feature to implement well and performantly, so that may have to wait until after 1.0, but at least the exploratory workflow should be well supported.

In the last 7 months, I’ve been working on a project where Julia is not involved. Now I’m back to Julia, realizing that a lot has happened. At the time when I left, v0.6 was just rolled out. Now it is fully-fledged and bundled with JuliaPro, which is really nice. What I care most is the debugger since I often need to understand large packages written by others (more than 30,000 lines of code per package on average). Stepping through using debugger is the only efficient way to approach for a quick digest, to be honest. I was excited when I checked the downloads page for JuliaPro, where my eyeballs were caught be this line: It includes the Juno IDE, the Gallium debugger, and a number of packages for plotting, optimization, machine learning, databases and much more (requires registration). I spent the whole day yesterday playing with JuliaPro and didn’t see any trace of the debugger functionality being in effect. My reading of some of the posts in this thread seems to have confirmed my understanding - debugger is not ready for v6.0, unfortunately. Here is my question - If I connect Juno (that I obtained via installation of JuliaPro) with v5.0+, am I able to use debugger within Juno? Two more questions - When will a mature debugger be in place for v0.6? May I have a rough estimate? I’m really curious to know. Are we going to have something close to the Matlab debugger - you set breakpoints by simply clicking the corresponding line? Anyway, big thank you to Julia team and all contributors!

If you are a developer and your daily life is coding and writing robust codes to be reused, yes you might really need to have a very good mental model of what is going on, and debugger is not needed. TL;DR: as a scientific researcher who writes code just sometimes and throws them away in most cases, debugger is a huge time saver. The use of debugger is of course to get fix it quickly without maintaining a good mental model of what is going on. As a researcher, I spend 90% of time on something else, but spend only 5% of my time coding. This involves testing my algorithmic idea, which ends up not interesting most times, and I just want to find out ‘early failure’. In this case, I just want to load my shitty data quickly (quickly in coding time, not run time), write the code that just works for the core case, and when I get an error / unexpected behavior, I just want to quickily set a breakpoint and starting printing values. Sometimes, starting a script even involves loading my data and processing it and takes more than 10 seconds, and so on. In a long run when my shitty algorithm seems to work and I want to run a serious experiment, yes I should process the data well, save the processed data somewhere, optimize code, and so on. But, why would I want to spend my time on these things when my new algorithm is not interesting 90% of the time? I also want to emphasize that scientific computing requires more need for the debugger since there are numerical issues you need to carefully examine but hard to expect ahead of time. I often find negative eigen values in (supposedly) positive semi-definite matrices, or the optimization method just does not find the right solution and so on. The best thing about using python here is that I don’t even need to setup a breakpoint ahead of time. When it fails, I just call the post-mortem analysis function, and it gets me to the place where I can examine eigen values and check optimality conditions and so on… And these are often rare cases that happens once every 1000 random runs… I’ve been there. Anyway, I really would like to emphasize that having a debugger is really important in attracting many users into Julia. No matter how you argue well, they will still want a debugger. I really like where Julia is going. But as I learn more about it, Julia is more like providing convenience for people who write library, but not that much for people who use it “sometimes” to check things quickly and produce code just to write a paper. In this use case, you mostly write scripts that won’t be reused. Or, it could be that I just belong to a community that Julia does not need to care…

[image] deltakam: Or, it could be that I just belong to a community that Julia does not need to care… They developers do care about people who want debuggers, and it is said to be in the works. The constraint is developer time, not perceived/assumed lack of need for a debugger. See [image] GitHub - JuliaDebug/ASTInterpreter2.jl: Re-write of ASTInterpreter for julia... Re-write of ASTInterpreter for julia 0.6+. Contribute to JuliaDebug/ASTInterpreter2.jl development by creating an account on GitHub.

How do you use debuggers?

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mzaffalon August 30, 2017, 8:42am 57

To back up on @DNF reply, see also this comment.

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How do you use debuggers?

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