I am having a very horrible time coding in scala using sbt.
I know compilation in scala is inherently slow as compared to java.
I have tried both eclipse and intellij, to do development in scala + sbt, and both the well knows IDE sucks at the job. Please guide me with the following horrors I am facing:
How to reduce the compilation time to milliseconds in scala(just like it was for java) even for big projects....in the IDEs(eclipse/intellij)....given that I am using sbt
How to ensure the builds in the IDEs work incrementally and on changed files only. I observe that full build happens in the IDE on every code change/save of the file.....again keep in mind that I am using sbt
Please suggest the same for the command line, after every code change, when I do sbt package, and it seems sbt recompiles the complete project rather than changed files.
In intellij, when I try to run a unit test cases, the whole sbt based project is compiled again
Also, if I import a project in intellij and use sbt command line at the same time, the intellij build and the command line build don't play well with each other and I start to observe full compilations in intellij and weired compilation errors
This is only a partial answer, because it depends a lot on what you're doing and what your code looks like - but I tend not to use an IDE for compilation/tests. Instead, I run this in sbt (sometimes with other commands, depending on what I'm doing)
> ~test-quick
which (quoting the docs):
The tests that failed in the previous run
The tests that were not run before
The tests that have one or more transitive dependencies, maybe in a different project, recompiled.
The tilde makes it run every time there has been a code change
For me anyway, it's very fast and importantly only runs what could have changed
Another thing which I have heard (but can't promise will speed things up) is to explicitly type as much as you can. The type inferrer is meant to be quite slow (which makes sense when you think about what it must have to do)
Edit as requested by Saby
Before I go through the points you've raised, I just want to point out that these aren't really horrors and eclipse/intellij don't actually suck at what they do. In fact, when you think about it, it's impressive they work at all.
Scala is a far more complicated language than java and that means the compiler has to do a lot more than java's. What I'm talking about here is features such as macros, implicits and type inference. Those features aren't free and compilation time and memory will take hits here. (basically because the compiler has to all sorts of crazy stuff for type inference; run through the code multiple times for macros; etc, etc, etc)
Obviously, like any other language, your compilation time is determined by a lot of things: what features you use, what patterns you use, what dependencies you have to name just a few.
Anyway, point by point:
I honestly don't know how to answer this one. I am currently working on a smallish java project (think a dozen dependencies, a few thousand lines of code, some spring but not much else going on) and I am certainly not getting millisecond compilation times in Intellij. If this really is causing problems, then my only suggestion is to use the command line.
I don't really know anything at all about eclipse, but if you are using Intellij 13 you can set the incremental compiler like this. The sbt plugin was changed quite a bit in Intellij 14 so I don't think this is an option anymore (ie it does whatever it does)
I think my answer above covers this. The point is you don't have to use sbt package, and I don't typically. Instead type sbt and when it loads type ~test-quick and only run sbt package when you need to
That's probably just how intellij works. Like 3, I don't think you can change this anymore
I don't know what these are, but you should probably Google the error and if you can't find anything create a new Stack Overflow question with some examples.
Other things to consider
Setup can be important. Most hardcore Scala developers I know code in sublime text or emacs using a plugin called ensime and sbt on the command line to test/compile it (along with a repl or two). Otherwise (at the time of writing this anyway), most other people (including me) use Intellij to write their code and then either use sbt on the command line or Intellij itself to test/compile. You need to play about and find what's best for you.
Another thing you want to think about is the version of sbt you're on. I don't have benchmarks for this, but I remember older versions being slower and it would be painful to change the way you work just because you're running an old version of something.
Also make sure you have the java 8 sdk installed - I know the girls and guys at Typesafe are spending more and more time optimising sbt for java 8.
Points 2 and 4 just work for me (and have for a long time), no special setup required.
Also, if I import a project in intellij and use sbt command line at the same time, the intellij build and the command line build don't play well with each other and I start to observe full compilations in intellij and weired compilation errors
This should be fixed in the new Scala plugin version.
Related
I've been searching for a long time now to find a decent IDE for Scala.
Eclipse is not satisfying at all, as auto completion doesn't work, somehow. Also, I can't modify the libraries at all in the build path e.g. set the docs/source.
IntelliJ seems better, however, there are some major bugs:
When the drop down menu appears that lists all the function, some of them are sometimes just not shown! I think it's because of scala-library / scala-compiler, it mixes them up or something...
The docs cannot be fetched, I get this message over and over again (here the functions are listed, strange enough...):
This is the library window:
The dependencies and the compiler are set right, I strongly suppose.
Does anyone know what the problem is? And how to fix it? Or is it a known bug?
Is there an IDE that can handle Scala?
Regards!
Typically, searching for names (values/classes/functions/etc.) for auto-complete can be quite slow compared to Java in IntelliJ simply because the automatically imported namespace can be quite large, and it also searches through all implicit conversions. However, I've never seen it refuse to show functions like your screenshot, what version of IntelliJ and Scala plugin are you using?
I've never gotten the pop-up docs to work via attaching JavaDocs (I haven't tried remote fetching), so I'd recommend just ctrl+click to go through to the source to read the documentation there. (However, the function/type definition does popup correctly when sources are attached). I'd suggest posting an issue at http://youtrack.jetbrains.com/issues/SCL if you have the opportunity.
To your final question, the answer is unfortunately no. The tooling for Scala is nowhere near that of Java, but both Scala IDE for Eclipse and IntelliJ are making great progress in changing that, and both are strong in some areas while weak in others. In the end, you'll get limited support either way, so choose whichever fits you best.
I have found the solution to the problem:
The bug was caused by Java Decompiler Plugin. It tried to decompile the binaries of Scala's class-files, which obviously failed. This led to that error message and further led to the Scala plugin not working as it should, thus not displaying some of the functions.
This took me a long time to figure out, I installed 2 other versions of IntelliJ (which apparently imported the JD plugin), NetBeans and downloaded several builds of the Scala Plugin, only to discover this cause. Deactivating Java Decompiler solved it.
Regards.
I use eclipse as my scala IDE. But It seems not so good. I can build my project using maven successfully. But eclipse always warn me there's compilation error. Any has experience of scala eclipse plugin ? Thanks BTW I use scala IDE for 2.8.1
There is a new Eclipse plug-in which is in the final stages of release, currently in beta 4 which offers numerous improvements including stability. It runs with Scala 2.9.
You can download and try it for yourself. More information and download available here:
http://www.scala-ide.org/
Also, be sure to read on improving Eclipse performance, I find a few of these tweaks makes a big difference. Here are some answers on Stackoverflow regarding that:
How can you speed up Eclipse?
What are the best JVM settings for Eclipse?
I've been using all three major IDEs over the last few days for Scala.
Eclipse is pretty good and perfectly useable although you will encounter a few bugs - silly things like you can't load compiler plugins if you have a space in your plugin folder pathname. It also behaved pretty badly a few times and wouldn't run anything until I restarted Eclipse, but this might be partly because I'm new to it and maybe have been doing something wrong. One thing that is good about Eclipse is that the build time is a lot quicker than for the other two - I think this is because it does and "incremental build". Or maybe it's just more optimized, but it's noticeable.
I would recommend trying the latest version of IntelliJ (10.5). It seems to be the best at the moment with the fewest rough edges, and the only one to have Scaladoc support integrated. I haven't used it much but first impressions are good.
The NetBeans plugin seems to be getting left behind a bit (there's only one guy working on it), which is a shame because it has IMO easily the best code editor for Java, with excellent predictive capabilities which you don't get for Scala at the moment. I'll continue to use it for Java, but the Scala plugin development is a bit sparse. (Although it might be because I'm using a beta version, because that's all that's available right now for Scala 2.9.)
I'm coming from a PHP/Python/Javascript background, and recently became very interested in Scala - specifically Akka coming from the web standpoint.
I'm having an extremely hard time though with general workflow, issues compared to interpreted languages such as the ones I described.
In general I tend to code, test results, code and repeat. This comes to a standstill when even changing a single line in a 20 line class takes up to 30secs to compile and run. Is this really normal? Do I need to just build, build, build then go back 30 minutes or an hour later and compile/test?
(I'm using IDEA with SBT) Do I need to specifically learn how to use Maven other than linking to the repos?
Thoughts? Advice?
I think you're on the right track with Idea and SBT. Have you tried
~compile
That will detect changes to your source automatically. For web applications, you can do a
jetty-run
followed by
~prepare-webapp
To continuously compile and redeploy your app to jetty. Makes Scala dev feel a lot like Python web development.
Usually I've found SBT to be very fast when compiling, especially the size file you're talking about. By the time I save my change and go to my SBT prompt, it's done.
Another handy SBT aspect is the REPL which will load your project and its dependencies:
console
You can reload any compiled changes with
:replay
in the scala REPL.
EDIT:
Guess I should mention that you can play around with a simple class with a main method. If you create a file called src/main/scala/Foo.scala that looks like this:
object Foo {
def main(args: Array[String]) {
println("Hello World")
}
}
And a file project/build/Build.scala like this:
import sbt._
class Build(info: ProjectInfo) extends DefaultProject(info) {
override def mainClass = Some("Foo")
}
Then at the sbt prompt, you can do
~run
To continuously compile and run the Foo.main method. You may need to do a 'reload' in sbt first. It seemed to take 2-3 seconds from saving change to seeing output. Then you just edit away, save and see changes. It's a pretty good workflow.
Also, don't forget the REPL - definitely a critical tool for learning Scala. You can learn a ton just playing with it interactively.
IDE Assistance:
With static typing language I find myself doing less of that workflow than I do with dynamic typing, but that was only possible because of excellent IDE assistance (the typing information allows it to detect errors early, and give accurate suggestions while you are editing), so it does save some time in that code-test loop you described.
However Scala IDE support in IDEA isn't yet at the level of Java for example,
both in catching errors while editing (IMHO) and speed of compilation.
REPL/Script support:
Do not forget that you can still use the Scala REPL, the workflow is pretty much like what you would be used to in Python for example.
IDEA + Scala speed :
You can refer to this question for more discussion on IDEA+Scala speed.
I use JRebel plugin with maven. I turn off the NetBeans compile on save feature,(don't know if intellij has similar) and run scala:cc - continuous compilation goal from console. It waits for any changes in source code, so after you make some, the file gets compiled, copied to /target directory and then hotswapped into running virtual machine. The procedure takes units of seconds depending on the size of the file.(I assume you do web development since you mentioned PHP and JavaScript) There is fsc server running in the background, that is also one of the reasons, why the compiling is speeded up.There are some minor disadvantages, you can't change the superclass, which means you can't go from AbstractFunction1 to AbstractFunction2 (which represent anonymous functions) - changing (x) => x to (x,y) => x + y means that you need to restart the server.
Useful links:
scala:cc
jrebel
One of the advantages to statically typed languages is that the type system can catch several types of mistakes/bugs. So, in theory, you shouldn't need to go through the rigmarole quite so often.
Of course there are many changes, especially in the UI, that only eyeballs on screen can check. All I can suggest there is good modularization to keep the compile/build time down. And unit tests. I don't know about the community that you're coming from, but in java/scala, unit tests are highly, highly recommended. You find out if the code worked right much faster that way.
The answer boils down to this: try and avoid having to build and restart to check your work as much as possible.
My Python-like workflow--which leaves me with very little time waiting--usually goes as follows:
Turn what I'm trying to do into a library (stick it in a .jar and add it to the classpath).
Work on the new code in an editor, but paste it into the REPL instead of compiling separately. Once it's working well, add a unit test.
Place the new code into the library. Repeat.
I can do this on a netbook and not wait longer than ~3 seconds for any one step.
What Tools do you people use to work with Scala? For my learning phase, I used the Scala REPL and hacked some code with TextMate and compiled it with the scalac CLI. But as the projects grow in size, much more sophisticated tools are required.
I am aware of the Scala plugins for Elipse, IntelliJ and Netbeans and I tried them all. The best one is IMHO IntelliJ, but still far away from being perfect.
The major issue I have is the lack of auto completion. As a not-so-advanced Scala coder, I still dont know the whole standard API and have to switch between the Scaladoc and IDE regularly. This feels like "killing productivity". But they all fail to auto-complete method arguments. (I heard that method arguments are not included in compiled scala code, but what about attaching source to do auto completion?)
Another very annoying issue is the build process. I am using Maven to build my Scala projects and manage their dependencies. But nevertheless, I have to do a full rebuild to test my changes. Maybe I am spoiled by Eclipses incremental rebuild available in the Java world, but it feels like a big issue to me.
I like Scala very much and I feel way more productive while coding, but the lack of sophisticed tools let me feel less productive. And both seem to cancel out themselves.
So, whats my question? I doubt every single Scala programmer uses good ol' vim or emacs along with scalac to do their work. So what tools do you use? What workflows have you developed to bring speed into developing with the Scala language?
Edit
Clarification what I ment with auto-completion of method arguments.
val myList = "foo" :: "all your base" :: Nil
myList.partition(_.length > 3)
For the code above, IntelliJ fail to provide me with the information that partition requires that I have to pass a () => Boolean function. In fact, IntelliJ does not check for this contraint. I can pass a String and IntelliJ will not indicate my error until I do a compile.
scalac
Get familiar with command line options to Scalac.
-deprecation
-Xprint:all: watch your code progress through compiler phases, very useful to see what implicits are applied.
-help / -X' /-Y` list all options.
The latest nightly builds of scalac include a bash completion file that makes these easier to use.
IntelliJ IDEA
Method completion with Javadoc (CTRL-Space, CTRL-Q/Apple-J) Screenshot
Parameter Info for the example in the question (CTRL-P) Screenshot
Method Argument Completion (CTRL-SHIFT-Space). Screenshot
You need to have the source or javadocs linked into the dependencies in IntelliJ to see the Javadoc.
It doesn't currently highlight type errors on the fly, as there are still too many false-positives in complex code. This is coming, though.
Simple Build Tool
SBT keeps the compiler resident, and analyzes dependencies between classes to allow incremental recompilation. It can also monitor for changes to source files and automatically trigger recompilation and/or test execution.
Continous Compilation: >~compile
Continuous Compilation + Test: ~test-quick
I have SBT and IntelliJ project configured in http://github.com/scalaz/scalaz, you could use this as a reference.
I've been using Scala daily for the last six months. I'm still using vim (and ctags to find stuff), and Maven for builds. I've gotten some good mileage out of JRebel when working on Lift web apps -- it will reload changes on the fly without server restarts.
I spent some time looking into IDEs, but it got depressing really fast. I really missed a lot of Eclipse features at first, but after a period of adjustment I don't think I'm significantly less productive now.
I've heard some rumblings that NetBeans is the current champ for Scala IDEs, but I haven't tried it first hand.
One simple way is to use fsc, an offline compiler. It maintains caches of information, and the standard compiler will talk to fsc (running as a daemon) and use its cached information during compilation, thus speeding up your compilation cycle.
Here's my answer on a similar thread. After giving about an hour to Ensime. I just can't help but get the word out. I must say it's very, very well written for an Emacs package.
I am afraid you have to wait for Scala to become rock-solid.
I had exactly the same issue with Java ten years ago. It was even worse.
I also tried them all. For Scala 2.7.7 IntelliJ is the winner, but for Scala 2.8.0-SNAPSHOT Eclipse is not that bad.
Wait half of a year after 2.8.0 is released and check again. It should become bearable.
With Scala 2.8, please see this for getting better performance out of Maven.
You should also give Netbeans 6.8 a try with the nightly Scala build. I am very satisfied programming Scala with this IDE. For building, I sometimes also use Ant. The best thing about NB Scala plugin is that it is fast and code-completion works flawlessly.
For the example you gave: NB gives me this error
code-completion:
The Eclipse Scala IDE is quite mature now (as of 3.0).
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I've seen questions about IDE's here -- Which is the best IDE for Scala development? and What is the current state of tooling for Scala?, but I've had mixed experiences with IDEs. Right now, I'm using the Eclipse IDE with the automatic workspace refresh option, and KDE 4's Kate as my text editor. Here are some of the problems I'd like to solve:
use my own editor IDEs are really geared at everyone using their components. I like Kate better, but the refresh system is very annoying (it doesn't use inotify, rather, maybe a 10s polling interval). The reason I don't use the built-in text editor is because broken auto-complete functionalities cause the IDE to hang for maybe 10s.
rebuild only modified files The Eclipse build system is broken. It doesn't know when to rebuild classes. I find myself almost half of the time going to project->clean. Worse, it seems even after it has finished building my project, a few minutes later it will pop up with some bizarre error (edit - these errors appear to be things that were previously solved with a project > clean, but then come back up...). Finally, setting "Preferences / Continue launch if project contains errors" to "prompt" seems to have no effect for Scala projects (i.e. it always launches even if there are errors).
build customization I can use the "nightly" release, but I'll want to modify and use my own Scala builds, not the compiler that's built into the IDE's plugin. It would also be nice to pass [e.g.] -Xprint:jvm to the compiler (to print out lowered code).
fast compiling Though Eclipse doesn't always build right, it does seem snappy -- even more so than fsc.
I looked at Ant and Maven, though haven't employed either yet (I'll also need to spend time solving #3 and #4). I wanted to see if anyone has other suggestions before I spend time getting a suboptimal build system working. Thanks in advance!
UPDATE - I'm now using Maven, passing a project as a compiler plugin to it. It seems fast enough; I'm not sure what kind of jar caching Maven does. A current repository for Scala 2.8.0 is available [link]. The archetypes are very cool, and cross-platform support seems very good. However, about compile issues, I'm not sure if fsc is actually fixed, or my project is stable enough (e.g. class names aren't changing) -- running it manually doesn't bother me as much. If you'd like to see an example, feel free to browse the pom.xml files I'm using [github].
UPDATE 2 - from benchmarks I've seen, Daniel Spiewak is right that buildr's faster than Maven (and, if one is doing incremental changes, Maven's 10 second latency gets annoying), so if one can craft a compatible build file, then it's probably worth it...
Points 2 and 4 are extremely difficult to manage with the current scalac. The problem is that Scala's compiler is a little dumb about building files. Basically, it will build whatever you feed it, regardless of whether or not that file really needs to be built. Scala 2.8.0 will have some tremendous improvements in this respect, but until then... Eclipse SDT actually has some very elaborate (and very hackish) code for doing change detection and dependency tracking. On the whole, it does a decent job, but as you have seen, there are wrinkles. Eclipse SDT 2.8.0 will rely on the aforementioned improvements to scalac itself.
So, building only modified files is pretty much out of the question. Aside from SDT, the only tool I know of which even tries this is SBT (Simple Build Tool). It uses a compiler plugin to track files as they are compiled and query the dependency graph computed by the compiler itself. In practice, this yields about a 50% improvement over the recompile-the-world approach. Once again, this is a hack to get around deficiencies in pre-2.8.0 scalac.
The good news is that reasonably fast compilation is still achievable even without worrying about change detection. FSC uses the same technology (ooh, that sounded so "Charlie Eppes") that Eclipse SDT uses to implement fast incremental compilation. In short, it's pretty snappy.
Personally, I use Apache Buildr. Its configuration is significantly cleaner than either Maven's or SBT's and its startup time is orders of magnitude less (when running under MRI). It integrates with FSC and attempts to do some basic change detection on its own (fairly primitive). It also has auto-magical support for the major Scala test frameworks (ScalaTest, ScalaCheck and Specs) as well as support for joint compilation with Java sources and IDE meta generation for IntelliJ and Eclipse. Oh, and it supports all of Maven's features (dependency resolution, etc) and then some. I'm even working on an extension which would allow interactive shell support integrated with JavaRebel and supporting several shell providers (Scala, JIRB, Clojure REPL, etc). It's not ready for the SVN yet, but I'll commit once it's ready (possibly in time for 1.3.5).
As you can see, I'm very firmly of the opinion that Buildr is the best Scala build tool out there. Its documentation is a little spotty where Scala is concerned, but that's because everything is so straightforward that it's hard to document without feeling verbose. You can always check out one of my GitHub repositories for examples. Good luck!
Have you looked at Intellij IDEA and its Scala integration ? Intellij has a loyal (fanatical?) following amongst Java developers, so you may find this is appropriate for your needs.
Am also quite frustrated with the scala plugin on Eclipse and I can add a few more problems to the list:
auto-complete only works some of the time
the debugger doesn't work properly (especially when trying to debug scala xml)
the debugger forgets breakpoints
'go to definition' doesn't work more often than not.
I'm glad to hear that Buildr sounds like a better alternative (on the build front anyhow), I'll give that a try - thanks!
If you use Emacs, I think Ensime is a pretty good IDE. I think at the time writing, Ensime is the only IDE that will give you fast and accurate autocompletion on both Scala and Java objects, including implicit conversions.
There's code browsing support using Speedbar, code templates using the excellent Yasnippet, and code completion menu using Autocomplete. These are all very modern, actively maintained Emacs packages. There's also out of the box incremental building support for Maven and SBT.
There's a lot more in there such as interactive debugging, refactoring, and the Scala interpreter in an inferior process. All the things you want in a modern IDE for Scala is already there in Ensime. Highly recommended for Emacsens.
For the reasons of completeness, I have to say that there is also Pants -- the build tool that in use in Twitter (one of the early scala adopters)
The main difference it that it is intended not only for scala (and written in python, by the way) and is modeled after google build system.
It's not so bloated as sbt, so for the freshmans it's much simplier, but I've never heard about Pants usage outside of twitter and foursquare.
If you scared of SBT, maybe another no-so-popular build tool, ABT, could be an alternative for you?
I went down the same road, and here is where I am at:
- After some initial investigation, I dropped Kate. I love to use it for most things, but when it came to things like defining tab completions, I found it sorely lacking. I would recommend that you look into gedit instead, which is much more robust for Scala development
- With gedit as my editor, I use SBT and have found it to be a great build tool. I can put it into a 'test' mode where when any code changes it recompiles the relevant files and runs my test suite. This has been an extremely effective way to work.
I have not taken a look at Buildr yet. I would like to say that I will, but honestly with SBT at my disposal I don't really have a compelling need to look at another build tool.
If you want to use Eclipse, but build the project using sbt, and still be able to debug, take a look at this post here:
zikaprog.wordpress.com/2010/04/19/scala-eclipse-sbt-and-debugging/
It also can be applied to builders other than sbt.
The latest version of the Maven Scala plugin supports Zinc/Nailgun for faster start times and faster incremental builds. See Zinc and Incremental Compilation.