scalariform server to format scala faster
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A server for scalariform

Scalariform is a great tool for formatting scala code, but the JVM warmup makes it too slow for a CLI application.

By using a client/server architecture, we can fix it.


time java -jar ~/bin/scalariform.jar src/main/scala/Scalariver.scala
3.09s user 0.08s system 129% cpu 2.456 total

Scalariform CLI = 3.09 seconds

time ./scalariver src/main/scala/Scalariver.scala
0.07s user 0.03s system 84% cpu 0.153 total

Scalariver CLI = 0.07 seconds

Scalariver is 44 times faster than scalariform \o/ Bye bye, JVM warmup.

Command line client

Get the client, make it executable and run it on some scala file.

chmod +x scalariver
./scalariver src/main/scala/Scalariver.scala

By default, this scalariver script takes a file argument, sends an HTTP request to the server at, then writes the formatted code to the file.

The client script supports standard scalariform options.

For example, this line will use some formatting preferences, read from stdin and write to stdout even if the source cannot be parsed correctly:

echo src/main/scala/Scalariver.scala | ./scalariver +rewriteArrowSymbols --indentSpaces=4 --stdin --stdout -f

Using your private server

Everybody can use API freely. By default, the scalariver CLI client uses it.

But if you need to format offline, or if you feel uncomfortable about having your code sent to the Internet, then you should run your own scalariver instance.

java -jar scalariver-1.0.jar


You can now specify the new server url to the client:

./scalariver --url=http://localhost:8098 src/main/scala/Scalariver.scala

To make the url change permanent for the scalariver client, add this to your .bashrc/.zshrc:

export SCALARIVER_URL=http://localhost:8098

Listen to a custom port

java -jar scalariver-1.0.jar 12345 # listen to port 12345

Scalariver now listens to port 12345


To modify or contribute to scalariver, clone this repository and launch sbt. sbt run 12345 will start scalariver on port 12345.



Simplest integration:

au BufEnter *.scala setl formatprg=/path/to/scalariver\ --stdin\ --stdout\ -f

Exemple with custom server URL and formatting preferences:

au BufEnter *.scala setl formatprg=/path/to/scalariver\ --url=http://localhost\:8098\ --stdin\ --stdout\ -f\ +rewriteArrowSymbols\ +alignSingleLineCaseStatements\ +compactControlReadability\ +doubleIndentConstructorArguments\ +rewriteArrowSymbols


" Format the whole file by pressing <leader>f
" This sets a marker on y, goes to the top, formats to the bottom, and returns to the y marker
nmap <leader>f mygggqG'y

Sublime Text

Check the scalariver sublime text plugin created by dohzya

More wanted!

Do you use your favorite text editor? Wanna integrate scalariver? Cool.

You need to find a way to send the content of the current file to an external program, then replace the file content with that program output. Sounds easy, right? Please share your work!


Another way to run scalariform without the JVM warmup is to integrate it with SBT.

See these project skeletons for playframework 2.1.5 or playframework 2.2.1.

Web UI

The server also exposes its functionality through a web form:


The only entry point is a POST request on /.

curl -d source="class A ( n  :Int )"

It accepts the following optional parameters:

name description default
source scala source code to format ""
scalaVersion scala version of the source code 2.10
initialIndentLevel indent level to add to every line 0
forceOutput print the source unchanged if it cannot be parsed correctly false

And all scalariform formatting preference options.

More complex example:

curl \
  --data-urlencode source@src/main/scala/Scalariver.scala \
  -d scalaVersion=2.11 \
  -d rewriteArrowSymbols=true \
  -d indentSpaces=4


  • scalariform - best scala formatter in the wild
  • tiscaf - a minimalist and dependency-less HTTP server for scala


It would be nice to have scalariver integration for SBT and your favorite code editor.