See http://www.scalapeno.org.il/#!tzach-zohar/jwhyy: One of the most common criticisms of Scala, and indeed one of the most concerning ones - is its "Syntactic Diabetes": There's so much "Syntactic Sugar" - so many different ways to code the same thing - that developers might easily get lost. This makes many developers and organizations weary of adopting Scala as a primary language, fearing the training and maintenance costs this problem might entail. In this talk we'll explain the problem through some real-life examples from Kenshoo's 2- year experience with Scala, and move on to the solutions applied at Kenshoo and elsewhere to resolve this. Among these, we'll discuss style guides, automatic style checkers, Odersky's "Scala Levels", code review tips and more. If you're a developer thinking about trying Scala out, or a Scala enthusiast trying to convince your teammates or bosses to do so - this talk is for you.

1. “Insulin” for Scala’s
Syntactic Diabetes
Tzach Zohar // Kenshoo // Scalapeño 2016

2. OR:
How to adopt Scala and
survive
source

4. source

5. Who am I
NOT Chuck Norris!
Scala “Advanced Beginner” / “Competent”
System Architect @ Kenshoo

6. Who’s Kenshoo
10-year Tel-Aviv based startup
Industry Leader in Digital Marketing
Java + JavaScript shop
http://kenshoo.com/

7. Scala @ Kenshoo
5 services written in Scala
More to come...
Internal Scala course on the go

8. What’s so scary?

9. trait GeneralizedCategory {
type U <: Hom
type =>:[A >: U#L <: U#H, B >: U#L <: U#H] = U#C[A, B]
def id[A >: U#L <: U#H]: A =>: A
def compose[A >: U#L <: U#H, B >: U#L <: U#H, C >: U#L <: U#H](
f: B =>: C, g: A =>: B): A =>: C
def *[UY<:Hom](that : GeneralizedCategory {type U=UY}) =
Category.ProductCategory[U,UY](this,that)
}
source

10. source

11. source
def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That

12. Now for some sane examples
source

13. val tuples = List((1, 374), (3, 42), (5, 693))
val ids = tuples.map(_._1)
val ids = tuples.map(tuple => tuple._1)
val ids = tuples.map { tuple => tuple._1 }

14. val tuples = List((1, 374), (3, 42), (5, 693))
val ids = tuples.map(_._1)
val ids = tuples.map(tuple => tuple._1)
val ids = tuples.map { tuple => tuple._1 }
val ids = tuples.map(t => t match { case (id, value)=> id })
val ids = tuples.map(_ match { case (id, value) => id })
val ids = tuples.map({ case (id, value) => id })
val ids = tuples.map { case (id, value) => id }
val ids = tuples.map { case (id, _) => id }

15. case class Profile() { … }
case class ProfileId(id: Int)
def loadProfile(profileId: ProfileId): Profile = ???

16. case class Profile() { … }
case class ProfileId(id: Int)
def loadProfile(profileId: ProfileId): Profile = ???
loadProfile(ProfileId(3))
loadProfile(new ProfileId(3))
loadProfile(profileId = ProfileId(3))
loadProfile(profileId = new ProfileId(3))

17. case class Profile() { … }
case class ProfileId(id: Int)
implicit def toId(i :Int): ProfileId = ProfileId(i)
def loadProfile(profileId: ProfileId): Profile = ???
loadProfile(ProfileId(3))
loadProfile(new ProfileId(3))
loadProfile(profileId = ProfileId(3))
loadProfile(profileId = new ProfileId(3))
loadProfile(3)
loadProfile(profileId = 3)

18. def loadInt(): Int = { … }
def f(value: () => Int) = { … }
f(() => 2 + loadInt())

19. def loadInt(): Int = { … }
def f(value: () => Int) = { … }
f(() => 2 + loadInt())
def f(value: => Int) = { … }
f(2 + loadInt())

20. Too Much Sugar?
source

21. Issues so far
Too many ways to write the same thing
Tradeoff between short and readable
Advanced features getting in the way

22. Insulin to the rescue

23. 1. Style Guides
source

24. Style Guides
1. The basic: Official Scala-Lang Style Guide
2. The conservative: Databricks' Scala Style Guide
3. The exhaustive: Twitter's Effective Scala
4. Your own!

25. Style Guides
implicit def toId(i :Int): ProfileId = ProfileId(i)
loadProfile(ProfileId(3))
loadProfile(3)
“Do not use implicits to do automatic
conversions between similar datatypes”

26. Style Guides
“Avoid infix notation for methods
that aren't symbolic methods”
list map func
string contains "foo"
list.map(func)
string.contains("foo")
val x = y + 2

27. Style Guides
val ids = tuples.map(t => t match { case (id, value)=> id })
val ids = tuples.map(_ match { case (id, value) => id })
val ids = tuples.map { case (id, value) => id }
val ids = tuples.map { case (id, _) => id }
“Use pattern matching directly in function
definitions whenever applicable”

28. Style Guides
def f(value: => Int) = ???
f(2 + 3)
def f(value: () => Int) = ???
f(() => 2 + 3)
“Avoid using call by name.
Use () => T explicitly”

29. @throws[IOException]
def mightThrowException(): Int
def neverThrowsException(): Option[Int]
def neverThrowsException(): Try[Int]
def neverThrowsException(): Either[Int, String]
def neverThrowsException(): MyResult
Style Guides
“Scala provides an exception facility, but do not
use it for commonplace errors”

30. val ids = tuples.map(_._1)
val ids = tuples.map(tuple => tuple._1)
val ids = tuples.map { case (id, value) => id }
val ids = tuples.map { case (id, _) => id }
Style Guides
“Avoid using tuple field names
like _1, prefer pattern matching or
a dedicated case class”

31. 2. Code Reviews
source

32. Code Reviews
Refer author to Style Guides
Mix “Scala Levels” - juniors should review seniors’ code

33. Code Reviews

34. Code Reviews

35. Code Reviews
[Only] methods which act as
accessors [...] should be declared
without parentheses, except if they
have side effects

36. 3. Style Checkers
source

37. Style Checkers
Automate some of the (simpler) rules
1. Scalastyle (SBT/Gradle/Maven/Eclipse/IntelliJ)
2. Scalafmt (SBT/Vim/CLI/IntelliJ) [NEW]

38. ⌚ 18:45:25 ➜ sbt scalastyle
[info] Loading project definition from /.../project
[info] Set current project to myProject (in build file:/.../)
[warn] MyJob.scala:31:6: parameter.number.message
[error]MyService.scala:42:6: public.methods.have.type.message
[info] Processed 42 file(s)
[info] Found 1 errors
[info] Found 2 warnings
[info] Found 0 infos
[info] Finished in 39 ms
Style Checkers

39. 4. Scala Levels
source

40. Scala Levels
Application Programmer Library Designer
A1: Beginner L1: Junior
A2: Intermediate L2: Senior
A3: Expert L3: Expert
Defined by Martin Odersky in a 2011 post

41. Scala Levels
Application Includes
A1: Beginner Basic syntax; Simple Closures;
Collections; For-expressions; …
A2: Intermediate Pattern matching; Trait composition;
(Tail) Recursion; …
A3: Expert Folds; Streams + other lazy data
structures; Actors; …

42. Scala Levels
Library Includes
L1: Junior Type parameters; Traits; Lazy vals;
Currying; By-name parameters
L2: Senior Variance; Existential types; Cake Pattern;
Structural types; Extractors; …
L3: Expert Early initializers; Abstract types; Implicit
definitions; Higher-kinded types; …

43. source
def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That

44. source

45. Conclusions

46. 1. Intermediate Scala works
(might be better than Expert Java!)
2. Style and Feature-set can
be controlled
3. No Chuck-Norrisness Required
source

47. Thank You