All I learned while working on a Scala OSS project for over six years #ScalaMatsuri

* http://2018.scalamatsuri.org/index_en.html
* https://www.youtube.com/watch?v=y7BxvT-Jm6w

In 2011, I started a Scala open source project named ScalikeJDBC. Thanks to many contributors, I am still working on the project after six years. In the meantime, the Scala community has been growing sharply, and the trends have been continuously changing. Despite the fact that the number of developers who work on OSS projects has increased, there are not many developers who have been working on a Scala project for several years. In this talk, I will share my experiences and pieces of knowledge through maintaining the OSS project for more than six years.

Transcript

1. All I learned
   while working on a Scala
   OSS project
   for over six years
   Kazuhiro Sera
   @seratch
   1
   4DBMB044QSPKFDUΛ೥Ҏ্ଓ͚ΔͨΊʹඞཁͳ͜ͱ
   ͱ͍͏ςʔϚͰɺ੉ྑ࿨߂!TFSBUDI@KB͕͓࿩͠͠·͢ɻ
   

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2. In 2011, I started a Scala open source project named ScalikeJDBC.
   Thanks to many contributors, I am still working on the project after six
   years.
   In the meantime, the Scala community has been growing sharply, and
   the trends have been continuously changing.
   Despite the fact that the number of developers who work on OSS
   projects has increased, there are not many developers
   who have been working on a single Scala
   project for several years.
   In this talk, I will share my experiences and pieces of knowledge
   through maintaining a single OSS project for more than six years.
   ೥͔ΒऔΓ૊ΜͰ͖ͨ4DBMJLF+%#$Λ͸͡Ίͱ͢Δ
   4DBMB044։ൃ͔Βಘͨ஌ݟͳͲΛ͓࿩͠͠·͢ɻ 2
   

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3. Agenda
   Who Am I?
   My “Hello World” in Scala (2009)
   ScalikeJDBC, My Long-lived Scala Project
   Tips for Continuation
   Avoiding Depending on Scala Libraries
   Cross-building Tips
   Ensuring binary-compatibility (MiMa)
   Building a Community of Friends
   ͜ͷΑ͏ͳ಺༰ʹ͍͓ͭͯ࿩͠͠·͢ɻ্ڃऀͷํʹ͸ͪΐͬ
   ͱ෺଍Γͳ͍಺༰͔΋͠Ε·ͤΜ͕ɺ͝༰ࣻΛɻ 3
   

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4. Who Am I?
   ·ͣ͸ࣗݾ঺հ͔Βɻ
   4
   

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5. Kazuhiro Sera @seratch
   Software Engineer, VPoE at SmartNews, Inc.
   We’re a samurai sponsor
   Server-side software engineer (Scala, Java, Ruby)
   Love coding, open-source community
   A Scala enthusiast for 7+ years
   Creator of ScalikeJDBC, Skinny Framework
   One of the maintainers of Scalate, json4s, Scalatra
   4NBSU/FXTͰಇ͍͍ͯ·͢ɻαʔόαΠυΤϯδχΞɺ
   4DBMJLF+%#$ɺ4LJOOZͳͲͷ4DBMB044Λ΍͍ͬͯ·͢ɻ5
   

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6. Star as an endorsement
   Increment the number of stargazers
   ޷͖ͳϥΠϒϥϦͷελʔ਺ΛJODSFNFOU͠·͠ΐ͏ɻ
   ελʔ͕૿͑Δͷɺ͔ͳΓྭΈʹͳΔͷͰ͢ɹ 6
   

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7. My “Hello World” in Scala
   (2009)
   ࢲͷ044ʹ͍ͭͯ࿩͢લʹɺࢲͷ4DBMBͱͷग़ձ͍͔Β
   4DBMBͷ͜Ε·Ͱͷมભʹ͍͓ͭͯ࿩͍ͨ͠͠ͱࢥ͍·͢ɻ 7
   

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8. Scala 2.7.3 (9 yrs ago)
   4DBMB͸೥಄ʹϦϦʔε͞Ε͍ͯ·͢ɻ
   Կͱ΋͏೥΋લͰ͢Ͷʂ
   2009-01-14
   8
   

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9. My “Hello World” in Scala
   In 2009, I was a Java developer at the time
   Looking for a new one / unsatisfied with Groovy
   At the beginning, I tried with Scala 2.7.3
   My first impression of Scala
   “IDE integration was still very poor. It’s a bit early to
   seriously use it at work.”
   Excited with hybrid paradigms, actors, concise syntax
   I started learning it seriously in the following year
   ॳΊͯ࢖ͬͨͷ͸Ͱ౰࣌͸+BWBΤϯδχΞͰͨ͠ɻ
   ࢓ࣄʹ͸·ͩ࢖͑ͳ͍͚Ͳ໘ന͍ݴޠͩͳͱࢥ͍·ͨ͠ɻ 9
   

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10. Let’s try Scala 2.7.3
    4DBMBΛࢼͯ͠Έ·͠ΐ͏ɻͱɺ+BWBͰಈ͖·ͤ
    ΜͶɻTCU͔Β3&1-ͷىಈ͕Ͱ͖·ͤΜɻ
    $ java -version
    java version "1.8.0_151"
    Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
    Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)
    $ sbt ++2.7.3 console
    [info] 'compiler-interface' not yet compiled for Scala 2.7.3.final. Compiling...
    error: error while loading Consumer, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/util/function/Consumer.class)'
    is broken
    (bad constant pool tag 18 at byte 15)
    one error found
    

    On JDK 8+,
    it fails to run the REPL…
    10
    

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11. Let’s try 2.8.0..
    4DBMBͳΒͲ͏͔Τϥʔ಺༰ҧ͍·͕͢
    ͪ͜Β΋࢒೦͔Βಈ࡞͠ͳ͍Α͏Ͱ͢ɻ
    $ sbt ++2.8.0 console
    [info] 'compiler-interface' not yet compiled for Scala 2.8.0.final. Compiling...
    error: error while loading CharSequence, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/lang/CharSequence.class)' is broken
    (bad constant pool tag 18 at byte 10)
    error: error while loading AnnotatedElement, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/lang/reflect/AnnotatedElement.class)' is
    broken
    (bad constant pool tag 18 at byte 76)
    error: error while loading Arrays, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/util/Arrays.class)' is broken
    (bad constant pool tag 18 at byte 765)
    error: error while loading Comparator, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/util/Comparator.class)' is broken
    (bad constant pool tag 18 at byte 20)
    /var/folders/vl/bxx80tvs2gd8tzrtyd_b0p9r0000gp/T/sbt_6e129fa2/xsbt/ExtractAPI.scala:549:
    error: java.util.Comparator does not take type parameters
    private[this] val sortClasses = new Comparator[Symbol] {
    ^
    5 errors found
    11
    On JDK 8+,
    it fails to run the REPL…
    

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12. Let’s try 2.9.0..
    ΋ಈ͔ͳ͍ͩͱ
    $ sbt ++2.9.0 console
    [info] 'compiler-interface' not yet compiled for Scala 2.9.0.final. Compiling...
    error: error while loading CharSequence, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/lang/CharSequence.class)' is broken
    (bad constant pool tag 18 at byte 10)
    error: error while loading AnnotatedElement, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/lang/reflect/AnnotatedElement.class)' is
    broken
    (bad constant pool tag 18 at byte 76)
    error: error while loading Arrays, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/util/Arrays.class)' is broken
    (bad constant pool tag 18 at byte 765)
    error: error while loading Comparator, class file '/Library/Java/JavaVirtualMachines/
    jdk1.8.0_151.jdk/Contents/Home/jre/lib/rt.jar(java/util/Comparator.class)' is broken
    (bad constant pool tag 18 at byte 20)
    /var/folders/vl/bxx80tvs2gd8tzrtyd_b0p9r0000gp/T/sbt_a0025195/xsbt/ExtractAPI.scala:549:
    error: java.util.Comparator does not take type parameters
    private[this] val sortClasses = new Comparator[Symbol] {
    ^
    5 errors found
    12
    On JDK 8+,
    it fails to run the REPL…
    

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13. 2.10.2+ runs on JDK 8 ☺
    ͔Β+BWBͰಈ͘Α͏ʹͳΓɺͦΕ·Ͱͷόʔδϣ
    ϯ͸ಈ͖·ͤΜͰͨ͠ɻࠓޙ΋ࣅͨΑ͏ͳ͜ͱ͸ى͖Δ͔΋ɻ
    $ sbt ++2.10.2 console
    [info] 'compiler-interface' not yet compiled for Scala 2.10.2. Compiling...
    [info] Compilation completed in 7.522 s
    [info] Starting scala interpreter...
    [info]
    Welcome to Scala version 2.10.2 (Java HotSpot(TM) 64-Bit Server VM, Java
    1.8.0_151).
    Type in expressions to have them evaluated.
    Type :help for more information.
    scala>
    13
    Scala 2.10.2+ works on Java 8 ☺
    

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14. 2.7.3 on JDK7..
    ͱ͍͏͜ͱͰΛࢼ͚ͨ͠Ε͹+BWBΛ࢖Θͳ͍ͱ
    ͓΍ɺ͜Ε΋ಈ͔ͳ͍ͷͰ͠ΐ͏͔ʁʁ
    $ export JAVA_HOME=`/usr/libexec/java_home -v 1.7`
    $ java -version
    java version "1.7.0_80"
    Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
    Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)
    $ sbt ++2.7.3 console
    [info] 'compiler-interface' not yet compiled for Scala 2.7.3.final. Compiling...
    /var/folders/vl/bxx80tvs2gd8tzrtyd_b0p9r0000gp/T/sbt_7f1250db/
    CompilerInterface.scala:9: error: value interactive is not a member of package
    scala.tools.nsc
    import scala.tools.nsc.interactive.RangePositions
    ^
    (omitted)
    42 errors found
    [error] (run-main) Error compiling sbt component 'compiler-interface'
    

    14
    Somehow, it fails to boot on
    Java7 ..
    

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15. 2.7.3 without sbt ☺
    ࣮͸ݱߦTCUͰ౰࣌ͷ4DBMBΛಈ͔͢͜ͱ͕Ͱ͖·ͤΜɻ
    TCUΛ࢖Θͣʹىಈ͢Ε͹+BWBͰ౰વಈ࡞͠·͢ɻ
    $ export JAVA_HOME=`/usr/libexec/java_home -v 1.7`
    $ java -version
    java version "1.7.0_80"
    Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
    Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)
    $ bin/scala
    Welcome to Scala version 2.7.3.final (Java HotSpot(TM) 64-Bit Server VM, Java
    1.7.0_80).
    Type in expressions to have them evaluated.
    Type :help for more information.
    15
    “sbt console” supports only Scala 2.9.0+.
    You have to use the scala script instead.
    

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16. Scala 2.7 and beyond
    ೥ܦͬͯ4DBMB͸ͲΕ͘Β͍มΘͬͨͷͰ͠ΐ͏͔
    ͜Ε͸Ҏ߱ͷϝδϟʔόʔδϣϯϦϦʔεͷ೥දͰ͢ɻ
    Scala 2.8 2010-07-15
    Scala 2.9 2011-05-12
    Scala 2.10 2012-12-20
    Scala 2.11 2014-05-20
    Scala 2.12 2016-10-29
    Scala 2.13.0-M3 2018-01-31
    Scala 3.0 (with Dotty) ???
    16
    

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17. Missing parts (2.8, 2.9)
    Named and default arguments (2.8+)
    Package objects (2.8+)
    The App trait (2.9+)
    JavaConverters/JavaConversions (2.9+)
    ͱͰ͸͜ΕΒͷػೳ͕௥Ճ͞Ε·ͨ͠ɻ
    ౰࣌͸YͱYʹޓ׵ੑ͕͋Γ·ͤΜͰͨ͠ɻ 17
    

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18. Missing parts (2.10)
    2.x binary compatibility (2.10+)
    Value classes (2.10+)
    Implicit classes (2.10+)
    String Interpolation (2.10+)
    Futures and Promises (2.10+)
    Dynamic (2.10+)
    Macros (2.10+)
    ͸λʔχϯάϙΠϯτͱͳΔϦϦʔεͰͨ͠ɻ
    όΠφϦޓ׵ੑͷվળଟ͘ͷػೳ͕௥Ճ͞Ε·ͨ͠ɻ 18
    

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19. Missing parts (2.11, 2.12)
    Blackbox/whitebox macros (2.11+)
    Quasiquotes (2.11+)
    Java 8 SAM types compatibility (2.12.+)
    Using invokeDynamic for lambda (2.12+)
    ͸ϚΫϩͷվળͱ಺෦తͳ࠷దԽ͕ओͰͨ͠ɻ
    ݴޠͷར༻ऀͱͯ͠͸৽͍͠ػೳ͸͋·Γ͋Γ·ͤΜɻ 19
    

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20. Moderate changes recently
    ͜ͷΑ͏ʹҎ߱ͷݴޠͷมߋ͸͋·Γଟ͋͘Γ·ͤΜɻ
    044Λ࢝ΊΔλΠϛϯάͱͯ͠͸Α͍͔΋͠Ε·ͤΜͶɻ
    Scala 2.8 2010-07-15
    Scala 2.9 2011-05-12
    Scala 2.10 2012-12-20
    Scala 2.11 2014-05-20
    Scala 2.12 2016-10-29
    Scala 2.13.0-M3 2018-01-31
    Scala 3.0 (with Dotty) ???
    20
    

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21. ScalikeJDBC,
    My Long-lived Scala Project
    Ͱ͸ɺͦΖͦΖຊ୊ɺ·ͣࢲͷ4DBMB044ʹ͍ͭͯ։ൃʹ
    ࢸͬͨഎܠ΍େࣄʹ͍ͯ͠Δࢥ૝ͳͲɺ؆୯ʹઆ໌͠·͢ɻ21
    

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22. Why I Started My Project
    I needed a practical DB library in 2011
    I was going to start using Scala for real projects
    Twitter’s querulous looked reasonable, but it
    supported MySQL only
    ScalaQuery looked hard to master for me
    For Fun / To learn new things
    At the time, I was new to both Scala and OSS
    I wanted to try something exciting by myself
    ೥౰࣌ɺ࣮༻తͳ%#MJCSBSZΛඞཁͱ͍ͯͨ͠ͷͱɺ
    ৽͍͜͠ͱΛ΍ͬͯΈ͍ͨͱ͍͏ؾ͔࣋ͪΒ࢝Ί·ͨ͠ɻ 22
    

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23. History of DB Libraries
    4DBMBͷ3%#BDDFTTMJCSBSZͷมભͰ͢ɻ
    ࠓ͸ϝϯς͞Ε͍ͯͳ͍΋ͷ΋͍͔ͭ͋͘Γ·͢ɻ 23
    

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24. Non-practical Libraries
    In return for fancy APIs
    Not designed to solve real-world business problems
    New team members need long time to catch up
    Troubleshooting can be bothersome
    Insufficient information for debugging
    Frequently breaking API compatibilities
    Author suddenly stopped maintaining the library..
    Χοί͍͍"1*͕ͩݱ࣮ͷ໰୊ʹରԠͰ͖ͳ͍ɾֶशίετ
    ߴ͍ɻσόοά͠ʹ͍͘ɻޓ׵ੑΛΑ่͘͢ɻϝϯς͕ಥવࢭ
    ·Δɻ͜ΕΒʹ֘౰͠ͳ͍͜ͱ͕ࢲͷʮ࣮༻తʯͷج४Ͱ͢ɻ
    24
    

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25. Philosophy of ScalikeJDBC
    “Just write SQL and get things done!”
    Easy-to-understand
    Requires only Scala basics + JDBC basics
    No steep learning curve! (except for Scala )
    Well-considered flexibility to deal with edge cases
    No breaking API changes as much as possible
    4DBMJLF+%#$͕େࣄʹ͍ͯ͠Δ͜ͱɿ͙͢ʹཧղ͠࢖͑Δɺ
    ಛघέʔεʹରԠͰ͖Δɺޓ׵ੑΛۃྗ่͞ͳ͍ 25
    

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26. Tips for Continuation
    ࣍ʹ௕͘ଓ͚ΔͨΊʹඞཁͩͬͨߟ͑ํ΍޻෉
    ʹ͍͓ͭͯ࿩͍ͨ͠͠ͱࢥ͍·͢ɻ 26
    

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27. More than 6 Years
    ೥Ҏ্ಛఆͷMJCSBSZͷ։ൃΛܧଓ͖ͯ͠·ͨ͠ɻ
    ͜Ε͸4DBMBDPNNVOJUZͷதͰ΋௕͍ํͰ͠ΐ͏ɻ
    I’ve been working on it for more than 6 years
    Scala 2.9 ~ 2.10 ~ 2.11 ~ 2.12 ~ 2.13
    27
    

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28. Tips for Continuation
    KISS (Keep It Simple, Stupid) Principle
    Keep it Contributors Friendly
    Avoiding Depending on Scala Libraries
    Knowledge on Important Factors
    Cross-building
    Binary-compatibilities
    Building a Community of Friends
    You’re not alone!
    ܧଓͰେࣄͳ͜ͱɿγϯϓϧʹอͭ͜ͱɺॏཁͳཁૉʢΫϩε
    ϏϧυόΠφϦޓ׵ʣͷཧղɺίϛϡχςΟͷܗ੒ 28
    

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29. Avoiding Depending on
    Scala Libraries
    4DBMBMJCSBSZ΁ͷґଘΛආ͚Δ΂͖ɿ࢒೦ͳ͜ͱͰ͕͢
    MJCSBSZΛ௕͘ϝϯς͢Δʹ͸େࣄͳ͜ͱͰ͢ɻ 29
    

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30. Common reasons to do that
    Await their releases every Scala major upgrade
    If you depend on short-lived libraries..
    When becoming unmaintained, you’ll have to fork
    and maintain them by yourself
    May bring binary compatibility issues
    4DBMBNBKPSVQHSBEFͷ౓ʹSFMFBTF଴ͪɺ୹໋MJCSBSZΛ
    ࠷ѱGPSL͢ΔӋ໨ɺόΠφϦޓ׵ੑͷ໰୊ͳͲ͋Γ͑·͢ɻ
    30
    

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31. Fetters for Cross-building
    So difficult to do cross-building while depending on
    other Scala libraries
    All depending Scala libraries must do the exactly
    same cross-building (unrealistic..)
    If you give cross-building high priority, you should
    consider to depend on not Scala libraries but Java
    libraries (or no dependencies..)
    ΫϩεϏϧυͰଞͷ4DBMBMJCSBSZ΁ͷґଘ͸૬౰ͳ଍͔ͤͰ
    ͢ɻશͯͷґଘ͕ΫϩεϏϧυΛ͠ͳ͚Ε͹੒ཱ͠·ͤΜɻ31
    

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32. Depending on Java libraries
    Depending on well-maintained Java libraries is a
    reasonable way to reduce your efforts
    No extra efforts when Scala major upgrade
    Stability (well-tested by large number of users)
    Downside of using Java libraries?
    Have to understand Java interoperability tips
    Have to completely encapsulate Java world which
    brings you lots of null
    +BWBMJCSBSZґଘ͸ѱ͘ͳ͍બ୒ࢶͰ৭ʑָʹͳΓ·͕͢
    +BWBͳੈք؍ΛӅณ͢ΔͳͲͷέΞ͸ඞཁʹͳΔͰ͠ΐ͏ɻ
    32
    

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33. Cross-building Tips
    ಛʹ4DBMJLF+%#$͸ݹ͍4DBMBΛ࢖͏Ϣʔβʹ΋഑ྀ͖ͯ͠
    ·ͨ͠ɻͦͷͨΊʹඞཁͳ޻෉ʹ͍ͭͯઆ໌͠·͢ɻ 33
    

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34. Supported Versions
    4DBMJLF+%#$͸!YVXFJLͷਚྗͷ͓͔͛΋͋Γ
    ΫϩεϏϧυΛ͔ͳΓؤு͍ͬͯΔϥΠϒϥϦͰ͢ɻ
    ScalikeJDBC Release date Scala binary versions sbt versions
    1.0 2012-05
    2.9.0
    2.9.1
    2.9.2
    -
    2.0 2014-05
    2.10
    2.11
    0.13.x
    3.0 2017-06
    2.10
    2.11
    2.12
    0.13.x
    3.2 2018-01
    2.10
    2.11
    2.12
    0.13.x
    1.x
    34
    

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35. CI Build Configuration
    Properly configuring CI builds
    is the most important practice
    for cross-building
    If you don’t configure CI to
    check cross-building
    automatically, it’ll be very
    annoying to manually check
    the validity of pull requests
    $*ϏϧυΛద੾ʹઃఆͯ͠ӡ༻͢Δ͜ͱ͕࠷΋େࣄͰ͢ɻΫϩ
    εϏϧυΛؾʹ͠ͳ͕Β13Λड͚෇͚Δʹ͸ඞਢͰ͢ɻ 35
    

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36. src/main/scala-2.x
    Dealing with deprecated APIs between Scala major
    versions / 3rd party libraries’ upgrades
    src/main/scala-{Scala binary version}
    ඇਪ঑ͱͳͬͨ"1*Λ࢖͍෼͚Δ৔߹TSDNBJOͷ഑Լʹ
    CJOBSZWFSTJPOຖʹҧ͏ιʔείʔυΛஔ͍ͯରॲ͠·͢ɻ36
    

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37. Ensuring binary-compatibility
    (MiMa)
    ࣍ʹόΠφϦޓ׵ੑΛकΔํ๏ʹ͍ͭͯ঺հ͠·͢ɻ4DBMBͰ
    ͸όΠφϦޓ׵ੑΛ࢓૊ΈʹΑͬͯकΔ͜ͱ͕Ͱ͖·͢ɻ 37
    

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38. Are Java Libraries Safe?
    Java language itself is binary compatible between
    major versions
    Great efforts for backward compatibilities
    However, it’s not true for 3rd party Java libraries
    Even famous libraries sometimes break their binary
    compatibilities between releases
    (e.g) Jackson 2.x are basically binary incompatible
    +BWBϥΠϒϥϦͰόΠφϦޓ׵ੑΛؾʹͨ͜͠ͱ͕ͳ͍͋ͳ
    ͨ͸޾ӡͳਓͰ͢ɻඇޓ׵͸͠͹͠͹ൃੜ͍ͯ͠ΔͷͰ͢ɻ38
    

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39. How to Ensure It
    Use “MiMa”
    MiMa = Migration Manager
    lightbend/migration-manager
    Using it via the sbt plugin is convenient
    .J.BʢϛʔϚʣͱ͍͏πʔϧ͕όΠφϦඇޓ׵Λݕ஌ͯ͘͠
    ΕΔͷͰ͜ΕΛTCUϓϥάΠϯܦ༝Ͱ࢖͏ͷ͕ҰൠతͰ͢ɻ
    39
    

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40. When to Be Strict About It
    Up to the type of your library
    If you provide a low-level library that other libraries
    may depend on it
    you should be very careful
    As for directly used libraries / in-house libraries
    you don’t need to be so strict
    ࣾ಺΍ଞͷMJCSBSZ͕ґଘ͢ΔMJCSBSZΛఏڙ͠ͳ͍ͳΒɺඞ
    ͣ͠΋όΠφϦޓ׵ੑʹݫີʹऔΓ૊Ήඞཁੑ͸͋Γ·ͤΜɻ
    40
    

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41. ScalikeJDBC’s Policy
    Bump major/minor version when introducing some
    binary incompatibilities
    All patch version releases are bin-compatible
    GitHub branch strategies
    Having a corresponding git branch for each bin-
    compatible minor version (e.g. 3.2.x, 3.1.x, .. )
    master branch: the latest (3.3.x as of March 2018)
    ϙϦγʔɿόΠφϦඇޓ׵͸NBKPSNJOPSWFSɺQBUDIWFSؒ
    ͸όΠφϦޓ׵ΛอূɺHJUCSBODIΛNJOPS୯ҐͰӡ༻ 41
    

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42. MiMa Configuration
    4DBMJLF+%#$ͷઃఆྫɿΫϩεϏϧυͰTUBCMFNBKPSͷΈΛ
    νΣοΫɺ͢΂ͯͷQBUDIWFSTJPOTͱͷಥ͖߹Θͤ
    Skipping unstable Scala versions
    such as 2.13.0-M3
    42
    

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43. Building a Community of
    Friends
    044Λଓ͚Δ͜ͱ͸ҰਓͰͰ͖Δ͜ͱͰ͸͋Γ·ͤΜɻ
    ίϛϡχςΟͷதͰ஥ؒΛݟ͚ͭɺҰॹʹาΈ·͠ΐ͏ɻ 43
    

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44. Scala Ninja @xuwei-k
    ,FOKJ:PTIJEB͞Μ͸ʮจࣈ௨Γ4DBMB೜ऀʯͱͯ͠஌ΒΕͯ
    ͍Δɺ·͞ʹ೔ຊΛ୅ද͢ΔίϛϡχςΟߩݙऀͰ͢ɻ 44
    

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45. Not only the “Scala Ninja”
    ࢲͷ044͸:PTIJEB͞Μͷਚྗ͸΋ͪΖΜͰ͕͢ɺଟ͘ͷ
    ํʑͷߩݙͷ͓͔͛Ͱܧଓ͢Δ͜ͱ͕Ͱ͖͍ͯ·͢ɻ 45
    

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46. OSS Open/Closed Principle
    Open/Closed Principle
    Open for extension, but closed for modification
    OSS Open/Closed Principle
    Open for contribution,
    Friendly for new contributors; easy-to-..
    but closed for confusion (to be long-lived)
    CI / test suites which detect common mistakes
    Clearly stipulated rules (CONTRIBUTING.md)
    ߩݙʹ։͍͍ͯΔϓϩδΣΫτͷ৚݅ɿಈ͔͠΍͢͞ɺཧղ͠
    ΍͢͞ɺ҆શͳมߋɺςετίʔυɺ໌ه͞Εͨϧʔϧ 46
    

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47. Just Keep Working on It
    Library maintainers must overcome upgrades
    Scala major upgrades / Cross-building
    sbt build settings upgrades
    I’m still taking time to adapt sbt 1.x ..
    It’s like a battle of patience..
    Keep it simple, avoid hacky code/configuration
    Keep working on it at your own pace
    -JCSBSZϝϯςφ͸4DBMB΍TCUͷߋ৽ʹରԠ͠ଓ͚ͳ͚Ε
    ͹͍͚·ͤΜɻڽͬͨ͜ͱ͸ͤͣɺίπίπ࣋ٱઓͰ 47
    

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48. Let’s build our long-lived
    Scala community

    together!
    ΈΜͳͰ௕͘ଓ͘4DBMBίϛϡχςΟΛ࡞͍͖ͬͯ·͠ΐ͏ʂ
    ͜ͷൃදͰ͝঺հͨ͜͠ͱ͕ͦͷ͓໾ʹཱͯ͹޾͍Ͱ͢ɻ 48
    

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