Lessons From Librarians Makers

Transcript

1. Photo by Gabriel Sollmann on Unsplash Lessons From a Librarian

   James Barr - @JBarr21 Zac Sweers - @ZacSweers

2. cutt.ly/lessons-from-libs

3. cutt.ly/lessons-from-libs

4. subscribe()

5. subscribe(new Consumer<String>() { @Override public void accept(String value) { //

   Do stuff } })

6. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

   Do stuff } })

7. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

   Do stuff } })

8. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

   Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } })

9. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

   Do stuff } })

10. subscribe(value -> { // Do stuff })

11. subscribe(value -> { // Do stuff }) github.com/uber/rxdogtag

12. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

    Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(value -> { // Do stuff })

13. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

    Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(value -> { // Do stuff })

14. subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { //

    Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(new CrashOnErrorConsumer<String>() { @Override public void accept(String value) { // Do stuff } }) subscribe(value -> { // Do stuff }) And thousands more

15. subscribe(value -> { // Do stuff }) subscribe(value -> {

    // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff }) subscribe(value -> { // Do stuff })

16. - Anonymous audience member "But how?!"

17. Lessons from a Librarian

18. "Writing Code That Lasts Forever" - Jesse Wilson - Droidcon

    NYC 2018

19. Writing Code That Lasts Forever

20. Helping Everyone Write Code That Lasts Forever

21. Codebase Health ✅ Builds quickly ✅ Test coverage ✅ Well

    documented ❌ Duplicate code ❌ Deprecated APIs ❌ Large modules/classes

22. Name Build Time Undocumented Public Methods Module Size Deprecated Method

    Calls Quality Score (Overall: 75%) app 5m25s 0 10,000 LOC 0 75% feature1 4m20s 0 120,000 LOC 0 50% feature2 20s 0 4,000 LOC 0 100% library1 7s 90 1,000 LOC 0 75% library2 5s 0 2,000 LOC 88 75% Codebase Health

23. Name Build Time Undocumented Public Methods Module Size Deprecated Method

    Calls Quality Score (Overall: 75%) app 5m25s 0 10,000 LOC 0 75% feature1 4m20s 0 120,000 LOC 0 50% feature2 20s 0 4,000 LOC 0 100% library1 7s 90 1,000 LOC 0 75% library2 5s 0 2,000 LOC 88 75% Codebase Health

24. How does tech debt happen?

25. API Design

26. Limit Surface Area

27. Limit Surface Area class Hammer { public void hammer(Nail nail)

    { // ow } }

28. Limit Surface Area • Final by default final class Hammer

    { public void hammer(Nail nail) { // ow } }

29. Limit Surface Area • Final by default • Visibility final

    class Hammer { public void hammer(Nail nail) { // ow } }

30. Limit Surface Area • Final by default • Visibility •

    Factories final class Hammer { public static Hammer create() { // Stuff } private Hammer() { ... } }

31. Limit Surface Area final class Hammer { public void hammer(Nail

    nail) { // ow } } • Final by default • Visibility • Factories

32. API Design • Limit surface area • Final by default

    • Visibility • Factories • Consume interfaces interface Nail { void onHammer(); int length(); }

33. API Design • Limit surface area • Final by default

    • Visibility • Factories • Consume interfaces interface Nail { void onHammer(); int length(); }

34. - you, writing libraries "How easy is it to do

    the wrong thing?"

35. - you, writing libraries "How easy is it to do

    the wrong thing?" "Is this going to limit me later?"

36. API vs Implementation

37. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } }

38. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer

39. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer libA libA App

40. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer libA libA App

41. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer libA libA App

42. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer libA libA App :hammer-api interface Hammer { void hammer(Nail nail) }

43. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer libA libA App :hammer-api interface Hammer { void hammer(Nail nail) }

44. API vs Implementation class Hammer { public void hammer(Nail nail)

    { // ow } } :hammer libA libA App :hammer-api interface Hammer { void hammer(Nail nail) }

45. BuildConfig

46. BuildConfig public class BuildConfig { public static final String VERSION_NAME

    = "1.0"; public static final int VERSION_CODE = 1; public static final boolean DEBUG == false; }

47. BuildConfig public class BuildConfig { public static final String VERSION_NAME

    = "1.0"; public static final int VERSION_CODE = 1; public static final boolean DEBUG == false; } public interface AppBuildConfig { String versionName(); int versionCode(); boolean isDebug(); }

48. BuildConfig final class RealAppBuildConfig implements AppBuildConfig { // ... }

    public interface AppBuildConfig { String versionName(); int versionCode(); boolean isDebug(); } :appbuildconfig :app

49. BuildConfig final class RealAppBuildConfig implements AppBuildConfig { // ... }

    public interface AppBuildConfig { String versionName(); int versionCode(); boolean isDebug(); } :appbuildconfig :realappbuildconfig :app

50. BuildConfig final class RealAppBuildConfig implements AppBuildConfig { // ... }

    public interface AppBuildConfig { String versionName(); int versionCode(); boolean isDebug(); } :appbuildconfig :realappbuildconfig :app android { // or libraryVariants applicationVariants { generateBuildConfigProvider { enabled = true } } }

51. More Resources • API Design As An Art: youtube.com/watch?v=Ve9HlnJ0wCM •

    Writing Code That Lasts Forever: youtube.com/watch?v=YZstpc2939s • Effective Java • AppBuildConfig pattern: github.com/ZacSweers/CatchUp/pull/200

52. Code Review

53. Static Analysis

54. Static Analysis

55. Static Analysis

56. Removing Tech Debt

57. Replace in Path (⌘⇧R) Find/Replace

58. Find/Replace Replace in Path (⌘⇧R) Command line tools > find

    . -name "*.java" | xargs sed -i '' “s/import foo/import barr/g”

59. Kotlin ReplaceWith class Example { fun foo(s: String) {a/* old

    */ } fun usage() { foo("hello") } }

60. Kotlin ReplaceWith class Example { @Deprecated("Use Example.bar") fun foo(s: String)

    { /* old */ } fun bar(s: String) { /* new */ } fun usage() { foo("hello") } }

61. Kotlin ReplaceWith class Example { @Deprecated("Use Example.bar", replaceWith = ReplaceWith(“bar(s)"))

    fun foo(s: String) { /* old */ } fun bar(s: String) { /* new */ } fun usage() { foo("hello") } }

62. Kotlin ReplaceWith class Example { @Deprecated("Use Example.bar", replaceWith = ReplaceWith(“bar(s)"))

    fun foo(s: String) { /* old */ } fun bar(s: String) { /* new */ } fun usage() { foo("hello") } }

63. Kotlin ReplaceWith class Example { @Deprecated("Use Example.bar", replaceWith = ReplaceWith(“bar(s)"))

    fun foo(s: String) { /* old */ } fun bar(s: String) { /* new */ } fun usage() { bar("hello") } }

64. import android.util.Pair fun doSomething() { val pair = Pair.create(“a”, “b”)

    } <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent"> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent"> <View /> </FrameLayout> </FrameLayout> Android Lint SuggestedFix

65. import androidx.core.util.Pair fun doSomething() { val pair = Pair.create(“a”, “b”)

    } <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent"> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent"> <View /> </FrameLayout> </FrameLayout> Android Lint SuggestedFix

66. Structural Find & Replace void main( Example ex, Other other)

    { ex.foo() ex.foo(“hi") other.foo() }

67. Structural Find & Replace void main( Example ex, Other other)

    { ex.foo() ex.foo(“hi") other.foo() } void main( Example ex, Other other) { ex.foo() ex.foo(“hi") other.foo() }

68. Structural Find & Replace void main( Example ex, Other other)

    { ex.foo() ex.foo(“hi") other.foo() } $Instance$ type=com.example.Example .foo($Parameter$ [0,∞]) $Instance$ type=com.example.Example .bar($Parameter$ [0,∞])

69. Structural Find & Replace void main( Example ex, Other other)

    { ex.bar() ex.bar(“hi") other.foo() } $Instance$ type=com.example.Example .foo($Parameter$ [0,∞]) $Instance$ type=com.example.Example .bar($Parameter$ [0,∞]) youtrack.jetbrains.com/issue/KT-10176

70. IntelliJ Plugin • Add your own refactor options • Leverage

    IntelliJ’s tools • Good for automating multiple refactor operations https://cutt.ly/find-matches-action

71. Kotlin Script File(args[0]).walkTopDown() .filter { it.extension in setOf("java", "kt") }

    .filter { "/test/" !in it.absolutePath } .forEach {}

72. Kotlin Script File(args[0]).walkTopDown() .filter { it.extension in setOf("java", "kt") }

    .filter { "/test/" !in it.absolutePath } .forEach { file: File -> val fileLines = file.readLines().toMutableList() // modify lines of file file.writeText(fileLines.joinToString("\n")) }

73. Kotlin Script File(args[0]).walkTopDown() .filter { it.extension in setOf("java", "kt") }

    .filter { "/test/" !in it.absolutePath } .forEach { file: File -> val fileLines = file.readLines().toMutableList() // modify lines of file file.writeText(fileLines.joinToString("\n")) } $ brew install holgerbrandl/tap/kscript $ kscript MigrateToAndroidX.kts ~/project-root 16,866 files changed, 31,454 insertions(+), 31,415 deletions(-)

74. De-risking Change

75. Shadow Jobs

76. Shadow Jobs Android Gradle Plugin 4 beta/4.1 alpha Kotlin 1.4-M1

    Gradle 6.4-rc -SNAPSHOT Androidx alphas JDK 8-14 Shadow Jobs

77. Offensive Programming

78. b7cb262 - Migrate lib1 d43aa98 - Migrate lib2 a1dc8d1 -

    Migrate lib3 d843d8f - Migrate lib4 vs a13ab55 - Migrate all libs Safety Without Feature Flags

79. Photo by Webaroo on Unsplash

80. Photo by Pankaj Patel on Unsplash

81. Photo by Margarida CSilva on Unsplash

82. Photo by Hannes Wolf on Unsplash

83. Wrap Up

84. Photo by Gabriel Sollmann on Unsplash Lessons From a Librarian

    James Barr - @JBarr21 Zac Sweers - @ZacSweers