Lessons From Librarians Makers

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