Lessons From a Librarian

Transcript

1. Photo by Gabriel Sollmann on Unsplash
   Lessons From a Librarian
   James Barr - @JBarr21
   Zac Sweers - @ZacSweers
   

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2. subscribe()
   

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3. subscribe(new Consumer() {
   @Override
   public void accept(String value) {
   // Do stuff
   }
   })
   

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

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

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6. subscribe(new CrashOnErrorConsumer() {
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7. subscribe(new CrashOnErrorConsumer() {
   @Override
   public void accept(String value) {
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   }
   })
   

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8. subscribe(value -> {
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   })
   

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9. subscribe(value -> {
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   github.com/uber/rxdogtag
   

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10. subscribe(new CrashOnErrorConsumer() {
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11. subscribe(new CrashOnErrorConsumer() {
    @Override
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12. subscribe(new CrashOnErrorConsumer() {
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    }
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    And thousands more
    

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13. subscribe(value -> {
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14. - Anonymous audience member
    "But how?!"
    

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15. Lessons from a Librarian
    

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16. "Writing Code That Lasts Forever" - Jesse Wilson - Droidcon NYC 2018
    

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17. Writing Code That Lasts
    Forever
    

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18. Helping Everyone Write
    Code That Lasts Forever
    

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19. Codebase Health
    ✅ Builds quickly
    ✅ Test coverage
    ✅ Well documented
    ❌ Duplicate code
    ❌ Deprecated APIs
    ❌ Large modules/classes
    

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20. 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
    

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21. 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
    

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22. How does tech debt
    happen?
    

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23. API Design
    

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24. Limit Surface Area
    

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25. Limit Surface Area
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    

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26. Limit Surface Area
    • Final by default
    final class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    

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27. Limit Surface Area
    • Final by default
    • Visibility final class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    

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28. Limit Surface Area
    • Final by default
    • Visibility
    • Factories
    final class Hammer {
    public static Hammer create() {
    // Stuff
    }
    private Hammer() { ... }
    }
    

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29. Limit Surface Area
    final class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    • Final by default
    • Visibility
    • Factories
    

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30. API Design
    • Limit surface area
    • Final by default
    • Visibility
    • Factories
    • Consume interfaces
    interface Nail {
    void onHammer();
    int length();
    }
    

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31. API Design
    • Limit surface area
    • Final by default
    • Visibility
    • Factories
    • Consume interfaces
    • Fluent APIs as
    navigation
    final class Hammer {
    public void removeNail(Nail nail) {
    //
    }
    }
    

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32. API Design
    • Limit surface area
    • Final by default
    • Visibility
    • Factories
    • Consume interfaces
    • Fluent APIs as
    navigation
    final class Hammer {
    public RemovedNail removeNail(Nail nail) {
    //
    }
    }
    

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33. API Design
    final class Hammer {
    public RemovedNail removeNail(Nail nail) {
    //
    }
    }
    hammer.removeNail()
    .dispose()
    • Limit surface area
    • Final by default
    • Visibility
    • Factories
    • Consume interfaces
    • Fluent APIs as
    navigation
    

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34. API Design
    final class Hammer {
    public RemovedNail removeNail(Nail nail) {
    //
    }
    }
    hammer.removeNail()
    .dispose()
    • Limit surface area
    • Final by default
    • Visibility
    • Factories
    • Consume interfaces
    • Fluent APIs as
    navigation
    

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35. - you, writing libraries
    "Does this put the user on the
    right track?"
    

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36. - you, writing libraries
    "Does this put the user on the
    right track?"
    "Is this going to limit me
    later?"
    

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37. API vs Implementation
    

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

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39. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    

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40. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    libA
    libA
    App
    

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41. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    libA
    libA
    App
    

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42. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    libA
    libA
    App
    

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43. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    libA
    libA
    App
    :hammer-api
    interface Hammer {
    void hammer(Nail nail)
    }
    

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44. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    libA
    libA
    App
    :hammer-api
    interface Hammer {
    void hammer(Nail nail)
    }
    

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45. API vs Implementation
    class Hammer {
    public void hammer(Nail nail) {
    // ow
    }
    }
    :hammer
    libA
    libA
    App
    :hammer-api
    interface Hammer {
    void hammer(Nail nail)
    }
    

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46. BuildConfig
    

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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;
    }
    

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48. 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();
    }
    

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49. BuildConfig
    final class RealAppBuildConfig implements AppBuildConfig {
    // ...
    }
    public interface AppBuildConfig {
    String versionName();
    int versionCode();
    boolean isDebug();
    }
    :appbuildconfig
    :app
    

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50. BuildConfig
    final class RealAppBuildConfig implements AppBuildConfig {
    // ...
    }
    public interface AppBuildConfig {
    String versionName();
    int versionCode();
    boolean isDebug();
    }
    :appbuildconfig
    :realappbuildconfig
    :app
    

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51. 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
    }
    }
    }
    

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52. 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
    

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53. Code Review
    

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54. Code Review
    Teach, don't tell
    

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55. Code Review
    Approve with nits
    

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56. Code Review
    

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57. Static Analysis
    

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58. Static Analysis
    

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59. Static Analysis
    

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60. Removing Tech Debt
    

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

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62. Find/Replace
    Replace in Path (⌘⇧R)
    Command line tools
    > find . -name "*.java" | xargs sed -i '' “s/import foo/import barr/g”
    

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63. Kotlin ReplaceWith
    class Example {
    fun foo(s: String) {a/* old */ }
    fun usage() {
    foo("hello")
    }
    }
    

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64. Kotlin ReplaceWith
    class Example {
    @Deprecated("Use Example.bar")
    fun foo(s: String) { /* old */ }
    fun bar(s: String) { /* new */ }
    fun usage() {
    foo("hello")
    }
    }
    

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65. 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")
    }
    }
    

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66. 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")
    }
    }
    

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67. 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")
    }
    }
    

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68. import android.util.Pair
    fun doSomething() {
    val pair = Pair.create(“a”, “b”)
    }
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    
    
    Android Lint SuggestedFix
    

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69. import androidx.core.util.Pair
    fun doSomething() {
    val pair = Pair.create(“a”, “b”)
    }
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    
    
    Android Lint SuggestedFix
    

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70. Structural Find & Replace
    void main(
    Example ex,
    Other other) {
    ex.foo()
    ex.foo(“hi")
    other.foo()
    }
    

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71. 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()
    }
    

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72. 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,∞])
    

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73. 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
    

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74. IntelliJ Plugin
    • Add your own refactor options
    • Leverage IntelliJ’s tools
    • Good for automating multiple
    uses of refactors
    https://cutt.ly/find-matches-action
    

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75. Kotlin Script
    File(args[0]).walkTopDown()
    .filter { it.extension in setOf("java", "kt") }
    .filter { "/test/" !in it.absolutePath }
    .forEach {}
    

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76. 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"))
    }
    

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77. 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(-)
    

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78. De-risking Change
    

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79. Shadow Jobs
    

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80. 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
    

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81. Offensive Programming
    

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82. Offensive Programming
    abstract class Model {
    abstract List modelList();
    }
    

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83. Offensive Programming
    abstract class Model {
    abstract ImmutableList modelList();
    }
    

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84. Offensive Programming
    abstract class Model {
    abstract List modelList();
    }
    ImmutableList
    

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85. b7cb262 - Migrate lib1
    d43aa98 - Migrate lib2
    a1dc8d1 - Migrate lib3
    d843d8f - Migrate lib4
    vs
    a13ab55 - Migrate all libs
    
    Safety Without Feature Flags
    

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86. Photo by Webaroo on Unsplash
    

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87. Photo by Pankaj Patel on Unsplash
    

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88. Photo by Margarida CSilva on Unsplash
    

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89. Photo by Hannes Wolf on Unsplash
    

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90. Wrap Up
    

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91. Photo by Gabriel Sollmann on Unsplash
    Lessons From a Librarian
    James Barr - @JBarr21
    Zac Sweers - @ZacSweers
    

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