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Lessons From a Librarian
jbarr21
April 19, 2020
Programming
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110
Lessons From a Librarian
jbarr21
April 19, 2020
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Transcript
Photo by Gabriel Sollmann on Unsplash Lessons From a Librarian
James Barr - @JBarr21 Zac Sweers - @ZacSweers
subscribe()
subscribe(new Consumer<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 } }) 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 })
subscribe(value -> { // Do stuff }) github.com/uber/rxdogtag
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 })
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 })
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
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 })
- Anonymous audience member "But how?!"
Lessons from a Librarian
"Writing Code That Lasts Forever" - Jesse Wilson - Droidcon
NYC 2018
Writing Code That Lasts Forever
Helping Everyone Write Code That Lasts Forever
Codebase Health ✅ Builds quickly ✅ Test coverage ✅ Well
documented ❌ Duplicate code ❌ Deprecated APIs ❌ Large modules/classes
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
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
How does tech debt happen?
API Design
Limit Surface Area
Limit Surface Area class Hammer { public void hammer(Nail nail)
{ // ow } }
Limit Surface Area • Final by default final class Hammer
{ public void hammer(Nail nail) { // ow } }
Limit Surface Area • Final by default • Visibility final
class Hammer { public void hammer(Nail nail) { // ow } }
Limit Surface Area • Final by default • Visibility •
Factories final class Hammer { public static Hammer create() { // Stuff } private Hammer() { ... } }
Limit Surface Area final class Hammer { public void hammer(Nail
nail) { // ow } } • Final by default • Visibility • Factories
API Design • Limit surface area • Final by default
• Visibility • Factories • Consume interfaces interface Nail { void onHammer(); int length(); }
API Design • Limit surface area • Final by default
• Visibility • Factories • Consume interfaces • Fluent APIs as navigation final class Hammer { public void removeNail(Nail nail) { // } }
API Design • Limit surface area • Final by default
• Visibility • Factories • Consume interfaces • Fluent APIs as navigation final class Hammer { public RemovedNail removeNail(Nail nail) { // } }
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
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
- you, writing libraries "Does this put the user on
the right track?"
- you, writing libraries "Does this put the user on
the right track?" "Is this going to limit me later?"
API vs Implementation
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } }
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer libA libA App
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer libA libA App
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer libA libA App
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer libA libA App :hammer-api interface Hammer { void hammer(Nail nail) }
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer libA libA App :hammer-api interface Hammer { void hammer(Nail nail) }
API vs Implementation class Hammer { public void hammer(Nail nail)
{ // ow } } :hammer libA libA App :hammer-api interface Hammer { void hammer(Nail nail) }
BuildConfig
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; }
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(); }
BuildConfig final class RealAppBuildConfig implements AppBuildConfig { // ... }
public interface AppBuildConfig { String versionName(); int versionCode(); boolean isDebug(); } :appbuildconfig :app
BuildConfig final class RealAppBuildConfig implements AppBuildConfig { // ... }
public interface AppBuildConfig { String versionName(); int versionCode(); boolean isDebug(); } :appbuildconfig :realappbuildconfig :app
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 } } }
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
Code Review
Code Review Teach, don't tell
Code Review Approve with nits
Code Review
Static Analysis
Static Analysis
Static Analysis
Removing Tech Debt
Replace in Path (⌘⇧R) Find/Replace
Find/Replace Replace in Path (⌘⇧R) Command line tools > find
. -name "*.java" | xargs sed -i '' “s/import foo/import barr/g”
Kotlin ReplaceWith class Example { fun foo(s: String) {a/* old
*/ } fun usage() { foo("hello") } }
Kotlin ReplaceWith class Example { @Deprecated("Use Example.bar") fun foo(s: String)
{ /* old */ } fun bar(s: String) { /* new */ } fun usage() { foo("hello") } }
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") } }
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") } }
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") } }
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
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
Structural Find & Replace void main( Example ex, Other other)
{ ex.foo() ex.foo(“hi") other.foo() }
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() }
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,∞])
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
IntelliJ Plugin • Add your own refactor options • Leverage
IntelliJ’s tools • Good for automating multiple uses of refactors https://cutt.ly/find-matches-action
Kotlin Script File(args[0]).walkTopDown() .filter { it.extension in setOf("java", "kt") }
.filter { "/test/" !in it.absolutePath } .forEach {}
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")) }
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(-)
De-risking Change
Shadow Jobs
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
Offensive Programming
Offensive Programming abstract class Model { abstract List<String> modelList(); }
Offensive Programming abstract class Model { abstract ImmutableList<String> modelList(); }
Offensive Programming abstract class Model { abstract List<String> modelList(); }
ImmutableList
b7cb262 - Migrate lib1 d43aa98 - Migrate lib2 a1dc8d1 -
Migrate lib3 d843d8f - Migrate lib4 vs a13ab55 - Migrate all libs Safety Without Feature Flags
Photo by Webaroo on Unsplash
Photo by Pankaj Patel on Unsplash
Photo by Margarida CSilva on Unsplash
Photo by Hannes Wolf on Unsplash
Wrap Up
Photo by Gabriel Sollmann on Unsplash Lessons From a Librarian
James Barr - @JBarr21 Zac Sweers - @ZacSweers