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Code Generation beyond APT Ragunath Jawahar

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An Android developer walks into the bar…

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An Android developer walks into the bar office…

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Analytics Code MixpanelAPI mixpanel = MixpanelAPI.getInstance(this, token); try { JSONObject payload  = new JSONObject(); payload.put("Gender", "Female"); payload.put("Logged  in", false); payload.put("Source", "Twitter"); mixpanel.track("Signup", payload); } catch (JSONException exception) { Log.e("Frodo", "JsonException", exception); }

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Analytics Code MixpanelAPI mixpanel = MixpanelAPI.getInstance(this, token); try  { JSONObject payload  =  new  JSONObject(); payload.put("Gender",  "Female"); payload.put("Logged  in",  false); payload.put("Source",  "Twitter"); mixpanel.track("Signup",  payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }

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Analytics Code MixpanelAPI mixpanel =  MixpanelAPI.getInstance(this,  token); try  { JSONObject payload  = new JSONObject(); payload.put("Gender", "Female"); payload.put("Logged  in", false); payload.put("Source", "Twitter"); mixpanel.track("Signup",  payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }

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Analytics Code MixpanelAPI mixpanel =  MixpanelAPI.getInstance(this,  token); try  { JSONObject payload  =  new  JSONObject(); payload.put("Gender",  "Female"); payload.put("Logged  in",  false); payload.put("Source",  "Twitter"); mixpanel.track("Signup", payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }

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GREMLINS

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…and only 300 more rows

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MAY THE “BRUTE” FORCE BE WITH YOU

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Problems •Slow •Boring •Inaccurate •Error Prone •Hard to Test •Difficult to Change •Multiple Platforms •Multiple Apps

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Requirements • Accuracy • Accommodate Changes • Don’t Leak Cognitive Resources • Testability • Support Multiple Apps and Platforms

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AOP

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AOP

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WORKFLOW – SCREEN – EVENT

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workflow().screen().event()

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Java Poet – Method MethodSpec mainMethod = MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC, Modifier.STATIC) .addParameter(String[].class, "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();

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Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();

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Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC, Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();

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Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class, "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();

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Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();

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Java Poet – Method MethodSpec mainMethod =  MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC,  Modifier.STATIC) .addParameter(String[].class,  "args") .addStatement( "$T.out.println($S)", System.class, "Hello,  World!" ).build();

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Java Poet – Class TypeSpec greeterClass = TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();

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Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();

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Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();

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Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();

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Java Poet – Class TypeSpec greeterClass =  TypeSpec.classBuilder("Greeter") .addModifiers(Modifier.PUBLIC) .addMethod(mainMethod) .build();

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Java Poet – Compilation Unit JavaFile greeterFile = JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);

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Java Poet – Compilation Unit JavaFile greeterFile =  JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);

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Java Poet – Compilation Unit JavaFile greeterFile =  JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);

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Java Poet – Compilation Unit JavaFile greeterFile =  JavaFile.builder("in.kitecash", greeterClass).build(); greeterFile.writeTo(System.out);

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Java Poet – Generated Class package in.kitecash; import java.lang.String; import java.lang.System; public class Greeter { public static void main(String[] args) { System.out.println("Hello,  World!"); } }

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BLUEPRINT

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ITERATE ON PAPER

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Components •CSV Parser •Source Code Generator

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Objective workflow().screen().event()

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High-Level Design •Top-level Workflow classes •Inner Screen classes •Top-level Analytics class •Top-level Tracker abstract class

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Class Diagram …  more  workflow  classes

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Class Diagram …  more  inner  screen  classes

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workflow().screen().event() •Methods present inside Analytics class •Workflows are generated as top-level classes •Workflows encapsulate Screen inner classes

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workflow().screen().event() •Methods present inside Workflow classes •Screens are generated as inner classes in Workflows •Screens encapsulate event methods

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workflow().screen().event() •Methods present inside Screen classes •May accept parameters for collecting additional data

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Analytics •Contains  Workflow methods  that  provide   instances  of  Workflow classes •Instantiated  by  supplying  a  Tracker implementation

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Tracker public abstract class Tracker { public  abstract  void track(String event, Map payload); }

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Tracker public  abstract  class  Tracker  { public  abstract  void track(String event, Map payload); }

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Tracker public  abstract  class  Tracker  { public  abstract  void  track(String event, Map  payload); }

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Tracker public  abstract  class  Tracker  { public  abstract  void  track(String  event, Map payload); }

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ACCURACY

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WRITE CODE TO GENERATE CODE

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CHANGES

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CSV Removals – Red Markers

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CSV Additions – Yellow Markers

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PRODUCTIVITY

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Auto-Completion

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versus this? MixpanelAPI mixpanel =  MixpanelAPI.getInstance(this,  token); try  { JSONObject payload  =  new  JSONObject(); payload.put("Gender",  "Female"); payload.put("Logged  in",  false); payload.put("Source",  "Twitter"); mixpanel.track("Signup",  payload); }  catch  (JSONException exception)  { Log.e("Frodo",  "JsonException",  exception); }

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Checklist

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Checklist

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Checklist

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TESTING

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Gradle & Dagger •Multiple Build Types •Multiple Modules and Components

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Trackers •Logcat Tracker •Mixpanel Tracker •Dialog Tracker •Verifying Tracker

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LogcatTracker public class LogcatTracker implements Tracker { private static final String TAG  = "LogcatTracker"; @Override public void track(String trigger, Map payload) { Log.d(TAG, "Received  trigger:  " + trigger  +  ",  " + payload); } }

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LogcatTracker public  class  LogcatTracker implements  Tracker  { private  static  final  String  TAG  =  "LogcatTracker"; @Override public  void  track(String  trigger,  Map  payload)  { Log.d(TAG, "Received  trigger:  " + trigger  +  ",  " + payload); } }

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AlertDialogTracker public class AlertDialogTracker implements Tracker { private final Context context; public AlertDialogTracker(Context context) { this.context = context; } @Override public void track(String trigger, Map payload) { StringBuilder messageBuilder = new StringBuilder(); //  Create  a  String  message  from  the  payload... showAlertDialog(trigger, stringBuilder.toString()); } }

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AlertDialogTracker public  class  AlertDialogTracker implements  Tracker  { private  final  Context  context; public  AlertDialogTracker(Context  context)  { this.context =  context; } @Override public  void  track(String  trigger,  Map  payload)  { StringBuilder messageBuilder = new StringBuilder(); //  Create  a  String  message  from  the  payload... showAlertDialog(trigger, stringBuilder.toString()); } }

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MixpanelTracker public class MixpanelTracker implements Tracker { private final MixpanelAPI mixpanel; public MixpanelTracker(Context context, String projectToken) { this.mixpanel = MixpanelAPI.getInstance(context, projectToken); } @Override public void track(String trigger, Map payload) { JSONObject properties  = new JSONObject(); //  Populate  the  JSONObject from  payload... mixpanel.track(trigger, properties); } }

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MixpanelTracker public  class  MixpanelTracker implements  Tracker  { private  final  MixpanelAPI mixpanel; public  MixpanelTracker(Context context, String projectToken)  { this.mixpanel =  MixpanelAPI.getInstance(context,  projectToken); } @Override public  void  track(String  trigger,  Map  payload)  { JSONObject properties  =  new  JSONObject(); //  Populate  the  JSONObject from  payload... mixpanel.track(trigger,  properties); } }

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MixpanelTracker public  class  MixpanelTracker implements  Tracker  { private  final  MixpanelAPI mixpanel; public  MixpanelTracker(Context  context,  String  projectToken)  { this.mixpanel =  MixpanelAPI.getInstance(context,  projectToken); } @Override public  void  track(String  trigger,  Map  payload)  { JSONObject properties  = new JSONObject(); //  Populate  the  JSONObject from  payload... mixpanel.track(trigger, properties); } }

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iOS + Swift

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Difficulties •Swift •No Transpilers •No Code Generation Libraries

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J2ObjC

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J2ObjC Java Objective-C Swift

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J2ObjC Java Objective-C Swift

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J2ObjC Java Objective-C Swift

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PEACE

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PEACE

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abstract  class(es) NOT interface(s)

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J2ObjC Nuances •Runtime Library •Adds ~10 MB

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PROCESS

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Overview • Export spreadsheet from BI team as CSV • Check exported CSV into analytics project • Run Gradle task to generate source code from CSV • Copy generated source code into Android projects • Send generated source code to iOS team • iOS team includes transpiled source code to iOS projects

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Gradle Task task  generateAnalyticsSource(type: JavaExec) { classpath files('../sidekick/analytics/bin/grumpy-­‐old-­‐man.jar') main  'in.kitecash.sidekick.analytics.GrumpyOldMan' }

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Gradle Task task  generateAnalyticsSource(type:  JavaExec)  { classpath files('../sidekick/analytics/bin/grumpy-­‐old-­‐man.jar') main  'in.kitecash.sidekick.analytics.GrumpyOldMan' }

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Gradle Task task  generateAnalyticsSource(type:  JavaExec)  { classpath files('../sidekick/analytics/bin/grumpy-­‐old-­‐man.jar') main  'in.kitecash.sidekick.analytics.GrumpyOldMan' }

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TAKEAWAY

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Code Generation Tips • Iterate through the design several times • Doesn’t have to be DRY • Use a prefix in generated source files • Add “Auto-Generated” comments and Javadoc • Prefer abstract classes over interfaces • Extract platform-specific code, use abstraction

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2 Moar Cents •Make tools work for you •Communicate with all teams that are involved, this is the key

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ragunathjawahar GitHub / Twitter / Speakerdeck