Living With Legacy Code

Living

with

Legacy Code

@rowan_m

@rowan_m

Ibuildings

Plusnet

What is“Legacy Code”?

Code without tests

Code you've “inherited”

Code no-one understands

Technical debt

What is“Legacy Code”?

Who hasnever created

Legacy Code?

My own

story

little

My own

story

little

Pragmatic, not idealistic

Starting a project

Aim to understandthe concepts

and motivations

Try usingthe application

Find and then readany / all

documentation

Checklist

Official:Project brief ( )Requirements ( )Tech. Spec. ( )

Actual:Emails ( )Meeting notes ( )

Progress:Gant charts ( )Burndowns ( )Overtime logs ( )

Quality:Bug tracker ( )Complaints ( )User Forums ( )

Talk to theoriginal developers

Talk to the users

… especially the“different” ones

Approachingthe code

Catalogue thelive platform& environment

Recreate it!

Deploy the code

Checklist

PHP:php.ini ( )PEAR / PECL modules ( )Compile options ( )Patches ( )

The Rest:OS ( )Package manager ( )Web server ( )Web server modules ( )Site config. ( )Database ( )Cache ( )JS libraries ( )Firewall rules ( )Proxies ( )Services running ( )

Time to enterThe Code

Reading

Static analysis

Dynamic analysis

Time to enterThe Code

phpdoc

phpdoc -ti 'Sweet Application' \ -pp -o HTML:Smarty:PHP \ -d Libraries \ -t Docs

http://www.phpdoc.org/

Title

Style

Code in here

Docs out here!

Beware of type-hiding!

Type-hinting

Type-hiding

/** * @param array $opts Current options * @return array Options with flag set */function setFlag(array $opts) { $opts['flag'] = true; return $opts;}

/** * @param int $fullPence Full price in pence * @return float Discounted price in pence */function applyDiscount($fullPence) { return ($fullPence * 0.8);}

doxygen

http://www.stack.nl/~dimitri/doxygen/

doxygen -s -g ~/doxy.confvim ~/doxy.conf

# edit at least thisOUPUT_DIRECTORY# play with the rest

cd ~/dev/projectdoxygen ~/doxy.conf

Docs out here

Code in here

ctags

#!/bin/bashcd ~/Dev/ &&ctags-exuberant -f ~/.vimtags \-h ".php" -R \--exclude="\.git" \--links=no \--totals=yes \--tag-relative=yes \--PHP-kinds=+cf \--regex-PHP='/abstract\s+class\s+([^ ]+)/\1/c/' \--regex-PHP='/interface\s+([^ ]+)/\1/c/' \--regex-PHP='/(public\s+|static\s+|abstract\s+|protected\s+|private\s+) ↵ function\s+\&?\s*([^ (]+)/\2/f/'

Code in here

Tags out here

Voodoo

http://ctags.sourceforge.net/

bouml http://www.bouml.fr/

bouml http://bouml.free.fr/

bouml http://bouml.free.fr/

bouml http://bouml.free.fr/

bouml http://bouml.free.fr/

bouml http://bouml.free.fr/

bouml

codesniffer

rowan@swordbean:~/Dev/ZendFramework-1.9.4/library/Zend/Service$ phpcs \ --standard=Zend Exception.php

FILE: /home/rowan/Dev/ZendFramework-1.9.4/library/Zend/Service/Exception.php--------------------------------------------------------------------------------FOUND 1 ERROR(S) AND 2 WARNING(S) AFFECTING 3 LINE(S)-------------------------------------------------------------------------------- 17 | WARNING | Line exceeds 80 characters; contains 87 characters 32 | WARNING | Line exceeds 80 characters; contains 87 characters 36 | ERROR | Opening class brace must be on a line by itself 36 | ERROR | Closing brace must be on a line by itself--------------------------------------------------------------------------------

http://pear.php.net/package/PHP_CodeSniffer/

Continuo

us

Integrat

ion

http://jenkins-ci.org/

http://phpundercontrol.org/

http://sismo.sensiolabs.org/

Decision time!

Decision time!

Ignore it,code anyway

Rewrite,

refactor

,

test, tes

t, test

Ignore it,code anyway

Ignore it,code anyway

Please don't.

Ignore it,code anyway

Please don't.

however...

Deadlines, clients,money, etc.

Deadlines, clients,money, etc.

Secure afollow-up project

Make everyoneaware of the risks

Why do you need the code?

Why do you need the code?

Library dependency

Adding new behaviour

Changing behaviour

simple

complex

Isolatelegacy dependencies

Isolatelegacy dependencies

Create ananti-corruption layer

Complete isolation

Create alegacy service

Partial isolation

Wrapper classesor methods

<?phpinclude('/home/victorvon/secrets.inc');

/** * @param array $person willing volunteer */function extract_brain(&$person) { $brain = $person['brain']; unset($person['brain']);

return $brain;}

/** * @param array $person * @return bool living or not */function create_life($person) { require_once(LIB_DIR.'../nuts_n_bolts.inc'); kerzap(); $person['living'] = true; return $person;}?>

Some codeyou need

:(

Wrapper class

class VictorWrapper{

public function __construct() {

require_once '/home/victorvon/tragedy.php';}

public function extractBrain(Person $p) {// format to legacy style$pLgcy = $this->toArray($p);// run legacy code$bLgy = extract_brain($pLgcy);// format to new style$p = $this->toPerson($pLgcy);$b = $this->toBrain($bLgcy);return array($p, $b);

}

public function createLife(Person $p) {

// validateif ($person->isAlive()) throw new LivingException();// format to legacy style$pLgcy = $this->toArray($p);// run legacy code$pLgy = create_life($pLgcy);// format to new stylereturn $this->toPerson($pLgcy);

}}

Some codeyou can use

:)

Wrapper class

Changing the code

Changing the code

Take anincremental approach

Commit to 1 dayat a time

Why?

Difficult to estimate

Hidden dependencies

Unknown behaviour

1. Get it intoversion control

2. Identify theinflection point

3. Create integration& acceptance tests

4. Set up yourcontinuous integration

environment

5. Rewrite and refactor!

Types

of

changes

Mixed Procedural→

includes

HTML PHP

PHP

HTML

HTML

PHP

HTML

HTML

HTML

PHP

PHPPHP

HTML

PHP

PHP HTML

HTML

includes

HTML PHP

PHP

HTML

HTML

PHP

HTML

HTML

HTML

PHP

PHPPHP

HTML

includes

HTML echo

foreach

foreach

HTML

HTML

HTML

echo

ifif

HTML

PHP

PHP HTML

HTML

HTML

HTML echo

echo HTML

HTML

function

function

function

Procedural OO→

includes

function

function

function

free code

function

includes

static method

static method

static method

static method

static method

includes

function

function

function

free code

function

includes

static method

static method

static method

static method

static method

includes

method

method

method

method

constructor

includes

function

function

function

free code

function

Sprout method / class

public function createInvoice(Account $acc, array $charges){ $invoice = new Invoice();

foreach ($charges as $chg) { $invoice->addLine($chg->getDesc(), $chg->getAmount()); }

return $invoice;}

The existing code

“We just need to be able to give each client their own personal discount on certain charges.”

public function createInvoice(Account $acc, array $charges){ $invoice = new Invoice();

foreach ($charges as $chg) { $invoice->addLine($chg->getDesc(), $chg->getAmount()); }

return $invoice;}

private function calcDiscount(Account $acc, Charge $chg){ $accDisc = new AccountDiscounter($acc);

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;}

The new code

public function createInvoice(Account $acc, array $charges){ $invoice = new Invoice();

foreach ($charges as $chg) {

// Sprout new behaviour!$chg = $this->calcDiscount($acc, $chg);

$invoice->addLine($chg->getDesc(), $chg->getAmount()); }

return $invoice;}

private function calcDiscount(Account $acc, Charge $chg){ $accDisc = new AccountDiscounter($acc);

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;}

Call it

Untestable OO testable OO→

Dependency Inversion / Extraction

The Problempublic function calcDiscount(Account $acc, Charge $chg){ $accDisc = new AccountDiscounter($acc);

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;} Untestable!

The Problempublic function calcDiscount(Account $acc, Charge $chg){ $accDisc = new AccountDiscounter($acc);

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;} Untestable!

class AccountDiscounter{ public function __construct(Account $acc) { // check cache // contact the database // call a web service }}

Quick Solutionpublic function calcDiscount(Account $acc, Charge $chg){ $accDisc = $this->getAccountDiscounter($acc);

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;}

protected function getAccountDiscounter(Account $acc){ return new AccountDiscounter($acc);}

Mock object in your testOverride method

Dependency Injection Solution

public function calcDiscount(Account $acc, Charge $chg){ $accDisc = $this->discounter;

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;}

public function __construct(AccountDiscounter $ad){ $this->discounter = $ad;}

Pass it into the class

(v2) Dependency Injection Solution→

public function calcDiscount(Account $acc, Charge $chg){ $accDisc = $this->discounter;

$discountedCharge = $accDisc->calculate($chg); return $discountedCharge;}

public function __construct(IAccountDiscounter $ad){ $this->discounter = $ad;}

Make an interface

Analyse

Plan

Test

IsolatE

Change

Test MORE

Summary

Any questions?

Feedback to:

https://joind.in/6020

@rowan_m

Credits

http://www.flickr.com/photos/flatlinevision/1514971535/http://commons.wikimedia.org/wiki/File:Weird_Tales_November_1950.jpghttp://commons.wikimedia.org/wiki/File:AdventuresIntoDarkness1401.jpghttp://www.flickr.com/photos/locationscout/3594432797/http://www.flickr.com/photos/rawhead/3466304669/http://commons.wikimedia.org/wiki/File:Rocket_to_the_Moon_54893.jpghttp://commons.wikimedia.org/wiki/File:Weird_Chills_July.jpghttp://commons.wikimedia.org/wiki/File:Terrific_01.jpghttp://commons.wikimedia.org/wiki/File:Strange_Fantasy_01.jpghttp://commons.wikimedia.org/wiki/File:Beware_01.JPGhttp://www.flickr.com/photos/erokcom/2873449983/http://www.flickr.com/photos/locationscout/3594433235/http://commons.wikimedia.org/wiki/File:Weird_Chills_Sept.JPGhttp://commons.wikimedia.org/wiki/File:Weird_Comics_01.JPGhttp://www.flickr.com/photos/x-ray_delta_one/3972988193/http://commons.wikimedia.org/wiki/File:Weird_Tales_January_1950.jpghttp://commons.wikimedia.org/wiki/File:Plan_nine_from_outer_space.jpghttp://www.flickr.com/photos/javyer/3545217741/http://www.flickr.com/photos/76074333@N00/318034222/http://commons.wikimedia.org/wiki/File:Dime_Mystery_Magazine_July_1934.jpghttp://www.flickr.com/photos/quinnanya/3802177022/

Further reading:Michael FeathersMartin Fowler