Measuring Maintainability Dennis de Greef

Dennis de Greef Software Developer at TransIP Meetup addict

Tech enthousiast Occasional speaker Bass player

Domotica Software architect Hardware hacker Infrastructure engineer

Talk roadmap - About static software analysis - Measuring lines of code - Measuring complexity - Measuring coupling

About software statistics

Measuring Lines of Code

How many lines of code? 1 <?php 2 3 /* this is a for-loop */ 4 for ($i = 0; $i < 100; $i++) 5 { 6 printf("hello"); 7 }

How many lines of code? 1 <?php 2 3 /** 4 * This is a for-loop 5 */ 6 for ($i = 0; $i < 100; $i++) printf("hello");

Depends on your definition

LOC: Physical lines of code LLOC: Logical lines of code CLOC: Comment lines of code NCLOC: Non-comment lines of code

Different types:

How many lines of code?

7 physical lines of code 3 logical lines of code 1 comment lines of code 6 non-comment lines of code

1 <?php 2 3 /* this is a for-loop */ 4 for ($i = 0; $i < 100; $i++) 5 { 6 printf("hello"); 7 }

How many lines of code?

6 physical lines of code 3 logical lines of code 3 comment lines of code 3 non-comment lines of code

1 <?php 2 3 /** 4 * This is a for-loop 5 */ 6 for ($i = 0; $i < 100; $i++) printf("hello");

Some statisticsLOC

PhysicalCLOC

CommentNCLOC

Non-CommentLLOCLogical

symfony-standard 371490 102161(27.50%)

269329(72.50%)

84262(22.68%)

zend-framework2 306097 112498(36.75%)

193599(63.25%)

56053(18.31%)

laravel-framework 78191 35156 (44.96%)

43035(55.04%)

11970 (15.31%)

cakephp 93455 42454 (45.43%)

51001 (54.57%)

17235 (18.44%)

phploc 2.1.2-17-gb6bfd40

PSR-2

PSR-2

PSR-2

PSR-2

WARNING!Don’t use these statistics as a form of measuring quality or productivity!

People will just ‘game’ the system

*applies different codestyle*

Use it to gain more insight about the application

“Measuring programming progress by lines of code is like measuring aircraft building progress by weight.”

--Bill Gates

composer require phploc/phploc$ phploc loc1.php phploc 2.0.2 by Sebastian Bergmann.!

Size Lines of Code (LOC) 7 Comment Lines of Code (CLOC) 1 (14.29%) Non-Comment Lines of Code (NCLOC) 6 (85.71%) Logical Lines of Code (LLOC) 3 (42.86%) Classes 0 (0.00%) Average Class Length 0 Average Method Length 0 Functions 0 (0.00%) Average Function Length 0 Not in classes or functions 3 (100.00%)

Measuring Complexity

• Cyclomatic Complexity • N-path Complexity

Complexity and quality are strongly related

Cyclomatic Complexity“It is a quantitative measure of the number of

linearly independent paths through a program's source code.”

M = E − N + 2PE = the number of edges of the graph. N = the number of nodes of the graph. P = the number of connected components.

http://www.literateprogramming.com/mccabe.pdf

Simply put:Counting of decision trees: - function - for(each) - while - if - case

Cyclomatic Complexity 1 <?php 2 3 function foo($a, $b) { 4 if($a) { 5 if($b) { 6 echo "Hello World"; 7 } 8 } 9 } 10

5 edges 4 nodes 1 compound

M = 5 − 4 + 2x1 = 3M = E − N + 2P

Cyclomatic Complexity8 edges 7 nodes 1 compound

M = 8 − 7 + 2x1 = 3M = E − N + 2P

1 <?php 2 3 function foo() { 4 if($a) { 5 echo '1'; 6 } else { 7 echo '2'; 8 } 9 if($b) { 10 echo '3'; 11 } else { 12 echo '4'; 13 } 14 }

Cyclomatic ComplexityHow many tests do we need?

M = 8 − 7 + 2x1 = 3

Complete branch coverage: foo(true, false) foo(false, true)

Code Coverage 1 <?php 2 3 function foo($a, $b) { 4 if($a) { 5 // ... 6 } 7 8 if($b) { 9 // ... 10 } 11 } 12 13 foo(true, false); 14 foo(false, true);

All paths are tested with these two function calls. This implies 100% code coverage. !

Or does it? What about: foo(false, false) foo(true, true) ?

Code CoveragePath coverage:

http://derickrethans.nl/path-branch-coverage.html

Xdebug 2.3.0

PHP_CodeCoverage: not supported

N-path Complexity

“The NPath complexity of a method is the number of acyclic execution paths through that method.”

“The NPath complexity of a method is the number of acyclic execution paths through that method.”

N-path Complexity

“The NPath complexity of a method is the number of acyclic execution paths through that method.”

N-path Complexity

N-path Complexity

Path coverage

M = E − N + 2PE = the number of edges of the graph. N = the number of nodes of the graph. P = the number of connected components.

N-path Complexity

foo(false, false) foo(true, false) foo(false, true) foo(true, true)

Cyclomatic Complexity = 3 N-path Complexity = 4

N-path is exponential

N-path Complexity

foo(false, false) foo(true, false) foo(false, true) foo(true, true)

Cyclomatic Complexity = 3 N-path Complexity = 4

N-path is exponential

Number of unique paths

N-path Complexity // … $count['staticMethods'], $count['methods'] > 0 ? ($count['staticMethods'] / $count['methods']) * 100 : 0, $count['publicMethods'], $count['methods'] > 0 ? ($count['publicMethods'] / $count['methods']) * 100 : 0, $count['nonPublicMethods'], $count['methods'] > 0 ? ($count['nonPublicMethods'] / $count['methods']) * 100 : 0, $count['functions'], $count['namedFunctions'], $count['functions'] > 0 ? ($count['namedFunctions'] / $count['functions']) * 100 : 0, // …

N-path Complexity

The method printResult() has an NPath complexity of 47683715820312500.

The configured NPath complexity threshold is 200.

Measuring Coupling

http://www.codemanship.co.uk/parlezuml/metrics/OO%20Design%20Principles%20&%20Metrics.pdf

Martin’s Metrics

Measuring CouplingCoupling between packages

Packages being either a namespace or composer package

Measuring Coupling

Afferent Coupling (Ca):"Amount of other packages depending on this class (incoming) !

Efferent Coupling (Ce):"Amount of dependencies of this class !

Instability (I):"Resilience to change, metric between 0 and 1. Where 0 is stable.

I = Ce / (Ce + Ca)

Measuring Coupling

Ca = 2

Ce = 3

I = Ce / (Ce + Ca)

I = 3 / (3+2)

I = 0,6

I = 0,0 = Completely stableI = 1,0 = Completely unstable

Measuring Coupling

Abstract:"Either an abstract class or interface !

Concrete:"Any class that is neither abstract or final !

Abstractness (A):"How abstract a package is, ratio between 0 and 1. Where 0 is concrete.

A = Abstract / (Abstract + Concrete)

Measuring CouplingPHPMD (PHP Mess Detector)

Can detect (code size rules): - Cyclomatic complexity - N-path complexity - Excessive method length - Too many methods - etcetera

1020010010

And other things- Clean Code - Design Rules - Naming Rules - Unused Code Rules

Integrating it all

http://jenkins-php.org/

Questions?

Thank youBig thanks to: !

Derick Rethans (Xdebug) Sebastian Bergmann"(PHPLOC, PHPunit, PHP_CodeCoverage) Thomas J. McCabe Sr: Cyclomatic Complexity Robert C. Martin: Lots of things!(nicknamed ‘Uncle Bob’) !

Many more…

Twitter: @dennisdegreef Blog: dennisdegreef.net IRC (Freenode): link0 Github: dennisdegreef / link0 PHPNL-Slack: link0 Joind.in: https://joind.in/14991