Improving Code Quality with Static Analysis

DrupalCamp St. Louis

Joseph D. Purcell

Who am I?

Who are you?

Typoglycemia

Woh nedes a sepll cehcker?

... computers aren't so forgiving

goto Fail

if ((err = SSLHashSHA1.update(&hashCtx, &signedParams)) != 0)
    goto fail;
    goto fail;
            

The "goto fail" bug could have been caught by static analysis

Source: Martin Fowler

If you're not using static analysis you're wasting time.

• Trivial back and forth on code style
• Bug resolution for obvious problems (dead code, typos, etc)
• The "grind" on poor code (complex, highly coupled)

Overview

1. What is static analysis?
2. What can the analysis find?
3. How do I do continuous inspection?

What is static analysis?

Anything you can learn from code without executing it.

Imagine goto fail in PHP

if (($err = SSLHashSHA1::update($hashCtx, $signedParams)) != 0)
  goto fail;
  goto fail;
            

• The method HashHandshake() utilizes a goto statement. (PHPMD)
• Inline control structures are not allowed (PHPCS)
• Line indented incorrectly; expected 4 spaces, found 6 (PHPCS)

How is this done?

Read the file off disk and look for a pattern.

Static Analysis Tools

• PHP Code Sniffer (PHPCS) e.g. Drupal Coder
• PHP Mess Detector (PHPMD)
• PHP Copy and Paste Detector (PHPCPD)
• PHP Lines of Code (PHPLOC)
• Many more...

Let's try it out...

Check: Global variable access

protected function doLoadMultiple(array $names, $immutable = TRUE) {
  ...
  if (isset($GLOBALS['config'][$name])) {
    $this->cache[$cache_key]->setSettingsOverride($GLOBALS['config'][$name]);
  ...

Check: Unused variable or method parameter

  protected function formSingleElement(FieldItemListInterface $items, $delta...
    $entity = $items->getEntity();

    $element += array(
      '#field_parents' => $form['#parents'],
      // Only the first widget should be required.
      '#required' => $delta == 0 && $this->fieldDefinition->isRequired(),
      '#delta' => $delta,
      '#weight' => $delta,
    );

    $element = $this->formElement($items, $delta, $element, $form, $form_state);

    if ($element) { 
      ...

If it stinks, change it.
- Grandma Beck, "Refactoring"

What can the analysis find?

Characteristics of Checks

Readability

How easy is it to read and understand?

Maintainability

How easy is it to bugfix and apply updates?

Extensibility

How easy is it to add a feature?

Security

How vulnerable is it to malicious users?

Testability

How easily can a test be written to verify behavior?

Correctness (i.e. bugs, technical debt)

How efficiently does it meet requirements?

Check: Global variable access

protected function doLoadMultiple(array $names, $immutable = TRUE) {
  ...
  if (isset($GLOBALS['config'][$name])) {
    $this->cache[$cache_key]->setSettingsOverride($GLOBALS['config'][$name]);
  ...

• Testability: You don't have control over global state, e.g. flaky test.
• Security: No sanitization of inputs.
• Extensibility: There is no abstraction possible.

Check: Unused variable or method parameter

  protected function formSingleElement(FieldItemListInterface $items, $delta...
    $entity = $items->getEntity();

    $element += array(
      '#field_parents' => $form['#parents'],
      // Only the first widget should be required.
      '#required' => $delta == 0 && $this->fieldDefinition->isRequired(),
      '#delta' => $delta,
      '#weight' => $delta,
    );

    $element = $this->formElement($items, $delta, $element, $form, $form_state);

    if ($element) { 
      ...

• Readability: It's unclear what $entity is supposed to do.
• Correctness: Is the lack of use of $entity a bug?

Check: Dead code

  private function getProxyInstantiator()
  {
    if (!$this->proxyInstantiator) {
      $this->proxyInstantiator = new RealServiceInstantiator();
    }
    ...

• Readability: Why is this method still here?
• Testability: You can't test code that can't be executed.
• Correctness: Code that isn't executed is usually a bug.

Check: Number of public methods

class EntityType implements EntityTypeInterface { 
  public function get($property) {
  public function set($property, $value) {
  public function isStaticallyCacheable() {
  public function isRenderCacheable() {
  public function isPersistentlyCacheable() {
  public function getKeys() {
  public function getKey($key) {
  public function hasKey($key) {
  public function id() {
  public function getProvider() {
  public function getClass() {
  public function getOriginalClass() {
  public function setClass($class) {
  public function isSubclassOf($class) {
  public function getHandlerClasses() {
  public function getHandlerClass($handler_type, $nested = FALSE) {
  public function setHandlerClass($handler_type, $value) {
  public function hasHandlerClass($handler_type, $nested = FALSE) {
  public function getStorageClass() {
  public function setStorageClass($class) {
  ... 49 more methods!

• Extensibility: Likely difficult to vary behavior.
• Correctness: Likely violates Single Responsibility Principle.

Check: Use of statics

class WorkspaceController extends ControllerBase {

  public function add() {
    $types = WorkspaceType::loadMultiple();
    if ($types && count($types) == 1) {
      $type = reset($types);
      return $this->addForm($type);
    }
    ...

• Testability: difficult to stub return of ::loadMultiple()
• Extensibility: cannot replace WorkspaceType with subclass

Check: Missing doc comment

  public function update(WorkspacePointerInterface $source, WorkspacePointerInterface $target) { 
    return $this->doReplication($source, $target);
  } 

• Readability: update is generic, why is it just a wrapper to doReplication?
• Extensibility: How do you know you've changed this class according to author's intent?

Check: NPath or Cyclomatic Complexity

  public function disableEntityTypes() { 
    foreach ($entity_types as $entity_type_id => $entity_type) { 
      try { 
        if ($storage->hasData()) { 
      catch (\Exception $e) { 
      if ($has_data[$entity_type_id]) { 
        if ($entity_type_id == 'file') { 
    foreach ($entity_manager->getDefinitions() as $entity_type) { 
      if ($entity_type->isSubclassOf(FieldableEntityInterface::CLASS)) { 
        foreach ($entity_manager->getFieldStorageDefinitions($entity_type_id)...
          if ($storage_definition->getProvider() == 'multiversion' && !$storage...
    foreach ($enabled_entity_types as $entity_type_id) { 
    foreach ($entity_types as $entity_type_id => $entity_type) { 
      if ($has_data[$entity_type_id]) { 
    ...

• Readability: We can't comprehend that much complexity.
• Maintainability: Try to debug this!
• Correctness: Likely violates Single Responsibility Principle.

Check: Efferent/Afferent Coupling

...
namespace Drupal\multiversion;

use Drupal\Core\Entity\ContentEntityInterface;
use Drupal\Core\Entity\ContentEntityTypeInterface;
use Drupal\Core\Entity\EntityTypeInterface;
use Drupal\Core\Entity\EntityManagerInterface;
use Drupal\Core\Entity\FieldableEntityInterface;
use Drupal\Core\State\StateInterface;
use Drupal\Core\Language\LanguageManagerInterface;
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\Database\Connection;
use Drupal\multiversion\Workspace\WorkspaceManagerInterface;
use Symfony\Component\DependencyInjection\ContainerAwareInterface;
use Symfony\Component\DependencyInjection\ContainerAwareTrait;
use Symfony\Component\Serializer\Serializer;

class MultiversionManager implements MultiversionManagerInterface, ContainerAwareInterface {
...

• Extensibility: High coupling = hard to change.
• Testability: You have to double all those classes!
• Correctness: Likely violates Single Responsibility Principle.

How do I do
continuous inspection?

Code Climate

A static analysis platform, free for open source (on GitHub).

How to configure

Examples on GitHub:
github.com/josephdpurcell/code-climate-and-drupal

.codeclimate.yml

---
engines:
  phpmd:
    enabled: true
    config:
      file_extensions: "php,inc,module,install"
      rulesets: ".phpmd.xml"
  phpcodesniffer:
    enabled: true
    config:
      file_extensions: "php,inc,module,install"
      encoding: utf-8
      standard: "Drupal"
      ignore_warnings: true
ratings:
  paths:
  - "web/modules/custom/**.php"
  - "web/modules/custom/**.inc"
  - "web/modules/custom/**.module"
  - "web/modules/custom/**.install"
exclude_paths:
- conf
- web/core
- web/modules/contrib
- web/profiles
- web/sites
- web/themes
- web/*.php

.phpmd.xml

<?xml version="1.0"?>
<ruleset xmlns="http://pmd.sourceforge.net/ruleset/2.0.0" xmlns:xsi="http://www.w3...
  <description>
    A PMD Ruleset for Drupal coding standards.
  </description>

  <!-- Code Size -->
  <rule ref="rulesets/codesize.xml/CyclomaticComplexity"/>
  <rule ref="rulesets/codesize.xml/NPathComplexity"/>
  <rule ref="rulesets/codesize.xml/ExcessiveMethodLength"/>
  <rule ref="rulesets/codesize.xml/ExcessiveClassLength"/>
  <rule ref="rulesets/codesize.xml/ExcessiveParameterList"/>
  <rule ref="rulesets/codesize.xml/ExcessivePublicCount"/>
  <rule ref="rulesets/codesize.xml/TooManyFields"/>
  ...

Ways to use static analysis

1. Development workflow (continuous inspection)
2. Code audit

1. Development Workflow

1. Commit and push code
2. Automated tests and static analysis run
3. If build fails, contributor revises
4. If build succeeds, code is reviewed and merged

2. Code Audit

1. Planned refactoring
2. Sprint retrospectives

What not to do...

Static anlysis is only as good
as it's configured to be.

Static anlysis is not a
replacement for you're brain.

Don't compare GPAs of projects
that use different configurations.

Don't avoid static analyisis
because there's too much to tackle.

Don't only run static analysis locally--they should be shared just like tests.

Cost of Owning a Mess

Savings of Static Analysis

• You're not wasting time looking for code style
• You're not worring about obvious bugs or typos
• You can clean as you go
• You know the parts that are hard to change

What's next?

• Agree on static analysis config for D7 and D8, core, contrib, projects
• Code Climate support for Drupal.org
• Start using static anlaysis on Drupal Core and Contrib
  (see #1299710)
• Add GPAs to compare contrib modules
• Every PHP or Drupal CVE gets a sniff (see Ruby handbrake)
• Automated code quality spike tickets: CVEs or GPA threshold
• Use these checks in autocorrect: PHP Code Beautifier and Fixer (PHPCBF)
• Write a Drupal project analysis engine for Code Climate

You are the Lorax.

Speak for the code.

Thank you!

Come to the sprints tomorrow!

Slides: github.com/josephdpurcell/code-climate-and-drupal

Want help setting up Code Climate?

@josephdpurcell

References and
Further Reading

• Mariner 1 report
• Linux Kernel Developer Responses to Static Analysis Bug Reports
• Goto Fail, Heartbleed, and Unit Testing Culture
• List of PHP static analysis tools
• Drupal Secure Code Sniffs
• When Software Catastrophe Strikes
• Build your own Code Climate Analysis Engine
• Technical Pollution: Insights from the Lorax
• Drupal 8 code metrics generated by phpmetrics.org