Building a Better Codebase with Lint - Droidcon Americas

Transcript

1. KeepTruckin Subhrajyoti Sen Droidcon Americas 2020 Building a Better Codebase with Lint
2. What is Lint? < / >
3. What is Lint? • Static analysis tool
4. What is Lint? • Static analysis tool • Open Source
5. What is Lint? • Static analysis tool • Open Source • Works on .java, .kt, .gradle and a lot more
6. What is Lint? • Static analysis tool • Open Source • Works on .java, .kt, .gradle and a lot more • Can be used outside Android as well
7. What is Lint? • Static analysis tool • Open Source • Works on .java, .kt, .gradle and a lot more • Can be used outside Android as well • Can be extended to write custom rules
8. What is Lint? • Static analysis tool • Open Source • Works on .java, .kt, .gradle and a lot more • Can be used outside Android as well • Can be extended to write custom rules • Can be run from both Android Studio and CLI
9. What does Lint look like? < / >
10. Internationalization
11. Security
12. Performance
13. Accessibility
14. Why consider Lint? < / >
15. Why consider Lint? • Opinionated codebase
16. Why consider Lint? • Opinionated codebase • Simpler code reviews
17. Why consider Lint? • Opinionated codebase • Simpler code reviews • Adherence to style guide
18. Setup < / >
19. Create a new module
20. Dependencies dependencies { compileOnly "org.jetbrains.kotlin:kotlin stdlib:$kotlin_version" compileOnly 'com.android.tools.lint:lint api:27.1.1' compileOnly 'com.android.tools.lint:lint checks:27.1.1' }
21. Issue Registry class Registry : IssueRegistry() { override val api: Int = CURRENT_API @get:NotNull override val issues: List<Issue> get() = listOf() }
22. Register Issue Registry jar { manifest { attributes 'Lint-Registry-V2': 'me.subhrajyoti.lint.Registry' } }
23. Register Issue Registry dependencies { lintChecks project(':lint') }
24. The Basic Elements Scope The kind of files the lint rule applies to • JAVA_FILE_SCOPE • GRADLE_SCOPE • MANIFEST_SCOPE • PROGUARD_SCOPE • RESOURCE_FILE_SCOPE
25. The Basic Elements Severity How severe is the issue • INFORMATIONAL • WARNING • ERROR • FATAL
26. The Basic Elements Category The category the issue falls in, from a pre-defined list of categories • SECURITY • PERFORMANCE • L18N • A11Y
27. Use case - TextView
28. Custom Rule Structure val ISSUE: Issue = Issue.create( "MissingStyleAttribute", "style attribute is missing", "We should use style to style a TextView " + "in order to provide consistent design", Category.CORRECTNESS, 5, Severity.ERROR, Implementation( MissingStyleAttributeDetector::class.java, Scope.RESOURCE_FILE_SCOPE ) )
29. Custom Rule Structure class MissingStyleAttributeDetector : ResourceXmlDetector() { }
30. Custom Rule Structure class MissingStyleAttributeDetector : ResourceXmlDetector() { @Nullable override fun getApplicableElements(): Collection<String>? { return listOf("TextView") } }
31. Custom Rule Structure class MissingStyleAttributeDetector : ResourceXmlDetector() { @Nullable override fun getApplicableElements(): Collection<String>? { return listOf(SdkConstants.TEXT_VIEW) } }
32. Custom Rule Structure class MissingStyleAttributeDetector : ResourceXmlDetector() { //.. override fun appliesTo(folderType: ResourceFolderType): Boolean { return folderType == ResourceFolderType.LAYOUT } }
33. Custom Rule Structure class MissingStyleAttributeDetector : ResourceXmlDetector() { //.. override fun visitElement(context: XmlContext, element: Element) { if (!element.hasAttribute(SdkConstants.ATTR_STYLE)) { context.report( ISSUE, element, context.getLocation(element), "Add style to TextView in order to provide consistent design" ) } } }
34. Remember this? class MissingStyleAttributeDetector : ResourceXmlDetector() { @Nullable override fun getApplicableElements(): Collection<String>? { return listOf(SdkConstants.TEXT_VIEW) } }
35. A small bug
36. Integration
37. Integration • Incremental fixes
38. Integration • Incremental fixes • Using a baseline
39. Baseline android { lintOptions { baseline file("lint baseline.xml") } }
40. Baseline - Pass 1
41. Baseline - Pass 2
42. lint-baseline.xml <issues format="5" by="lint 3.6.3" client="gradle" variant="debug" version="3.6.3"> <issue id="MissingStyleAttribute" message="Add style to TextView in order to provide consistent design" errorLine1=" &lt;TextView" errorLine2=" ^"> <location file="src/main/res/layout/activity_main.xml" line="10" column="5"/> </issue> </issues>
43. Performance
44. Performance • Single pass • Missing attribute • Fast • Enable in IDE
45. Performance • Single pass • Missing attribute • Fast • Enable in IDE • Multiple pass • Unused resources • Slow • Disable in IDE
46. Kotlin Considerations?
47. Kotlin Considerations? • No explicit return statements
48. Kotlin Considerations? • No explicit return statements • No explicit type declarations
49. Kotlin Considerations? • No explicit return statements • No explicit type declarations • Write one test case for Kotlin usage
50. References • https://groups.google.com/g/lint-dev • https://github.com/SubhrajyotiSen/LintTalk • https://github.com/vanniktech/lint-rules • https://www.youtube.com/watch?v=p8yX5-lPS6o
51. @iamsubhrajyoti