Building a Better Codebase with Lint - Droidcon Americas

Transcript

1. KeepTruckin
   Subhrajyoti Sen Droidcon Americas 2020
   Building a Better Codebase
   with Lint
   

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2. What is Lint?
   < / >
   

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3. What is Lint?
   • Static analysis tool
   

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4. What is Lint?
   • Static analysis tool
   • Open Source
   

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5. What is Lint?
   • Static analysis tool
   • Open Source
   • Works on .java, .kt, .gradle and a lot more
   

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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
   

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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
   

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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
   

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9. What does Lint look like?
   < / >
   

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10. Internationalization
    

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11. Security
    

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12. Performance
    

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13. Accessibility
    

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14. Why consider Lint?
    < / >
    

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15. Why consider Lint?
    • Opinionated codebase
    

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16. Why consider Lint?
    • Opinionated codebase
    • Simpler code reviews
    

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17. Why consider Lint?
    • Opinionated codebase
    • Simpler code reviews
    • Adherence to style guide
    

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18. Setup
    < / >
    

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19. Create a new module
    

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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'
    }
    

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21. Issue Registry
    class Registry : IssueRegistry() {
    override val api: Int = CURRENT_API
    @get:NotNull
    override val issues: List
    get() = listOf()
    }
    

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22. Register Issue Registry
    jar {
    manifest {
    attributes 'Lint-Registry-V2': 'me.subhrajyoti.lint.Registry'
    }
    }
    

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23. Register Issue Registry
    dependencies {
    lintChecks project(':lint')
    }
    

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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
    

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25. The Basic Elements
    Severity
    How severe is the issue
    • INFORMATIONAL
    • WARNING
    • ERROR
    • FATAL
    

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26. The Basic Elements
    Category
    The category the issue falls in, from a pre-defined list of categories
    • SECURITY
    • PERFORMANCE
    • L18N
    • A11Y
    

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27. Use case - TextView
    

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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
    )
    )
    

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29. Custom Rule Structure
    class MissingStyleAttributeDetector : ResourceXmlDetector() {
    }
    

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30. Custom Rule Structure
    class MissingStyleAttributeDetector : ResourceXmlDetector() {
    @Nullable
    override fun getApplicableElements(): Collection? {
    return listOf("TextView")
    }
    }
    

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31. Custom Rule Structure
    class MissingStyleAttributeDetector : ResourceXmlDetector() {
    @Nullable
    override fun getApplicableElements(): Collection? {
    return listOf(SdkConstants.TEXT_VIEW)
    }
    }
    

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32. Custom Rule Structure
    class MissingStyleAttributeDetector : ResourceXmlDetector() {
    //..
    override fun appliesTo(folderType: ResourceFolderType): Boolean {
    return folderType == ResourceFolderType.LAYOUT
    }
    }
    

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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"
    )
    }
    }
    }
    

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34. Remember this?
    class MissingStyleAttributeDetector : ResourceXmlDetector() {
    @Nullable
    override fun getApplicableElements(): Collection? {
    return listOf(SdkConstants.TEXT_VIEW)
    }
    }
    

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35. A small bug
    

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36. Integration
    

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37. Integration
    • Incremental fixes
    

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38. Integration
    • Incremental fixes
    • Using a baseline
    

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39. Baseline
    android {
    lintOptions {
    baseline file("lint baseline.xml")
    }
    }
    

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40. Baseline - Pass 1
    

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41. Baseline - Pass 2
    

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42. lint-baseline.xml
    
    id="MissingStyleAttribute"
    message="Add style to TextView in order to provide consistent design"
    errorLine1=" <TextView"
    errorLine2=" ^">
    file="src/main/res/layout/activity_main.xml"
    line="10"
    column="5"/>
    
    
    

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43. Performance
    

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44. Performance
    • Single pass
    • Missing attribute
    • Fast
    • Enable in IDE
    

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45. Performance
    • Single pass
    • Missing attribute
    • Fast
    • Enable in IDE
    • Multiple pass
    • Unused resources
    • Slow
    • Disable in IDE
    

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46. Kotlin Considerations?
    

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47. Kotlin Considerations?
    • No explicit return statements
    

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48. Kotlin Considerations?
    • No explicit return statements
    • No explicit type declarations
    

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49. Kotlin Considerations?
    • No explicit return statements
    • No explicit type declarations
    • Write one test case for Kotlin usage
    

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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
    

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51. @iamsubhrajyoti
    

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