Lint to the Finish Line (Droidcon NYC 2017)

With the release of Android Gradle Plugin 3.0, Lint will have changed quite a bit. In this talk, we'll:

* Learn about the Unified AST (UAST)
* Hash out the differences between UAST, PSI and Lombok
* Go through examples of custom lint checks with quick fixes
...and more!

You’ll learn enough to write your own lint checks in no time flat!

Video: https://www.youtube.com/watch?v=wFe0WZm_xm8

1. Lint to the Finish Line John Rodriguez
5. public class MainActivity extends AppCompatActivity { private TextView mUserNameView; private static Map<String, String> sMap;
6. apply plugin:e'java'e dependenciese{e def toolsVersion = "25.3.3" provided "com.android.tools.lint:lint-api:${toolsVersion}" provided "com.android.tools.lint:lint-checks:${toolsVersion}" }e lint/build.gradle v(Lint) = 23 + v(AGP)
7. apply plugin:e'java-library'e dependenciese{e def toolsVersion = "26.0.0-beta6" eprovidede"com.android.tools.lint:lint-api:${toolsVersion}" eprovidede"com.android.tools.lint:lint-checks:${toolsVersion}" }e lint/build.gradle
8. apply plugin:e'java-library'e dependenciese{e def toolsVersion = "26.0.0-beta6" compileOnly "com.android.tools.lint:lint-api:${toolsVersion}" compileOnly "com.android.tools.lint:lint-checks:${toolsVersion}" }e lint/build.gradle
9. class HungarianDetector {e }e src/main/java/…/HungarianDetector.java
10. import com.android.tools.lint.detector.api.Detector; import com.android.tools.lint.detector.api.Detector.UastScanner; class HungarianDetector extends Detector implements UastScanner {e }e src/main/java/…/HungarianDetector.java
11. import com.android.tools.lint.detector.api.Detector; import com.android.tools.lint.detector.api.Detector.UastScanner; class HungarianDetector extends Detector implements UastScanner {e static final Issue ISSUE_HUNGARIAN = Issue.create(“HungarianNotationDetected”, …); …e }e src/main/java/…/HungarianDetector.java
12. import com.android.tools.lint.detector.api.Detector; import com.android.tools.lint.detector.api.Detector.UastScanner; class HungarianDetector extends Detector implements UastScanner {e static final Issue ISSUE_HUNGARIAN = Issue.create(“HungarianNotationDetected”, "Just say mNo to ” + "Hungarian notation. mmKay?”, …); …e }e src/main/java/…/HungarianDetector.java
13. import com.android.tools.lint.detector.api.Detector; import com.android.tools.lint.detector.api.Detector.UastScanner; class HungarianDetector extends Detector implements UastScanner {e static final Issue ISSUE_HUNGARIAN = Issue.create(“HungarianNotationDetected”, "Just say mNo to ” + "Hungarian notation. mmKay?”, …, Severity.ERROR, …); …e }e src/main/java/…/HungarianDetector.java
14. import com.android.tools.lint.detector.api.Detector; import com.android.tools.lint.detector.api.Detector.UastScanner; class HungarianDetector extends Detector implements UastScanner {e static final Issue ISSUE_HUNGARIAN = Issue.create(“HungarianNotationDetected”, "Just say mNo to ” + "Hungarian notation. mmKay?”, …, Severity.ERROR, new Implementation(HungarianDetector.class, Scope.JAVA_FILE_SCOPE)); …e }e src/main/java/…/HungarianDetector.java
15. import com.android.tools.lint.detector.api.Detector; import com.android.tools.lint.detector.api.Detector.UastScanner; class HungarianDetector extends Detector implements UastScanner {e static final Issue ISSUE_HUNGARIAN = … …e }e src/main/java/…/HungarianDetector.java
16. class HungarianDetector extends Detector implements UastScanner {e …e }e src/main/java/…/HungarianDetector.java
17. public interface UastScanner { UElementHandler createUastHandler(JavaContext); }e Detector.UastScanner
18. public interface UastScanner {e UElementHandler createUastHandler(JavaContext); List<Class<? extends UElement>> getApplicableUastTypes();e }e Detector.UastScanner
19. public interface UastScanner {e … }e Detector.UastScanner
20. public interface UastScanner {e … List<String> getApplicableMethodNames(); List<String> getApplicableConstructorTypes(); List<String> getApplicableReferenceNames(); boolean appliesToResourceRefs(); List<String> applicableSuperClasses(); }e Detector.UastScanner
21. public interface UastScanner {e … List<String> getApplicableMethodNames(); void visitMethod(JavaContext, UCallExpression, PsiMethod); List<String> getApplicableConstructorTypes(); void visitConstructor(JavaContext, UCallExpression, PsiMethod); List<String> getApplicableReferenceNames(); void visitReference(JavaContext, UReferenceExpression, PsiElement); boolean appliesToResourceRefs(); void visitResourceReference( JavaContext, UElement, ResourceType, String, boolean); List<String> applicableSuperClasses(); void visitClass(JavaContext, UClass); void visitClass(JavaContext, ULambdaExpression); }e Detector.UastScanner
22. public interface XmlScanner { void visitDocument(XmlContext context, Document document); void visitElement(XmlContext context, Element element); void visitElementAfter(XmlContext context, Element element); void visitAttribute(XmlContext context, Attr attribute); Collection<String> getApplicableElements(); Collection<String> getApplicableAttributes(); } Detector.XmlScanner
23. public interface ClassScanner { void checkClass(ClassContext context, ClassNode classNode); int[] getApplicableAsmNodeTypes(); void checkInstruction(ClassContext context, ClassNode classNode, MethodNode method, AbstractInsnNode instruction); List<String> getApplicableCallNames(); List<String> getApplicableCallOwners(); void checkCall(ClassContext context, ClassNode classNode, MethodNode method, MethodInsnNode call); } Detector.ClassScanner
24. public interface GradleScanner { void visitBuildScript(Context context, Map<String, Object> data); } public interface BinaryResourceScanner { void checkBinaryResource(ResourceContext context); boolean appliesTo(ResourceFolderType folderType); } public interface ResourceFolderScanner { void checkFolder(ResourceContext context, String folderName); boolean appliesTo(ResourceFolderType folderType); } public interface OtherFileScanner { EnumSet<Scope> getApplicableFiles(); } Etc…
25. classeHungarianDetector extends Detector implements UastScanner {e … }e src/main/java/…/HungarianDetector.java
26. public abstract class Detector { public void beforeCheckProject(Context context) {} public void afterCheckProject(Context context) {} public void beforeCheckLibraryProject(Context context) {} public void afterCheckLibraryProject(Context context) {} public void beforeCheckFile(Context context) {} public void afterCheckFile(Context context) {} }e Detector.java
27. public abstracteclass Detector { public void beforeCheckProject(Context context) {} public void afterCheckProject(Context context) {} public void beforeCheckLibraryProject(Context context) {} public void afterCheckLibraryProject(Context context) {} public void beforeCheckFile(Context context) {} public void afterCheckFile(Context context) {} // dummy implementations of *Scanner interface methods }e Detector.java
28. classeHungarianDetector extends Detector implements UastScanner {e … }e src/main/java/…/HungarianDetector.java
29. classeHungarianDetector extends Detector implements UastScanner {e … @Override public List<Class<? extends UElement>> getApplicableUastTypes() { return Collections.singletonList(UField.class); } }e src/main/java/…/HungarianDetector.java
30. classeHungarianDetector extends Detector implements UastScanner {e … }e src/main/java/…/HungarianDetector.java
31. classeHungarianDetector extends Detector implements UastScanner {e … @Override public UElementHandler createUastHandler(JavaContext context) { return new UElementHandler() { @Override public void visitField(UField node) { } }; } }e src/main/java/…/HungarianDetector.java
32. classeHungarianDetector extends Detector implements UastScanner {e … @Override public UElementHandler createUastHandler(JavaContext context) { return new UElementHandler() { @Override public void visitField(UField node) { String name = node.getName(); char[] c = name.toCharArray(); if (node.isStatic()) { if (!node.isFinal() && c[0] == 's' && isUpperCase(c[1])) { report(node, name, context); } } } }; } }e src/main/java/…/HungarianDetector.java
33. classeHungarianDetector extends Detector implements UastScanner {e … @Override public UElementHandler createUastHandler(JavaContext context) { return new UElementHandler() { @Override public void visitField(UField node) { … else if (!node.hasModifierProperty("public")) { if (c[0] == 'm' && isUpperCase(c[1])) { report(node, name, context); } } }; } }e src/main/java/…/HungarianDetector.java
34. classeHungarianDetector extends Detector implements UastScanner {e … private void report(UField node, String name, JavaContext context) { context.report(ISSUE_HUNGARIAN, context.getLocation(node), "Y u Hungarian?"); } }e src/main/java/…/HungarianDetector.java
35. package com.example.lint; public class SampleRegistry {e }e src/main/java/…/SampleRegistry.java
36. package com.example.lint; import com.android.tools.lint.client.api.IssueRegistry; public class SampleRegistry extends IssueRegistry {e }e src/main/java/…/SampleRegistry.java
37. package com.example.lint; import com.android.tools.lint.client.api.IssueRegistry; import com.android.tools.lint.detector.api.Issue; import java.util.List; public class SampleRegistry extends IssueRegistry {e @Override public List<Issue> getIssues() { }f }e src/main/java/…/SampleRegistry.java
38. package com.example.lint; import com.android.tools.lint.client.api.IssueRegistry; import com.android.tools.lint.detector.api.Issue; import java.util.Collections; import java.util.List; import static com.example.lint.HungarianDetector.ISSUE_HUNGARIAN; public class SampleRegistry extends IssueRegistry {e @Override public List<Issue> getIssues() { return Collections.singletonList(ISSUE_HUNGARIAN); }f }e src/main/java/…/SampleRegistry.java
39. apply plugin: 'java-library' dependencies {e def toolsVersion = "26.0.0-beta6" compileOnly "com.android.tools.lint:lint-api:${toolsVersion}" compileOnly "com.android.tools.lint:lint-checks:${toolsVersion}" }e lint/build.gradle
40. apply plugin: 'java-library' dependencies {e def toolsVersion = "26.0.0-beta6" compileOnly "com.android.tools.lint:lint-api:${toolsVersion}" compileOnly "com.android.tools.lint:lint-checks:${toolsVersion}" }e jar { manifest { attributes(‘Lint-Registry-v2': 'com.example.lint.SampleRegistry') } } lint/build.gradle
42. public class HungarianDetectorTest {e }e src/test/java/…/HungarianDetectorTest.java
43. import static com.android.tools.lint…TestLintTask.lint; public class HungarianDetectorTest {e @Test public void notHungarian() { lint() …; } }e src/test/java/…/HungarianDetectorTest.java
44. import static com.android.tools.lint…TestFiles.java; import static com.android.tools.lint…TestLintTask.lint; public class HungarianDetectorTest {e @Test public void notHungarian() { lint() .files( java(“" + "package test;\n" + "class TestClass {\n" + " public int foo;\n" + "}\n") ) …; } }e src/test/java/…/HungarianDetectorTest.java
45. public class HungarianDetectorTest {e @Test public void notHungarian() { lint() .files( java(“" + "package test;\n" + "class TestClass {\n" + " public int foo;\n" + "}\n") ) …; } }e src/test/java/…/HungarianDetectorTest.java
46. public class HungarianDetectorTest {e @Test public void notHungarian() { lint() .files( java(“" + "package test;\n" + "class TestClass {\n" + " public int foo;\n" + "}\n") ) .issues(ISSUE_HUNGARIAN) .run() .expectClean(); } }e src/test/java/…/HungarianDetectorTest.java
47. public class HungarianDetectorTest {e @Test public void staticMember() { lint() .files( java("" + "package test;\n" + "class TestClass {\n" + " static int sFoo = 5;\n" + “}\n") ) .issues(ISSUE_HUNGARIAN) .run() .expect(…); } }e src/test/java/…/HungarianDetectorTest.java
48. public class HungarianDetectorTest {e @Test public void staticMember() { lint() .files( java("" + "package test;\n" + "class TestClass {\n" + " static int sFoo = 5;\n" + “}\n") ) .issues(ISSUE_HUNGARIAN) .run() .expect("src/test/TestClass.java:3: Error: Y u Hungarian? ” + “[HungarianNotationNotAllowed]\n" + " static int sFoo = 5;\n" + " ~~~~~~~~~~~~~~~~~~~~\n" + "1 errors, 0 warnings\n"); } src/test/java/…/HungarianDetectorTest.java
50. apply plugin: 'com.android.application'
 
 android {a d…d
 }f
 
 dependencies { g…g
 }h app/build.gradle
51. apply plugin: 'com.android.application'
 apply plugin: 'com.kageiit.lintrules' 
 android {a
 lintOptions {e d…d }e
 }f
 
 dependencies { g…g 
 lintRules project(':lint')
 }h https://github.com/kageiit/gradle-lintrules-plugin app/build.gradle AGP 3.0-BETA5
52. apply plugin: 'com.android.application'
 
 android {a
 lintOptions {e d…d }e
 }f
 
 dependencies { g…g 
 lintChecks project(':lint')
 }h app/build.gradle
54. apply plugin: 'com.android.library'
 
 android {a
 lintOptions {e d…d }e
 }f
 
 dependencies { g…g 
 lintChecks project(':lint')
 }h library/build.gradle
59. class SnapshotDetector {e }e src/main/java/…/SnapshotDetector.java
60. class SnapshotDetector extends Detector implements GradleScanner {e }e src/main/java/…/SnapshotDetector.java
61. class SnapshotDetector extends Detector implements GradleScanner {e static final Issue ISSUE_SNAPSHOT = Issue.create("SnapshotVersionNotAllowed", …, Severity.ERROR, …); …e }e src/main/java/…/SnapshotDetector.java
62. class SnapshotDetector extends Detector implements GradleScanner {e static final Issue ISSUE_SNAPSHOT = Issue.create("SnapshotVersionNotAllowed", …, Severity.ERROR, new Implementation(SnapshotDetector.class, Scope.GRADLE_SCOPE)); …e }e src/main/java/…/SnapshotDetector.java
63. class SnapshotDetector extends Detector implements GradleScanner {e …e }e src/main/java/…/SnapshotDetector.java
64. class SnapshotDetector extends Detector implements GradleScanner {e …e @Override public void afterCheckProject(Context context) { Project project = context.getProject(); Dependencies compileDependencies = getCompileDependencies(project); … }e }e src/main/java/…/SnapshotDetector.java
65. class SnapshotDetector extends Detector implements GradleScanner {e …e @Override public void afterCheckProject(Context context) { Project project = context.getProject(); Dependencies compileDependencies = getCompileDependencies(project); Set<Library> allLibraries = Sets.newHashSet(); allLibraries.addAll(compileDependencies.getJavaLibraries()); allLibraries.addAll(compileDependencies.getLibraries()); … }e }e src/main/java/…/SnapshotDetector.java
66. class SnapshotDetector extends Detector implements GradleScanner {e …e @Override public void afterCheckProject(Context context) { Project project = context.getProject(); Dependencies compileDependencies = getCompileDependencies(project); Set<Library> allLibraries = Sets.newHashSet(); allLibraries.addAll(compileDependencies.getJavaLibraries()); allLibraries.addAll(compileDependencies.getLibraries()); for (Library library : allLibraries) { MavenCoordinates coordinates = library.getResolvedCoordinates(); checkIfSnapshot(context, coordinates); } }e }e src/main/java/…/SnapshotDetector.java
67. class SnapshotDetector extends Detector implements GradleScanner {e …e }e src/main/java/…/SnapshotDetector.java
68. class SnapshotDetector extends Detector implements GradleScanner {e …e void checkIfSnapshot(Context context, MavenCoordinates coordinates) { Project project = context.getProject(); String version = coordinates.getVersion(); … } }e src/main/java/…/SnapshotDetector.java
69. class SnapshotDetector extends Detector implements GradleScanner {e …e void checkIfSnapshot(Context context, MavenCoordinates coordinates) { Project project = context.getProject(); String version = coordinates.getVersion(); if (version.contains("SNAPSHOT")) { Location location = guessGradleLocation(context.getClient(), project.getDir(), version); context.report(ISSUE_SNAPSHOT, location, “Don’t use SNAPSHOT versions"); } } }e src/main/java/…/SnapshotDetector.java
70. class SnapshotDetector extends Detector implements GradleScanner {e …e void checkIfSnapshot(Context context, MavenCoordinates coordinates) { … context.report(ISSUE_SNAPSHOT, location, “Don’t use SNAPSHOT versions"); } } }e src/main/java/…/SnapshotDetector.java
71. class SnapshotDetector extends Detector implements GradleScanner {e …e Set<Position> alreadyReported = new LinkedHashSet<>(); void checkIfSnapshot(Context context, MavenCoordinates coordinates) { … if (!alreadyReported.contains(location)) { context.report(ISSUE_SNAPSHOT, location, “Don’t use SNAPSHOT versions"); alreadyReported.add(location); } } } }e src/main/java/…/SnapshotDetector.java
72. import static com.example.lint.HungarianDetector.ISSUE_HUNGARIAN; public class SampleRegistry extends IssueRegistry {e @Override public List<Issue> getIssues() { return Collections.singletonList(ISSUE_HUNGARIAN); }f }e src/main/java/…/SampleRegistry.java
73. import static com.example.lint.HungarianDetector.ISSUE_HUNGARIAN; public class SampleRegistry extends IssueRegistry {e @Override public List<Issue> getIssues() { return Arrays.asList(ISSUE_HUNGARIAN); }f }e src/main/java/…/SampleRegistry.java
74. import static com.example.lint.HungarianDetector.ISSUE_HUNGARIAN; import static com.example.lint.SnapshotDetector.ISSUE_SNAPSHOT; public class SampleRegistry extends IssueRegistry {e @Override public List<Issue> getIssues() { return Arrays.asList(ISSUE_HUNGARIAN, ISSUE_SNAPSHOT); }f }e src/main/java/…/SampleRegistry.java
77. /** * Lint client for command line usage. … * <p> * Minimal example: * <pre> * IssueRegistry registry = new BuiltinIssueRegistry(); * LintCliFlags flags = new LintCliFlags(); * LintCliClient client = new LintCliClient(flags); * int exitCode = client.run(registry, files); * </pre> */ @Beta public class LintCliClient extends LintClient { LintCliClient.java
85. jar { manifest { attributes(‘Lint-Registry-v2’: …) } }
88. class SampleRegistry extends IssueRegistry {e public List<Issue> getIssues() { return Arrays.asList(ISSUE_HUNGARIAN, …); }f }e
89. class SampleRegistry extends IssueRegistry {e public List<Issue> getIssues() { return Arrays.asList(ISSUE_HUNGARIAN, …); }f }e
90. public class HungarianDetectorTest {e @Test public void notHungarian() { lint() .files( java(“" + "package test;\n" + "class TestClass {\n" + " public int foo;\n" + "}\n") ) .issues(ISSUE_HUNGARIAN) .run() .expectClean(); } }e src/test/java/…/HungarianDetectorTest.java
91. public class HungarianDetectorTest {e @Test public void notHungarian() { lint() .files( java(“" + "package test;\n" + "class TestClass {\n" + " public int foo;\n" + "}\n") ) .issues(ISSUE_HUNGARIAN) .run() .expectClean(); } }e src/test/java/…/HungarianDetectorTest.java
92. class SampleRegistry extends IssueRegistry {e public List<Issue> getIssues() { return Arrays.asList(ISSUE_HUNGARIAN, …); }f }e
94. class HungarianDetector extends Detector … {e static final Issue ISSUE_HUNGARIAN = Issue.create(…, new Implementation(HungarianDetector.class, …)); …e }e
95. class HungarianDetector extends Detector … {e static final Issue ISSUE_HUNGARIAN = Issue.create(…, new Implementation(HungarianDetector.class, …)); …e }e
96. class HungarianDetector extends Detector … {e static final Issue ISSUE_HUNGARIAN = Issue.create(…, new Implementation(HungarianDetector.class, Scope.JAVA_FILE_SCOPE)); …e }e
97. class HungarianDetector extends Detector … {e static final Issue ISSUE_HUNGARIAN = Issue.create(…, new Implementation(HungarianDetector.class, Scope.JAVA_FILE_SCOPE)); …e }e
98. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 }
99. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } File
100. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File
101. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class
102. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList
103. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier
104. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method
105. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method ModifierList
106. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList
107. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList Identifier
108. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList Parameter Identifier
109. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList Parameter TypeElement Identifier
110. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList Parameter TypeElement Identifier Identifier
111. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList Parameter Identifier CodeBlock TypeElement Identifier
112. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement PackageStatement File Class ModifierList Identifier Method TypeElement ModifierList Parameter Identifier CodeBlock TypeElement Identifier
113. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement
114. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BinaryExpression
115. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BlockStatement BinaryExpression
116. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BlockStatement BinaryExpression ExpressionStatement AssignmentExpression
117. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BlockStatement BinaryExpression ExpressionStatement AssignmentExpression Identifier
118. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BlockStatement BinaryExpression ExpressionStatement AssignmentExpression Identifier LiteralExpression
119. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BlockStatement BinaryExpression BlockStatement ExpressionStatement AssignmentExpression Identifier LiteralExpression
120. package com.example;
 
 public class Example { private void foo(int b) {
 if (b != 5) {
 b = 3;
 } else {
 throw new RuntimeException();
 }
 }
 } IfStatement BlockStatement BinaryExpression BlockStatement ExpressionStatement AssignmentExpression Identifier LiteralExpression ThrowStatement
122. Lombok
123. Lombok PSI AGP 2.2
124. Lombok PSI UAST AGP 2.2 AGP 3.0
126. Lombok PSI UAST AGP 2.2 AGP 3.0
127. Lombok PSI UAST AGP 2.2 AGP 3.0 AGP 3.1
130. class WrongTimberUsageDetector … { 
 @Override public void visitMethod(JavaContext context, UCallExpression call, PsiMethod method) { String methodName = call.getMethodName(); JavaEvaluator evaluator = context.getEvaluator(); … } … }
131. class WrongTimberUsageDetector … { 
 @Override public void visitMethod(JavaContext context, UCallExpression call, PsiMethod method) { String methodName = call.getMethodName(); JavaEvaluator evaluator = context.getEvaluator(); if ("tag".equals(methodName) && evaluator.isMemberInClass(method, "timber.log.Timber") && context.getMainProject().getMinSdk() <= 23) { checkTagLength(context, call); } } }
132. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { List<UExpression> arguments = call.getValueArguments(); UExpression argument = arguments.get(0); } }
133. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { List<UExpression> arguments = call.getValueArguments(); UExpression argument = arguments.get(0); String tag = evaluateString(context, argument, true); } }
134. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { … if (tag.length() > 23) { Location location = context.getLocation(argument); context.report(ISSUE_TAG_LENGTH, argument, location, message); } } }
136. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { … if (tag.length() > 23) { Location location = context.getLocation(argument); context.report(ISSUE_TAG_LENGTH, argument, location, message); } } }
137. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { … LintFix fix = fix().replace().build(); context.report(ISSUE_TAG_LENGTH, argument, location, message, fix); … } }
138. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { … LintFix fix = fix().replace() .text(node.asSourceString()) .with("\"" + tag.substring(0, 23) + "\"") .build(); context.report(ISSUE_TAG_LENGTH, argument, location, message, fix); … } }
139. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { … int toTrim = tag.length() - 23; String s = toTrim == 1 ? "char" : toTrim + " chars”; LintFix fix = fix().replace() .text(node.asSourceString()) .with("\"" + tag.substring(0, 23) + "\"") .build(); context.report(ISSUE_TAG_LENGTH, argument, location, message, fix); … } }
140. class WrongTimberUsageDetector … {
 … void checkTagLength(JavaContext context, UCallExpression call) { … int toTrim = tag.length() - 23; String s = toTrim == 1 ? "char" : toTrim + " chars”; LintFix fix = fix().replace() .name("Strip last " + s) .text(node.asSourceString()) .with("\"" + tag.substring(0, 23) + "\"") .build(); context.report(ISSUE_TAG_LENGTH, argument, location, message, fix); … } }
142. @Test public void tagTooLong() { lint() .files(…) .issues(WrongTimberUsageDetector.ISSUE_TAG_LENGTH) .run() .expect("src/foo/Example.java:5: " + "Error: The logging tag can be at most 23 characters, " + "was 24 (abcdefghijklmnopqrstuvwx) [TimberTagLength]\n” + " Timber.tag(\"abcdefghijklmnopqrstuvwx\");\n" + " ~~~~~~~~~~~~~~~~~~~~~~~~~~\n” + "1 errors, 0 warnings\n”); }e
143. @Test public void tagTooLong() { lint() .files(…) .issues(WrongTimberUsageDetector.ISSUE_TAG_LENGTH) .run() .expect(…); }e
144. @Test public void tagTooLong() { lint() .files(…) .issues(WrongTimberUsageDetector.ISSUE_TAG_LENGTH) .run() .expect(…) .expectFixDiffs(""); }e
145. org.junit.ComparisonFailure: <Click to see difference> at org.junit.Assert.assertEquals(Assert.java:115) at org.junit.Assert.assertEquals(Assert.java:144) at com.android…LintFixVerifier.expectFixDiffs(LintFixVerifier.java:124) at com.android…TestLintResult.expectFixDiffs(TestLintResult.java:482) at timber.lint.WrongTimberUsageDetectorTest.tagTooLong(WrongTimber…:487)
147. @Test public void tagTooLong() { lint() .files(…) .issues(WrongTimberUsageDetector.ISSUE_TAG_LENGTH) .run() .expect(…) .expectFixDiffs(""); }e
148. @Test public void tagTooLong() { lint() .files(…) .issues(WrongTimberUsageDetector.ISSUE_TAG_LENGTH) .run() .expect(…) .expectFixDiffs("Fix for … line 4: Strip last char:\n" + "@@ -5 +5\n" + "- Timber.tag(\"abcdefghijklmnopqrstuvwx\");\n" + "+ Timber.tag(\"abcdefghijklmnopqrstuvw\");\n"); }e
149. Resources • Lint Google Group: https://goo.gl/LSUYqq • Lint sources: https://goo.gl/o8GCcD • Google samples: https://git.io/vdJDb • Butterknife lint checks: https://git.io/vPrdV • Timber lint checks: https://git.io/vPr2t
150. Lint to the Finish Line @jrodbx