Introduce Slf4jLogDeclaration to canonicalize slf4j's variable's de…

…claration

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/Slf4jLogDeclaration.java

@@ -0,0 +1,129 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.BugPattern.StandardTags.LIKELY_ERROR;
+import static com.google.errorprone.matchers.Matchers.allOf;
+import static com.google.errorprone.matchers.Matchers.hasIdentifier;
+import static com.google.errorprone.matchers.Matchers.isSubtypeOf;
+import static com.google.errorprone.matchers.Matchers.staticMethod;
+import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.ErrorProneFlags;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.fixes.SuggestedFixes;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MemberSelectTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.tree.Tree.Kind;
+import com.sun.source.tree.VariableTree;
+import javax.inject.Inject;
+import javax.lang.model.element.Modifier;
+import javax.lang.model.element.Name;
+import javax.tools.JavaFileObject;
+import tech.picnic.errorprone.bugpatterns.util.SourceCode;
+
+/**
+ * A {@link BugChecker} that warns when SLF4J declarations are not canonicalized across the project.
+ *
+ * @apiNote The default canonicalized logger name can be overriden through {@link ErrorProneFlags
+ *     flag arguments}.
+ */
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary = "Make sure SLF4J log declarations follow the SLF4J conventions inside classes.",
+    link = BUG_PATTERNS_BASE_URL + "Slf4jLogDeclaration",
+    linkType = CUSTOM,
+    severity = WARNING,
+    tags = LIKELY_ERROR)
+public final class Slf4jLogDeclaration extends BugChecker
+    implements ClassTreeMatcher, MethodInvocationTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final Matcher<ClassTree> TEST_CLASS_WITH_LOGGER =
+      allOf(hasIdentifier(isSubtypeOf("org.slf4j.Logger")));
+  private static final Matcher<Tree> LOGGER = isSubtypeOf("org.slf4j.Logger");
+  private static final String CANONICALIZED_LOGGER_NAME_FLAG =
+      "Slf4jLogDeclaration:CanonicalizedLoggerName";
+  private static final String DEFAULT_CANONICALIZED_LOGGER_NAME = "LOG";
+  private static final Matcher<ExpressionTree> GET_LOGGER_METHOD =
+      staticMethod().onDescendantOf("org.slf4j.LoggerFactory").named("getLogger");
+
+  private final String canonicalizedLoggerName;
+
+  /** Instantiates a default {@link Slf4jLogDeclaration} instance. */
+  public Slf4jLogDeclaration() {
+    this(ErrorProneFlags.empty());
+  }
+
+  /**
+   * Instantiates a customized {@link Slf4jLogDeclaration}.
+   *
+   * @param flags Any provided command line flags.
+   */
+  @Inject
+  Slf4jLogDeclaration(ErrorProneFlags flags) {
+    canonicalizedLoggerName = getCanonicalizedLoggerName(flags);
+  }
+
+  @Override
+  public Description matchClass(ClassTree tree, VisitorState state) {
+    if (tree.getKind() == Kind.INTERFACE || !TEST_CLASS_WITH_LOGGER.matches(tree, state)) {
+      return Description.NO_MATCH;
+    }
+
+    SuggestedFix.Builder fixBuilder = SuggestedFix.builder();
+    for (Tree member : tree.getMembers()) {
+      if (LOGGER.matches(member, state)) {
+        VariableTree variable = (VariableTree) member;
+        SuggestedFixes.addModifiers(
+                member, state, Modifier.PRIVATE, Modifier.STATIC, Modifier.FINAL)
+            .ifPresent(fixBuilder::merge);
+        if (!variable.getName().toString().startsWith(canonicalizedLoggerName)) {
+          fixBuilder.merge(SuggestedFixes.renameVariable(variable, canonicalizedLoggerName, state));
+        }
+      }
+    }
+
+    return describeMatch(tree, fixBuilder.build());
+  }
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    if (!GET_LOGGER_METHOD.matches(tree, state)) {
+      return Description.NO_MATCH;
+    }
+    SuggestedFix.Builder fixBuilder = SuggestedFix.builder();
+
+    for (ExpressionTree arg : tree.getArguments()) {
+      MemberSelectTree memberArgument = (MemberSelectTree) arg;
+
+      for (Tree typeDeclaration : state.getPath().getCompilationUnit().getTypeDecls()) {
+        if (typeDeclaration instanceof ClassTree) {
+          Name className = ((ClassTree) typeDeclaration).getSimpleName();
+          String argumentName = SourceCode.treeToString(memberArgument.getExpression(), state);
+
+          if (!className.contentEquals(argumentName)) {
+            fixBuilder.merge(
+                SuggestedFix.replace(arg, className + JavaFileObject.Kind.CLASS.extension));
+          }
+        }
+      }
+    }
+
+    return describeMatch(tree, fixBuilder.build());
+  }
+
+  private static String getCanonicalizedLoggerName(ErrorProneFlags flags) {
+    return flags.get(CANONICALIZED_LOGGER_NAME_FLAG).orElse(DEFAULT_CANONICALIZED_LOGGER_NAME);
+  }
+}

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/Slf4jLogDeclarationTest.java

@@ -0,0 +1,91 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import org.junit.jupiter.api.Test;
+
+final class Slf4jLogDeclarationTest {
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(Slf4jLogDeclaration.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import org.slf4j.Logger;",
+            "import org.slf4j.LoggerFactory;",
+            "",
+            "class A {",
+            "  Logger LOG1 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private Logger LOG2 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static Logger LOG3 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  static final Logger LOG4 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private final Logger LOG5 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG6 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger NOT_PROPER_LOGGER_NAME = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOGGER_WITH_WRONG_CLASS_AS_ARGUMENT = LoggerFactory.getLogger(B.class);",
+            "",
+            "  class B {}",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import org.slf4j.Logger;",
+            "import org.slf4j.LoggerFactory;",
+            "",
+            "class A {",
+            "  private static final Logger LOG1 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG2 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG3 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG4 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG5 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG6 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOG = LoggerFactory.getLogger(A.class);",
+            "",
+            "  private static final Logger LOGGER_WITH_WRONG_CLASS_AS_ARGUMENT = LoggerFactory.getLogger(A.class);",
+            "",
+            "  class B {}",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+
+  @Test
+  void doNotAddModifiersToDeclarationsInsideInterfaces() {
+    BugCheckerRefactoringTestHelper.newInstance(Slf4jLogDeclaration.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import org.slf4j.Logger;",
+            "import org.slf4j.LoggerFactory;",
+            "",
+            "interface A {",
+            "  Logger LOG = LoggerFactory.getLogger(A.class);",
+            "",
+            "  Logger LOG1 = LoggerFactory.getLogger(B.class);",
+            "",
+            "  class B {}",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import org.slf4j.Logger;",
+            "import org.slf4j.LoggerFactory;",
+            "",
+            "interface A {",
+            "  Logger LOG = LoggerFactory.getLogger(A.class);",
+            "",
+            "  Logger LOG1 = LoggerFactory.getLogger(A.class);",
+            "",
+            "  class B {}",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}