IG: warn on equalsIgnoreCase(), compareTo() and compareToIgnoreCase() call to itself (IDEA-162797)

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/EqualsWithItselfInspection.java

@@ -16,7 +16,8 @@
 package com.siyeh.ig.bugs;
 
 import com.intellij.psi.*;
-import com.siyeh.InspectionGadgetsBundle;import com.siyeh.ig.BaseInspection;
+import com.siyeh.InspectionGadgetsBundle;
+import com.siyeh.ig.BaseInspection;
 import com.siyeh.ig.BaseInspectionVisitor;
 import com.siyeh.ig.psiutils.EquivalenceChecker;
 import com.siyeh.ig.psiutils.MethodCallUtils;
@@ -52,7 +53,10 @@ public class EqualsWithItselfInspection extends BaseInspection {
     @Override
     public void visitMethodCallExpression(PsiMethodCallExpression expression) {
       super.visitMethodCallExpression(expression);
-      if (!MethodCallUtils.isEqualsCall(expression)) {
+      if (!MethodCallUtils.isEqualsCall(expression) &&
+          !MethodCallUtils.isEqualsIgnoreCaseCall(expression) &&
+          !MethodCallUtils.isCompareToCall(expression) &&
+          !MethodCallUtils.isCompareToIgnoreCaseCall(expression)) {
         return;
       }
       final PsiReferenceExpression methodExpression = expression.getMethodExpression();

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/psiutils/MethodCallUtils.java

@@ -72,6 +72,15 @@ public class MethodCallUtils {
     return MethodUtils.isCompareTo(method);
   }
 
+  public static boolean isCompareToIgnoreCaseCall(@NotNull PsiMethodCallExpression expression) {
+    final PsiReferenceExpression methodExpression = expression.getMethodExpression();
+    if (!"compareToIgnoreCase".equals(methodExpression.getReferenceName())) {
+      return false;
+    }
+    final PsiMethod method = expression.resolveMethod();
+    return MethodUtils.isCompareToIgnoreCase(method);
+  }
+
   public static boolean isEqualsCall(PsiMethodCallExpression expression) {
     final PsiReferenceExpression methodExpression = expression.getMethodExpression();
     final String name = methodExpression.getReferenceName();
@@ -82,6 +91,16 @@ public class MethodCallUtils {
     return MethodUtils.isEquals(method);
   }
 
+  public static boolean isEqualsIgnoreCaseCall(PsiMethodCallExpression expression) {
+    final PsiReferenceExpression methodExpression = expression.getMethodExpression();
+    final String name = methodExpression.getReferenceName();
+    if (!HardcodedMethodConstants.EQUALS_IGNORE_CASE.equals(name)) {
+      return false;
+    }
+    final PsiMethod method = expression.resolveMethod();
+    return MethodUtils.isEqualsIgnoreCase(method);
+  }
+
   public static boolean isSimpleCallToMethod(@NotNull PsiMethodCallExpression expression, @NonNls @Nullable String calledOnClassName,
     @Nullable PsiType returnType, @NonNls @Nullable String methodName, @NonNls @Nullable String... parameterTypeStrings) {
     if (parameterTypeStrings == null) {

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/psiutils/MethodUtils.java

@@ -49,6 +49,15 @@ public class MethodUtils {
       && InheritanceUtil.isInheritor(method.getContainingClass(), CommonClassNames.JAVA_LANG_COMPARABLE);
   }
 
+  @Contract("null -> false")
+  public static boolean isCompareToIgnoreCase(@Nullable PsiMethod method) {
+    if (method == null) {
+      return false;
+    }
+    final PsiClassType stringType = TypeUtils.getStringType(method);
+    return methodMatches(method, "java.lang.String", PsiType.INT, "compareToIgnoreCase", stringType);
+  }
+
   @Contract("null -> false")
   public static boolean isHashCode(@Nullable PsiMethod method) {
     return method != null && methodMatches(method, null, PsiType.INT, HardcodedMethodConstants.HASH_CODE);
@@ -77,6 +86,15 @@ public class MethodUtils {
     return methodMatches(method, null, PsiType.BOOLEAN, HardcodedMethodConstants.EQUALS, objectType);
   }
 
+  @Contract("null -> false")
+  public static boolean isEqualsIgnoreCase(@Nullable PsiMethod method) {
+    if (method == null) {
+      return false;
+    }
+    final PsiClassType stringType = TypeUtils.getStringType(method);
+    return methodMatches(method, "java.lang.String", PsiType.BOOLEAN, HardcodedMethodConstants.EQUALS_IGNORE_CASE, stringType);
+  }
+
   /**
    * @param method              the method to compare to.
    * @param containingClassName the name of the class which contiains the

plugins/InspectionGadgets/src/inspectionDescriptions/EqualsWithItself.html

@@ -1,8 +1,8 @@
 <html>
 <body>
-Reports call to <b>equals()</b> were an object is compared for equality with itself.
-This means that the argument and the qualifier to the call are identical.
-In this case <b>equals()</b> will always return <b>true</b>.
+Reports calls to <b>equals()</b> or <b>compareTo()</b> were an object is compared for equality with itself.
+This means the argument and the qualifier to the call are identical, and it will always return <b>true</b> for <b>equals()</b>
+or always <b>0</b> for <b>compareTo()</b>.
 <!-- tooltip end -->
 <p>
 </body>

plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/equals_with_itself/EqualsWithItself.java

@@ -24,4 +24,20 @@ class EqualsWithItself {
   public Object build() {
     return new Object();
   }
+
+  boolean string(String s) {
+    return s.<warning descr="'equalsIgnoreCase()' called on itself">equalsIgnoreCase</warning>(s);
+  }
+
+  int compareTo(String s) {
+    return s.<warning descr="'compareTo()' called on itself">compareTo</warning>(s);
+  }
+
+  int compareToIgnoreCase(String s) {
+    return s.<warning descr="'compareToIgnoreCase()' called on itself">compareToIgnoreCase</warning>(s);
+  }
+
+  boolean safe(String a, String b) {
+    return a.equals(b) && a.equalsIgnoreCase(b) && a.compareTo(b) == 0;
+  }
 }