IgnoreResultOfCallInspection: report Optional.get() under isPresent() (IDEA-205785)

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/CommonDataflow.java

@@ -28,6 +28,7 @@ public class CommonDataflow {
     @Nullable Set<Object> myPossibleValues = Collections.emptySet();
     // null = top; empty = bottom
     @Nullable Set<Object> myNotValues = null;
+    boolean myMayFailByContract = false;
 
     DataflowPoint() {}
 
@@ -35,6 +36,7 @@ public class CommonDataflow {
       myFacts = other.myFacts;
       myPossibleValues = other.myPossibleValues;
       myNotValues = other.myNotValues == null || other.myNotValues.isEmpty() ? other.myNotValues : new THashSet<>(other.myNotValues);
+      myMayFailByContract = other.myMayFailByContract;
     }
 
     void addNotValues(DfaMemoryStateImpl memState, DfaValue value) {
@@ -109,6 +111,10 @@ public class CommonDataflow {
 
     void add(PsiExpression expression, DfaMemoryStateImpl memState, DfaValue value) {
       DataflowPoint point = myData.computeIfAbsent(expression, e -> new DataflowPoint());
+      if (DfaConstValue.isContractFail(value)) {
+        point.myMayFailByContract = true;
+        return;
+      }
       if (point.myFacts != DfaFactMap.EMPTY) {
         PsiElement parent = PsiUtil.skipParenthesizedExprUp(expression.getParent());
         if (parent instanceof PsiConditionalExpression &&
@@ -147,6 +153,18 @@ public class CommonDataflow {
       return myData.containsKey(expression);
     }
 
+    /**
+     * Returns true if given call cannot fail according to its contracts 
+     * (e.g. {@code Optional.get()} executed under {@code Optional.isPresent()}).
+     * 
+     * @param call call to check
+     * @return true if it cannot fail by contract; false if unknown or can fail
+     */
+    public boolean cannotFailByContract(PsiCallExpression call) {
+      DataflowPoint point = myData.get(call);
+      return point != null && !point.myMayFailByContract;
+    }
+    
     /**
      * Returns a fact of specific type which is known for given expression or null if fact is not known
      *
@@ -289,7 +307,7 @@ public class CommonDataflow {
                                      @NotNull PsiExpression expression,
                                      @Nullable TextRange range,
                                      @NotNull DfaMemoryState state) {
-      if (range == null && !DfaConstValue.isContractFail(value)) {
+      if (range == null) {
         // Do not track instructions which cover part of expression
         myResult.add(expression, (DfaMemoryStateImpl)state, value);
       }

plugins/InspectionGadgets/src/com/siyeh/ig/bugs/IgnoreResultOfCallInspection.java

@@ -16,6 +16,7 @@
 package com.siyeh.ig.bugs;
 
 import com.intellij.codeInsight.AnnotationUtil;
+import com.intellij.codeInspection.dataFlow.CommonDataflow;
 import com.intellij.codeInspection.dataFlow.ContractReturnValue;
 import com.intellij.codeInspection.dataFlow.JavaMethodContractUtil;
 import com.intellij.codeInspection.dataFlow.MethodContract;
@@ -201,7 +202,7 @@ public class IgnoreResultOfCallInspection extends BaseInspection {
 
       if (isKnownExceptionalSideEffectCaught(call)) return;
 
-      if (isPureMethod(method)) {
+      if (isPureMethod(method, call)) {
         registerMethodCallOrRefError(call, aClass);
         return;
       }
@@ -272,12 +273,14 @@ public class IgnoreResultOfCallInspection extends BaseInspection {
       return false;
     }
 
-    private boolean isPureMethod(PsiMethod method) {
+    private boolean isPureMethod(PsiMethod method, PsiExpression call) {
       final boolean honorInferred = Registry.is("ide.ignore.call.result.inspection.honor.inferred.pure");
       if (!honorInferred && !JavaMethodContractUtil.hasExplicitContractAnnotation(method)) return false;
-      return JavaMethodContractUtil.isPure(method) &&
-             !SideEffectChecker.mayHaveExceptionalSideEffect(method) &&
-             !hasTrivialReturnValue(method);
+      if (!JavaMethodContractUtil.isPure(method) || hasTrivialReturnValue(method)) return false;
+      if (!SideEffectChecker.mayHaveExceptionalSideEffect(method)) return true;
+      if (!(call instanceof PsiCallExpression)) return false;
+      CommonDataflow.DataflowResult result = CommonDataflow.getDataflowResult(call);
+      return result != null && result.cannotFailByContract((PsiCallExpression)call);
     }
 
     private boolean hasTrivialReturnValue(PsiMethod method) {

plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/IgnoreResultOfCallInspectionTest.groovy

@@ -348,6 +348,7 @@ public static int atLeast(int min, int actual, String varName) {
   }
   
   void testInForExpressionList() {
+    //noinspection StatementWithEmptyBody
     doTest """class X {
   void test(String s) {
     for(int i=0; i<10; i++, s./*Result of 'String.trim()' is ignored*/trim/**/()) {}
@@ -356,12 +357,23 @@ public static int atLeast(int min, int actual, String varName) {
   }
 
   void testInSwitchExpression() {
+    //noinspection SwitchStatementWithTooFewBranches
     doTest """class X {
   String test(String s) {
     return switch(s) {
       default -> s.trim();
     };
   }
+}"""
+  }
+  
+  void testOptionalGet() {
+    //noinspection ALL
+    doTest """class X {
+  void test(java.util.Optional<String> opt) {
+    opt.get();
+    if (opt.isPresent()) opt./*Result of 'Optional.get()' is ignored*/get/**/();
+  }
 }"""
   }
 }