From 00eb2845083139b98ae785c7b70aaaa99236b140 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <tagir.valeev@jetbrains.com>
Date: Wed, 6 Sep 2023 10:34:46 +0200
Subject: [PATCH] [java-dfa] Support empty component in STR template
 (IDEA-327154)

GitOrigin-RevId: b7ef312b3b35b8aa7aa55ecb1f6bdc7a99c3aac6
---
 .../dataFlow/java/ControlFlowAnalyzer.java           | 12 +++++++++---
 .../dataFlow/java/inst/StringConcatInstruction.java  |  6 +++++-
 .../inspection/dataFlow/fixture/StringTemplates.java |  2 ++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/ControlFlowAnalyzer.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/ControlFlowAnalyzer.java
index fe07ce3cd083..7add501df752 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/ControlFlowAnalyzer.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/ControlFlowAnalyzer.java
@@ -37,6 +37,7 @@ import com.intellij.codeInspection.dataFlow.value.DfaControlTransferValue.Trap;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.pom.java.LanguageLevel;
 import com.intellij.psi.*;
+import com.intellij.psi.impl.source.tree.java.PsiEmptyExpressionImpl;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.InheritanceUtil;
 import com.intellij.psi.util.*;
@@ -1288,7 +1289,7 @@ public class ControlFlowAnalyzer extends JavaElementVisitor {
     for (int i = 0; i < count; i++) {
       PsiFragment fragment = fragments.get(i);
       Object value = fragment.getValue();
-      if (value instanceof String) {
+      if (value != null) {
         addInstruction(new PushValueInstruction(DfTypes.referenceConstant(value, stringType)));
       } else {
         pushUnknown();
@@ -1296,12 +1297,17 @@ public class ControlFlowAnalyzer extends JavaElementVisitor {
       if (i > 0) {
         addInstruction(new StringConcatInstruction(null, constraint));
       }
-      expressions.get(i).accept(this);
+      PsiExpression embeddedExpression = expressions.get(i);
+      if (embeddedExpression instanceof PsiEmptyExpressionImpl) {
+        addInstruction(new PushValueInstruction(DfTypes.NULL));
+      } else {
+        embeddedExpression.accept(this);
+      }
       addInstruction(new StringConcatInstruction(null, constraint));
     }
     PsiFragment lastFragment = fragments.get(count);
     Object value = lastFragment.getValue();
-    if (value instanceof String) {
+    if (value != null) {
       addInstruction(new PushValueInstruction(DfTypes.referenceConstant(value, stringType)));
     } else {
       pushUnknown();
diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/StringConcatInstruction.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/StringConcatInstruction.java
index 21811b3318c6..5465561dd26e 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/StringConcatInstruction.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/StringConcatInstruction.java
@@ -69,7 +69,11 @@ public class StringConcatInstruction extends EvalInstruction {
   
   @Nullable
   private static String getString(@NotNull DfaMemoryState state, DfaValue value) {
-    Object constant = state.getDfType(value).getConstantOfType(Object.class);
+    DfType dfType = state.getDfType(value);
+    if (dfType.equals(NULL)) {
+      return "null";
+    }
+    Object constant = dfType.getConstantOfType(Object.class);
     // Do not process float/double constants, as their string representation may depend on JDK version
     return constant instanceof String || constant instanceof Integer || constant instanceof Long || 
            constant instanceof Boolean ? constant.toString() : null;
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/StringTemplates.java b/java/java-tests/testData/inspection/dataFlow/fixture/StringTemplates.java
index 8ae43cff902a..511ec4bb9ccd 100644
--- a/java/java-tests/testData/inspection/dataFlow/fixture/StringTemplates.java
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/StringTemplates.java
@@ -38,6 +38,8 @@ class Main {
     if (<warning descr="Condition 's3.equals(\"a123b\")' is always 'true'">s3.equals("a123b")</warning>) {}
     String s4 = STR."x = \{x}";
     if (<warning descr="Condition 's4.length() >= 5 && s4.length() <= 15' is always 'true'"><warning descr="Condition 's4.length() >= 5' is always 'true'">s4.length() >= 5</warning> && <warning descr="Condition 's4.length() <= 15' is always 'true' when reached">s4.length() <= 15</warning></warning>) {}
+    String s5 = STR."hello\{}";
+    if (<warning descr="Condition 's5.equals(\"hellonull\")' is always 'true'">s5.equals("hellonull")</warning>) {}
   }
   
   void testIncomplete() {