From 02a063f866a245662896589c35875f61d3303e45 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <tagir.valeev@jetbrains.com>
Date: Fri, 26 Sep 2025 18:03:07 +0200
Subject: [PATCH] [java-dfa] Test for IDEA-375523 False positive "Argument
 might be null" with Guava Streams

GitOrigin-RevId: b6569cf1c45c5de3486d823f37a1426f81d0382d
---
 .../fixture/GenericVarargNullability.java     | 44 +++++++++++++++++++
 .../DataFlowInspection21Test.java             |  4 ++
 2 files changed, 48 insertions(+)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/GenericVarargNullability.java

diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/GenericVarargNullability.java b/java/java-tests/testData/inspection/dataFlow/fixture/GenericVarargNullability.java
new file mode 100644
index 000000000000..a15259e92a0c
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/GenericVarargNullability.java
@@ -0,0 +1,44 @@
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.NotNullByDefault;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+abstract class StreamsNull {
+  @NotNullByDefault
+  static class Streams {
+    @SafeVarargs
+    static native <T extends @Nullable Object> Stream<T> concat(Stream<? extends T>... streams);
+  }
+
+  List<String> calc(Stream<Leg> positions, Stream<Leg> leg1, Stream<Leg> leg2, double v) {
+    return Streams.concat(
+        positions.map(Leg::getInstrument),
+        leg1.map(Leg::getInstrument),
+        leg2.map(Leg::getInstrument)
+      )
+      .filter(i -> isInteresting(i, v))
+      .toList();
+  }
+
+  List<String> calc2(Stream<Leg> positions, Stream<Leg> leg1, Stream<Leg> leg2, double v) {
+    return Streams.concat(
+        positions.map(Leg::getInstrument),
+        leg1.map(Leg::getInstrument2),
+        leg2.map(Leg::getInstrument)
+      )
+      .filter(i -> isInteresting(<warning descr="Argument 'i' might be null">i</warning>, v))
+      .toList();
+  }
+
+  protected abstract boolean isInteresting(@NotNull String instrument,
+                                           double v);
+}
+
+interface Leg {
+  @NotNull
+  String getInstrument();
+  @Nullable
+  String getInstrument2();
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java
index e65611bfa14a..07f9fc252699 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection21Test.java
@@ -215,6 +215,10 @@ public class DataFlowInspection21Test extends DataFlowInspectionTestCase {
   public void testGuavaIterablesProblems() {
     doTest();
   }
+  
+  public void testGenericVarargNullability() {
+    doTest();
+  }
 
   public void testPassthroughGenericParameter() {
     doTestWith((dfi, cvi) -> dfi.TREAT_UNKNOWN_MEMBERS_AS_NULLABLE = true);