From e6495387cef8848daf93cb0be6c9f3d2210479da Mon Sep 17 00:00:00 2001
From: Morgan Bartholomew <morgan.bartholomew@jetbrains.com>
Date: Tue, 10 Mar 2026 23:38:28 +1000
Subject: [PATCH] misc python: support unions in `PyStringFormatInspection`

(cherry picked from commit b57bf859f88dbe3508e87c5d88609e84f8ae0452)

GitOrigin-RevId: 21e3b7972f3efe1c4e5f4d52d75f5c21d3bef901
---
 .../inspections/PyStringFormatInspection.java    | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/python/python-psi-impl/src/com/jetbrains/python/inspections/PyStringFormatInspection.java b/python/python-psi-impl/src/com/jetbrains/python/inspections/PyStringFormatInspection.java
index 133224ac3297..89b4c3360343 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/inspections/PyStringFormatInspection.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/inspections/PyStringFormatInspection.java
@@ -46,6 +46,7 @@ import com.jetbrains.python.psi.types.PyTupleType;
 import com.jetbrains.python.psi.types.PyType;
 import com.jetbrains.python.psi.types.PyTypeChecker;
 import com.jetbrains.python.psi.types.PyTypeParser;
+import com.jetbrains.python.psi.types.PyTypeUtil;
 import com.jetbrains.python.psi.types.PyUnionType;
 import com.jetbrains.python.psi.types.TypeEvalContext;
 import org.jetbrains.annotations.NotNull;
@@ -166,12 +167,15 @@ public final class PyStringFormatInspection extends PyInspection {
         else if (PsiTreeUtil.instanceOf(rightExpression, SIMPLE_RHS_EXPRESSIONS)) {
           if (s != null) {
             final PyType rightType = myTypeEvalContext.getType(rightExpression);
-            if (rightType instanceof PyTupleType tupleType) {
-              matchEntireTupleTypes(problemTarget, tupleType);
-              return tupleType.getElementCount();
-            }
-            else {
-              checkExpressionType(rightExpression, s, problemTarget);
+
+            for (var member : PyTypeUtil.toStream(rightType)) {
+              if (member instanceof PyTupleType tupleType) {
+                matchEntireTupleTypes(problemTarget, tupleType);
+                return tupleType.getElementCount();
+              }
+              else {
+                checkExpressionType(rightExpression, s, problemTarget);
+              }
             }
           }
           return 1;