From 8bb949fc30677ea7a5c71b91f176dbbb12f15d5c Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Mon, 23 Oct 2023 10:53:28 -0400
Subject: source_group: Restore behavior of TREE with empty FILES

Since commit d85238a2f2 (source_group: Fix TREE without FILES,
2023-06-29, v3.28.0-rc1~399^2~1) we incorrectly treat a FILES
argument with no values as if it were not given at all.

Fixes: #25353
---
 Source/cmSourceGroupCommand.cxx | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Source/cmSourceGroupCommand.cxx b/Source/cmSourceGroupCommand.cxx
index 4b1685f..bb92856 100644
--- a/Source/cmSourceGroupCommand.cxx
+++ b/Source/cmSourceGroupCommand.cxx
@@ -280,8 +280,11 @@ static bool processTree(cmMakefile& mf, ParsedArguments& parsedArguments,
     ? ""
     : parsedArguments[kPrefixOptionName].front();
 
-  std::vector<std::string> files = parsedArguments[kFilesOptionName];
-  if (files.empty()) {
+  std::vector<std::string> files;
+  auto filesArgIt = parsedArguments.find(kFilesOptionName);
+  if (filesArgIt != parsedArguments.end()) {
+    files = filesArgIt->second;
+  } else {
     const std::vector<std::unique_ptr<cmSourceFile>>& srcFiles =
       mf.GetSourceFiles();
     for (const auto& srcFile : srcFiles) {
-- 
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