From f2edccea666662ce93af29e397c50702a675f3f4 Mon Sep 17 00:00:00 2001
From: Cristian Adam <cristian.adam@gmail.com>
Date: Tue, 16 Jul 2019 10:42:00 +0200
Subject: find_package: Fix NO_MODULE under CMAKE_FIND_PACKAGE_PREFER_CONFIG

The module mode fallback added by commit 22e65d10c1 (find_package: Fixed
CMAKE_FIND_PACKAGE_PREFER_CONFIG Module fallback, 2019-06-13,
v3.15.0-rc2~6^2) should not be used unless the `find_package` call
allows module mode.  Doing so can lead to infinite recursion if a find
module tries to call config mode with `find_package(...  NO_MODULE)`.
Fix the logic and add a test case.

Fixes: #19478
---
 Source/cmFindPackageCommand.cxx                    |  5 ++--
 Tests/FindPackageTest/CMakeLists.txt               | 33 ++++++++++++++++++++++
 .../PreferConfigRecurse/ACMEConfig.cmake           |  1 +
 .../PreferConfigRecurse/FindACME.cmake             |  1 +
 4 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 Tests/FindPackageTest/PreferConfigRecurse/ACMEConfig.cmake
 create mode 100644 Tests/FindPackageTest/PreferConfigRecurse/FindACME.cmake

diff --git a/Source/cmFindPackageCommand.cxx b/Source/cmFindPackageCommand.cxx
index 828488f..1d4a8ed 100644
--- a/Source/cmFindPackageCommand.cxx
+++ b/Source/cmFindPackageCommand.cxx
@@ -823,8 +823,9 @@ bool cmFindPackageCommand::HandlePackageMode(
     }
   }
 
-  if (this->Makefile->IsOn("CMAKE_FIND_PACKAGE_PREFER_CONFIG") && !found &&
-      handlePackageModeType == HandlePackageModeType::Config) {
+  if (this->UseFindModules && !found &&
+      handlePackageModeType == HandlePackageModeType::Config &&
+      this->Makefile->IsOn("CMAKE_FIND_PACKAGE_PREFER_CONFIG")) {
     // Config mode failed. Allow Module case.
     result = false;
   }
diff --git a/Tests/FindPackageTest/CMakeLists.txt b/Tests/FindPackageTest/CMakeLists.txt
index affe5d5..da79f5d 100644
--- a/Tests/FindPackageTest/CMakeLists.txt
+++ b/Tests/FindPackageTest/CMakeLists.txt
@@ -579,6 +579,26 @@ endif()
 
 set(CMAKE_FIND_PACKAGE_PREFER_CONFIG OFF)
 set(CMAKE_PREFIX_PATH)
+set(CMAKE_MODULE_PATH)
+
+############################################################################
+##Test FIND_PACKAGE CMAKE_FIND_PACKAGE_PREFER_CONFIG - Do not recurse
+
+# No CMAKE_PREFIX_PATH
+set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/PreferConfigRecurse)
+
+# Now prefer config mode
+set(CMAKE_FIND_PACKAGE_PREFER_CONFIG ON)
+unset(ACME_FOUND)
+unset(ACME_CONFIG)
+
+find_package(ACME)
+if(ACME_FOUND AND ACME_CONFIG)
+    message(SEND_ERROR "Incorrectly found ACME in CONFIG mode, from the MODULE package")
+endif()
+
+set(CMAKE_FIND_PACKAGE_PREFER_CONFIG OFF)
+set(CMAKE_MODULE_PATH)
 
 ############################################################################
 ##Test find_package CMAKE_FIND_PACKAGE_PREFER_CONFIG with module fallback
@@ -592,3 +612,16 @@ find_package(ACME REQUIRED)
 if(NOT ACME_FOUND)
     message(SEND_ERROR "Did not find ACME package")
 endif()
+
+############################################################################
+##Test find_package CMAKE_FIND_PACKAGE_PREFER_CONFIG with NO_MODULE
+
+set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/PreferConfigOnlyModule)
+
+set(CMAKE_FIND_PACKAGE_PREFER_CONFIG ON)
+
+find_package(ACME NO_MODULE)
+
+if(ACME_FOUND)
+    message(SEND_ERROR "Should not find ACME package")
+endif()
diff --git a/Tests/FindPackageTest/PreferConfigRecurse/ACMEConfig.cmake b/Tests/FindPackageTest/PreferConfigRecurse/ACMEConfig.cmake
new file mode 100644
index 0000000..7a4e1b3
--- /dev/null
+++ b/Tests/FindPackageTest/PreferConfigRecurse/ACMEConfig.cmake
@@ -0,0 +1 @@
+set(ACME_FOUND TRUE)
diff --git a/Tests/FindPackageTest/PreferConfigRecurse/FindACME.cmake b/Tests/FindPackageTest/PreferConfigRecurse/FindACME.cmake
new file mode 100644
index 0000000..9bdc7db
--- /dev/null
+++ b/Tests/FindPackageTest/PreferConfigRecurse/FindACME.cmake
@@ -0,0 +1 @@
+find_package(ACME NO_MODULE)
-- 
cgit v0.12