From 692ef5ecea850e8de349ba2e2119257300bd0da9 Mon Sep 17 00:00:00 2001
From: Andrej730 <azhilenkov@gmail.com>
Date: Thu, 20 Nov 2025 20:01:56 +0500
Subject: [PATCH] cmake - fix error finding `Eigen::Eigen` target #7390

`EIgen::Eigen` target used in #7340 for linking exists only if there's a cmake config, while there are cases when there's just include directory. Added same name interface target to mimic config.
---
 cmake/CMakeLists.txt   | 20 +++-----------------
 cmake/FindEigen3.cmake | 27 +++++++++++++++++++++++++++
 win/run-cmake.bat      |  2 ++
 3 files changed, 32 insertions(+), 17 deletions(-)
 create mode 100644 cmake/FindEigen3.cmake

diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index 821ceed891..1cb01a814e 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -200,7 +200,6 @@ endif()
 
 UNIFY_ENVVARS_AND_CACHE(BOOST_ROOT)
 UNIFY_ENVVARS_AND_CACHE(BOOST_LIBRARYDIR)
-UNIFY_ENVVARS_AND_CACHE(EIGEN_DIR)
 
 if(NOT MINIMAL_BUILD)
     UNIFY_ENVVARS_AND_CACHE(PYTHON_INCLUDE_DIR)
@@ -487,25 +486,12 @@ else()
 endif(MSVC)
 
 
-# Ensure other dependencies are provided.
-if(NOT EXISTS "${EIGEN_DIR}")
-    find_package(Eigen3 CONFIG)
-    if(Eigen3_DIR)
-        message(STATUS "Eigen3: found config at '${Eigen3_DIR}'.")
-    else()
-        message(
-            FATAL_ERROR
-            "EIGEN_DIR is not provided or provided folder doesn't exist (current value: '${EIGEN_DIR}'). "
-            "Also couldn't find Eigen3 as a package."
-        )
-    endif()
-    link_libraries(Eigen3::Eigen)
-endif()
-
+find_package(Eigen3 REQUIRED)
+link_libraries(Eigen3::Eigen)
 
 include_directories(${INCLUDE_DIRECTORIES} ${OCC_INCLUDE_DIR} ${OPENCOLLADA_INCLUDE_DIRS}
 	${Boost_INCLUDE_DIRS} ${LIBXML2_INCLUDE_DIR} ${JSON_INCLUDE_DIR} ${HDF5_INCLUDE_DIR}
-    ${EIGEN_DIR} ${CGAL_INCLUDE_DIR} ${GMP_INCLUDE_DIR} ${MPFR_INCLUDE_DIR} ${USD_INCLUDE_DIR}
+    ${CGAL_INCLUDE_DIR} ${GMP_INCLUDE_DIR} ${MPFR_INCLUDE_DIR} ${USD_INCLUDE_DIR}
     ${TBB_INCLUDE_DIR}
 )
 
diff --git a/cmake/FindEigen3.cmake b/cmake/FindEigen3.cmake
new file mode 100644
index 0000000000..e886310e89
--- /dev/null
+++ b/cmake/FindEigen3.cmake
@@ -0,0 +1,27 @@
+#
+# Input variables:
+# - `EIGEN_DIR`
+# If input variables are not specified, try to find Eigen3 config.
+# Input variables could also be provided as environment variables.
+#
+# Output targets:
+# - `Eigen3::Eigen`
+
+UNIFY_ENVVARS_AND_CACHE(EIGEN_DIR)
+
+if(EXISTS "${EIGEN_DIR}")
+    # Mimic Eigen3Config.cmake target.
+    add_library(Eigen3::Eigen INTERFACE IMPORTED)
+    target_include_directories(Eigen3::Eigen INTERFACE "${EIGEN_DIR}")
+else()
+    find_package(Eigen3 CONFIG)
+    if(Eigen3_DIR)
+        message(STATUS "Eigen3: found config at '${Eigen3_DIR}'.")
+    else()
+        message(
+            FATAL_ERROR
+            "EIGEN_DIR is not provided or provided folder doesn't exist (current value: '${EIGEN_DIR}'). "
+            "Also couldn't find Eigen3 as a package."
+        )
+    endif()
+endif()
diff --git a/win/run-cmake.bat b/win/run-cmake.bat
index 9dfbbd6df3..68863fc847 100755
--- a/win/run-cmake.bat
+++ b/win/run-cmake.bat
@@ -110,6 +110,8 @@ set GMP_INCLUDE_DIR=%INSTALL_DIR%\mpir
 set GMP_LIBRARY_DIR=%INSTALL_DIR%\mpir
 set MPFR_INCLUDE_DIR=%INSTALL_DIR%\mpfr
 set MPFR_LIBRARY_DIR=%INSTALL_DIR%\mpfr
+:: We don't install Eigen currently,
+:: so there's no Eigen3config.cmake and therefore we provide path explicitly.
 set EIGEN_DIR=%INSTALL_DIR%\Eigen
 set USD_INCLUDE_DIR=%INSTALL_DIR%\usd\include
 set USD_LIBRARY_DIR=%INSTALL_DIR%\usd\lib