Use ROOT_LIBRARY_PATH and adjust other environment variables (#45109)

* Use ROOT_LIBRARY_PATH and adjust other environment variables

* Accommodate versions older than ROOT 6.26

* Use os instead of pathlib

1 files changed, 21 insertions, 7 deletions

diff --git a/var/spack/repos/builtin/packages/root/package.py b/var/spack/repos/builtin/packages/root/package.py
index c441dea5c1..eab2be9e5c 100644
--- a/var/spack/repos/builtin/packages/root/package.py
+++ b/var/spack/repos/builtin/packages/root/package.py
@@ -4,6 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 
+import os
 import sys
 
 from spack.operating_systems.mac_os import macos_version
@@ -773,6 +774,15 @@ class Root(CMakePackage):
             # warnings when building against ROOT
             env.unset("MACOSX_DEPLOYMENT_TARGET")
 
+    @property
+    def root_library_path(self):
+        # Where possible, we do not use LD_LIBRARY_PATH as that is non-portable
+        # and pollutes the standard library-loading mechanisms on Linux systems.
+        # The ROOT_LIBRARY_PATH environment variable was added to ROOT 6.26.
+        if self.spec.satisfies("@:6.25"):
+            return "LD_LIBRARY_PATH"
+        return "ROOT_LIBRARY_PATH"
+
     def setup_run_environment(self, env):
         env.set("ROOTSYS", self.prefix)
         env.set("ROOT_VERSION", "v{0}".format(self.version.up_to(1)))
@@ -780,6 +790,8 @@ class Root(CMakePackage):
         # the following vars are copied from thisroot.sh; silence a cppyy warning
         env.set("CLING_STANDARD_PCH", "none")
         env.set("CPPYY_API_PATH", "none")
+        if "+rpath" not in self.spec:
+            env.prepend_path(self.root_library_path, self.prefix.lib.root)
 
     def setup_dependent_build_environment(
         self, env: spack.util.environment.EnvironmentModifications, dependent_spec
@@ -791,7 +803,7 @@ class Root(CMakePackage):
         env.append_path("CMAKE_MODULE_PATH", self.prefix.cmake)
         env.prepend_path("ROOT_INCLUDE_PATH", dependent_spec.prefix.include)
         if "+rpath" not in self.spec:
-            env.prepend_path("LD_LIBRARY_PATH", self.prefix.lib.root)
+            env.prepend_path(self.root_library_path, self.prefix.lib.root)
         if "platform=darwin" in self.spec:
             # Newer deployment targets cause fatal errors in rootcling
             env.unset("MACOSX_DEPLOYMENT_TARGET")
@@ -799,10 +811,12 @@ class Root(CMakePackage):
     def setup_dependent_run_environment(
         self, env: spack.util.environment.EnvironmentModifications, dependent_spec
     ):
-        env.set("ROOTSYS", self.prefix)
-        env.set("ROOT_VERSION", "v{0}".format(self.version.up_to(1)))
-        env.prepend_path("PYTHONPATH", self.prefix.lib.root)
-        env.prepend_path("PATH", self.prefix.bin)
         env.prepend_path("ROOT_INCLUDE_PATH", dependent_spec.prefix.include)
-        if "+rpath" not in self.spec:
-            env.prepend_path("LD_LIBRARY_PATH", self.prefix.lib.root)
+        # For dependents that build dictionaries, ROOT needs to know where the
+        # dictionaries have been installed.  This can be facilitated by
+        # automatically prepending dependent package library paths to
+        # ROOT_LIBRARY_PATH (for @6.26:) or LD_LIBRARY_PATH (for older
+        # versions).
+        for lib_path in (dependent_spec.prefix.lib, dependent_spec.prefix.lib64):
+            if os.path.exists(lib_path):
+                env.prepend_path(self.root_library_path, lib_path)