build_environment.py: deal with rpathing identical packages (#44219)

When multiple gcc-runtime packages exist in the same link sub-dag, only rpath
the latest.

lib/spack/spack/build_environment.py

@@ -43,7 +43,7 @@
 from collections import defaultdict
 from enum import Flag, auto
 from itertools import chain
-from typing import List, Set, Tuple
+from typing import Dict, List, Set, Tuple
 
 import llnl.util.tty as tty
 from llnl.string import plural
@@ -730,12 +730,28 @@ def _static_to_shared_library(arch, compiler, static_lib, shared_lib=None, **kwa
     return compiler(*compiler_args, output=compiler_output)
 
 
-def get_rpath_deps(pkg):
-    """Return immediate or transitive RPATHs depending on the package."""
-    if pkg.transitive_rpaths:
-        return [d for d in pkg.spec.traverse(root=False, deptype=("link"))]
-    else:
-        return pkg.spec.dependencies(deptype="link")
+def _get_rpath_deps_from_spec(
+    spec: spack.spec.Spec, transitive_rpaths: bool
+) -> List[spack.spec.Spec]:
+    if not transitive_rpaths:
+        return spec.dependencies(deptype=dt.LINK)
+
+    by_name: Dict[str, spack.spec.Spec] = {}
+
+    for dep in spec.traverse(root=False, deptype=dt.LINK):
+        lookup = by_name.get(dep.name)
+        if lookup is None:
+            by_name[dep.name] = dep
+        elif lookup.version < dep.version:
+            by_name[dep.name] = dep
+
+    return list(by_name.values())
+
+
+def get_rpath_deps(pkg: spack.package_base.PackageBase) -> List[spack.spec.Spec]:
+    """Return immediate or transitive dependencies (depending on the package) that need to be
+    rpath'ed. If a package occurs multiple times, the newest version is kept."""
+    return _get_rpath_deps_from_spec(pkg.spec, pkg.transitive_rpaths)
 
 
 def get_rpaths(pkg):

lib/spack/spack/test/build_environment.py

@@ -14,6 +14,7 @@
 
 import spack.build_environment
 import spack.config
+import spack.deptypes as dt
 import spack.package_base
 import spack.spec
 import spack.util.spack_yaml as syaml
@@ -716,3 +717,21 @@ def test_build_system_globals_only_set_on_root_during_build(default_mock_concret
     for depth, spec in root.traverse(depth=True, root=True):
         for variable in build_variables:
             assert hasattr(spec.package.module, variable) == should_be_set(depth)
+
+
+def test_rpath_with_duplicate_link_deps():
+    """If we have two instances of one package in the same link sub-dag, only the newest version is
+    rpath'ed. This is for runtime support without splicing."""
+    runtime_1 = spack.spec.Spec("runtime@=1.0")
+    runtime_2 = spack.spec.Spec("runtime@=2.0")
+    child = spack.spec.Spec("child@=1.0")
+    root = spack.spec.Spec("root@=1.0")
+
+    root.add_dependency_edge(child, depflag=dt.LINK, virtuals=())
+    root.add_dependency_edge(runtime_2, depflag=dt.LINK, virtuals=())
+    child.add_dependency_edge(runtime_1, depflag=dt.LINK, virtuals=())
+
+    rpath_deps = spack.build_environment._get_rpath_deps_from_spec(root, transitive_rpaths=True)
+    assert child in rpath_deps
+    assert runtime_2 in rpath_deps
+    assert runtime_1 not in rpath_deps