Perl - allow package activation without PERL5LIB variable (#4540)

* perl: prepend default perl @INC path to support package activation

* perl: remove stray comma from list of configure arguments

* perl: final comma in configure arguments makes adding arguments safer

This reverts commit fdc10cd611f525ebc31ca1953e048095b1c75350.

* perl: add comment about modified @INC (thanks to George Hartzell)

* perl: use self.prefix.lib and self.prefix.bin for clarity

* perl: convert tabs added by editor to spaces for flake8

* perl: use new path syntax: prefix.lib.perl5

* perl: avoid line break before binary operator

* perl: use compact spack syntax for perl executable

1 files changed, 22 insertions, 9 deletions

diff --git a/var/spack/repos/builtin/packages/perl/package.py b/var/spack/repos/builtin/packages/perl/package.py
index d9952cc936..1e5e93a2f4 100644
--- a/var/spack/repos/builtin/packages/perl/package.py
+++ b/var/spack/repos/builtin/packages/perl/package.py
@@ -93,6 +93,23 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
             '-Dloclibpth=' + self.spec['gdbm'].prefix.lib,
         ]
 
+        # Extensions are installed into their private tree via
+        # `INSTALL_BASE`/`--install_base` (see [1]) which results in a
+        # "predictable" installation tree that sadly does not match the
+        # Perl core's @INC structure.  This means that when activation
+        # merges the extension into the extendee[2], the directory tree
+        # containing the extensions is not on @INC and the extensions can
+        # not be found.
+        #
+        # This bit prepends @INC with the directory that is used when
+        # extensions are activated [3].
+        #
+        # [1] https://metacpan.org/pod/ExtUtils::MakeMaker#INSTALL_BASE
+        # [2] via the activate method in the PackageBase class
+        # [3] https://metacpan.org/pod/distribution/perl/INSTALL#APPLLIB_EXP
+        config_args.append('-Accflags=-DAPPLLIB_EXP=\\"' +
+                           self.prefix.lib.perl5 + '\\"')
+
         # Discussion of -fPIC for Intel at:
         # https://github.com/LLNL/spack/pull/3081 and
         # https://github.com/LLNL/spack/pull/4416
@@ -130,10 +147,6 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
                 make()
                 make('install')
 
-    def setup_environment(self, spack_env, run_env):
-        """Set PERL5LIB to support activation of Perl packages"""
-        run_env.set('PERL5LIB', join_path(self.prefix, 'lib', 'perl5'))
-
     def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         """Set PATH and PERL5LIB to include the extension and
            any other perl extensions it depends on,
@@ -143,8 +156,8 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
         for d in dependent_spec.traverse(
                 deptype=('build', 'run'), deptype_query='run'):
             if d.package.extends(self.spec):
-                perl_lib_dirs.append(join_path(d.prefix, 'lib', 'perl5'))
-                perl_bin_dirs.append(join_path(d.prefix, 'bin'))
+                perl_lib_dirs.append(d.prefix.lib.perl5)
+                perl_bin_dirs.append(d.prefix.bin)
         perl_bin_path = ':'.join(perl_bin_dirs)
         perl_lib_path = ':'.join(perl_lib_dirs)
         spack_env.prepend_path('PATH', perl_bin_path)
@@ -159,10 +172,10 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
         """
 
         # perl extension builds can have a global perl executable function
-        module.perl = Executable(join_path(self.spec.prefix.bin, 'perl'))
+        module.perl = self.spec['perl'].command
 
         # Add variables for library directory
-        module.perl_lib_dir = join_path(dependent_spec.prefix, 'lib', 'perl5')
+        module.perl_lib_dir = dependent_spec.prefix.lib.perl5
 
         # Make the site packages directory for extensions,
         # if it does not exist already.
@@ -179,7 +192,7 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
         kwargs = {'ignore_absent': True, 'backup': False, 'string': False}
 
         # Find the actual path to the installed Config.pm file.
-        perl = Executable(join_path(prefix.bin, 'perl'))
+        perl = self.spec['perl'].command
         config_dot_pm = perl('-MModule::Loaded', '-MConfig', '-e',
                              'print is_loaded(Config)', output=str)