init: remove spack.concretizer global variable

5 files changed, 104 insertions, 82 deletions

diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index b6492dc1a0..2467596a34 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -62,11 +62,6 @@ except spack.error.SpackError as e:
     tty.die('while initializing Spack RepoPath:', e.message)
 
 
-#: Concretizer class implements policy decisions for concretization
-from spack.concretize import Concretizer
-concretizer = Concretizer()
-
-
 #: Needed for test dependencies
 from spack.package_prefs import PackageTesting
 package_testing = PackageTesting()
diff --git a/lib/spack/spack/cmd/mirror.py b/lib/spack/spack/cmd/mirror.py
index 6777c76030..34f342fb9e 100644
--- a/lib/spack/spack/cmd/mirror.py
+++ b/lib/spack/spack/cmd/mirror.py
@@ -31,6 +31,7 @@ from llnl.util.tty.colify import colify
 
 import spack
 import spack.cmd
+import spack.concretize
 import spack.config
 import spack.mirror
 import spack.cmd.common.arguments as arguments
@@ -168,57 +169,57 @@ def mirror_create(args):
     """Create a directory to be used as a spack mirror, and fill it with
        package archives."""
     # try to parse specs from the command line first.
-    spack.concretizer.disable_compiler_existence_check()
-    specs = spack.cmd.parse_specs(args.specs, concretize=True)
-
-    # If there is a file, parse each line as a spec and add it to the list.
-    if args.file:
-        if specs:
-            tty.die("Cannot pass specs on the command line with --file.")
-        specs = _read_specs_from_file(args.file)
-
-    # If nothing is passed, use all packages.
-    if not specs:
-        specs = [Spec(n) for n in spack.repo.all_package_names()]
-        specs.sort(key=lambda s: s.format("$_$@").lower())
-
-    # If the user asked for dependencies, traverse spec DAG get them.
-    if args.dependencies:
-        new_specs = set()
-        for spec in specs:
-            spec.concretize()
-            for s in spec.traverse():
-                new_specs.add(s)
-        specs = list(new_specs)
-
-    # Default name for directory is spack-mirror-<DATESTAMP>
-    directory = args.directory
-    if not directory:
-        timestamp = datetime.now().strftime("%Y-%m-%d")
-        directory = 'spack-mirror-' + timestamp
-
-    # Make sure nothing is in the way.
-    existed = False
-    if os.path.isfile(directory):
-        tty.error("%s already exists and is a file." % directory)
-    elif os.path.isdir(directory):
-        existed = True
-
-    # Actually do the work to create the mirror
-    present, mirrored, error = spack.mirror.create(
-        directory, specs, num_versions=args.one_version_per_spec)
-    p, m, e = len(present), len(mirrored), len(error)
-
-    verb = "updated" if existed else "created"
-    tty.msg(
-        "Successfully %s mirror in %s" % (verb, directory),
-        "Archive stats:",
-        "  %-4d already present"  % p,
-        "  %-4d added"            % m,
-        "  %-4d failed to fetch." % e)
-    if error:
-        tty.error("Failed downloads:")
-        colify(s.cformat("$_$@") for s in error)
+    with spack.concretize.disable_compiler_existence_check():
+        specs = spack.cmd.parse_specs(args.specs, concretize=True)
+
+        # If there is a file, parse each line as a spec and add it to the list.
+        if args.file:
+            if specs:
+                tty.die("Cannot pass specs on the command line with --file.")
+            specs = _read_specs_from_file(args.file)
+
+        # If nothing is passed, use all packages.
+        if not specs:
+            specs = [Spec(n) for n in spack.repo.all_package_names()]
+            specs.sort(key=lambda s: s.format("$_$@").lower())
+
+        # If the user asked for dependencies, traverse spec DAG get them.
+        if args.dependencies:
+            new_specs = set()
+            for spec in specs:
+                spec.concretize()
+                for s in spec.traverse():
+                    new_specs.add(s)
+            specs = list(new_specs)
+
+        # Default name for directory is spack-mirror-<DATESTAMP>
+        directory = args.directory
+        if not directory:
+            timestamp = datetime.now().strftime("%Y-%m-%d")
+            directory = 'spack-mirror-' + timestamp
+
+        # Make sure nothing is in the way.
+        existed = False
+        if os.path.isfile(directory):
+            tty.error("%s already exists and is a file." % directory)
+        elif os.path.isdir(directory):
+            existed = True
+
+        # Actually do the work to create the mirror
+        present, mirrored, error = spack.mirror.create(
+            directory, specs, num_versions=args.one_version_per_spec)
+        p, m, e = len(present), len(mirrored), len(error)
+
+        verb = "updated" if existed else "created"
+        tty.msg(
+            "Successfully %s mirror in %s" % (verb, directory),
+            "Archive stats:",
+            "  %-4d already present"  % p,
+            "  %-4d added"            % m,
+            "  %-4d failed to fetch." % e)
+        if error:
+            tty.error("Failed downloads:")
+            colify(s.cformat("$_$@") for s in error)
 
 
 def mirror(parser, args):
diff --git a/lib/spack/spack/concretize.py b/lib/spack/spack/concretize.py
index 6efc365b5d..c38dfd024a 100644
--- a/lib/spack/spack/concretize.py
+++ b/lib/spack/spack/concretize.py
@@ -36,6 +36,7 @@ TODO: make this customizable and allow users to configure
 from __future__ import print_function
 from itertools import chain
 from functools_backport import reverse_order
+from contextlib import contextmanager
 from six import iteritems
 
 import spack
@@ -47,23 +48,48 @@ import spack.error
 from spack.version import ver, Version, VersionList, VersionRange
 from spack.package_prefs import PackagePrefs, spec_externals, is_spec_buildable
 
+#: controls whether we check that compiler versions actually exist during
+#: concretization.  Used for testing.
+check_for_compiler_existence = True
+
+
+#: Concretizer singleton
+_concretizer = None
+
 
 #: impements rudimentary logic for ABI compatibility
-abi = spack.abi.ABI()
+_abi_checker = None
+
+
+def _abi():
+    """Get an ABI checker object."""
+    global _abi_checker
+    if _abi_checker is None:
+        _abi_checker = spack.abi.ABI()
+    return _abi_checker
+
+
+def concretizer():
+    """Get concretizer singleton."""
+    global _concretizer
+    if _concretizer is None:
+        _concretizer = Concretizer()
+    return _concretizer
+
+
+@contextmanager
+def disable_compiler_existence_check():
+    global check_for_compiler_existence
+    saved = check_for_compiler_existence
+    check_for_compiler_existence = False
+    yield
+    check_for_compiler_existence = saved
 
 
 class Concretizer(object):
     """You can subclass this class to override some of the default
        concretization strategies, or you can override all of them.
     """
-    def __init__(self):
-        self.check_for_compiler_existence = True
-
-    def disable_compiler_existence_check(self):
-        self.check_for_compiler_existence = False
-
-    def enable_compiler_existence_check(self):
-        self.check_for_compiler_existence = True
 
     def _valid_virtuals_and_externals(self, spec):
         """Returns a list of candidate virtual dep providers and external
@@ -137,8 +163,8 @@ class Concretizer(object):
         return sorted(candidates,
                       reverse=True,
                       key=lambda spec: (
-                          abi.compatible(spec, abi_exemplar, loose=True),
-                          abi.compatible(spec, abi_exemplar)))
+                          _abi().compatible(spec, abi_exemplar, loose=True),
+                          _abi().compatible(spec, abi_exemplar)))
 
     def concretize_version(self, spec):
         """If the spec is already concrete, return.  Otherwise take
@@ -299,7 +325,7 @@ class Concretizer(object):
             return spack.compilers.compilers_for_spec(cspec, arch_spec=aspec)
 
         if spec.compiler and spec.compiler.concrete:
-            if (self.check_for_compiler_existence and not
+            if (check_for_compiler_existence and not
                     _proper_compiler_style(spec.compiler, spec.architecture)):
                 _compiler_concretization_failure(
                     spec.compiler, spec.architecture)
@@ -313,7 +339,7 @@ class Concretizer(object):
 
         # Check if the compiler is already fully specified
         if (other_compiler and other_compiler.concrete and
-                not self.check_for_compiler_existence):
+                not check_for_compiler_existence):
             spec.compiler = other_compiler.copy()
             return True
 
@@ -407,7 +433,7 @@ class Concretizer(object):
             compiler = spack.compilers.compiler_for_spec(
                 spec.compiler, spec.architecture)
         except spack.compilers.NoCompilerForSpecError:
-            if self.check_for_compiler_existence:
+            if check_for_compiler_existence:
                 raise
             return ret
         for flag in compiler.flags:
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 72b83440df..cb21e551f0 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -1675,13 +1675,15 @@ class Spec(object):
             # to presets below, their constraints will all be merged, but we'll
             # still need to select a concrete package later.
             if not self.virtual:
+                import spack.concretize
+                concretizer = spack.concretize.concretizer()
                 changed |= any(
-                    (spack.concretizer.concretize_architecture(self),
-                     spack.concretizer.concretize_compiler(self),
-                     spack.concretizer.concretize_compiler_flags(
-                         self),  # has to be concretized after compiler
-                     spack.concretizer.concretize_version(self),
-                     spack.concretizer.concretize_variants(self)))
+                    (concretizer.concretize_architecture(self),
+                     concretizer.concretize_compiler(self),
+                     # flags must be concretized after compiler
+                     concretizer.concretize_compiler_flags(self),
+                     concretizer.concretize_version(self),
+                     concretizer.concretize_variants(self)))
             presets[self.name] = self
 
         visited.add(self.name)
@@ -1742,8 +1744,9 @@ class Spec(object):
                 if not replacement:
                     # Get a list of possible replacements in order of
                     # preference.
-                    candidates = spack.concretizer.choose_virtual_or_external(
-                        spec)
+                    import spack.concretize
+                    concretizer = spack.concretize.concretizer()
+                    candidates = concretizer.choose_virtual_or_external(spec)
 
                     # Try the replacements in order, skipping any that cause
                     # satisfiability problems.
diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index f23c20fd6e..989699bbf3 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -152,13 +152,10 @@ class TestConcretize(object):
         with pytest.raises(spack.concretize.UnavailableCompilerVersionError):
             check_concretize('dttop %gcc@100.100')
 
-        try:
-            spack.concretizer.disable_compiler_existence_check()
+        with spack.concretize.disable_compiler_existence_check():
             spec = check_concretize('dttop %gcc@100.100')
             assert spec.satisfies('%gcc@100.100')
             assert spec['dtlink3'].satisfies('%gcc@100.100')
-        finally:
-            spack.concretizer.enable_compiler_existence_check()
 
     def test_concretize_with_provides_when(self):
         """Make sure insufficient versions of MPI are not in providers list when