stage: make source_path available before stage is built

- `stage.source_path` was previously overloaded; it returned `None` if it
  didn't exist and this was used by client code
  - we want to be able to know the `source_path` before it's created

- make stage.source_path available before it exists.
  - use a well-known stage source path name, `$stage_path/src` that is
    available when `Stage` is instantiated but does not exist until it's
    "expanded"
  - client code can now use the variable before the stage is created.
  - client code can test whether the tarball is expanded by using the new
    `stage.expanded` property instead of testing whether `source_path` is
    `None`

- add tests for the new source_path semantics

lib/spack/spack/cmd/location.py

@@ -107,7 +107,7 @@ def location(parser, args):
                     print(pkg.stage.path)
 
                 else:  # args.build_dir is the default.
-                    if not pkg.stage.source_path:
+                    if not pkg.stage.expanded:
                         tty.die("Build directory does not exist yet. "
                                 "Run this to create it:",
                                 "spack stage " + " ".join(args.spec))

lib/spack/spack/fetch_strategy.py

@@ -60,6 +60,13 @@ def wrapper(self, *args, **kwargs):
     return wrapper
 
 
+def _ensure_one_stage_entry(stage_path):
+    """Ensure there is only one stage entry in the stage path."""
+    stage_entries = os.listdir(stage_path)
+    assert len(stage_entries) == 1
+    return os.path.join(stage_path, stage_entries[0])
+
+
 class FSMeta(type):
     """This metaclass registers all fetch strategies in a list."""
     def __init__(cls, name, bases, dict):
@@ -302,6 +309,7 @@ def fetch(self):
             raise FailedDownloadError(self.url)
 
     @property
+    @_needs_stage
     def archive_file(self):
         """Path to the source archive within this stage directory."""
         return self.stage.archive_file
@@ -313,7 +321,13 @@ def cachable(self):
     @_needs_stage
     def expand(self):
         if not self.expand_archive:
-            tty.msg("Skipping expand step for %s" % self.archive_file)
+            tty.msg("Staging unexpanded archive %s in %s" % (
+                    self.archive_file, self.stage.source_path))
+            if not self.stage.expanded:
+                mkdirp(self.stage.source_path)
+            dest = os.path.join(self.stage.source_path,
+                                os.path.basename(self.archive_file))
+            shutil.move(self.archive_file, dest)
             return
 
         tty.msg("Staging archive: %s" % self.archive_file)
@@ -326,6 +340,10 @@ def expand(self):
         if not self.extension:
             self.extension = extension(self.archive_file)
 
+        if self.stage.expanded:
+            tty.debug('Source already staged to %s' % self.stage.source_path)
+            return
+
         decompress = decompressor_for(self.archive_file, self.extension)
 
         # Expand all tarballs in their own directory to contain
@@ -337,26 +355,37 @@ def expand(self):
         with working_dir(tarball_container):
             decompress(self.archive_file)
 
-        # Check for an exploding tarball, i.e. one that doesn't expand
-        # to a single directory.  If the tarball *didn't* explode,
-        # move contents up & remove the container directory.
+        # Check for an exploding tarball, i.e. one that doesn't expand to
+        # a single directory.  If the tarball *didn't* explode, move its
+        # contents to the staging source directory & remove the container
+        # directory.  If the tarball did explode, just rename the tarball
+        # directory to the staging source directory.
         #
-        # NOTE: The tar program on Mac OS X will encode HFS metadata
-        # in hidden files, which can end up *alongside* a single
-        # top-level directory.  We ignore hidden files to accomodate
-        # these "semi-exploding" tarballs.
+        # NOTE: The tar program on Mac OS X will encode HFS metadata in
+        # hidden files, which can end up *alongside* a single top-level
+        # directory.  We initially ignore presence of hidden files to
+        # accomodate these "semi-exploding" tarballs but ensure the files
+        # are copied to the source directory.
         files = os.listdir(tarball_container)
         non_hidden = [f for f in files if not f.startswith('.')]
         if len(non_hidden) == 1:
-            expanded_dir = os.path.join(tarball_container, non_hidden[0])
-            if os.path.isdir(expanded_dir):
-                for f in files:
-                    shutil.move(os.path.join(tarball_container, f),
-                                os.path.join(self.stage.path, f))
+            src = os.path.join(tarball_container, non_hidden[0])
+            if os.path.isdir(src):
+                shutil.move(src, self.stage.source_path)
+                if len(files) > 1:
+                    files.remove(non_hidden[0])
+                    for f in files:
+                        src = os.path.join(tarball_container, f)
+                        dest = os.path.join(self.stage.path, f)
+                        shutil.move(src, dest)
                 os.rmdir(tarball_container)
+            else:
+                # This is a non-directory entry (e.g., a patch file) so simply
+                # rename the tarball container to be the source path.
+                shutil.move(tarball_container, self.stage.source_path)
 
-        if not files:
-            os.rmdir(tarball_container)
+        else:
+            shutil.move(tarball_container, self.stage.source_path)
 
     def archive(self, destination):
         """Just moves this archive to the destination."""
@@ -390,7 +419,7 @@ def reset(self):
                 "Tried to reset URLFetchStrategy before fetching",
                 "Failed on reset() for URL %s" % self.url)
 
-        # Remove everythigng but the archive from the stage
+        # Remove everything but the archive from the stage
         for filename in os.listdir(self.stage.path):
             abspath = os.path.join(self.stage.path, filename)
             if abspath != self.archive_file:
@@ -549,6 +578,15 @@ def fetch(self):
     def archive(self, destination):
         super(GoFetchStrategy, self).archive(destination, exclude='.git')
 
+    @_needs_stage
+    def expand(self):
+        tty.debug(
+            "Source fetched with %s is already expanded." % self.url_attr)
+
+        # Move the directory to the well-known stage source path
+        repo_root = _ensure_one_stage_entry(self.stage.path)
+        shutil.move(repo_root, self.stage.source_path)
+
     @_needs_stage
     def reset(self):
         with working_dir(self.stage.source_path):
@@ -634,8 +672,9 @@ def _repo_info(self):
 
         return '{0}{1}'.format(self.url, args)
 
+    @_needs_stage
     def fetch(self):
-        if self.stage.source_path:
+        if self.stage.expanded:
             tty.msg("Already fetched {0}".format(self.stage.source_path))
             return
 
@@ -645,17 +684,16 @@ def fetch(self):
         if self.commit:
             # Need to do a regular clone and check out everything if
             # they asked for a particular commit.
-            with working_dir(self.stage.path):
-                if spack.config.get('config:debug'):
-                    git('clone', self.url)
-                else:
-                    git('clone', '--quiet', self.url)
+            args = ['clone', self.url, self.stage.source_path]
+            if not spack.config.get('config:debug'):
+                args.insert(1, '--quiet')
+            git(*args)
 
             with working_dir(self.stage.source_path):
-                if spack.config.get('config:debug'):
-                    git('checkout', self.commit)
-                else:
-                    git('checkout', '--quiet', self.commit)
+                args = ['checkout', self.commit]
+                if not spack.config.get('config:debug'):
+                    args.insert(1, '--quiet')
+                git(*args)
 
         else:
             # Can be more efficient if not checking out a specific commit.
@@ -674,45 +712,46 @@ def fetch(self):
             if self.git_version > ver('1.7.10'):
                 args.append('--single-branch')
 
-            with working_dir(self.stage.path):
-                cloned = False
-                # Yet more efficiency, only download a 1-commit deep tree
-                if self.git_version >= ver('1.7.1'):
-                    try:
-                        git(*(args + ['--depth', '1', self.url]))
-                        cloned = True
-                    except spack.error.SpackError:
-                        # This will fail with the dumb HTTP transport
-                        # continue and try without depth, cleanup first
-                        pass
+            cloned = False
+            # Yet more efficiency, only download a 1-commit deep tree
+            if self.git_version >= ver('1.7.1'):
+                try:
+                    git(*(args + ['--depth', '1', self.url,
+                                  self.stage.source_path]))
+                    cloned = True
+                except spack.error.SpackError as e:
+                    # This will fail with the dumb HTTP transport
+                    # continue and try without depth, cleanup first
+                    tty.debug(e)
 
-                if not cloned:
-                    args.append(self.url)
-                    git(*args)
+            if not cloned:
+                args.extend([self.url, self.stage.source_path])
+                git(*args)
 
-                with working_dir(self.stage.source_path):
-                    # For tags, be conservative and check them out AFTER
-                    # cloning.  Later git versions can do this with clone
-                    # --branch, but older ones fail.
-                    if self.tag and self.git_version < ver('1.8.5.2'):
-                        # pull --tags returns a "special" error code of 1 in
-                        # older versions that we have to ignore.
-                        # see: https://github.com/git/git/commit/19d122b
-                        if spack.config.get('config:debug'):
-                            git('pull', '--tags', ignore_errors=1)
-                            git('checkout', self.tag)
-                        else:
-                            git('pull', '--quiet', '--tags', ignore_errors=1)
-                            git('checkout', '--quiet', self.tag)
+            with working_dir(self.stage.source_path):
+                # For tags, be conservative and check them out AFTER
+                # cloning.  Later git versions can do this with clone
+                # --branch, but older ones fail.
+                if self.tag and self.git_version < ver('1.8.5.2'):
+                    # pull --tags returns a "special" error code of 1 in
+                    # older versions that we have to ignore.
+                    # see: https://github.com/git/git/commit/19d122b
+                    pull_args = ['pull', '--tags']
+                    co_args = ['checkout', self.tag]
+                    if not spack.config.get('config:debug'):
+                        pull_args.insert(1, '--quiet')
+                        co_args.insert(1, '--quiet')
 
-        with working_dir(self.stage.source_path):
-            # Init submodules if the user asked for them.
-            if self.submodules:
-                if spack.config.get('config:debug'):
-                    git('submodule', 'update', '--init', '--recursive')
-                else:
-                    git('submodule', '--quiet', 'update', '--init',
-                        '--recursive')
+                    git(*pull_args, ignore_errors=1)
+                    git(*co_args)
+
+        # Init submodules if the user asked for them.
+        if self.submodules:
+            with working_dir(self.stage.source_path):
+                args = ['submodule', 'update', '--init', '--recursive']
+                if not spack.config.get('config:debug'):
+                    args.insert(1, '--quiet')
+                git(*args)
 
     def archive(self, destination):
         super(GitFetchStrategy, self).archive(destination, exclude='.git')
@@ -720,12 +759,14 @@ def archive(self, destination):
     @_needs_stage
     def reset(self):
         with working_dir(self.stage.source_path):
+            co_args = ['checkout', '.']
+            clean_args = ['clean', '-f']
             if spack.config.get('config:debug'):
-                self.git('checkout', '.')
-                self.git('clean', '-f')
-            else:
-                self.git('checkout', '--quiet', '.')
-                self.git('clean', '--quiet', '-f')
+                co_args.insert(1, '--quiet')
+                clean_args.insert(1, '--quiet')
+
+            self.git(*co_args)
+            self.git(*clean_args)
 
     def __str__(self):
         return '[git] {0}'.format(self._repo_info())
@@ -778,7 +819,7 @@ def get_source_id(self):
 
     @_needs_stage
     def fetch(self):
-        if self.stage.source_path:
+        if self.stage.expanded:
             tty.msg("Already fetched %s" % self.stage.source_path)
             return
 
@@ -787,10 +828,8 @@ def fetch(self):
         args = ['checkout', '--force', '--quiet']
         if self.revision:
             args += ['-r', self.revision]
-        args.append(self.url)
-
-        with working_dir(self.stage.path):
-            self.svn(*args)
+        args.extend([self.url, self.stage.source_path])
+        self.svn(*args)
 
     def _remove_untracked_files(self):
         """Removes untracked files in an svn repository."""
@@ -881,7 +920,7 @@ def get_source_id(self):
 
     @_needs_stage
     def fetch(self):
-        if self.stage.source_path:
+        if self.stage.expanded:
             tty.msg("Already fetched %s" % self.stage.source_path)
             return
 
@@ -895,13 +934,11 @@ def fetch(self):
         if not spack.config.get('config:verify_ssl'):
             args.append('--insecure')
 
-        args.append(self.url)
-
         if self.revision:
             args.extend(['-r', self.revision])
 
-        with working_dir(self.stage.path):
-            self.hg(*args)
+        args.extend([self.url, self.stage.source_path])
+        self.hg(*args)
 
     def archive(self, destination):
         super(HgFetchStrategy, self).archive(destination, exclude='.hg')

lib/spack/spack/test/conftest.py

@@ -519,12 +519,12 @@ def mock_archive(tmpdir_factory):
     tar = spack.util.executable.which('tar', required=True)
 
     tmpdir = tmpdir_factory.mktemp('mock-archive-dir')
-    expanded_archive_basedir = 'mock-archive-repo'
-    tmpdir.ensure(expanded_archive_basedir, dir=True)
-    repodir = tmpdir.join(expanded_archive_basedir)
+    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
+    repodir = tmpdir.join(spack.stage._source_path_subdir)
 
     # Create the configure script
-    configure_path = str(tmpdir.join(expanded_archive_basedir, 'configure'))
+    configure_path = str(tmpdir.join(spack.stage._source_path_subdir,
+                                     'configure'))
     with open(configure_path, 'w') as f:
         f.write(
             "#!/bin/sh\n"
@@ -541,8 +541,8 @@ def mock_archive(tmpdir_factory):
 
     # Archive it
     with tmpdir.as_cwd():
-        archive_name = '{0}.tar.gz'.format(expanded_archive_basedir)
-        tar('-czf', archive_name, expanded_archive_basedir)
+        archive_name = '{0}.tar.gz'.format(spack.stage._source_path_subdir)
+        tar('-czf', archive_name, spack.stage._source_path_subdir)
 
     Archive = collections.namedtuple('Archive',
                                      ['url', 'path', 'archive_file',
@@ -554,7 +554,7 @@ def mock_archive(tmpdir_factory):
         url=('file://' + archive_file),
         archive_file=archive_file,
         path=str(repodir),
-        expanded_archive_basedir=expanded_archive_basedir)
+        expanded_archive_basedir=spack.stage._source_path_subdir)
 
 
 @pytest.fixture(scope='session')
@@ -565,9 +565,8 @@ def mock_git_repository(tmpdir_factory):
     git = spack.util.executable.which('git', required=True)
 
     tmpdir = tmpdir_factory.mktemp('mock-git-repo-dir')
-    expanded_archive_basedir = 'mock-git-repo'
-    tmpdir.ensure(expanded_archive_basedir, dir=True)
-    repodir = tmpdir.join(expanded_archive_basedir)
+    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
+    repodir = tmpdir.join(spack.stage._source_path_subdir)
 
     # Initialize the repository
     with repodir.as_cwd():
@@ -639,9 +638,8 @@ def mock_hg_repository(tmpdir_factory):
     hg = spack.util.executable.which('hg', required=True)
 
     tmpdir = tmpdir_factory.mktemp('mock-hg-repo-dir')
-    expanded_archive_basedir = 'mock-hg-repo'
-    tmpdir.ensure(expanded_archive_basedir, dir=True)
-    repodir = tmpdir.join(expanded_archive_basedir)
+    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
+    repodir = tmpdir.join(spack.stage._source_path_subdir)
 
     get_rev = lambda: hg('id', '-i', output=str).strip()
 
@@ -685,9 +683,8 @@ def mock_svn_repository(tmpdir_factory):
     svnadmin = spack.util.executable.which('svnadmin', required=True)
 
     tmpdir = tmpdir_factory.mktemp('mock-svn-stage')
-    expanded_archive_basedir = 'mock-svn-repo'
-    tmpdir.ensure(expanded_archive_basedir, dir=True)
-    repodir = tmpdir.join(expanded_archive_basedir)
+    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
+    repodir = tmpdir.join(spack.stage._source_path_subdir)
     url = 'file://' + str(repodir)
 
     # Initialize the repository

lib/spack/spack/test/mirror.py

@@ -155,7 +155,8 @@ def successful_fetch(_class):
             pass
 
     def successful_expand(_class):
-        expanded_path = os.path.join(_class.stage.path, 'expanded-dir')
+        expanded_path = os.path.join(_class.stage.path,
+                                     spack.stage._source_path_subdir)
         os.mkdir(expanded_path)
         with open(os.path.join(expanded_path, 'test.patch'), 'w'):
             pass

lib/spack/spack/test/patch.py

@@ -63,9 +63,9 @@ def test_url_patch(mock_stage, filename, sha256, archive_sha256):
         # TODO: there is probably a better way to mock this.
         stage.mirror_path = mock_stage  # don't disrupt the spack install
 
-        # fake a source path
+        # Fake a source path and ensure the directory exists
         with working_dir(stage.path):
-            mkdirp('spack-expanded-archive')
+            mkdirp(spack.stage._source_path_subdir)
 
         with working_dir(stage.source_path):
             # write a file to be patched

lib/spack/spack/test/stage.py

@@ -6,6 +6,9 @@
 """Test that the Stage class works correctly."""
 import os
 import collections
+import shutil
+import tempfile
+import getpass
 
 import pytest
 
@@ -18,27 +21,108 @@
 from spack.resource import Resource
 from spack.stage import Stage, StageComposite, ResourceStage
 
+# The following values are used for common fetch and stage mocking fixtures:
+_archive_base = 'test-files'
+_archive_fn = '%s.tar.gz' % _archive_base
+_extra_fn = 'extra.sh'
+_hidden_fn = '.hidden'
+_readme_fn = 'README.txt'
 
-def check_expand_archive(stage, stage_name, mock_archive):
+_extra_contents = '#!/bin/sh\n'
+_hidden_contents = ''
+_readme_contents = 'hello world!\n'
+
+# TODO: Replace the following with an enum once guarantee supported (or
+# include enum34 for python versions < 3.4.
+_include_readme = 1
+_include_hidden = 2
+_include_extra = 3
+
+# Mock fetch directories are expected to appear as follows:
+#
+# TMPDIR/
+#     _archive_fn     archive_url = file:///path/to/_archive_fn
+#
+# Mock expanded stage directories are expected to have one of two forms,
+# depending on how the tarball expands.  Non-exploding tarballs are expected
+# to have the following structure:
+#
+# TMPDIR/                 temp stage dir
+#     src/                well-known stage source directory
+#         _readme_fn      Optional test_readme (contains _readme_contents)
+#     _hidden_fn          Optional hidden file (contains _hidden_contents)
+#     _archive_fn         archive_url = file:///path/to/_archive_fn
+#
+# while exploding tarball directories are expected to be structured as follows:
+#
+# TMPDIR/                 temp stage dir
+#     src/                well-known stage source directory
+#         archive_name/   archive dir
+#             _readme_fn  test_readme (contains _readme_contents)
+#         _extra_fn       test_extra file (contains _extra_contents)
+#     _archive_fn         archive_url = file:///path/to/_archive_fn
+#
+
+
+def check_expand_archive(stage, stage_name, expected_file_list):
+    """
+    Ensure the expanded archive directory contains the expected structure and
+    files as described in the module-level comments above.
+    """
     stage_path = get_stage_path(stage, stage_name)
-    archive_name = 'test-files.tar.gz'
-    archive_dir = 'test-files'
-    assert archive_name in os.listdir(stage_path)
-    assert archive_dir in os.listdir(stage_path)
+    archive_dir = spack.stage._source_path_subdir
 
-    assert os.path.join(stage_path, archive_dir) == stage.source_path
+    stage_contents = os.listdir(stage_path)
+    assert _archive_fn in stage_contents
+    assert archive_dir in stage_contents
 
-    readme = os.path.join(stage_path, archive_dir, 'README.txt')
-    assert os.path.isfile(readme)
-    with open(readme) as file:
-        'hello world!\n' == file.read()
+    source_path = os.path.join(stage_path, archive_dir)
+    assert source_path == stage.source_path
+
+    source_contents = os.listdir(source_path)
+
+    for _include in expected_file_list:
+        if _include == _include_hidden:
+            # The hidden file represent the HFS metadata associated with Mac
+            # OS X tar files so is expected to be in the same directory as
+            # the archive directory.
+            assert _hidden_fn in stage_contents
+
+            fn = os.path.join(stage_path, _hidden_fn)
+            contents = _hidden_contents
+
+        elif _include == _include_readme:
+            # The standard README.txt file will be in the source directory if
+            # the tarball didn't explode; otherwise, it will be in the
+            # original archive subdirectory of it.
+            if _archive_base in source_contents:
+                fn = os.path.join(source_path, _archive_base, _readme_fn)
+            else:
+                fn = os.path.join(source_path, _readme_fn)
+            contents = _readme_contents
+
+        elif _include == _include_extra:
+            assert _extra_fn in source_contents
+
+            fn = os.path.join(source_path, _extra_fn)
+            contents = _extra_contents
+
+        else:
+            assert False
+
+        assert os.path.isfile(fn)
+        with open(fn) as _file:
+            _file.read() == contents
 
 
 def check_fetch(stage, stage_name):
-    archive_name = 'test-files.tar.gz'
+    """
+    Ensure the fetch resulted in a properly placed archive file as described in
+    the module-level comments.
+    """
     stage_path = get_stage_path(stage, stage_name)
-    assert archive_name in os.listdir(stage_path)
-    assert os.path.join(stage_path, archive_name) == stage.fetcher.archive_file
+    assert _archive_fn in os.listdir(stage_path)
+    assert os.path.join(stage_path, _archive_fn) == stage.fetcher.archive_file
 
 
 def check_destroy(stage, stage_name):
@@ -76,7 +160,7 @@ def check_setup(stage, stage_name, archive):
 
     else:
         # Make sure the stage path is NOT a link for a non-tmp stage
-        assert os.path.islink(stage_path)
+        assert not os.path.islink(stage_path)
 
 
 def get_stage_path(stage, stage_name):
@@ -93,71 +177,187 @@ def get_stage_path(stage, stage_name):
         return stage.path
 
 
-@pytest.fixture()
-def tmpdir_for_stage(mock_archive):
-    """Uses a temporary directory for staging"""
-    current = spack.paths.stage_path
-    spack.config.set(
-        'config',
-        {'build_stage': [str(mock_archive.test_tmp_dir)]},
-        scope='user')
+@pytest.fixture
+def no_tmp_root_stage(monkeypatch):
+    """
+    Disable use of a temporary root for staging.
+
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
+    monkeypatch.setattr(spack.stage, '_tmp_root', None)
+    monkeypatch.setattr(spack.stage, '_use_tmp_stage', False)
     yield
-    spack.config.set('config', {'build_stage': [current]}, scope='user')
 
 
-@pytest.fixture()
-def mock_archive(tmpdir, monkeypatch):
-    """Creates a mock archive with the structure expected by the tests"""
-    # Mock up a stage area that looks like this:
-    #
-    # TMPDIR/                    test_files_dir
-    #     tmp/                   test_tmp_path (where stage should be)
-    #     test-files/            archive_dir_path
-    #         README.txt         test_readme (contains "hello world!\n")
-    #     test-files.tar.gz      archive_url = file:///path/to/this
-    #
-    test_tmp_path = tmpdir.join('tmp')
-    # set _test_tmp_path as the default test directory to use for stages.
-    spack.config.set(
-        'config', {'build_stage': [str(test_tmp_path)]}, scope='user')
+@pytest.fixture
+def non_user_path_for_stage():
+    """
+    Use a non-user path for staging.
 
-    archive_dir = tmpdir.join('test-files')
-    archive_name = 'test-files.tar.gz'
-    archive = tmpdir.join(archive_name)
-    archive_url = 'file://' + str(archive)
-    test_readme = archive_dir.join('README.txt')
-    archive_dir.ensure(dir=True)
-    test_tmp_path.ensure(dir=True)
-    test_readme.write('hello world!\n')
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
+    current = spack.config.get('config:build_stage')
+    spack.config.set('config', {'build_stage': ['/var/spack/non-path']},
+                     scope='user')
+    yield
+    spack.config.set('config', {'build_stage': current}, scope='user')
 
-    with tmpdir.as_cwd():
-        tar = spack.util.executable.which('tar', required=True)
-        tar('czf', str(archive_name), 'test-files')
 
-    # Make spack use the test environment for tmp stuff.
+@pytest.fixture
+def stage_path_for_stage():
+    """
+    Use the basic stage_path for staging.
+
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
+    current = spack.config.get('config:build_stage')
+    spack.config.set('config',
+                     {'build_stage': spack.paths.stage_path}, scope='user')
+    yield
+    spack.config.set('config', {'build_stage': current}, scope='user')
+
+
+@pytest.fixture
+def tmp_path_for_stage(tmpdir):
+    """
+    Use a built-in, temporary, test directory for staging.
+
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
+    current = spack.config.get('config:build_stage')
+    spack.config.set('config', {'build_stage': [str(tmpdir)]}, scope='user')
+    yield
+    spack.config.set('config', {'build_stage': current}, scope='user')
+
+
+@pytest.fixture
+def tmp_root_stage(monkeypatch):
+    """
+    Enable use of a temporary root for staging.
+
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
     monkeypatch.setattr(spack.stage, '_tmp_root', None)
     monkeypatch.setattr(spack.stage, '_use_tmp_stage', True)
-
-    Archive = collections.namedtuple(
-        'Archive', ['url', 'tmpdir', 'test_tmp_dir', 'archive_dir']
-    )
-    yield Archive(
-        url=archive_url,
-        tmpdir=tmpdir,
-        test_tmp_dir=test_tmp_path,
-        archive_dir=archive_dir
-    )
+    yield
 
 
-@pytest.fixture()
+@pytest.fixture
+def tmpdir_for_stage(mock_stage_archive):
+    """
+    Use the mock_stage_archive's temporary directory for staging.
+
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
+    archive = mock_stage_archive()
+    current = spack.config.get('config:build_stage')
+    spack.config.set(
+        'config',
+        {'build_stage': [str(archive.test_tmp_dir)]},
+        scope='user')
+    yield
+    spack.config.set('config', {'build_stage': current}, scope='user')
+
+
+@pytest.fixture
+def tmp_build_stage_dir(tmpdir):
+    """Establish the temporary build_stage for the mock archive."""
+    test_tmp_path = tmpdir.join('tmp')
+
+    # Set test_tmp_path as the default test directory to use for stages.
+    current = spack.config.get('config:build_stage')
+    spack.config.set('config',
+                     {'build_stage': [str(test_tmp_path)]}, scope='user')
+
+    yield (tmpdir, test_tmp_path)
+
+    spack.config.set('config', {'build_stage': current}, scope='user')
+
+
+@pytest.fixture
+def mock_stage_archive(tmp_build_stage_dir, tmp_root_stage, request):
+    """
+    Create the directories and files for the staged mock archive.
+
+    Note that it can be important for other tests that the previous settings be
+    restored when the test case is over.
+    """
+    # Mock up a stage area that looks like this:
+    #
+    # tmpdir/                test_files_dir
+    #     tmp/               test_tmp_path (where stage should be)
+    #     <_archive_base>/   archive_dir_path
+    #         <_readme_fn>   Optional test_readme (contains _readme_contents)
+    #     <_extra_fn>        Optional extra file (contains _extra_contents)
+    #     <_hidden_fn>       Optional hidden file (contains _hidden_contents)
+    #     <_archive_fn>      archive_url = file:///path/to/<_archive_fn>
+    #
+    def create_stage_archive(expected_file_list=[_include_readme]):
+        tmpdir, test_tmp_path = tmp_build_stage_dir
+        test_tmp_path.ensure(dir=True)
+
+        # Create the archive directory and associated file
+        archive_dir = tmpdir.join(_archive_base)
+        archive = tmpdir.join(_archive_fn)
+        archive_url = 'file://' + str(archive)
+        archive_dir.ensure(dir=True)
+
+        # Create the optional files as requested and make sure expanded
+        # archive peers are included.
+        tar_args = ['czf', str(_archive_fn), _archive_base]
+        for _include in expected_file_list:
+            if _include == _include_hidden:
+                # The hidden file case stands in for the way Mac OS X tar files
+                # represent HFS metadata.  Locate in the same directory as the
+                # archive file.
+                tar_args.append(_hidden_fn)
+                fn, contents = (tmpdir.join(_hidden_fn), _hidden_contents)
+
+            elif _include == _include_readme:
+                # The usual README.txt file is contained in the archive dir.
+                fn, contents = (archive_dir.join(_readme_fn), _readme_contents)
+
+            elif _include == _include_extra:
+                # The extra file stands in for exploding tar files so needs
+                # to be in the same directory as the archive file.
+                tar_args.append(_extra_fn)
+                fn, contents = (tmpdir.join(_extra_fn), _extra_contents)
+            else:
+                break
+
+            fn.write(contents)
+
+        # Create the archive file
+        with tmpdir.as_cwd():
+            tar = spack.util.executable.which('tar', required=True)
+            tar(*tar_args)
+
+        Archive = collections.namedtuple(
+            'Archive', ['url', 'tmpdir', 'test_tmp_dir', 'archive_dir']
+        )
+        return Archive(url=archive_url, tmpdir=tmpdir,
+                       test_tmp_dir=test_tmp_path, archive_dir=archive_dir)
+
+    return create_stage_archive
+
+
+@pytest.fixture
 def mock_noexpand_resource(tmpdir):
+    """Set up a non-expandable resource in the tmpdir prior to staging."""
     test_resource = tmpdir.join('resource-no-expand.sh')
     test_resource.write("an example resource")
     return str(test_resource)
 
 
-@pytest.fixture()
+@pytest.fixture
 def mock_expand_resource(tmpdir):
+    """Sets up an expandable resource in tmpdir prior to staging."""
     resource_dir = tmpdir.join('resource-expand')
     archive_name = 'resource.tar.gz'
     archive = tmpdir.join(archive_name)
@@ -165,10 +365,10 @@ def mock_expand_resource(tmpdir):
     test_file = resource_dir.join('resource-file.txt')
     resource_dir.ensure(dir=True)
     test_file.write('test content\n')
-    current = tmpdir.chdir()
-    tar = spack.util.executable.which('tar', required=True)
-    tar('czf', str(archive_name), 'resource-expand')
-    current.chdir()
+
+    with tmpdir.as_cwd():
+        tar = spack.util.executable.which('tar', required=True)
+        tar('czf', str(archive_name), 'resource-expand')
 
     MockResource = collections.namedtuple(
         'MockResource', ['url', 'files'])
@@ -176,11 +376,13 @@ def mock_expand_resource(tmpdir):
     return MockResource(archive_url, ['resource-file.txt'])
 
 
-@pytest.fixture()
+@pytest.fixture
 def composite_stage_with_expanding_resource(
-        mock_archive, mock_expand_resource):
+        mock_stage_archive, mock_expand_resource):
+    """Sets up a composite for expanding resources prior to staging."""
     composite_stage = StageComposite()
-    root_stage = Stage(mock_archive.url)
+    archive = mock_stage_archive()
+    root_stage = Stage(archive.url)
     composite_stage.append(root_stage)
 
     test_resource_fetcher = spack.fetch_strategy.from_kwargs(
@@ -195,7 +397,7 @@ def composite_stage_with_expanding_resource(
     return composite_stage, root_stage, resource_stage
 
 
-@pytest.fixture()
+@pytest.fixture
 def failing_search_fn():
     """Returns a search function that fails! Always!"""
     def _mock():
@@ -203,7 +405,7 @@ def _mock():
     return _mock
 
 
-@pytest.fixture()
+@pytest.fixture
 def failing_fetch_strategy():
     """Returns a fetch strategy that fails."""
     class FailingFetchStrategy(spack.fetch_strategy.FetchStrategy):
@@ -215,7 +417,7 @@ def fetch(self):
     return FailingFetchStrategy()
 
 
-@pytest.fixture()
+@pytest.fixture
 def search_fn():
     """Returns a search function that always succeeds."""
     class _Mock(object):
@@ -234,28 +436,32 @@ class TestStage(object):
     stage_name = 'spack-test-stage'
 
     @pytest.mark.usefixtures('tmpdir_for_stage')
-    def test_setup_and_destroy_name_with_tmp(self, mock_archive):
-        with Stage(mock_archive.url, name=self.stage_name) as stage:
-            check_setup(stage, self.stage_name, mock_archive)
+    def test_setup_and_destroy_name_with_tmp(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        with Stage(archive.url, name=self.stage_name) as stage:
+            check_setup(stage, self.stage_name, archive)
         check_destroy(stage, self.stage_name)
 
-    def test_setup_and_destroy_name_without_tmp(self, mock_archive):
-        with Stage(mock_archive.url, name=self.stage_name) as stage:
-            check_setup(stage, self.stage_name, mock_archive)
+    def test_setup_and_destroy_name_without_tmp(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        with Stage(archive.url, name=self.stage_name) as stage:
+            check_setup(stage, self.stage_name, archive)
         check_destroy(stage, self.stage_name)
 
     @pytest.mark.usefixtures('tmpdir_for_stage')
-    def test_setup_and_destroy_no_name_with_tmp(self, mock_archive):
-        with Stage(mock_archive.url) as stage:
-            check_setup(stage, None, mock_archive)
+    def test_setup_and_destroy_no_name_with_tmp(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        with Stage(archive.url) as stage:
+            check_setup(stage, None, archive)
         check_destroy(stage, None)
 
     @pytest.mark.disable_clean_stage_check
     @pytest.mark.usefixtures('tmpdir_for_stage')
     def test_composite_stage_with_noexpand_resource(
-            self, mock_archive, mock_noexpand_resource):
+            self, mock_stage_archive, mock_noexpand_resource):
+        archive = mock_stage_archive()
         composite_stage = StageComposite()
-        root_stage = Stage(mock_archive.url)
+        root_stage = Stage(archive.url)
         composite_stage.append(root_stage)
 
         resource_dst_name = 'resource-dst-name.sh'
@@ -276,7 +482,7 @@ def test_composite_stage_with_noexpand_resource(
     @pytest.mark.disable_clean_stage_check
     @pytest.mark.usefixtures('tmpdir_for_stage')
     def test_composite_stage_with_expand_resource(
-            self, mock_archive, mock_expand_resource,
+            self, mock_stage_archive, mock_expand_resource,
             composite_stage_with_expanding_resource):
 
         composite_stage, root_stage, resource_stage = (
@@ -291,22 +497,26 @@ def test_composite_stage_with_expand_resource(
                 root_stage.source_path, 'resource-dir', fname)
             assert os.path.exists(file_path)
 
-    def test_setup_and_destroy_no_name_without_tmp(self, mock_archive):
-        with Stage(mock_archive.url) as stage:
-            check_setup(stage, None, mock_archive)
+    def test_setup_and_destroy_no_name_without_tmp(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        with Stage(archive.url) as stage:
+            check_setup(stage, None, archive)
         check_destroy(stage, None)
 
-    def test_fetch(self, mock_archive):
-        with Stage(mock_archive.url, name=self.stage_name) as stage:
-            stage.fetch()
-            check_setup(stage, self.stage_name, mock_archive)
-            check_fetch(stage, self.stage_name)
-        check_destroy(stage, self.stage_name)
+    @pytest.mark.parametrize('debug', [False, True])
+    def test_fetch(self, mock_stage_archive, debug):
+        archive = mock_stage_archive()
+        with spack.config.override('config:debug', debug):
+            with Stage(archive.url, name=self.stage_name) as stage:
+                stage.fetch()
+                check_setup(stage, self.stage_name, archive)
+                check_fetch(stage, self.stage_name)
+            check_destroy(stage, self.stage_name)
 
     def test_no_search_if_default_succeeds(
-            self, mock_archive, failing_search_fn):
-        stage = Stage(mock_archive.url,
-                      name=self.stage_name,
+            self, mock_stage_archive, failing_search_fn):
+        archive = mock_stage_archive()
+        stage = Stage(archive.url, name=self.stage_name,
                       search_fn=failing_search_fn)
         with stage:
             stage.fetch()
@@ -336,22 +546,49 @@ def test_search_if_default_fails(self, failing_fetch_strategy, search_fn):
         check_destroy(stage, self.stage_name)
         assert search_fn.performed_search
 
-    def test_expand_archive(self, mock_archive):
-        with Stage(mock_archive.url, name=self.stage_name) as stage:
+    def test_ensure_one_stage_entry(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        with Stage(archive.url, name=self.stage_name) as stage:
             stage.fetch()
-            check_setup(stage, self.stage_name, mock_archive)
-            check_fetch(stage, self.stage_name)
-            stage.expand_archive()
-            check_expand_archive(stage, self.stage_name, mock_archive)
+            stage_path = get_stage_path(stage, self.stage_name)
+            spack.fetch_strategy._ensure_one_stage_entry(stage_path)
         check_destroy(stage, self.stage_name)
 
-    def test_restage(self, mock_archive):
-        with Stage(mock_archive.url, name=self.stage_name) as stage:
+    @pytest.mark.parametrize("expected_file_list", [
+                             [],
+                             [_include_readme],
+                             [_include_extra, _include_readme],
+                             [_include_hidden, _include_readme]])
+    def test_expand_archive(self, expected_file_list, mock_stage_archive):
+        archive = mock_stage_archive(expected_file_list)
+        with Stage(archive.url, name=self.stage_name) as stage:
+            stage.fetch()
+            check_setup(stage, self.stage_name, archive)
+            check_fetch(stage, self.stage_name)
+            stage.expand_archive()
+            check_expand_archive(stage, self.stage_name, expected_file_list)
+        check_destroy(stage, self.stage_name)
+
+    def test_expand_archive_extra_expand(self, mock_stage_archive):
+        """Test expand with an extra expand after expand (i.e., no-op)."""
+        archive = mock_stage_archive()
+        with Stage(archive.url, name=self.stage_name) as stage:
+            stage.fetch()
+            check_setup(stage, self.stage_name, archive)
+            check_fetch(stage, self.stage_name)
+            stage.expand_archive()
+            stage.fetcher.expand()
+            check_expand_archive(stage, self.stage_name, [_include_readme])
+        check_destroy(stage, self.stage_name)
+
+    def test_restage(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        with Stage(archive.url, name=self.stage_name) as stage:
             stage.fetch()
             stage.expand_archive()
 
             with working_dir(stage.source_path):
-                check_expand_archive(stage, self.stage_name, mock_archive)
+                check_expand_archive(stage, self.stage_name, [_include_readme])
 
                 # Try to make a file in the old archive dir
                 with open('foobar', 'w') as file:
@@ -365,26 +602,29 @@ def test_restage(self, mock_archive):
             assert 'foobar' not in os.listdir(stage.source_path)
         check_destroy(stage, self.stage_name)
 
-    def test_no_keep_without_exceptions(self, mock_archive):
-        stage = Stage(mock_archive.url, name=self.stage_name, keep=False)
+    def test_no_keep_without_exceptions(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        stage = Stage(archive.url, name=self.stage_name, keep=False)
         with stage:
             pass
         check_destroy(stage, self.stage_name)
 
     @pytest.mark.disable_clean_stage_check
-    def test_keep_without_exceptions(self, mock_archive):
-        stage = Stage(mock_archive.url, name=self.stage_name, keep=True)
+    def test_keep_without_exceptions(self, mock_stage_archive):
+        archive = mock_stage_archive()
+        stage = Stage(archive.url, name=self.stage_name, keep=True)
         with stage:
             pass
         path = get_stage_path(stage, self.stage_name)
         assert os.path.isdir(path)
 
     @pytest.mark.disable_clean_stage_check
-    def test_no_keep_with_exceptions(self, mock_archive):
+    def test_no_keep_with_exceptions(self, mock_stage_archive):
         class ThisMustFailHere(Exception):
             pass
 
-        stage = Stage(mock_archive.url, name=self.stage_name, keep=False)
+        archive = mock_stage_archive()
+        stage = Stage(archive.url, name=self.stage_name, keep=False)
         try:
             with stage:
                 raise ThisMustFailHere()
@@ -394,11 +634,12 @@ class ThisMustFailHere(Exception):
             assert os.path.isdir(path)
 
     @pytest.mark.disable_clean_stage_check
-    def test_keep_exceptions(self, mock_archive):
+    def test_keep_exceptions(self, mock_stage_archive):
         class ThisMustFailHere(Exception):
             pass
 
-        stage = Stage(mock_archive.url, name=self.stage_name, keep=True)
+        archive = mock_stage_archive()
+        stage = Stage(archive.url, name=self.stage_name, keep=True)
         try:
             with stage:
                 raise ThisMustFailHere()
@@ -406,3 +647,55 @@ class ThisMustFailHere(Exception):
         except ThisMustFailHere:
             path = get_stage_path(stage, self.stage_name)
             assert os.path.isdir(path)
+
+    def test_source_path_available(self, mock_stage_archive):
+        """Ensure source path available but does not exist on instantiation."""
+        archive = mock_stage_archive()
+        stage = Stage(archive.url, name=self.stage_name)
+
+        source_path = stage.source_path
+        assert source_path
+        assert source_path.endswith(spack.stage._source_path_subdir)
+        assert not os.path.exists(source_path)
+
+    def test_first_accessible_path_error(self):
+        """Test _first_accessible_path handling of an OSError."""
+        with tempfile.NamedTemporaryFile() as _file:
+            assert spack.stage._first_accessible_path([_file.name]) is None
+
+    def test_get_tmp_root_no_use(self, no_tmp_root_stage):
+        """Ensure not using tmp root results in no path."""
+        assert spack.stage.get_tmp_root() is None
+
+    def test_get_tmp_root_non_user_path(self, tmp_root_stage,
+                                        non_user_path_for_stage):
+        """Ensure build_stage of tmp root with non-user path includes user."""
+        path = spack.stage.get_tmp_root()
+        assert path.endswith(os.path.join(getpass.getuser(), 'spack-stage'))
+
+    def test_get_tmp_root_use(self, tmp_root_stage, tmp_path_for_stage):
+        """Ensure build_stage of tmp root provides has right ancestors."""
+        path = spack.stage.get_tmp_root()
+        shutil.rmtree(path)
+        assert path.rfind('test_get_tmp_root_use') > 0
+        assert path.endswith('spack-stage')
+
+    def test_get_tmp_root_stage_path(self, tmp_root_stage,
+                                     stage_path_for_stage):
+        """
+        Ensure build_stage of tmp root with stage_path means use local path.
+        """
+        assert spack.stage.get_tmp_root() is None
+        assert not spack.stage._use_tmp_stage
+
+    def test_stage_constructor_no_fetcher(self):
+        """Ensure Stage constructor with no URL or fetch strategy fails."""
+        with pytest.raises(ValueError):
+            with Stage(None):
+                pass
+
+    def test_stage_constructor_with_path(self, tmpdir):
+        """Ensure Stage constructor with a path uses it."""
+        testpath = str(tmpdir)
+        with Stage('file:///does-not-exist', path=testpath) as stage:
+            assert stage.path == testpath