Fixes #502. Create install prefix before build, clean up do_install.

- Fix bug introduced during merge of stage refactor.
  - install prefix was not created before build_environment.fork()
    - build_environment.fork() calls setup_dependent_environment
    - python's setup_dependent_environment can inadvertently create
      the install prefix before directory_layout expects it.

- Clean up Package.do_install:
  - simplify control flow: parent process now entirely responsible for
    creating/destroying the install prefix. cleanup is now in one place.
  - Hoisting cleanup out of the child improves nesting of try/catch in
    `real_work`.
  - `real_work` renamed to `build_process`

lib/spack/spack/directory_layout.py

@@ -85,6 +85,16 @@ def create_install_directory(self, spec):
         raise NotImplementedError()
 
 
+    def check_installed(self, spec):
+        """Checks whether a spec is installed.
+
+        Return the spec's prefix, if it is installed, None otherwise.
+
+        Raise an exception if the install is inconsistent or corrupt.
+        """
+        raise NotImplementedError()
+
+
     def extension_map(self, spec):
         """Get a dict of currently installed extension packages for a spec.
 
@@ -246,17 +256,30 @@ def build_packages_path(self, spec):
     def create_install_directory(self, spec):
         _check_concrete(spec)
 
+        prefix = self.check_installed(spec)
+        if prefix:
+            raise InstallDirectoryAlreadyExistsError(prefix)
+
+        mkdirp(self.metadata_path(spec))
+        self.write_spec(spec, self.spec_file_path(spec))
+
+
+    def check_installed(self, spec):
+        _check_concrete(spec)
         path = self.path_for_spec(spec)
         spec_file_path = self.spec_file_path(spec)
 
-        if os.path.isdir(path):
+        if not os.path.isdir(path):
+            return None
+
         if not os.path.isfile(spec_file_path):
             raise InconsistentInstallDirectoryError(
-                    'No spec file found at path %s' % spec_file_path)
+                'Inconsistent state: install prefix exists but contains no spec.yaml:',
+                "  " + path)
 
         installed_spec = self.read_spec(spec_file_path)
-            if installed_spec == self.spec:
+        if installed_spec == spec:
-                raise InstallDirectoryAlreadyExistsError(path)
+            return path
 
         if spec.dag_hash() == installed_spec.dag_hash():
             raise SpecHashCollisionError(installed_hash, spec_hash)
@@ -264,9 +287,6 @@ def create_install_directory(self, spec):
             raise InconsistentInstallDirectoryError(
                 'Spec file in %s does not match hash!' % spec_file_path)
 
-        mkdirp(self.metadata_path(spec))
-        self.write_spec(spec, spec_file_path)
-
 
     def all_specs(self):
         if not os.path.isdir(self.root):
@@ -399,8 +419,8 @@ def remove_extension(self, spec, ext_spec):
 
 class DirectoryLayoutError(SpackError):
     """Superclass for directory layout errors."""
-    def __init__(self, message):
+    def __init__(self, message, long_msg=None):
-        super(DirectoryLayoutError, self).__init__(message)
+        super(DirectoryLayoutError, self).__init__(message, long_msg)
 
 
 class SpecHashCollisionError(DirectoryLayoutError):
@@ -422,8 +442,8 @@ def __init__(self, installed_spec, prefix, error):
 
 class InconsistentInstallDirectoryError(DirectoryLayoutError):
     """Raised when a package seems to be installed to the wrong place."""
-    def __init__(self, message):
+    def __init__(self, message, long_msg=None):
-        super(InconsistentInstallDirectoryError, self).__init__(message)
+        super(InconsistentInstallDirectoryError, self).__init__(message, long_msg)
 
 
 class InstallDirectoryAlreadyExistsError(DirectoryLayoutError):

lib/spack/spack/package.py

@@ -845,7 +845,8 @@ def do_install(self,
         if not self.spec.concrete:
             raise ValueError("Can only install concrete packages.")
 
-        if os.path.exists(self.prefix):
+        # Ensure package is not already installed
+        if spack.install_layout.check_installed(self.spec):
             tty.msg("%s is already installed in %s" % (self.name, self.prefix))
             return
 
@@ -857,18 +858,11 @@ def do_install(self,
                 keep_prefix=keep_prefix, keep_stage=keep_stage, ignore_deps=ignore_deps,
                 fake=fake, skip_patch=skip_patch, verbose=verbose, make_jobs=make_jobs)
 
-        def cleanup():
+        # Set parallelism before starting build.
-            """Handles removing install prefix on error."""
+        self.make_jobs = make_jobs
-            if not keep_prefix:
-                self.remove_prefix()
-            else:
-                tty.warn("Keeping install prefix in place despite error.",
-                         "Spack will think this package is installed. " +
-                         "Manually remove this directory to fix:",
-                         self.prefix, wrap=True)
 
         # Then install the package itself.
-        def real_work():
+        def build_process():
             """Forked for each build. Has its own process and python
                module space set up by build_environment.fork()."""
             start_time = time.time()
@@ -878,12 +872,6 @@ def real_work():
                 else:
                     self.do_stage()
 
-            # create the install directory.  The install layout
-            # handles this in case so that it can use whatever
-            # package naming scheme it likes.
-            spack.install_layout.create_install_directory(self.spec)
-
-            try:
             tty.msg("Building %s" % self.name)
 
             self.stage.keep = keep_stage
@@ -894,7 +882,6 @@ def real_work():
 
                 if fake:
                     self.do_fake_install()
-
                 else:
                     # Do the real install in the source directory.
                      self.stage.chdir_to_source()
@@ -902,6 +889,7 @@ def real_work():
                      # Save the build environment in a file before building.
                      env_path = join_path(os.getcwd(), 'spack-build.env')
 
+                     try:
                         # Redirect I/O to a build log (and optionally to the terminal)
                         log_path = join_path(os.getcwd(), 'spack-build.out')
                         log_file = open(log_path, 'w')
@@ -909,6 +897,11 @@ def real_work():
                             dump_environment(env_path)
                             self.install(self.spec, self.prefix)
 
+                     except ProcessError as e:
+                         # Annotate ProcessErrors with the location of the build log.
+                         e.build_log = log_path
+                         raise e
+
                      # Ensure that something was actually installed.
                      self._sanity_check_install()
 
@@ -930,23 +923,21 @@ def real_work():
                     % (_hms(self._fetch_time), _hms(build_time), _hms(self._total_time)))
             print_pkg(self.prefix)
 
-            except ProcessError as e:
+        try:
-                # Annotate with location of build log.
+            # Create the install prefix and fork the build process.
-                e.build_log = log_path
+            spack.install_layout.create_install_directory(self.spec)
-                cleanup()
+            spack.build_environment.fork(self, build_process)
-                raise e
-
         except:
-                # other exceptions just clean up and raise.
+            # remove the install prefix if anything went wrong during install.
-                cleanup()
+            if not keep_prefix:
+                self.remove_prefix()
+            else:
+                tty.warn("Keeping install prefix in place despite error.",
+                         "Spack will think this package is installed. " +
+                         "Manually remove this directory to fix:",
+                         self.prefix, wrap=True)
             raise
 
-        # Set parallelism before starting build.
-        self.make_jobs = make_jobs
-
-        # Do the build.
-        spack.build_environment.fork(self, real_work)
-
         # note: PARENT of the build process adds the new package to
         # the database, so that we don't need to re-read from file.
         spack.installed_db.add(self.spec, self.prefix)