Add snaps as a part source, from local file, from URL and from the store

demos/tomcat-snap/snapcraft.yaml

@@ -0,0 +1,26 @@
+name: snap-part-demo
+version: 1.0
+summary: Demo using a snap part
+description: This is a demo snap using Tomcat from another snap
+confinement: strict
+grade: devel
+
+apps:
+ tomcat:
+   command: run.sh
+   daemon: simple
+   plugs: [network-bind]
+
+parts:
+    tomcat:
+        plugin: dump
+        source: tomcat_8.5.5_amd64.snap
+    webapp:
+        plugin: dump
+        source: .
+        organize:
+            sample.war: webapps/sample.war
+        stage:
+            - webapps/sample.war
+        prime:
+            - webapps/sample.war

snapcraft/internal/sources/__init__.py

@@ -84,6 +84,7 @@
 from ._subversion import Subversion  # noqa
 from ._tar import Tar                # noqa
 from ._zip import Zip                # noqa
+from ._snap import Snap              # noqa
 
 logging.getLogger('urllib3').setLevel(logging.CRITICAL)
 
@@ -134,6 +135,7 @@ def get(sourcedir, builddir, options):
     'svn': Subversion,
     'tar': Tar,
     'zip': Zip,
+    'snap': Snap,
 }
 
 
@@ -164,6 +166,8 @@ def _get_source_type_from_uri(source, ignore_errors=False):
         source_type = 'deb'
     elif source.endswith('rpm'):
         source_type = 'rpm'
+    elif source.endswith('.snap'):
+        source_type = 'snap'
     elif common.isurl(source) and not ignore_errors:
         raise ValueError('no handler to manage source ({})'.format(source))
     elif not os.path.isdir(source) and not ignore_errors:

snapcraft/internal/sources/_snap.py

@@ -0,0 +1,84 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright (C) 2015, 2016 Canonical Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import debian.debfile
+import os
+import shutil
+import tempfile
+import logging
+import snapcraft
+import subprocess
+
+from . import errors
+from ._base import FileBase
+
+logger = logging.getLogger(__name__)
+
+class Snap(FileBase):
+
+    def __init__(self, source, source_dir, source_tag=None, source_commit=None,
+                 source_branch=None, source_depth=None):
+        super().__init__(source, source_dir, source_tag, source_commit,
+                         source_branch, source_depth)
+        if source_commit:
+            raise errors.IncompatibleOptionsError(
+                'can\'t specify a source-commit for a snap source')
+        self.source_channel = self.source_branch or 'stable'
+        self.snap_file = self.source
+
+    def pull(self):
+        logger.info("Pulling snap: %s" % self.source)
+        if self.source.endswith('.snap'):
+            super().pull()
+            self.snap_file = os.path.join(self.source_dir, self.source)
+        else:
+            self.snap_file = os.path.join(self.source_dir, '%s.snap' % self.source)
+            self._download()
+            self.provision(self.source_dir)
+
+    def _download(self):
+        logger.info("Downloading snap: %s" % self.snap_file)
+
+        store = snapcraft.storeapi.StoreClient()
+        try:
+            arch = snapcraft.ProjectOptions().deb_arch
+            package = store.cpi.get_package(self.source, self.source_channel, arch)
+            store._download_snap(
+                self.source, self.source_channel, arch, self.snap_file,
+                package['anon_download_url'], package['download_sha512'])
+        except snapcraft.storeapi.errors.SHAMismatchError:
+            raise RuntimeError(
+                'Failed to download {} at {} (mismatched SHA)'.format(
+                    self.source, self.source_dir))
+
+    def provision(self, dst, clean_target=True, keep_snap=False):
+        logger.info("Provisioning snap: %s to %s" % (self.snap_file, dst))
+
+        # Extract the source snap
+        output = subprocess.check_output(['unsquashfs', '-d', dst, '-f', self.snap_file])
+
+        # We don't want a part's snap.yaml conflicting with the parent snap's
+        snap_meta = os.path.join(dst, 'meta', 'snap.yaml')
+        if os.path.exists(snap_meta):
+            os.remove(snap_meta)
+
+        # Remove any previously generated snap command wrappers
+        for cmd_file in os.listdir(dst):
+            if cmd_file.startswith('command-') and cmd_file.endswith('.wrapper'):
+                os.remove(os.path.join(dst, cmd_file))
+
+        if not keep_snap:
+            os.remove(os.path.join(dst, os.path.basename(self.snap_file)))