Add a simple implementation of element dependency

This adds a new optional file to the root of elements. The
file lists dependencies which will be added to the list
requested by the user during disk image creation.

Change-Id: Id71c3b333563604bbbaf90f9cf40e24fa9738fc8

README.md

@@ -23,6 +23,8 @@ What tools are there?
 
 * elements can be found in the top level elements directory.
 
+* element-info : Extract information about elements.
+
 Why?
 ----
 
@@ -118,6 +120,9 @@ part of the process you need to customise:
 * first-boot.d: Runs inside the image before rc.local. Scripts from here are
   good for doing per-instance configuration based on cloud metadata.
 
+* element-deps : A plain text, newline separated list of elements which will
+  be added to the list of elements built into the image at image creation time.
+
 Ramdisk elements support the following files in their element directories:
 
 * binary-deps : executables required to be fed into the ramdisk. These need

bin/disk-image-create

@@ -18,6 +18,7 @@
 set -e
 
 SCRIPTNAME=$(basename $0)
+SCRIPT_HOME=$(dirname $0)
 export _LIB=$(dirname $0)/../lib
 source $_LIB/die
 
@@ -58,6 +59,8 @@ source $_LIB/img-defaults
 source $_LIB/common-functions
 source $_LIB/img-functions
 
+IMAGE_ELEMENT=$($SCRIPT_HOME/element-info --expand-dependencies $IMAGE_ELEMENT)
+
 echo "Building elements: $IMAGE_ELEMENT"
 echo "If prompted for sudo, install sudoers.d/img-build-sudoers into /etc/sudoers.d and restart the build."
 mkdir -p $IMG_PATH

bin/diskimage_builder

@@ -0,0 +1 @@
+../diskimage_builder

bin/element-info

@@ -0,0 +1,23 @@
+#!/usr/bin/python
+# Copyright 2013 Hewlett-Packard Development Company, L.P.
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import os
+import sys
+
+from diskimage_builder.elements import main
+
+
+sys.exit(main(sys.argv))

bin/ramdisk-image-create

@@ -20,6 +20,7 @@
 set -e
 
 SCRIPTNAME=$(basename $0)
+SCRIPT_HOME=$(dirname $0)
 export _DIR=$(dirname $0)
 export _LIB=${_DIR}/../lib
 source $_LIB/die
@@ -57,6 +58,8 @@ source $_LIB/ramdisk-defaults
 source $_LIB/common-functions
 source $_LIB/ramdisk-functions
 
+RAMDISK_ELEMENT=$($SCRIPT_HOME/element-info --expand-dependencies $RAMDISK_ELEMENT)
+
 echo "Building element(s): ${RAMDISK_ELEMENT}"
 
 echo "Discovering binary dependencies"

diskimage_builder/elements.py

@@ -0,0 +1,91 @@
+# Copyright 2013 Hewlett-Packard Development Company, L.P.
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import argparse
+from errno import ENOENT
+import os
+import sys
+
+
+def get_elements_dir():
+    if 'ELEMENTS_DIR' not in os.environ:
+        return os.path.abspath(
+            os.path.join(os.path.dirname(__file__), '..', 'elements'))
+    return os.environ['ELEMENTS_DIR']
+
+
+def dependencies(element, elements_dir=None):
+    """ Return the non-transitive list of dependencies for a single element
+    :param user_elements: iterable enumerating elements a user has requested
+    :param elements_dir: the elements dir to read from. If not supplied,
+                         inferred by calling get_elements_dir().
+
+    :return: a set just containing all elements that the specified element
+             depends on.
+    """
+    if elements_dir is None:
+        elements_dir = get_elements_dir()
+
+    element_deps_path = os.path.join(elements_dir, element, 'element-deps')
+    try:
+        with open(element_deps_path) as element_deps:
+            return set([line.strip() for line in element_deps])
+    except IOError as e:
+        if e.errno == 2:
+            return set()
+        else:
+            raise
+
+
+def expand_dependencies(user_elements, elements_dir=None):
+    """ Expand user requested elements using element-deps files.
+
+    Arguments:
+    :param user_elements: iterable enumerating the elements a user requested
+    :param elements_dir: the elements dir to read from. Passed directly to
+                         dependencies()
+
+    :return: a set containing user_elements and all dependent elements
+             including any transitive dependencies.
+    """
+    final_elements = set(user_elements)
+    check_queue = list(user_elements)
+
+    while check_queue:
+        element = check_queue.pop()
+        deps = dependencies(element, elements_dir)
+        check_queue.extend(deps - final_elements)
+        final_elements.update(deps)
+
+    return final_elements
+
+
+def main(argv):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('elements', nargs='+',
+                        help='elements to inspect')
+    parser.add_argument('--expand-dependencies', '-d', action='store_true',
+                        default=False,
+                        help='Print expanded dependencies of all args')
+
+    args = parser.parse_args(argv[1:])
+
+    if args.expand_dependencies:
+        print(' '.join(expand_dependencies(args.elements)))
+        return 0
+
+
+    sys.stderr.write("ERROR: please choose an option.\n")
+    return -1

diskimage_builder/test_elementdeps.py

@@ -0,0 +1,71 @@
+# Copyright 2013 Hewlett-Packard Development Company, L.P.
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import os
+
+from testtools import TestCase
+from fixtures import Fixture, TempDir
+
+from diskimage_builder.elements import expand_dependencies
+
+data_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), 'test-elements'))
+
+def _populate_element(element_dir, element_name, element_deps=[]):
+        element_home = os.path.join(element_dir, element_name)
+        os.mkdir(element_home)
+        deps_path = os.path.join(element_home, 'element-deps')
+        with open(deps_path, 'w') as deps_file:
+            deps_file.write("\n".join(element_deps))
+
+class TestElementDeps(TestCase):
+
+    def setUp(self):
+        super(TestElementDeps, self).setUp()
+        self.element_dir = self.useFixture(TempDir()).path
+        _populate_element(self.element_dir, 'requires-foo', ['foo'])
+        _populate_element(self.element_dir, 'foo')
+        _populate_element(self.element_dir,
+                          'requires-requires-foo',
+                          ['requires-foo'])
+        _populate_element(self.element_dir, 'self', ['self'])
+        _populate_element(self.element_dir, 'circular1', ['circular2'])
+        _populate_element(self.element_dir, 'circular2', ['circular1'])
+
+    def test_non_transitive_deps(self):
+        result = expand_dependencies(['requires-foo'],
+            elements_dir=self.element_dir)
+        self.assertEquals(set(['requires-foo', 'foo']), result)
+
+    def test_transitive_deps(self):
+        result = expand_dependencies(['requires-requires-foo'],
+            elements_dir=self.element_dir)
+        self.assertEquals(set(['requires-requires-foo',
+                               'requires-foo',
+                               'foo']), result)
+
+    def test_no_deps(self):
+        result = expand_dependencies(['foo'],
+            elements_dir=self.element_dir)
+        self.assertEquals(set(['foo']), result)
+
+    def test_self(self):
+        result = expand_dependencies(['self'],
+            elements_dir=self.element_dir)
+        self.assertEquals(set(['self']), result)
+
+    def test_circular(self):
+        result = expand_dependencies(['circular1'],
+            elements_dir=self.element_dir)
+        self.assertEquals(set(['circular1', 'circular2']), result)