avocado.core.tree: Support for including files from yaml

This patch defines "!include" tag for inserting other files from within
the yaml file.

Keep in mind that it's necessarily to separate the ':' from the tag,
otherwise yaml thinks it's a different tag.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

avocado/core/tree.py

@@ -34,6 +34,7 @@ original base tree code and re-license under GPLv2+, given that GPLv3 and GPLv2
 """
 
 import collections
+import os
 
 import yaml
 
@@ -44,6 +45,10 @@ except ImportError:
     from yaml import Loader
 
 
+# Mapping for yaml flags
+YAML_INCLUDE = 0
+
+
 class TreeNode(object):
 
     """
@@ -294,18 +299,43 @@ class Value(tuple):     # Few methods pylint: disable=R0903
     pass
 
 
+class Control(object):  # Few methods pylint: disable=R0903
+
+    """ Container used to identify node vs. control sequence """
+
+    def __init__(self, ctr_type):
+        self.ctr_type = ctr_type
+
+    def __eq__(self, other):
+        if isinstance(other, Control):
+            return self.ctr_type == other.ctr_type
+        else:
+            return self.ctr_type == other
+
+    def __req__(self, other):
+        return self == other
+
+    def __str__(self):
+        return self.ctr_type
+
+
 def _create_from_yaml(path, cls_node=TreeNode):
     """ Create tree structure from yaml stream """
     def tree_node_from_values(name, values):
         """ Create `name` node and add values  """
-        node_children = []
-        node_values = []
+        node = cls_node(str(name))
         for value in values:
             if isinstance(value, TreeNode):
-                node_children.append(value)
+                node.add_child(value)
+            elif isinstance(value[0], Control):
+                # Include file
+                ypath = value[1]
+                if not os.path.isabs(ypath):
+                    ypath = os.path.join(os.path.dirname(path), ypath)
+                node.merge(_create_from_yaml(ypath, cls_node))
             else:
-                node_values.append(value)
-        return cls_node(name, dict(node_values), children=node_children)
+                node.value[value[0]] = value[1]
+        return node
 
     def mapping_to_tree_loader(loader, node):
         """ Maps yaml mapping tag to TreeNode structure """
@@ -323,10 +353,13 @@ def _create_from_yaml(path, cls_node=TreeNode):
             if is_node(values):    # New node
                 objects.append(tree_node_from_values(name, values))
             elif values is None:            # Empty node
-                objects.append(cls_node(name))
+                objects.append(cls_node(str(name)))
             else:                           # Values
                 objects.append(Value((name, values)))
         return objects
+
+    Loader.add_constructor(u'!include',
+                           lambda loader, node: Control(YAML_INCLUDE))
     Loader.add_constructor(yaml.resolver.BaseResolver.DEFAULT_MAPPING_TAG,
                            mapping_to_tree_loader)
 

docs/source/MultiplexConfig.rst

@@ -155,6 +155,21 @@ results in::
     fast:
         CFLAGS: '-Ofast'    # appended
 
+It's also possilbe to include existing file into other file's node. This
+is done by `!include : $path` directive::
+
+    os:
+        fedora:
+            !include : fedora.yaml
+        gentoo:
+            !include : gentoo.yaml
+
+Due to yaml nature, it's __mandatory__ to put space between `!include` and `:`!
+
+The file location can be either absolute path or relative path to the yaml
+file where the `!include` is called (even when it's nested).
+
+Whole file is __merged__ into the node where it's defined.
 
 .. _variants:
 

examples/mux-selftest-advanced.yaml

+# Following line makes it look exactly as mux-selftest.yaml
+!include : mux-selftest.yaml
+distro:
+    # This line extends the distro branch using include
+    !include : mux-selftest-distro.yaml
+# This creates new branch the usual way
+new_node:
+    new_value: "something"

examples/mux-selftest-distro.yaml

+RHEL:
+    enterprise: true
+    6:
+        init: 'systemv'
+    7:
+        init: 'systemd'

selftests/all/unit/avocado/tree_unittest.py

@@ -152,6 +152,18 @@ class TestTree(unittest.TestCase):
         self.assertEqual({'nic': 'virtio'},
                          tree2.children[0].children[2].children[1].value)
 
+    def test_advanced_yaml(self):
+        tree2 = tree.create_from_yaml(['examples/mux-selftest-advanced.yaml'])
+        exp = ['intel', 'amd', 'arm', 'scsi', 'virtio', 'fedora', 'mint', '6',
+               '7', 'prod', 'new_node']
+        act = tree2.get_leaves()
+        self.assertEqual(exp, act)
+        self.assertEqual({'enterprise': True},
+                         tree2.children[1].children[2].value)
+        self.assertEqual({'init': 'systemd'},
+                         tree2.children[1].children[0].value)
+        self.assertEqual({'new_value': 'something'}, tree2.children[3].value)
+
 
 class TestPathParent(unittest.TestCase):