Keep merge suffix for nested dictionaries

This is necessary to make possible merging dictionaries
in adjust rules. Otherwise they would be always set (instead of update).

Fix: #276
Reopen: #190

docs/features.rst

@@ -98,6 +98,9 @@ or when merging a dictionary with a list.
 Exception ``MergeError`` is raised if types are not compatible. When
 the ``+`` suffix is applied on dictionaries ``update()`` method is
 used to merge content of given dictionary instead of replacing it.
+When such parent dictionary doesn't exist, but the suffix ``+`` is used
+at the top level, the dictionary is created and named without the suffix.
+However, for dictionaries at deeper levels, the suffix remains in their name.
 
 Example: Merging dictionary with a list::
 
@@ -159,6 +162,25 @@ results in::
             url: https://github.com/project2
             filter: "tier:2"
 
+Example: Merging with not yet defined dictionaries::
+
+    environment+:
+        CLEAR: "1"
+    adjust+:
+        when: distro == fedora
+        environment+:
+            FEDORA: "1"
+
+results in (no ``+`` suffix in ``adjust`` and top ``environment`` keys)::
+
+    adjust:
+        when: distro == fedora
+        environment+:
+            FEDORA: "1"
+    environment:
+        CLEAR: "1"
+
+
 The special suffix ``+<`` can be used to prepend values instead of
 appending them. This might be handy when adjusting lists::
 

examples/deep/main.fmf

@@ -21,6 +21,7 @@ hardware:
         model: e1000
 
 # A deep dictionary extending non-existent values
+# should keep '+' (important for adjust)
 /single:
     undefined+:
         deeper+:

fmf/base.py

@@ -190,13 +190,7 @@ def _merge_plus(self, data, key, value, prepend=False):
 
         # Set the value if key is not present
         if key not in data:
-            # Special handling for dictionaries as their keys might
-            # contain suffixes which should be removed
-            if isinstance(value, dict):
-                data[key] = {}
-                self._merge_special(data[key], value)
-            else:
-                data[key] = value
+            data[key] = value
             return
 
         # Parent is a list of dict and child is a dict

tests/unit/test_base.py

@@ -4,6 +4,7 @@
 import threading
 import time
 from shutil import rmtree
+from textwrap import dedent
 
 import pytest
 from ruamel.yaml import YAML
@@ -137,6 +138,21 @@ def test_adjust_strips_control_keys(self):
         assert 'because' not in child.data
         assert 'foo' in child.data
 
+    def test_adjust_can_extend(self):
+        """ It is possible to extend dictionary with adjust """
+        tree = Tree(YAML(typ='safe').load(dedent("""
+        /a:
+         environment+:
+          FOO: bar
+         adjust+:
+          environment+:
+            BAR: baz
+        """)))
+        tree.adjust(context=Context())
+        child = tree.find('/a')
+        assert child.data['environment']['FOO'] == "bar"
+        assert child.data['environment']['BAR'] == "baz"
+
     def test_deep_hierarchy(self):
         """ Deep hierarchy on one line """
         deep = Tree(EXAMPLES + "deep")
@@ -154,12 +170,12 @@ def test_deep_dictionary_undefined_keys(self):
         """ Extending undefined keys using '+' should work """
         deep = Tree(EXAMPLES + "deep")
         single = deep.find("/single")
-        assert single.get(["undefined", "deeper", "key"]) == "value"
+        assert single.get(["undefined", "deeper+", "key"]) == "value"
         child = deep.find("/parent/child")
         assert child.get("one") == 2
         assert child.get("two") == 4
         assert child.get("three") == 3
-        assert child.get(["undefined", "deeper", "key"]) == "value"
+        assert child.get(["undefined", "deeper+", "key"]) == "value"
 
     def test_merge_plus(self):
         """ Extending attributes using the '+' suffix """