Add support for merging list with dict

docs/features.rst

@@ -92,11 +92,72 @@ Append a ``+`` sign to the attribute name to add given value::
     /download:
         time+: 3
 
-This operation is possible only for attributes of the same type.
-Exception ``MergeError`` is raised if types are different. When
+This operation is possible only for attributes of the same type
+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.
 
+Example: Merging dictionary with a list::
+
+    discover:
+        how: fmf
+        filter: "tier:1"
+
+    /path:
+      discover+:
+        - name: upstream
+          url: https://some.url
+        - name: downstream
+          url: https://other.url
+
+results in::
+
+    /path:
+      discover:
+        - name: upstream
+          url: https://some.url
+          how: fmf
+          filter: "tier:1"
+        - name: downstream
+          url: https://other.url
+          how: fmf
+          filter: "tier:1"
+
+Example: Merging list with a dictionary::
+
+    discover:
+      - how: fmf
+        url: https://github.com/project1
+      - how: fmf
+        url: https://github.com/project2
+
+    /tier1:
+        discover+:
+            filter: "tier:1"
+    /tier2:
+        discover+:
+            filter: "tier:2"
+
+results in::
+
+    /tier1:
+        discover:
+          - how: fmf
+            url: https://github.com/project1
+            filter: "tier:1"
+          - how: fmf
+            url: https://github.com/project2
+            filter: "tier:1"
+    /tier2:
+        discover:
+          - how: fmf
+            url: https://github.com/project1
+            filter: "tier:2"
+          - how: fmf
+            url: https://github.com/project2
+            filter: "tier:2"
+
 The special suffix ``+<`` can be used to prepend values instead of
 appending them. This might be handy when adjusting lists::
 

examples/merge/parent-dict.fmf

@@ -0,0 +1,12 @@
+discover:
+    how: fmf
+    summary: test.
+
+/path:
+    discover+:
+      - name: upstream
+        url: https://some.url
+        summary+: upstream
+      - name: downstream
+        url: https://other.url
+        summary+: downstream

examples/merge/parent-list.fmf

@@ -0,0 +1,19 @@
+discover:
+  - how: fmf
+    url: https://github.com/project1
+    summary: project1.
+  - how: fmf
+    url: https://github.com/project2
+    summary: project2.
+
+/tier1:
+    summary: basic tests
+    discover+:
+        filter: "tier: 1"
+        summary+: tier1
+
+/tier2:
+    summary: detailed tests
+    discover+:
+        filter: "tier: 2"
+        summary+: tier2

fmf/base.py

@@ -172,14 +172,43 @@ def _initialize(self, path):
 
     def _merge_plus(self, data, key, value, prepend=False):
         """ Handle extending attributes using the '+' suffix """
+
         # Nothing to do if key not in parent
         if key not in data:
             data[key] = value
             return
+
+        # Parent is a list of dict and child is a dict
+        # (just update every parent list item using the special merge)
+        if isinstance(data[key], list) and isinstance(value, dict):
+            for list_item in data[key]:
+                if not isinstance(list_item, dict):
+                    raise utils.MergeError(
+                        "MergeError: Item '{0}' in {1} must be a dictionary.".format(
+                            list_item, self.name))
+                self._merge_special(list_item, value)
+            return
+
+        # Parent is a dict and child is a list of dict
+        # (replace parent dict with the list of its special-merged copies)
+        if isinstance(data[key], dict) and isinstance(value, list):
+            result_list = []
+            for list_item in value:
+                if not isinstance(list_item, dict):
+                    raise utils.MergeError(
+                        "MergeError: Item '{0}' in {1} must be a dictionary.".format(
+                            list_item, self.name))
+                result_dict = copy.deepcopy(data[key])
+                self._merge_special(result_dict, list_item)
+                result_list.append(result_dict)
+            data[key] = result_list
+            return
+
         # Use the special merge for merging dictionaries
         if type(data[key]) == type(value) == dict:
             self._merge_special(data[key], value)
             return
+
         # Attempt to apply the plus operator
         try:
             if prepend:

tests/unit/test_base.py

@@ -161,6 +161,32 @@ def test_merge_plus(self):
             child.data["time+"] = "string"
             child.inherit()
 
+    def test_merge_plus_parent_dict(self):
+        """ Merging parent dict with child list """
+        child = self.merge.find('/parent-dict/path')
+        assert len(child.data['discover']) == 2
+        assert child.data['discover'][0]['how'] == 'fmf'
+        assert child.data['discover'][0]['name'] == 'upstream'
+        assert child.data['discover'][0]['url'] == 'https://some.url'
+        assert child.data['discover'][0]['summary'] == 'test.upstream'
+        assert child.data['discover'][1]['how'] == 'fmf'
+        assert child.data['discover'][1]['name'] == 'downstream'
+        assert child.data['discover'][1]['url'] == 'https://other.url'
+        assert child.data['discover'][1]['summary'] == 'test.downstream'
+
+    def test_merge_plus_parent_list(self):
+        """ Merging parent list with child dict """
+        for i in [1, 2]:
+            child = self.merge.find(f'/parent-list/tier{i}')
+            assert child.data['summary'] == 'basic tests' if i == 1 else 'detailed tests'
+            assert len(child.data['discover']) == 2
+            assert child.data['discover'][0]['filter'] == f'tier: {i}'
+            assert child.data['discover'][0]['url'] == 'https://github.com/project1'
+            assert child.data['discover'][0]['summary'] == f'project1.tier{i}'
+            assert child.data['discover'][1]['filter'] == f'tier: {i}'
+            assert child.data['discover'][1]['url'] == 'https://github.com/project2'
+            assert child.data['discover'][1]['summary'] == f'project2.tier{i}'
+
     def test_merge_minus(self):
         """ Reducing attributes using the '-' suffix """
         child = self.merge.find('/parent/reduced')