schema: add Must class

This patches introduces a new Must class that represents a must
statement. A new musts method is added to access the must statements of
a node. The must_conditions method is updated to use this new class,
and factorized in the SNode class.

Fixes: #90
Signed-off-by: Stefan Gula <steweg@gmail.com>
Signed-off-by: Samuel Gauthier <samuel.gauthier@6wind.com>

Author: steweg

libyang/__init__.py

@@ -74,6 +74,7 @@
     IfNotFeature,
     IfOrFeatures,
     Module,
+    Must,
     Revision,
     SContainer,
     SLeaf,
@@ -138,6 +139,7 @@
     "MandatoryAdded",
     "MandatoryRemoved",
     "Module",
+    "Must",
     "MustAdded",
     "MustRemoved",
     "NodeTypeAdded",

libyang/schema.py

@@ -1036,6 +1036,21 @@ def __str__(self):
         return "(%s OR %s)" % (self.a, self.b)
 
 
+# -------------------------------------------------------------------------------------
+class Must:
+    __slots__ = ("context", "cdata")
+
+    def __init__(self, context: "libyang.Context", cdata):
+        self.context = context
+        self.cdata = cdata  # C type: "struct lysc_must *"
+
+    def condition(self) -> str:
+        return c2str(lib.lyxp_get_expr(self.cdata.cond))
+
+    def error_message(self) -> Optional[str]:
+        return c2str(self.cdata.emsg) if self.cdata.emsg != ffi.NULL else None
+
+
 # -------------------------------------------------------------------------------------
 class SNode:
     __slots__ = ("context", "cdata", "cdata_parsed", "__dict__")
@@ -1138,7 +1153,17 @@ def extensions(self) -> Iterator[ExtensionCompiled]:
             yield ExtensionCompiled(self.context, extension)
 
     def must_conditions(self) -> Iterator[str]:
-        return iter(())
+        for must in self.musts():
+            yield must.condition()
+
+    def musts(self) -> Iterator[Must]:
+        mc = lib.lysc_node_musts(self.cdata)
+        if mc == ffi.NULL:
+            return
+        for m in ly_array_iter(mc):
+            if not m:
+                continue
+            yield Must(self.context, m)
 
     def get_extension(
         self, name: str, prefix: Optional[str] = None, arg_value: Optional[str] = None
@@ -1269,13 +1294,6 @@ def is_key(self) -> bool:
             return True
         return False
 
-    def must_conditions(self) -> Iterator[str]:
-        pdata = self.cdata_leaf_parsed
-        if pdata.musts == ffi.NULL:
-            return
-        for must in ly_array_iter(pdata.musts):
-            yield c2str(must.arg.str)
-
     def __str__(self):
         return "%s %s" % (self.name(), self.type().name())
 
@@ -1324,13 +1342,6 @@ def defaults(self) -> Iterator[Union[None, bool, int, str, float]]:
             else:
                 yield val
 
-    def must_conditions(self) -> Iterator[str]:
-        pdata = self.cdata_leaflist_parsed
-        if pdata.musts == ffi.NULL:
-            return
-        for must in ly_array_iter(pdata.musts):
-            yield c2str(must.arg.str)
-
     def max_elements(self) -> int:
         return (
             self.cdata_leaflist.max
@@ -1363,13 +1374,6 @@ def presence(self) -> Optional[str]:
 
         return c2str(self.cdata_container_parsed.presence)
 
-    def must_conditions(self) -> Iterator[str]:
-        pdata = self.cdata_container_parsed
-        if pdata.musts == ffi.NULL:
-            return
-        for must in ly_array_iter(pdata.musts):
-            yield c2str(must.arg.str)
-
     def __iter__(self) -> Iterator[SNode]:
         return self.children()
 
@@ -1425,13 +1429,6 @@ def keys(self) -> Iterator[SNode]:
                 yield SLeaf(self.context, node)
             node = node.next
 
-    def must_conditions(self) -> Iterator[str]:
-        pdata = self.cdata_list_parsed
-        if pdata.musts == ffi.NULL:
-            return
-        for must in ly_array_iter(pdata.musts):
-            yield c2str(must.arg.str)
-
     def uniques(self) -> Iterator[List[SNode]]:
         for unique in ly_array_iter(self.cdata_list.uniques):
             nodes = []

tests/test_schema.py

@@ -12,6 +12,7 @@
     IOType,
     LibyangError,
     Module,
+    Must,
     Revision,
     SContainer,
     SLeaf,
@@ -530,6 +531,15 @@ def tearDown(self):
         self.ctx.destroy()
         self.ctx = None
 
+    def test_must(self):
+        leaf = next(self.ctx.find_path("/yolo-nodetypes:conf/percentage"))
+        self.assertIsInstance(leaf, SLeaf)
+        must = next(leaf.musts(), None)
+        self.assertIsInstance(must, Must)
+        self.assertEqual(must.error_message(), "ERROR1")
+        must = next(leaf.must_conditions(), None)
+        self.assertIsInstance(must, str)
+
     def test_leaf_default(self):
         leaf = next(self.ctx.find_path("/yolo-nodetypes:conf/percentage"))
         self.assertIsInstance(leaf.default(), float)

tests/yang/yolo/yolo-nodetypes.yang

@@ -31,6 +31,9 @@ module yolo-nodetypes {
         fraction-digits 2;
       }
       default 10.2;
+      must ". = 10.6" {
+        error-message "ERROR1";
+      }
     }
 
     leaf-list ratios {