Add description argument to DataModel constructor.

docs/datamodel.rst

@@ -25,14 +25,21 @@ document from :ref:`sec-ex1`.
 
 __ http://www.sphinx-doc.org/en/stable/ext/doctest.html
 
-.. class:: DataModel(yltxt: str, mod_path: List[str])
+.. class:: DataModel(yltxt: str, mod_path: List[str], \
+	   description: str = None)
 
    This class provides a basic user-level entry point to the *Yangson*
    library.
 
    The constructor argument *yltxt* is a string with JSON-encoded YANG
    library data [RFC7895]_, and *mod_path* is a list of filesystem
-   directories in which *Yangson* searches for YANG modules.
+   directories in which *Yangson* searches for YANG modules (by
+   default it is only the current directory).
+
+   The *description* argument allows for adding a description text to
+   the entire data model. If it is ``None``, then a default
+   description is added which contains the ``module-set-id`` value
+   from the YANG library data.
 
    The class constructor may raise the following exceptions:
 
@@ -55,14 +62,14 @@ __ http://www.sphinx-doc.org/en/stable/ext/doctest.html
 
    .. rubric:: Public Methods
 
-   .. classmethod:: from_file(name: str, mod_path: List[str] = ["."] ) \
-		    -> DataModel
+   .. classmethod:: from_file(name: str, mod_path: List[str] = ["."], \
+		    description: str = None) -> DataModel
 
       Initialize the data model from a file containing JSON-encoded
       YANG library data and return the :class:`DataModel`
-      instance. The *name* argument is the name of that file, and
-      *mod_path* has the same meaning as in the class constructor. By
-      default, *mod_path* includes only the current directory.
+      instance. The *name* argument is the name of that file. The
+      remaining two arguments are passed unchanged to the
+      :class:`DataModel` class constructor.
 
       This method may raise the same exceptions as the class
       constructor.
@@ -218,7 +225,7 @@ __ http://www.sphinx-doc.org/en/stable/ext/doctest.html
        .. doctest::
 
 	  >>> len(dm.schema_digest())
-	  134
+	  208
 
 .. _6.1: https://tools.ietf.org/html/rfc7951#section-6.1
 .. _7.5.1: https://tools.ietf.org/html/rfc7950#section-7.5.1

docs/quickstart.rst

@@ -34,6 +34,8 @@ by reading YANG library data [RFC7895]_ from a file:
 .. doctest::
 
    >>> dm = DataModel.from_file('yang-library-ex2.json')
+   >>> dm.schema.description
+   'Data model ID: 9a9b7d2d28d4d78fa42e12348346990e3fb1c1b9'
 
 Here is an ASCII art depicting the schema tree:
 

yangson/datamodel.py

@@ -38,12 +38,14 @@ class DataModel:
     """Basic user-level entry point to Yangson library."""
 
     @classmethod
-    def from_file(cls, name: str, mod_path: List[str] = ["."]) -> "DataModel":
+    def from_file(cls, name: str, mod_path: List[str] = ["."],
+                      description: str = None) -> "DataModel":
         """Initialize the data model from a file with YANG library data.
 
         Args:
             name: Name of a file with YANG library data.
             mod_path: List of directories where to look for YANG modules.
+            description:  Optional description of the data model.
 
         Returns:
             The data model instance.
@@ -53,14 +55,16 @@ class DataModel:
         """
         with open(name, encoding="utf-8") as infile:
             yltxt = infile.read()
-        return cls(yltxt, mod_path)
+        return cls(yltxt, mod_path, description)
 
-    def __init__(self, yltxt: str, mod_path: List[str]):
+    def __init__(self, yltxt: str, mod_path: List[str] = ["."],
+                     description: str = None):
         """Initialize the class instance.
         
         Args:
             yltxt: JSON text with YANG library data.
             mod_path: List of directories where to look for YANG modules.
+            description: Optional description of the data model.
 
         Raises:
             BadYangLibraryData: If YANG library data is invalid.
@@ -79,6 +83,8 @@ class DataModel:
             raise BadYangLibraryData(str(e)) from None
         self.schema_data = SchemaData(yl, mod_path)
         self._build_schema()
+        self.schema.description = description if description else (
+            "Data model ID: " + yl["ietf-yang-library:modules-state"]["module-set-id"])
 
     def module_set_id(self) -> str:
         """Compute unique id of YANG modules comprising the data model.