[sonic_yang.py]: Adding debug support in sonic_yang. (sonic-net#28)

src/sonic-yang-mgmt/_sonic_yang_ext.py

@@ -265,18 +265,22 @@ def xlateList(self, model, yang, config, table):
 
     leafDict = self.createLeafDict(model)
 
+    self.logInFile("Xlate {}".format(table))
     # Find and extracts key from each dict in config
     for pkey in config:
         try:
+            vKey = None
+            self.logInFile("xlate Extract pkey {} {}".format(pkey,keyExt[table]))
             keyDict = self.extractKey(pkey, keyExt[table])
             # fill rest of the values in keyDict
             for vKey in config[pkey]:
+                self.logInFile("xlate vkey {}".format(vKey), keyExt[table])
                 keyDict[vKey] = self.findYangTypedValue(vKey, \
                                     config[pkey][vKey], leafDict)
             yang.append(keyDict)
         except Exception as e:
             print("Exception while Config DB --> YANG: pkey:{}, "\
-            "vKey:{}, value: {}".format(pkey, vKey, config[pkey][vKey]))
+            "vKey:{}, value: {}".format(pkey, vKey, config[pkey].get(vKey)))
             raise e
 
     return

src/sonic-yang-mgmt/sonic_yang.py

@@ -1,17 +1,25 @@
 import yang as ly
 from json import dump
 from glob import glob
+from datetime import datetime
 
 """
 Yang schema and data tree python APIs based on libyang python
 """
 class sonic_yang:
-    def __init__(self, yang_dir):
+
+    def __init__(self, yang_dir, debug=True):
         self.yang_dir = yang_dir
         self.ctx = None
         self.module = None
         self.root = None
 
+        self.DEBUG_FILE = None
+        if debug:
+            self.DEBUG_FILE = '_debug_sonic_yang'
+            with open(self.DEBUG_FILE, 'w') as df:
+                df.write('--- Start sonic_yang logging ---\n\n')
+
         # yang model files, need this map it to module
         self.yangFiles = list()
         # map from TABLE in config DB to container and module
@@ -39,6 +47,23 @@ def fail(self, e):
     """
     from _sonic_yang_ext import *
 
+    """
+    Loggign in debug file, this function prints header then object
+    """
+    def logInFile(self, header="", obj=None, json=False):
+
+        if self.DEBUG_FILE:
+            with open(self.DEBUG_FILE, 'a') as df:
+                time = datetime.now()
+                df.write('\n\n{}: {}\n'.format(time, header))
+                if json:
+                    dump(obj, df, indent=4)
+                elif obj:
+                        df.write('{}: {}'.format(time, obj))
+                df.write('\n----')
+
+        return
+
     """
     load_schema_module(): load a Yang model file
     input:    yang_file - full path of a Yang model file