Add helper methods for initialisation from json data

Added helper methods to initialise model member variables.  Now
the models' constructors will not throw exception if a value is
missing, but instead just initialise the variable to None.

Change-Id: I7473ec9bb471f95ea0142067af4750c7e26a0339

3 files changed, 58 insertions, 59 deletions

diff --git a/pygerrit/__init__.py b/pygerrit/__init__.py
index cb77bdc..100380b 100644
--- a/pygerrit/__init__.py
+++ b/pygerrit/__init__.py
@@ -1,7 +1,13 @@
 """ Module to interface with Gerrit. """
 
 
-from pygerrit.error import *
-from pygerrit.events import *
-from pygerrit.models import *
-from pygerrit.stream import *
+def from_json(json_data, key):
+    """ Helper method to extract values from JSON data.
+
+    Return the value of `key` from `json_data`, or None if `json_data`
+    does not contain `key`.
+
+    """
+    if key in json_data:
+        return json_data[key]
+    return None
diff --git a/pygerrit/events.py b/pygerrit/events.py
index 90459f4..c07979a 100644
--- a/pygerrit/events.py
+++ b/pygerrit/events.py
@@ -81,10 +81,7 @@ class ChangeAbandonedEvent(GerritEvent):
         super(ChangeAbandonedEvent, self).__init__()
         try:
             self.change = Change(json_data["change"])
-            if "patchSet" in json_data:
-                self.patchset = Patchset(json_data["patchSet"])
-            else:
-                self.patchset = None
+            self.patchset = Patchset.from_json(json_data)
             self.abandoner = Account(json_data["abandoner"])
             self.reason = json_data["reason"]
         except KeyError, e:
@@ -99,10 +96,7 @@ class ChangeRestoredEvent(GerritEvent):
         super(ChangeRestoredEvent, self).__init__()
         try:
             self.change = Change(json_data["change"])
-            if "patchSet" in json_data:
-                self.patchset = Patchset(json_data["patchSet"])
-            else:
-                self.patchset = None
+            self.patchset = Patchset.from_json(json_data)
             self.restorer = Account(json_data["restorer"])
             self.reason = json_data["reason"]
         except KeyError, e:
@@ -117,9 +111,6 @@ class RefUpdatedEvent(GerritEvent):
         super(RefUpdatedEvent, self).__init__()
         try:
             self.ref_update = RefUpdate(json_data["refUpdate"])
-            if "submitter" in json_data:
-                self.submitter = Account(json_data["submitter"])
-            else:
-                self.submitter = None
+            self.submitter = Account.from_json(json_data, "submitter")
         except KeyError, e:
             raise GerritError("RefUpdatedEvent: %s" % e)
diff --git a/pygerrit/models.py b/pygerrit/models.py
index c8c70d5..813b53f 100644
--- a/pygerrit/models.py
+++ b/pygerrit/models.py
@@ -1,6 +1,6 @@
 """ Models for Gerrit JSON data. """
 
-from pygerrit.error import GerritError
+from pygerrit import from_json
 
 
 class Account(object):
@@ -8,14 +8,20 @@ class Account(object):
     """ Gerrit user account (name and email address). """
 
     def __init__(self, json_data):
-        try:
-            self.name = json_data["name"]
-            if "email" in json_data:
-                self.email = json_data["email"]
-            else:
-                self.email = ""
-        except KeyError, e:
-            raise GerritError("GerritAccount: %s" % e)
+        self.name = from_json(json_data, "name")
+        self.email = from_json(json_data, "email")
+
+    @staticmethod
+    def from_json(json_data, key):
+        """ Create an Account instance.
+
+        Return an instance of Account initialised with values from `key`
+        in `json_data`, or None if `json_data` does not contain `key`.
+
+        """
+        if key in json_data:
+            return Account(json_data[key])
+        return None
 
 
 class Change(object):
@@ -23,16 +29,13 @@ class Change(object):
     """ Gerrit change. """
 
     def __init__(self, json_data):
-        try:
-            self.project = json_data["project"]
-            self.branch = json_data["branch"]
-            self.change_id = json_data["id"]
-            self.number = json_data["number"]
-            self.subject = json_data["subject"]
-            self.url = json_data["url"]
-            self.owner = Account(json_data["owner"])
-        except KeyError, e:
-            raise GerritError("GerritChange: %s" % e)
+        self.project = from_json(json_data, "project")
+        self.branch = from_json(json_data, "branch")
+        self.change_id = from_json(json_data, "id")
+        self.number = from_json(json_data, "number")
+        self.subject = from_json(json_data, "subject")
+        self.url = from_json(json_data, "url")
+        self.owner = Account.from_json(json_data, "owner")
 
 
 class Patchset(object):
@@ -40,13 +43,22 @@ class Patchset(object):
     """ Gerrit patch set. """
 
     def __init__(self, json_data):
-        try:
-            self.number = json_data["number"]
-            self.revision = json_data["revision"]
-            self.ref = json_data["ref"]
-            self.uploader = Account(json_data["uploader"])
-        except KeyError, e:
-            raise GerritError("GerritPatchset: %s" % e)
+        self.number = from_json(json_data, "number")
+        self.revision = from_json(json_data, "revision")
+        self.ref = from_json(json_data, "ref")
+        self.uploader = Account.from_json(json_data, "uploader")
+
+    @staticmethod
+    def from_json(json_data):
+        r""" Create a Patchset instance.
+
+        Return an instance of Patchset initialised with values from "patchSet"
+        in `json_data`, or None if `json_data` does not contain "patchSet".
+
+        """
+        if "patchSet" in json_data:
+            return Patchset(json_data["patchSet"])
+        return None
 
 
 class Approval(object):
@@ -54,16 +66,9 @@ class Approval(object):
     """ Gerrit approval (verified, code review, etc). """
 
     def __init__(self, json_data):
-        if "type" not in json_data:
-            raise GerritError("GerritApproval: Missing type")
-        if "value" not in json_data:
-            raise GerritError("GerritApproval: Missing value")
-        self.category = json_data["type"]
-        self.value = json_data["value"]
-        if "description" in json_data:
-            self.description = json_data["description"]
-        else:
-            self.description = None
+        self.category = from_json(json_data, "type")
+        self.value = from_json(json_data, "value")
+        self.description = from_json(json_data, "description")
 
 
 class RefUpdate(object):
@@ -71,10 +76,7 @@ class RefUpdate(object):
     """ Gerrit ref update. """
 
     def __init__(self, json_data):
-        try:
-            self.oldrev = json_data["oldRev"]
-            self.newrev = json_data["newRev"]
-            self.refname = json_data["refName"]
-            self.project = json_data["project"]
-        except KeyError, e:
-            raise GerritError("GerritRefUpdate: %s" % e)
+        self.oldrev = from_json(json_data, "oldRev")
+        self.newrev = from_json(json_data, "newRev")
+        self.refname = from_json(json_data, "refName")
+        self.project = from_json(json_data, "project")