Add exception module.

lakesuperior/exceptions.py

@@ -0,0 +1,87 @@
+''' Put all exceptions here. '''
+
+class ResourceError(RuntimeError):
+    '''
+    Raised in an attempt to create a resource a URI that already exists and is
+    not supposed to.
+
+    This usually surfaces at the HTTP level as a 409.
+    '''
+    def __init__(self, uuid, msg=None):
+        self.uuid = uuid
+        self.msg = msg
+
+
+class ResourceExistsError(ResourceError):
+    '''
+    Raised in an attempt to create a resource a URI that already exists and is
+    not supposed to.
+
+    This usually surfaces at the HTTP level as a 409.
+    '''
+    def __repr__(self):
+        return self.msg or 'Resource #{} already exists.'.format(self.uuid)
+
+
+
+class ResourceNotExistsError(ResourceError):
+    '''
+    Raised in an attempt to create a resource a URN that does not exist and is
+    supposed to.
+
+    This usually surfaces at the HTTP level as a 404.
+    '''
+    def __repr__(self):
+        return self.msg or 'Resource #{} does not exist.'.format(self.uuid)
+
+
+
+class InvalidResourceError(ResourceError):
+    '''
+    Raised when an invalid resource is found.
+
+    This usually surfaces at the HTTP level as a 409 or other error.
+    '''
+    def __repr__(self):
+        return self.msg or 'Resource #{} is invalid.'.format(self.uuid)
+
+
+
+class ServerManagedTermError(RuntimeError):
+    '''
+    Raised in an attempt to change a triple containing a server-managed term.
+
+    This usually surfaces at the HTTP level as a 409 or other error.
+    '''
+    def __init__(self, terms, term_type):
+        if term_type == 's':
+            term_name = 'subject'
+        elif term_type == 'p':
+            term_name = 'predicate'
+        elif term_type == 't':
+            term_name = 'RDF type'
+        else:
+            term_name = 'term'
+
+        self.terms = terms
+        self.term_name = term_name
+
+    def __str__(self):
+        return 'Some {}s are server managed and cannot be modified: {}'\
+                .format(self.term_name, ' , '.join(self.terms))
+
+
+class SingleSubjectError(RuntimeError):
+    '''
+    Raised when a SPARQL-Update query or a RDF payload for a PUT contain
+    subjects that do not correspond to the resource being operated on.
+    '''
+    def __init__(self, uri, subject):
+        self.uri = uri
+        self.subject = subject
+
+    def __str__(self):
+        return '{} is not in the topic of this RDF, which is {}'.format(
+                self.uri, self.subject)
+
+