From 83ef120c6270bbf889a0be144fa07e33699df962 Mon Sep 17 00:00:00 2001
From: davidsarah <>
Date: Mon, 26 Sep 2011 22:41:20 +0000
Subject: [PATCH] s/_assert_consistency/_assert_invariants/

[Imported from Trac: page CodingStandards, version 16]
---
 CodingStandards.md | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/CodingStandards.md b/CodingStandards.md
index 2eccaf5..f32571c 100644
--- a/CodingStandards.md
+++ b/CodingStandards.md
@@ -81,7 +81,7 @@ The "error message" that will accompany a failed expression should be a statemen
 If your class has internal state which is complicated enough that a bug in the class's implementation could lead to garbled internal state, then you should have a class invariant. A class invariant is a method like this (an actual example from !BlockWrangler, but truncated for space):
 
 ```
-def _assert_consistency(self):
+def _assert_invariants(self):
     # All of the keys in all of these dicts are required to be ids.
     for d in (self.bId2chunkobj, self.bId2peers, self.Idsofwantedblocks, self.Idsoflocatedblocks,):
         _assert(not [key for key in d.keys() if not idlib.is_id(key)], "All of the keys in these dicts are required to be ids.", listofnonIds=[key for key in d.keys() if not idlib.is_id(key)])
@@ -94,7 +94,9 @@ def _assert_consistency(self):
         _assert((claim == "yes") == (peer in self.bId2peers.get(blockId, ())), "The blockId must appear in bId2peers if and only if the peer has claimed the block.", claim=claim, peer=peer, bId2peersentry=self.bId2peers.get(blockId, ()))
 ```      
 
-Now you can put `assert self._assert_consistency()` everywhere in your class where the class ought to be in an internally consistent state. For example, at the beginning of every externally-callable method. This technique can be very valuable in developing a complex class -- it catches bugs early, it isolates bugs into specific code paths, and it clarifies the internal structure of the class so that other developers can hack on it without subtle misunderstandings.
+Now you can put `assert self._assert_invariants()` everywhere in your class where the class ought to be in an internally consistent state. For example, at the beginning of every externally-callable method. This technique can be very valuable in developing a complex class -- it catches bugs early, it isolates bugs into specific code paths, and it clarifies the internal structure of the class so that other developers can hack on it without subtle misunderstandings.
+
+* we actually appear to only have one instance of this pattern in Tahoe at time of writing, in `allmydata.util.dictutil`. It has the disadvantage of cluttering up the logic with calls to `_assert_invariants`, and should probably be used sparingly. -- DavidSarah
 
 === configuration ===