register: make reporting intervals honour a display expression (#18)

Commands/Register.hs

@@ -33,7 +33,7 @@ showRegisterReport opts filterspec l
       summaryps = concatMap summarisespan spans
       summarisespan s = summarisePostingsInDateSpan s depth empty (postingsinspan s)
       postingsinspan s = filter (isPostingInDateSpan s) displayedps
-      spans = splitSpan interval (ledgerDateSpan l)
+      spans = splitSpan interval (postingsDateSpan displayedps)
       interval = intervalFromOpts opts
       empty = Empty `elem` opts
       depth = depthFromOpts opts

Ledger/Ledger.hs

@@ -138,11 +138,7 @@ ledgerAccountTreeAt l acct = subtreeat acct $ ledgerAccountTree 9999 l
 -- | The (fully specified) date span containing all the ledger's (filtered) transactions,
 -- or DateSpan Nothing Nothing if there are none.
 ledgerDateSpan :: Ledger -> DateSpan
-ledgerDateSpan l
-    | null ps = DateSpan Nothing Nothing
-    | otherwise = DateSpan (Just $ postingDate $ head ps) (Just $ addDays 1 $ postingDate $ last ps)
-    where
-      ps = sortBy (comparing postingDate) $ ledgerPostings l
+ledgerDateSpan = postingsDateSpan . ledgerPostings
 
 -- | Convenience aliases.
 accountnames :: Ledger -> [AccountName]

Ledger/Posting.hs

@@ -86,3 +86,10 @@ isPostingInDateSpan (DateSpan (Just b) (Just e)) p = d >= b && d < e where d = p
 isEmptyPosting :: Posting -> Bool
 isEmptyPosting = isZeroMixedAmount . pamount
 
+-- | Get the minimal date span which contains all the postings, or
+-- DateSpan Nothing Nothing if there are none.
+postingsDateSpan :: [Posting] -> DateSpan
+postingsDateSpan [] = DateSpan Nothing Nothing
+postingsDateSpan ps = DateSpan (Just $ postingDate $ head ps') (Just $ addDays 1 $ postingDate $ last ps')
+    where ps' = sortBy (comparing postingDate) ps
+