register: be better at showing empty intervals with --empty and a query pattern

hledger-lib/Hledger/Data/Dates.hs

@@ -116,6 +116,20 @@ orDatesFrom (DateSpan a1 b1) (DateSpan a2 b2) = DateSpan a b
     where a = if isJust a1 then a1 else a2
           b = if isJust b1 then b1 else b2
 
+-- | Calculate the intersection of two datespans.
+spanIntersect (DateSpan b1 e1) (DateSpan b2 e2) = DateSpan b e
+    where
+      b = latest b1 b2
+      e = earliest e1 e2
+
+latest d Nothing = d
+latest Nothing d = d
+latest (Just d1) (Just d2) = Just $ max d1 d2
+
+earliest d Nothing = d
+earliest Nothing d = d
+earliest (Just d1) (Just d2) = Just $ min d1 d2
+
 -- | Parse a period expression to an Interval and overall DateSpan using
 -- the provided reference date, or return a parse error.
 parsePeriodExpr :: Day -> String -> Either ParseError (Interval, DateSpan)

hledger-lib/Hledger/Reports.hs

@@ -224,17 +224,28 @@ postingsReport :: ReportOpts -> FilterSpec -> Journal -> PostingsReport
 postingsReport opts fspec j = (totallabel, postingsReportItems ps nullposting startbal (+))
     where
       ps | interval == NoInterval = displayableps
-         | otherwise              = summarisePostingsByInterval interval depth empty filterspan displayableps
+         | otherwise              = summarisePostingsByInterval interval depth empty reportspan displayableps
+      j' =                                journalSelectingDateFromOpts opts
+                                        $ journalSelectingAmountFromOpts opts
+                                        j
       (precedingps, displayableps, _) =   postingsMatchingDisplayExpr (display_ opts)
                                         $ depthClipPostings depth
                                         $ journalPostings
                                         $ filterJournalPostings fspec{depth=Nothing}
-                                        $ journalSelectingDateFromOpts opts
+                                        j'
-                                        $ journalSelectingAmountFromOpts opts
+      (interval, depth, empty, displayexpr) = (intervalFromOpts opts, depth_ opts, empty_ opts, display_ opts)
-                                        j
+      journalspan = journalDateSpan j'
+      -- requestedspan should be the intersection of any span specified
+      -- with period options and any span specified with display option.
+      -- The latter is not easily available, fake it for now.
+      requestedspan = periodspan `spanIntersect` displayspan
+      periodspan = datespan fspec
+      displayspan = postingsDateSpan ps
+          where (_,ps,_) = postingsMatchingDisplayExpr displayexpr $ journalPostings j'
+      matchedspan = postingsDateSpan displayableps
+      reportspan | empty     = requestedspan `orDatesFrom` journalspan
+                 | otherwise = requestedspan `spanIntersect` matchedspan
       startbal = sumPostings precedingps
-      filterspan = datespan fspec
-      (interval, depth, empty) = (intervalFromOpts opts, depth_ opts, empty_ opts)
 
 totallabel = "Total"
 balancelabel = "Balance"
@@ -309,13 +320,10 @@ depthClipPosting (Just d) p@Posting{paccount=a} = p{paccount=clipAccountName d a
 -- are one per account per interval and aggregated to the specified depth
 -- if any.
 summarisePostingsByInterval :: Interval -> Maybe Int -> Bool -> DateSpan -> [Posting] -> [Posting]
-summarisePostingsByInterval interval depth empty filterspan ps = concatMap summarisespan $ splitSpan interval reportspan
+summarisePostingsByInterval interval depth empty reportspan ps = concatMap summarisespan $ splitSpan interval reportspan
     where
       summarisespan s = summarisePostingsInDateSpan s depth empty (postingsinspan s)
       postingsinspan s = filter (isPostingInDateSpan s) ps
-      dataspan = postingsDateSpan ps
-      reportspan | empty = filterspan `orDatesFrom` dataspan
-                 | otherwise = dataspan
 
 -- | Given a date span (representing a reporting interval) and a list of
 -- postings within it: aggregate the postings so there is only one per

tests/register-intervals.test

@@ -0,0 +1,70 @@
+# 1. monthly reporting interval, no end dates, shows just the intervals with data:
+bin/hledger -f- register --period 'monthly'
+<<<
+2011/2/1
+  (a)  1
+>>>
+2011/02/01 - 2011/02/28         a                                 1            1
+>>>=0
+
+# 2. or with a query pattern, just the intervals with matched data:
+bin/hledger -f- register --period 'monthly' b
+<<<
+2011/1/1
+  (a)  1
+
+2011/2/1
+  (b)  1
+>>>
+2011/02/01 - 2011/02/28         b                                 1            1
+>>>=0
+
+# 3. with --empty, show all intervals spanned by the journal
+# (unlike current ledger, but more useful)
+bin/hledger -f- register --period 'monthly' b --empty
+<<<
+2011/1/1
+  (a)  1
+
+2011/2/1
+  (b)  1
+
+2011/3/1
+  (c)  1
+>>>
+2011/01/01 - 2011/01/31                                           0            0
+2011/02/01 - 2011/02/28         b                                 1            1
+2011/03/01 - 2011/03/31                                           0            1
+>>>=0
+
+# 4. any specified begin/end dates limit the intervals reported
+bin/hledger -f- register --period 'monthly to 2011/3/1' b --empty
+<<<
+2011/1/1
+  (a)  1
+
+2011/2/1
+  (b)  1
+
+2011/3/1
+  (c)  1
+>>>
+2011/01/01 - 2011/01/31                                           0            0
+2011/02/01 - 2011/02/28         b                                 1            1
+>>>=0
+
+# 5. likewise for date-restricting display expressions
+bin/hledger -f- register --period 'monthly to 2011/2/1' b --empty --display 'd<[2011/2/1]'
+<<<
+2011/1/1
+  (a)  1
+
+2011/2/1
+  (b)  1
+
+2011/3/1
+  (c)  1
+>>>
+2011/01/01 - 2011/01/31                                           0            0
+>>>=0
+

tests/reporting-intervals.test

@@ -1,50 +0,0 @@
-#
-# monthly reporting interval, no end dates, shows just the intervals with data:
-bin/hledger -f- register --period 'monthly'
-<<<
-2010/2/1 x
-  a  1
-  b
->>>
-2010/02/01 - 2010/02/28         a                                 1            1
-                                b                                -1            0
->>>=0
-
-#
-# with --empty, the same:
-bin/hledger -f- register --period 'monthly' --empty
-<<<
-2010/2/1 x
-  a  1
-  b
->>>
-2010/02/01 - 2010/02/28         a                                 1            1
-                                b                                -1            0
->>>=0
-
-#
-# with --empty and start/end dates, show all intervals covering the specified period
-bin/hledger -f- register --period 'monthly from 2010/1/10 to 2010/3/15' --empty
-<<<
-2010/2/1 x
-  a  1
-  b
->>>
-2010/01/01 - 2010/01/31                                           0            0
-2010/02/01 - 2010/02/28         a                                 1            1
-                                b                                -1            0
-2010/03/01 - 2010/03/31                                           0            0
->>>=0
-
-#
-# with just one start/end date, get the other from the data
-bin/hledger -f- register --period 'monthly from 2010/1/10' --empty
-<<<
-2010/2/1 x
-  a  1
-  b
->>>
-2010/01/01 - 2010/01/31                                           0            0
-2010/02/01 - 2010/02/28         a                                 1            1
-                                b                                -1            0
->>>=0