feat:import: resolve matchgroup references in ConditionalBlock scope (#2158)

Adjust getEffectiveAssignment to compute an intermediary form of the
active assignments (with an additional Either wrapper to distinguish
top-level and conditional assignments) and move the remaining work to
its only caller, hledgerField.

Rework hledgerFieldValue. Instead of calling hledgerField, call
getEffectiveAssignment and--in the conditional block case--construct
a CsvRules scoped just to the active ConditionalBlock before calling
renderTemplate.

Adjust regexMatchValue to use rconditionalblocks to access conditional
blocks from the CsvRules, rather than rblocksassigning, since we haven't
narrowed the scope of that field.

The result is match group references are only expanded for match groups
that occur within the in-scope ConditionalBlock. Fixes: #2158.

Signed-off-by: Jonathan Dowland <jon@dow.land>

hledger-lib/Hledger/Read/RulesReader.hs

@@ -710,12 +710,21 @@ csvRule rules = (`getDirective` rules)
 -- list/field assignment rules, taking into account the current record and
 -- conditional rules.
 hledgerField :: CsvRules -> CsvRecord -> HledgerFieldName -> Maybe FieldTemplate
-hledgerField = getEffectiveAssignment
+hledgerField rules record f = fmap
+  (either id (lastCBAssignmentTemplate f))
+  (getEffectiveAssignment rules record f)
 
 -- | Look up the final value assigned to a hledger field, with csv field
 -- references interpolated.
-hledgerFieldValue :: CsvRules -> CsvRecord -> HledgerFieldName -> Maybe Text
-hledgerFieldValue rules record f = (fmap (renderTemplate rules record f) . hledgerField rules record) f
+hledgerFieldValue rules record f = (flip fmap) (getEffectiveAssignment rules record f)
+  $ either (renderTemplate rules record)
+  $ \cb -> let
+      t = lastCBAssignmentTemplate f cb
+      r = rules { rconditionalblocks = [cb] } -- XXX handle rblocksassigning
+      in renderTemplate r record t
+
+lastCBAssignmentTemplate :: HledgerFieldName -> ConditionalBlock -> FieldTemplate
+lastCBAssignmentTemplate f = snd . last . filter ((==f).fst) . cbAssignments
 
 maybeNegate :: MatcherPrefix -> Bool -> Bool
 maybeNegate Not origbool = not origbool
@@ -728,15 +737,22 @@ maybeNegate _ origbool = origbool
 -- Note conditional blocks' patterns are matched against an approximation of the
 -- CSV record: all the field values, without enclosing quotes, comma-separated.
 --
-getEffectiveAssignment :: CsvRules -> CsvRecord -> HledgerFieldName -> Maybe FieldTemplate
-getEffectiveAssignment rules record f = lastMay $ map snd $ assignments
+getEffectiveAssignment
+  :: CsvRules
+     -> CsvRecord
+     -> HledgerFieldName
+     -> Maybe (Either FieldTemplate ConditionalBlock)
+getEffectiveAssignment rules record f = lastMay assignments
   where
     -- all active assignments to field f, in order
-    assignments = dbg9 "csv assignments" $ filter ((==f).fst) $ toplevelassignments ++ conditionalassignments
+    assignments = dbg9 "csv assignments" $ toplevelassignments ++ conditionalassignments
     -- all top level field assignments
-    toplevelassignments    = rassignments rules 
+    toplevelassignments    = map (Left . snd) $ filter ((==f).fst) $ rassignments rules
     -- all field assignments in conditional blocks assigning to field f and active for the current csv record
-    conditionalassignments = concatMap cbAssignments $ filter (isBlockActive rules record) $ (rblocksassigning rules) f
+    conditionalassignments = map Right
+                           $ filter (any (==f) . map fst . cbAssignments)
+                           $ filter (isBlockActive rules record)
+                           $ (rblocksassigning rules) f
 
 -- does this conditional block match the current csv record ?
 isBlockActive :: CsvRules -> CsvRecord -> ConditionalBlock -> Bool
@@ -812,7 +828,8 @@ regexMatchValue rules record f sgroup = let
   matchgroups  = concatMap (getMatchGroups rules record)
                $ concatMap cbMatchers
                $ filter (isBlockActive rules record)
-               $ rblocksassigning rules f
+               $ rconditionalblocks rules
+               -- ^ XXX adjusted to not use memoized field as caller might be sending a subset of rules with just one CB (hacky)
   group = (read (T.unpack sgroup) :: Int) - 1 -- adjust to 0-indexing
   in atMay matchgroups group