From da11d74ae6e16867bf3676c0e4eeabbfc5122b5f Mon Sep 17 00:00:00 2001
From: Simon Michael <simon@joyful.com>
Date: Thu, 17 Oct 2024 12:00:48 -1000
Subject: [PATCH] dev: refactor: clarify journalAccountTypes

---
 hledger-lib/Hledger/Data/Journal.hs | 34 +++++++++++++++++------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/hledger-lib/Hledger/Data/Journal.hs b/hledger-lib/Hledger/Data/Journal.hs
index 150e3e491..1235384a7 100644
--- a/hledger-lib/Hledger/Data/Journal.hs
+++ b/hledger-lib/Hledger/Data/Journal.hs
@@ -154,6 +154,7 @@ import System.FilePath (takeFileName)
 import Data.Ord (comparing)
 import Hledger.Data.Dates (nulldate)
 import Data.List (sort)
+import Data.Function ((&))
 -- import Data.Function ((&))
 
 
@@ -576,27 +577,31 @@ journalAccountType Journal{jaccounttypes} = accountNameType jaccounttypes
 journalAddAccountTypes :: Journal -> Journal
 journalAddAccountTypes j = j{jaccounttypes = journalAccountTypes j}
 
+-- | An account type inherited from the parent account(s),
+-- and whether it was originally declared by an account directive (true) or inferred from an account name (false).
+type ParentAccountType = ( AccountType, Bool )
+
 -- | Build a map of all known account types, explicitly declared
 -- or inferred from the account's parent or name.
 journalAccountTypes :: Journal -> M.Map AccountName AccountType
 journalAccountTypes j = M.fromList [(a,acctType) | (a, Just (acctType,_)) <- flatten t']
   where
     t = accountNameTreeFrom $ journalAccountNames j :: Tree AccountName
-    -- Map from the top of the account tree down to the leaves, propagating
-    -- account types downward. Keep track of whether the account is declared
-    -- (True), in which case the parent account should be preferred, or merely
-    -- inferred (False), in which case the inferred type should be preferred.
-    t' = settypes Nothing t :: Tree (AccountName, Maybe (AccountType, Bool))
+    -- Map from the top of the account tree down to the leaves, applying any explicitly declared account types,
+    -- otherwise inferring account types from account names when possible, and propagating account types downward.
+    -- Declared account types (possibly inherited from parent) are preferred, inferred types are used as a fallback.
+    t' = setTypeHereAndBelow Nothing t :: Tree (AccountName, Maybe (AccountType, Bool))
       where
-        settypes :: Maybe (AccountType, Bool) -> Tree AccountName -> Tree (AccountName, Maybe (AccountType, Bool))
-        settypes mparenttype (Node a subs) = Node (a, mtype) (map (settypes mtype) subs)
+        declaredtypesbyname = journalDeclaredAccountTypes j & fmap (,True)
+        setTypeHereAndBelow :: Maybe ParentAccountType -> Tree AccountName -> Tree (AccountName, Maybe ParentAccountType)
+        setTypeHereAndBelow mparenttype (Node a subs) = Node (a, mnewtype) (map (setTypeHereAndBelow mnewtype) subs)
           where
-            mtype = M.lookup a declaredtypes <|> minferred
-              where 
-                declaredtypes = (,True) <$> journalDeclaredAccountTypes j
-                minferred = if maybe False snd mparenttype
-                            then mparenttype
-                            else (,False) <$> accountNameInferType a <|> mparenttype
+            mnewtype = mthisacctdeclaredtype <|> mparentacctdeclaredtype <|> mthisacctinferredtype <|> mparentacctinferredtype
+              where
+                mthisacctdeclaredtype   = M.lookup a declaredtypesbyname
+                mparentacctdeclaredtype = if       fromMaybe False $ snd <$> mparenttype then mparenttype else Nothing
+                mparentacctinferredtype = if not $ fromMaybe True  $ snd <$> mparenttype then mparenttype else Nothing
+                mthisacctinferredtype   = accountNameInferType a & fmap (,False)
 
 -- | Build a map of the account types explicitly declared for each account.
 journalDeclaredAccountTypes :: Journal -> M.Map AccountName AccountType
@@ -616,7 +621,8 @@ journalPostingsAddAccountTags j = journalMapPostings addtags j
 journalBaseConversionAccount :: Journal -> AccountName
 journalBaseConversionAccount = headDef defaultBaseConversionAccount . journalConversionAccounts
 
--- | All the accounts declared or inferred as V/Conversion type in this journal.
+-- | All the accounts in this journal which are declared or inferred as V/Conversion type.
+-- This does not include new account names which might be generated by --infer-equity, currently.
 journalConversionAccounts :: Journal -> [AccountName]
 journalConversionAccounts = M.keys . M.filter (==Conversion) . jaccounttypes