From c062b14c5d4e34c8feafe8e8631e8fbe2a51cb08 Mon Sep 17 00:00:00 2001
From: Simon Michael <simon@joyful.com>
Date: Thu, 7 Dec 2023 08:55:05 -1000
Subject: [PATCH] imp: auto-declare builtin tag names like type: and t: (#2119)

Now using type: in account declarations or generating t: with timedot
letters won't cause the `tags` check to fail.

If a user declares any of these explicitly with a tag directive,
it does not cause an error.
---
 hledger-lib/Hledger/Data/JournalChecks.hs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/hledger-lib/Hledger/Data/JournalChecks.hs b/hledger-lib/Hledger/Data/JournalChecks.hs
index dba78ce7a..a5a3ba3a9 100644
--- a/hledger-lib/Hledger/Data/JournalChecks.hs
+++ b/hledger-lib/Hledger/Data/JournalChecks.hs
@@ -186,7 +186,7 @@ journalCheckTags j = do
                     -- where
                     --   col  = T.length (showTransactionLineFirstPart txn') + 2
                     --   col2 = col + T.length tagname - 1
-    declaredtags = journalTagsDeclared j
+    declaredtags = journalTagsDeclared j ++ builtinTags
     msg = (unlines [
       "%s:%d:"
       ,"%s"
@@ -197,6 +197,19 @@ journalCheckTags j = do
       ,"tag %s"
       ])
 
+-- | Tag names which have special significance to hledger.
+builtinTags = [
+   "type"  -- declares an account's type
+  ,"t"     -- generated by timedot letters notation
+  -- optionally generated on periodic transactions and auto postings
+  ,"generated-transaction"
+  ,"generated-posting"
+  -- used internally, not shown (but queryable)
+  ,"_generated-transaction"
+  ,"_generated-posting"
+  ,"_conversion-matched"
+  ]
+
 -- | In each tranaction, check that any conversion postings occur in adjacent pairs.
 journalCheckPairedConversionPostings :: Journal -> Either String ()
 journalCheckPairedConversionPostings j =