From 29349458b32fb1b8dc889a3735f9ebd74ae7b8ee Mon Sep 17 00:00:00 2001
From: Simon Michael <simon@joyful.com>
Date: Wed, 4 Dec 2024 17:45:28 -1000
Subject: [PATCH] imp:csv:if: go back to accepting unknown csv field names
 [#2289]

It makes life easier when reusing common rules with different CSVs.
---
 hledger-lib/Hledger/Read/RulesReader.hs | 6 ++++--
 hledger/hledger.m4.md                   | 8 ++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/hledger-lib/Hledger/Read/RulesReader.hs b/hledger-lib/Hledger/Read/RulesReader.hs
index d7bd83d7f..cc34e947e 100644
--- a/hledger-lib/Hledger/Read/RulesReader.hs
+++ b/hledger-lib/Hledger/Read/RulesReader.hs
@@ -808,8 +808,10 @@ isBlockActive rules record CB{..} = any (all matcherMatches) $ groupedMatchers c
     matcherMatches = \case
       RecordMatcher prefix             pat -> maybeNegate prefix $ match pat $ T.intercalate "," record
       FieldMatcher  prefix csvfieldref pat -> maybeNegate prefix $ match pat $
-        fromMaybe (warn msg "") $ replaceCsvFieldReference rules record csvfieldref
-        where msg = "if "<>T.unpack csvfieldref<>": this should be a name declared with 'fields', or %NUM"
+        fromMaybe "" $ replaceCsvFieldReference rules record csvfieldref
+        -- (warn msg "") where msg = "if "<>T.unpack csvfieldref<>": this should be a name declared with 'fields', or %NUM"
+        --  #2289: we'd like to warn the user when an unknown CSV field is being referenced,
+        --  but it's useful to ignore it for easier reuse of rules files.
       where match p v = regexMatchText (dbg7 "regex" p) (dbg7 "value" v)
 
     -- | Group matchers into associative pairs based on prefix, e.g.:
diff --git a/hledger/hledger.m4.md b/hledger/hledger.m4.md
index b7fae7d8e..1a007ef5d 100644
--- a/hledger/hledger.m4.md
+++ b/hledger/hledger.m4.md
@@ -3673,10 +3673,10 @@ When using these, there's two things to be aware of:
    Eg when reading an SSV record like:   `2023-01-01 ; "Acme, Inc. " ;  1,000`\
    the whole record matcher sees instead: `2023-01-01,Acme, Inc. ,1,000`
 
-2. In field matchers you must use either a CSV field number,
-   or a [CSV field name](#field-names) which has been set by a [`fields` list](#fields-list).
-   Anything else will print a warning, to avoid [confusion](https://github.com/simonmichael/hledger/issues/2289);
-   if you see it, you should adjust your matchers. This might become an error in future.
+2. Field matchers expect either a CSV field number, or a [CSV field name](#field-names) declared with [`fields`](#fields-list).
+   (Don't use a hledger field name here, unless it is also a CSV field name.)
+   A non-CSV field name will cause the matcher to match against `""` (the empty string),
+   and does not raise an error, allowing easier reuse of common rules with different CSV files.
 
 You can also prefix a matcher with `!` (and optional space) to negate it.
 Eg `! whole foods`, `! %3 whole foods`, `!%description whole foods` will match if "whole foods" is NOT present.