From 2f00c8ba656405d63b3fb3b4e24509e435366f2e Mon Sep 17 00:00:00 2001
From: Toddr Bot <toddbot@rinaldo.us>
Date: Mon, 23 Mar 2026 04:10:30 +0000
Subject: [PATCH] fix: correct tokenizer greediness with subtraction and
 division

The tokenizer had two bugs that caused incorrect parsing of arithmetic
expressions, especially visible when passing expressions as MACRO
arguments (GH #315):

1. The number regex `-?\d+` consumed the minus sign as part of a
   negative number literal even after identifiers, so `x-2` became
   `IDENT:x NUMBER:-2` instead of `IDENT:x MINUS NUMBER:2`.
   Fix: only treat leading `-` as unary when not preceded by a word
   character, closing paren, or closing bracket.

2. The filename regex matched `x/2` as `FILENAME:x/2` because path
   segments allowed any `\w` characters including pure digits.
   Fix: require path segments after `/` or `::` to start with a
   letter or underscore.

Closes #315

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 lib/Template/Parser.pm | 10 +++++++---
 t/binop.t              | 14 +++++++++++++-
 t/macro.t              | 10 ++++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/lib/Template/Parser.pm b/lib/Template/Parser.pm
index 9e094dc4d..008360e58 100644
--- a/lib/Template/Parser.pm
+++ b/lib/Template/Parser.pm
@@ -626,10 +626,14 @@ sub tokenise_directive {
                 \2                       # match opening quote
             |
                 # an unquoted number matches in $4
-                (-?\d+(?:\.\d+)?)       # numbers
+                # only treat leading - as unary when not after a
+                # word char, close-paren, or close-bracket (else
+                # it is a subtraction operator, e.g. x-2)
+                ((?:(?<![)\]\w])-)?  \d+(?:\.\d+)?)   # numbers
             |
-                # filename matches in $5
-                ( \/?\w+(?:(?:\/|::?)\w*)+ | \/\w+)
+                # filename matches in $5 — path segments after
+                # the separator must start with a letter
+                ( \/?\w+(?:(?:\/|::?)[a-zA-Z_]\w*)+ | \/[a-zA-Z_]\w+)
             |
                 # an identifier matches in $6
                 (\w+)                    # variable identifier
diff --git a/t/binop.t b/t/binop.t
index 591c5bfdd..48c81fec2 100644
--- a/t/binop.t
+++ b/t/binop.t
@@ -327,7 +327,19 @@ mega: 106
 3 3
 
 
--- stop -- 
+-- test --
+-- name subtraction vs negative literal (GH #315) --
+[% x = 10; y = x - 3 %][% y +%]
+[% z = -5 %][% z +%]
+[% a = x + -2 %][% a +%]
+[% b = x - -2 %][% b %]
+-- expect --
+7
+-5
+8
+12
+
+-- stop --
 # this is for testing the lt operator which isn't enabled by default.
 -- test --
 [% IF 'one' lt 'two' -%]
diff --git a/t/macro.t b/t/macro.t
index bb5ca6975..01ad619a2 100644
--- a/t/macro.t
+++ b/t/macro.t
@@ -163,3 +163,13 @@ two: 2[The Title] -> one: 2[The Title]
 [% triple(10) %]
 -- expect --
 30
+
+-- test --
+-- name macro with arithmetic expressions (GH #315) --
+[% MACRO show(n) BLOCK -%]
+[% n %]
+[%- END -%]
+[% x = 5 -%]
+[% show(x) %]:[% show(x+2) %]:[% show(x-2) %]:[% show(x*2) %]:[% show(x/2) %]
+-- expect --
+5:7:3:10:2.5