From bde8cd5e65984786471851309bd9c95be1f354a5 Mon Sep 17 00:00:00 2001
From: Charles Haley <cbhaley@i.wont.say.com>
Date: Sun, 7 Mar 2021 11:01:50 +0000
Subject: [PATCH] 1) Fix regression in template language: at some point in V5
 the template language was changed to disallow using an expression_list as a
 parameter. This was allowed in previous major revisions. 2) Allow expression
 lists in parameterized expressions. 3) Correct the grammar in the
 documentation.

---
 manual/template_lang.rst       | 8 ++++----
 src/calibre/utils/formatter.py | 6 ++++--
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/manual/template_lang.rst b/manual/template_lang.rst
index db39240097..f90da3ae47 100644
--- a/manual/template_lang.rst
+++ b/manual/template_lang.rst
@@ -217,7 +217,7 @@ General Program Mode replaces the template with a program written in the `templa
     top_expression  ::= or_expression
     or_expression   ::= and_expression [ '||' and_expression ]*
     and_expression  ::= not_expression [ '&&' not_expression ]*
-    not_expression  ::= ['!' not_expression]* | compare_exp
+    not_expression  ::= [ '!' not_expression ]* | compare_exp
     compare_expr    ::= add_sub_expr [ compare_op add_sub_expr ]
     compare_op      ::= '==' | '!=' | '>=' | '>' | '<=' | '<' | 'in' |
                         '==#' | '!=#' | '>=#' | '>#' | '<=#' | '<#'
@@ -227,13 +227,13 @@ General Program Mode replaces the template with a program written in the `templa
     times_div_op    ::= '*' | '/'
     unary_op_expr   ::= [ add_sub_op unary_op_expr ]* | expression
     expression      ::= identifier | constant | function | assignment |
-                        if_expression | for_expression | '(' top_expression ')'
+                        if_expression | for_expression | '(' expression_list ')'
     identifier      ::= sequence of letters or ``_`` characters
     constant        ::= " string " | ' string ' | number
-    function        ::= identifier '(' top_expression [ ',' top_expression ]* ')'
+    function        ::= identifier '(' expression_list [ ',' expression_list ]* ')'
     assignment      ::= identifier '=' top_expression
     if_expression   ::= 'if' condition 'then' expression_list
-                        [elif_expression] ['else' expression_list] 'fi'
+                        [ elif_expression ] [ 'else' expression_list ] 'fi'
     condition       ::= top_expression
     elif_expression ::= 'elif' condition 'then' expression_list elif_expression | ''
     for_expression  ::= 'for' identifier 'in' list_expression
diff --git a/src/calibre/utils/formatter.py b/src/calibre/utils/formatter.py
index e7783236e1..dd6f4df275 100644
--- a/src/calibre/utils/formatter.py
+++ b/src/calibre/utils/formatter.py
@@ -568,7 +568,7 @@ class _Parser(object):
     def expr(self):
         if self.token_op_is_lparen():
             self.consume()
-            rv = self.top_expr()
+            rv = self.expression_list()
             if not self.token_op_is_rparen():
                 self.error(_('Missing )'))
             self.consume()
@@ -598,7 +598,7 @@ class _Parser(object):
             arguments = list()
             while not self.token_op_is_rparen():
                 # evaluate the expression (recursive call)
-                arguments.append(self.top_expr())
+                arguments.append(self.expression_list())
                 if not self.token_op_is_comma():
                     break
                 self.consume()
@@ -906,6 +906,8 @@ class _Interpreter(object):
 
     def expr(self, prog):
         try:
+            if isinstance(prog, list):
+                return self.expression_list(prog)
             return self.NODE_OPS[prog.node_type](self, prog)
         except ValueError as e:
             raise e