From 7491cdbd1dcb6e9bad2517b727cbfe7e8c05632d Mon Sep 17 00:00:00 2001
From: Maria Matejka <mq@ucw.cz>
Date: Mon, 25 Nov 2024 15:14:27 +0100
Subject: [PATCH] Filter: multi-command case branches now need braces.

Removing an exception from the otherwise quite systematic syntax.
Closes #111.
---
 doc/bird.sgml          |  6 +++---
 doc/migration-bird3.md |  5 +++++
 filter/config.Y        | 12 ++++--------
 filter/test.conf       |  3 +++
 4 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/doc/bird.sgml b/doc/bird.sgml
index 3e7ae9dd..da887b1e 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -1974,8 +1974,8 @@ and name is used). In both cases, it must have the same type as elements.
 <m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
 ... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
 on the left side of the &tilde; operator and anything that could be a member of
-a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
-grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
+a set is allowed before <cf/:/. Multiple commands must be grouped by <cf/{}/.
+If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
 between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
 neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
 
@@ -1993,7 +1993,7 @@ for int asn in bgp_path do {
 }
 
 case arg1 {
-	2: print "two"; print "I can do more commands without {}";
+	2: { print "two"; print "Multiple commands must brace themselves."; }
 	3 .. 5: print "three to five";
 	else: print "something else";
 }
diff --git a/doc/migration-bird3.md b/doc/migration-bird3.md
index fc7cc433..1a088d59 100644
--- a/doc/migration-bird3.md
+++ b/doc/migration-bird3.md
@@ -60,6 +60,11 @@ the given prefix. Experimental.
 
 Reload of filters is now done by `reload filters` command, contrary to just `reload` in BIRD 2.
 
+## Filters
+
+We have removed the exception for `case` where multiple commands could be written
+after the case label without braces. This caused unneeded complexity in the parser.
+
 ## Route attributes
 
 All protocol attributes have been renamed in CLI to align with the filter language tokens.
diff --git a/filter/config.Y b/filter/config.Y
index 4d8b30c7..c21abd35 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -381,7 +381,7 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
 %nonassoc ELSE
 
 %type <xp> cmds_int cmd_prep
-%type <x> term term_bs cmd cmd_var cmds cmds_scoped constant constructor var var_list var_list_r function_call bgp_path_expr bgp_path bgp_path_tail term_dot_method method_name_cont
+%type <x> term term_bs cmd cmd_var cmds constant constructor var var_list var_list_r function_call bgp_path_expr bgp_path bgp_path_tail term_dot_method method_name_cont
 %type <fsa> static_attr
 %type <f> filter where_filter
 %type <fl> filter_body function_body
@@ -625,8 +625,6 @@ cmds: /* EMPTY */ { $$ = NULL; }
  | cmds_int { $$ = $1.begin; }
  ;
 
-cmds_scoped: { cf_push_soft_scope(new_config); } cmds { cf_pop_soft_scope(new_config); $$ = $2; } ;
-
 cmd_var: var | cmd ;
 
 cmd_prep: cmd_var {
@@ -781,14 +779,14 @@ fprefix_set:
  ;
 
 switch_body: /* EMPTY */ { $$ = NULL; }
- | switch_body switch_items ':' cmds_scoped  {
+ | switch_body switch_items ':' cmd  {
      /* Fill data fields */
      struct f_tree *t;
      for (t = $2; t; t = t->left)
        t->data = $4;
      $$ = f_merge_items($1, $2);
    }
- | switch_body ELSECOL cmds_scoped {
+ | switch_body ELSECOL cmd {
      struct f_tree *t = f_new_tree();
      t->from.type = t->to.type = T_VOID;
      t->right = t;
@@ -990,9 +988,7 @@ for_var:
  ;
 
 cmd:
-   '{' cmds_scoped '}' {
-     $$ = $2;
-   }
+   '{' { cf_push_soft_scope(new_config); } cmds { cf_pop_soft_scope(new_config); } '}' { $$ = $3; }
  | IF term THEN cmd {
      $$ = f_new_inst(FI_CONDITION, $2, $4, NULL);
    }
diff --git a/filter/test.conf b/filter/test.conf
index f27ad0b7..24094e80 100644
--- a/filter/test.conf
+++ b/filter/test.conf
@@ -195,8 +195,11 @@ bt_test_suite(t_bool, "Testing boolean expressions");
 
 function aux_t_int(int t; int u)
 {
+	int v;
 	case t {
 		1: {}
+		2: { int u; u = 1; v = 42; }
+		3: if true then v = t + u + 53; else v = 35 + u + t;
 		else: {}
 	}
 }