LDA Sieve plugin: Fixed assert failure caused by earlier sieve_discar…

…d changes.

The simplest case in which all normal scripts maintain the (implicit) keep action triggered an assert failure.
Fixed by restructuring the script execution loop to make it easy to understand.
Now handles each case explicitly.

src/plugins/lda-sieve/lda-sieve-plugin.c

@@ -410,7 +410,7 @@ static int lda_sieve_execute_scripts
 	bool debug = srctx->mdctx->dest_user->mail_debug;
 	struct sieve_script *last_script = NULL;
 	bool user_script, discard_script;
-	bool more = TRUE, compile_error = FALSE;
+	bool compile_error = FALSE;
 	enum sieve_error error;
 	unsigned int i;
 	int ret;
@@ -425,23 +425,24 @@ static int lda_sieve_execute_scripts
 	/* Execute scripts */
 
 	i = 0;
-	while ( more ) {
+	discard_script = FALSE;
+	for (;;) {
 		struct sieve_binary *sbin = NULL;
 		struct sieve_script *script;
 		enum sieve_compile_flags cpflags = 0;
 		enum sieve_execute_flags exflags = 0;
+		bool more;
 
-		if ( i < srctx->script_count ) {
+		if ( !discard_script ) {
 			/* normal script sequence */
+			i_assert( i < srctx->script_count );
 			script = srctx->scripts[i];
 			i++;
 			user_script = ( script == srctx->user_script );
-			discard_script = FALSE;
 		} else {
 			/* discard script */
 			script = srctx->discard_script;
 			user_script = FALSE;
-			discard_script = TRUE;
 		}
 
 		i_assert( script != NULL );
@@ -520,7 +521,6 @@ static int lda_sieve_execute_scripts
 				} else {
 					sieve_multiscript_run_discard(mscript, sbin,
 						exec_ehandler, action_ehandler, exflags);
-					i_assert(!more);
 				}
 				sieve_error_handler_unref(&action_ehandler);
 
@@ -533,11 +533,22 @@ static int lda_sieve_execute_scripts
 
 		sieve_close(&sbin);
 
-		if ( !discard_script && !more &&
-			sieve_multiscript_will_discard(mscript) &&
+		if ( discard_script ) {
+			/* Executed discard script, which is always final */
+			break;
+		} else if ( more ) {
+			/* The "keep" action is applied; execute next script */
+			i_assert( i <= srctx->script_count );
+			if ( i == srctx->script_count ) {
+				/* End of normal script sequence */
+				break;
+			}
+		} else if ( sieve_multiscript_will_discard(mscript) &&
 			srctx->discard_script != NULL ) {
-			i = srctx->script_count;
-			more = TRUE;
+			/* Mail is set to be discarded, but we have a discard script. */
+			discard_script = TRUE;
+		} else {
+			break;
 		}
 	}