Function exec_command_elif

src/bin/psql/command.c:1685–1752

* \elif -- alternative branch in an \if..\endif block * * is evaluated the same as in \if . */

 * <expr> is evaluated the same as in \if <expr>.
 */
static backslashResult
exec_command_elif(PsqlScanState scan_state, ConditionalStack cstack,
				  PQExpBuffer query_buf)
{
	bool		success = true;

	switch (conditional_stack_peek(cstack))
	{
		case IFSTATE_TRUE:

			/*
			 * Just finished active branch of this \if block.  Update saved
			 * state so we will keep whatever data was put in query_buf by the
			 * active branch.
			 */
			save_query_text_state(scan_state, cstack, query_buf);

			/*
			 * Discard \elif expression and ignore the rest until \endif.
			 * Switch state before reading expression to ensure proper lexer
			 * behavior.
			 */
			conditional_stack_poke(cstack, IFSTATE_IGNORED);
			ignore_boolean_expression(scan_state);
			break;
		case IFSTATE_FALSE:

			/*
			 * Discard any query text added by the just-skipped branch.
			 */
			discard_query_text(scan_state, cstack, query_buf);

			/*
			 * Have not yet found a true expression in this \if block, so this
			 * might be the first.  We have to change state before examining
			 * the expression, or the lexer won't do the right thing.
			 */
			conditional_stack_poke(cstack, IFSTATE_TRUE);
			if (!is_true_boolean_expression(scan_state, "\\elif expression"))
				conditional_stack_poke(cstack, IFSTATE_FALSE);
			break;
		case IFSTATE_IGNORED:

			/*
			 * Discard any query text added by the just-skipped branch.
			 */
			discard_query_text(scan_state, cstack, query_buf);

			/*
			 * Skip expression and move on.  Either the \if block already had
			 * an active section, or whole block is being skipped.
			 */
			ignore_boolean_expression(scan_state);
			break;
		case IFSTATE_ELSE_TRUE:
		case IFSTATE_ELSE_FALSE:
			pg_log_error("\\elif: cannot occur after \\else");
			success = false;