Function exec_command_else

src/bin/psql/command.c:1761–1821

* \else -- final alternative in an \if..\endif block * * Statements within an \else branch will only be executed if * all previous \if and \elif expressions evaluated to false * and the block was not itself being ignored. */

 * and the block was not itself being ignored.
 */
static backslashResult
exec_command_else(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);

			/* Now skip the \else branch */
			conditional_stack_poke(cstack, IFSTATE_ELSE_FALSE);
			break;
		case IFSTATE_FALSE:

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

			/*
			 * We've not found any true \if or \elif expression, so execute
			 * the \else branch.
			 */
			conditional_stack_poke(cstack, IFSTATE_ELSE_TRUE);
			break;
		case IFSTATE_IGNORED:

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

			/*
			 * Either we previously processed the active branch of this \if,
			 * or the whole \if block is being skipped.  Either way, skip the
			 * \else branch.
			 */
			conditional_stack_poke(cstack, IFSTATE_ELSE_FALSE);
			break;
		case IFSTATE_ELSE_TRUE:
		case IFSTATE_ELSE_FALSE:
			pg_log_error("\\else: cannot occur after \\else");
			success = false;
			break;
		case IFSTATE_NONE:
			/* no \if to else from */
			pg_log_error("\\else: no matching \\if");
			success = false;
			break;
	}