Ind AS 32 Financial Instruments

During the issue of the shares, a company explicitly states what kind of an instrument it is based on the substance of the contract and not its legal form. Here preference share are debt instruments, an asset if it purchased and a financial liability if it is issued. Discretionary or not, the dividend payment is solely cash and this is not classified as convertible debt at the moment. The preference share don’t have maturity date and hence the issuer does not have a contractual obligation to make any payments. 

It can be treated as an equity instrument, the issuer will settle it with his own equity instruments. 

Therefore, it is a liability.