As of 2015-Apr, Pier 3.1 was the active development version. For moving to Pharo 4.0, one of the main changes impacting Pier is that the TimeStamp class is being replaced by DateAndTime.
Several smaller changes are:
parameterAt:ifPresent: is missing, when going to http://localhost:8080/pier, this error came up:MessageNotUnderstood: PRInternalLink>>parameterAt:ifPresent: Your request could not be completed. An exception occurred.
This is coming from this - the description param-name is search-button:
WAComponent>>initializeAttribute: description with: aValue overridWith: anInternalLink
Added the missing PRInternalLink>>parameterAt:ifPresent: gets the code to proceed beyond that.
*value:children|link*
An error pops up about nil receiving #key. It seems that a loop is being performed over a dictionary which was previously an array in PRLinkRenderer>>attributesFor:, so adding a nil check can get past this error.