p:selectOneMenu preselects previous item when noSelectionOption item is present

Question

There is a problem with p:selectOneMenu selection when adding a f:selectItem.

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Answer 1

I could reproduce your problem. I looked in the PrimeFaces source code. It's a bug in PrimeFaces SelectOneMenuRenderer which exposes only when an item with noSelectionOption="true" is been used. The renderer won't generate the HTML <option> element of the backing <select> element for that, but it will generate the <li> of the visual <ul> list for that. In other words, the <select> contains in your case 4 items and the <ul> 5 items. The <li> is selected by JavaScript based on the index of the <option selected>, exactly as you suspected. That explains your problem.

Your best bet is to report it as a bug to PrimeFaces guys. The renderer should also generate the <option> for that, or the JavaScript should select the option based on value instead of on index.

In the meanwhile, replacing the noSelectionOption="true" by itemValue="#{null}", or also itemValue="" when JSF is configured to interpret empty string submitted values as null, should solve your problem.