Photoshop script to apply "select all" if no selection is active.

check_selection.jsx

#target photoshop

// Small script to manage selections for the creation of blog/teaser images.
// If the active document does not already have a selection, select all.
// (c) Mike Dickson www.photoshoptools.ca
// Licensed under the GPL

if ( !hasSelection(activeDocument) ) {
    activeDocument.selection.selectAll();
}

// Compares a history state taken before and after a deselect
function hasSelection (doc) {
    var ret = false;
    var as = doc.activeHistoryState;
    doc.selection.deselect();
    if (as != doc.activeHistoryState) {
        ret = true;
        doc.activeHistoryState = as;
    }
    return ret;
}

Heads up that this will fail if the calling function is wrapped in a suspendHistory() call...
ex. app.activeDocument.suspendHistory("My function with lots of loops", "bigAutomator()");

Luckily the "bounds" property on app.activeDocument.selection only exists if there's a user selection... but

I used a try/catch in my case, but you might try a better test?

function hasSelection ()
    {
        try{
            return (app.activeDocument.selection.bounds.length>0);
        }
        catch(err){
            return false;// not an real error... just a check.
        }
    }