How to use the showon attribute with multiple conditions?

Question

In a Joomla 3.9.3 module, I'm trying, with no luck, to show/hide a field with showon by checking the values on other three fields

My XML:

<field
    name="foo"
    type="text"
/>
<field
    name="bar"
    type="text"
/>
<field
     name="fooimg"
    type="media"
    showon="foo!:[OR]bar!:"
/>
<field
    name="baz"
    type="radio"
    class="btn-group btn-group-yesno"
    showon="foo!:[OR]bar!:[AND]fooimg!:"
    default=""
    >
    <option value="bazval">JYES</option>
    <option value="">JNO</option>
</field>

With: showon="foo!:[OR]bar!:[AND]fooimg!:" on baz field I expect that baz is shown when (foo or bar has a value) and fooimg has a value too.

But the results are:

    foo = true 
    bar = false
    fooimage = true
    baz is NOT SHOWED (should be showed)

    foo = false
    bar = true
    fooimage = true
    baz IS SHOWED (as aspected)

With fooimage or foo and bar set to False it work as expected.

I also tried: "fooimg!:[AND]foo!:[OR]bar!:"

What did I do wrong?

Answer 1

I'm not fully sure if this can help you, but since the fooimg field is only shown when either foo or bar is true, then in baz field you do not have to check that again, so it would be enough just to check if fooimg field is true or not, thus:

<field
    name="baz"
    type="radio"
    class="btn-group btn-group-yesno"
    showon="fooimg!:"
    default=""
    >
    <option value="bazval">JYES</option>
    <option value="">JNO</option>
</field>

This baz field will only be shown if the foo or bar is not empty and fooimg is not empty. So you actually get the same result simply (that you actually wanted to get).