[rules-dev] BUG: [5.3.0.Final] CollectSetAccumulateFunction should probably use IdentityHashMap internally

[SirMungus]

By the way, while checking into various scenarios prompted by Wolfgang's
response, I came up with a very interesting test program:

rule "Initialize"
    salience 100
    when
        eval(true)
    then
        insert("one");
        insert(new String("one"));
        insertLogical("two");
        insertLogical(new String("two"));
end

rule "Find strings"
    salience 50
    when
        $s : String()
    then
        System.out.println("I found string: " + $s);
end

rule "Gather strings"
    salience 50
    when
        accumulate(
            $s : String(),
            $sSet : collectSet( $s ),
            $sList : collectList( $s ) )
    then
        System.out.println("Here is the set of all strings: " + $sSet);
        System.out.println("Here is the list of all strings: " + $sList);
end

What would you expect that to output? How many "I found string: xxx" lines
would there be? How many entries in the "set of all strings"? How many
entries in the "list of all strings"?

For my part, I figured there would be four "I found string: xxx" lines, two
entries in the set, and four entries in the list.

I was very surprised to find the following output:

I found string: two
I found string: one
I found string: one
Here is the set of all strings: [two, one]
Here is the list of all strings: [one, one, two]

This strongly suggests that "insert" objects are held in an
identity-preserving structure, but that "insertLogical" objects are held in
an equals()-based structure.

I am glad for the identity-based handling of "insert" objects, especially
considering that all of my inserted objects come from "outside" the engine.
I would hate to see one of them fail to be considered by the rule engine.

I can almost see some usefulness for the equals() behavior of insertLogical
objects, but far more potential problems.

I think it's slightly dangerous that these behaviors differ and that it is
not, AFAIK, documented in a way that is clear to users of Drools.

--
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