Temporary variables with the same name across rules may override each other's values.

[dkkb]

Describe the bug

Temporary variables with the same name across rules may override each other's values.

To Reproduce

I wrote two tests to reproduce this issue, the code below is the first test, and it runs as expected.

func TestGruleSameNameVariableOverrideIssue1(t *testing.T) {
	rules := `
rule UpdateFirstName "Update first name" {
    when
        Fact.IsAdult == true
    then
        Fact.FirstName = "John";
		Retract("UpdateFirstName");
}

rule UpdateLastName "Update last name" {
	when
		Fact.IsAdult == true
	then
		Fact.LastName = "Doe";
		Retract("UpdateLastName");
}
`
	knowledgeLibrary := ast.NewKnowledgeLibrary()
	ruleBuilder := builder.NewRuleBuilder(knowledgeLibrary)
	err := ruleBuilder.BuildRuleFromResource("TestRules", "0.0.1", pkg.NewBytesResource([]byte(rules)))
	assert.NoError(t, err)
	knowledgeBase, err := knowledgeLibrary.NewKnowledgeBaseInstance("TestRules", "0.0.1")
	assert.NoError(t, err)
	dataContext := ast.NewDataContext()
	fact := &testFact{
		IsAdult: true,
	}
	err = dataContext.Add("Fact", fact)
	assert.NoError(t, err)
	eng := engine.NewGruleEngine()
	err = eng.Execute(dataContext, knowledgeBase)
	assert.NoError(t, err)

	assert.Equal(t, "John", fact.FirstName)
	assert.Equal(t, "Doe", fact.LastName)
}

After that, I wrote another test. As you can see, the only difference is that I use a temporary variable to store a value before assigning it to a field of the fact.

However, it appears that this temporary variable is shared across rules—if a value is assigned in ruleA, it can still be accessed in ruleB.

I'm not sure whether this is a bug, as I couldn't find any relevant explanation or example in the official documentation. But the behavior does seem unexpected.

func TestGruleSameNameVariableOverrideIssue2(t *testing.T) {
	rules := `
rule UpdateFirstName "Update first name" {
    when
        Fact.IsAdult == true
    then
		tmp = "John";
        Fact.FirstName = tmp;
		Retract("UpdateFirstName");
}

rule UpdateLastName "Update last name" {
	when
		Fact.IsAdult == true
	then
		tmp = "Doe";
		Fact.LastName = tmp;
		Retract("UpdateLastName");
}
`
	// ...
}

Output:

&{true John John} or &{true Doe Doe}

If I rename the variables to tmp1 and tmp2, everything works as expected again. It seems that Grule does support temporary variables within rules, but the behavior is somewhat unreliable.