Prevent foreach xml tag from polluting the global context

[nyer]

Mybatis currently shares one global bindings context during dynamic sql building and parametemapping construction. It is ok at most time, but when it comes to the foreach xml tag, something wrong will occur. Like the following mybatis mapper:

<select id="selectList" parameterType="java.util.Map">
select * from tb
<where>
  <if test="status != null>
    and status = #{status}
  </if>

  <if test="statusList != null">
    and status in
    <foreach collecion="statusList" item="status" open="( " separator=" , " close=" )">
      #{status}
    </foreach>
  </if>
</where>
</select>

When variable status is passed as 5, and statusList is passed as [4,5,6]，it is normal when final sql will equals to select * from tb where status = 5. However, the final sql is select * from tb where status =6. The reason is that the variable status in foreach tag overwrites the outside variable with the same name. It behaves like the dynamic scope feature in programming language. It is error-prone.
Please review. thank you

[harawata]

@nyer ,
I have not had the time to review, but please add test case(s).
Thank you!

[nyer]

@harawata test case is added.
Thank you!

[harawata]

Thanks for the update, @nyer !
I will look into it.

[Youmoo]

Similar to #423 ?

[harawata]

@Youmoo Yes, it is the same issue, but this patch does not break the existing test cases.

I may need some time to review this.

[nyer]

@harawata , I have updated the patch in case of null value.

[harawata]

@nyer ,
Sorry for a late response!
After taking a deeper look at this issue, I think I found a simpler solution (see bae02af).
Could you try the latest snapshot and see if the fix is OK?

Note that it still is a bad idea to use a conflicting variable name for item/index attribute.

[nyer]

@harawata ,
It works, and it is awesome.
Thank your for your work.

[harawata]

You are very welcome. Thank you both for your contribution!