Passing a list as the parameter of a template - mediawiki

Question

I have created a Template in my MediaWiki which I want to pass "free text" to. To keep it simple, imagine it as a table in which the first named parameter goes into cell 1 and the other named parameter goes into cell 2.
Writing the Template itself seemed easy enough, but I keep stumbling into errors when I try to pass certain structures in the arguments. My first issue was with a code block: if I wrote
{{MyTemplate|first=
// code...
|other=
// other code instead...
}}
then the wiki thought that the pipe character was part of the preformatted text block, and in the end I ended up without a second parameter. This issue was solved using <pre></pre>, but I thought it was more of a workaround than a solution.
Now I'm in trouble again when I try to pass a list:
{{MyTemplate|first=
* Item 1a
* Item 2a
|other=
* Item 1b
* Item 2b
}}
Again, I end up with the first item (Item 1a) ignored (not rendered as a list item), the second rendered ok (Item 2a, as a list item), then a double pipe, an asterisk and "Item 1b", then the list goes on with "Item 2b".
I am clearly doing something wrong, but I have no idea what to do, nor I could find any useful example in the docs. Please help me understand how to correctly pass any text (which may include lists or other markdown constructs) as a template argument.
EDIT
Here is the code of my Template:
{|
!First !!Other
|-
|{{{first|}}} ||{{{other|}}}
|}
Also, I'm sorry, but I typed the usage wrong: the four more spaces were a leftover from the snippet above. I've fixed that.
#Ivanhercaz I've tried your suggestion (which only differs from mine for the empty lines), and still got the same result.

Answer 1

In this case I have to suppose how is the template you created, because you didn't shared the structure, just how you call and two parameters. Because of this reason I am going to suppose that you create a template as:
{{{first|}}}
{{{other|}}}
About your first question, you can use {{!}} to escape the pipe character (|). From the version 1.24 this is a magic word, but before the solution to this issue was to create a template with a pipe and then replace the | by {{!}}. The use of the magic word is the same, but you is unnecessary to create the template.
About your second question, taking in account that you have a similar structure to what I wrote at the top of this answer, if I wrote a page with this:
{{MyTemplate|first=
* Item 1a
* Item 2a
|other=
* Item 1b
* Item 2b
}}
I get a two lists and two code blocks: list one with "Item 1a" and the first code block with * Item 2a; list two with "Item 2a" and the second code block with * Item 2b. It doesn't seem to what you get rendered:
the first item (Item 1a) ignored (not rendered as a list item), the second rendered ok (Item 2a, as a list item), then a double pipe, an asterisk and "Item 1b", then the list goes on with "Item 2b". This happened due to the extra space before the * in the parameters.
So I recommend to you to share the code of the template to check and answer to you better. Of course, if what you want is to pass two different lists in each parameter you could make something like:
{{Test|first=
* Item 1a
* Item 2a
|other=
* Item 1b
* Item 2b
}}
This structure solved the problem I mentioned. But I wait your comment to be sure and edit my answer if it is necessary.
Edit
Now, with the code of the template I understand your problem. To work correctly and without problems with templates, tables and lists you have to consider that the * need to have an line break after the | and ||. What I recommend to you is insert this line breaks
{|
! Wikitext !! Rendering
|-
|
{{{first|}}}
||
{{{other|}}}
|}
I think it is an easy and clean way to do what you are trying. So, if you use the template in this way:
{{Test
|first=* Item 1a
* Item 2a
|other=* Item 1b
* Item 2b
}}
Or in this other way:
{{Test
|first=
* Item 1a
* Item 2a
|other=
* Item 1b
* Item 2b
}}
You will have a table like that (I add a class=wikitable to have a more beautiful table to show):
I hope this trick has been helpful.