[stringtemplate-interest] separator: a fix or breaking backward compatibility?

[Terence Parr]

Wow. Apparently, I used to think that false conditional if statements  
yielded separators. Take a look at the following test case:

	public void testEmptyIteratedConditionalValueGetsSeparator() throws  
Exception {
		StringTemplateGroup group =
				new StringTemplateGroup("test");
		StringTemplateErrorListener errors = new ErrorBuffer();
		group.setErrorListener(errors);
		StringTemplate t = new StringTemplate(group,
			"$users:{$if(it.ok)$$it.name$$endif$}; separator=\",\"$");
		t.setAttribute("users.{name,ok}", "Terence", new Boolean(true));
		t.setAttribute("users.{name,ok}", "Tom", new Boolean(false));
		t.setAttribute("users.{name,ok}", "Frank", new Boolean(true));
		t.setAttribute("users.{name,ok}", "Johnny", new Boolean(false));
		// empty conditional values get no separator
		String expecting="Terence,,Frank,";
		String result = t.toString();
		assertEquals(expecting, result);
	}

Now, within else that's empty, it should definitely give the separator.

	public void testEmptyIteratedConditionalWithElseValueGetsSeparator()  
throws Exception {
		StringTemplateGroup group =
				new StringTemplateGroup("test");
		StringTemplateErrorListener errors = new ErrorBuffer();
		group.setErrorListener(errors);
		StringTemplate t = new StringTemplate(group,
			"$users:{$if(it.ok)$$it.name$$else$$endif$}; separator=\",\"$");
		t.setAttribute("users.{name,ok}", "Terence", new Boolean(true));
		t.setAttribute("users.{name,ok}", "Tom", new Boolean(false));
		t.setAttribute("users.{name,ok}", "Frank", new Boolean(true));
		t.setAttribute("users.{name,ok}", "Johnny", new Boolean(false));
		// empty conditional values get no separator
		String expecting="Terence,,Frank,";
		String result = t.toString();
		assertEquals(expecting, result);
	}

So, I'm going to fix it so the first test case gives the opposite  
result ;)

Ter

On Jul 2, 2009, at 11:47 AM, Terence Parr wrote:

> Hi,
>
> I've built an awesome example using ST for the book. Given a single
> Class object, ST will generate all of the SQL and Java code necessary
> to serialize and deserialize objects of that type. no Java code used
> at all to generate the output :)
>
> HOWEVER, it exposed a serious problem in ST behavior.  Unless I can
> fix this, I will have to add some Java code to do processing to
> generate the SQL, which I don't want to do.
>
> Consider the following generation of a comma separated list of names:
>
> <names; separator=",">
>
> There is a separator generated in between every name in the list. If
> names is null, nothing is generated. If names has length one, there is
> no separator generated.
>
> Now, consider the following anonymous template application to a list
> of names:
>
> <names:{n | <if(n.cool)><n><endif>}; separator=",">
>
> It will only a name if that name is "cool" (has field cool true or
> method isCool() true). The problem is that when n.cool is false, you
> still get an operator.
>
> This is a serious problem in terms of generating output because there
> is no way to get around this bug or feature! The answer must lie in
> what the result of a false IF is exactly. Is it missing (null) or
> empty ("")???
>
> If the result is missing, then no separator should be generated.
> However, if it's empty, we should get a separator.
>
> I'm proposing that the result is missing not empty. If we truly want
> empty, we can do this
>
> <names:{n | <if(n.cool)><n><else><endif>}; separator=",">
>
> The else clause is present but empty, right?
>
> I'm not sure how hard it is to fix this IF problem. But, I need a vote
> from people to tell me if it will break something they rely on.
>
> This would be a bug fix release like 3.2.1 or perhaps 3.3 if I add any
> small features. This will not be the overall rewrite, which I will
> begin after the book.
>
> Amazing how writing a book exposes all of the weird nooks and crannies
> in a tool. Ha! Book-driven functionality testing :)
>
> So, should I "fix" it?
>
> Ter
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