Long awaited line directive View as Markdown

Hello Stanislav,

Sunday, July 16, 2006, 9:52:59 AM, you wrote:

RC>>>will tell them in what included template source file and on what line
RC>>>they screwed up rather than them seeing an error that has no obvious
RC>>>relationship whatsoever to what they did (did I get that right
RC>>>Marcus?).

Why can't you make your engine put comments in the code?

He most likely can. But then he still has to do some arithmetic in the
error messages after having looked up the code. Ok let's get this in
a more detailed exxample. Lets look at what a potential xml-template
based code generator might do. Not that the example makes much sense

• sorry for that - but i had to find an easy warning. and I also had
  to come up with a very easy generator, for that i hope my mini template
  stuff is self explanatory....

file-a.pxp: The template

1. <template><code><![CDATA[include 'file-b.php';]]></code>
2. <include file='file-c.inc'/>
3. <code><![CDATA[var_dump(in_array(1,1));]]</code>
4. <finalize/>
5. </template>

file-b.php: Some valid php file

1. <?php
2. var_dump(in_array(1,1));
3. ?>

file-c.inc: Some code note that we do not have '<?php' here

1. var_dump(in_array(1,1));
2. var_dump(in_array(1,1));

output.php: generated file

1. <?php #line 1 "file-a.pxp"
2. include 'file-b.php'; // line 1, file-a.pxp, include errors unchanged
3. #line 1 "file-c.inc"
4. var_dump(in_array(1,1)); // line 1, file-c.php
5. var_dump(in_array(1,1)); // line 2, file-c.php
6. #line 3 "file-a.pxp"
7. var_dump(in_array(1,1)); // line 3, file-a.pxp
8. #line 9 "output.php"
9. var_dump(in_array(1,1));

Now the above works quite fine and for all errors you get the correct
original source location:

Warning: in_array() expects parameter 2 to be array, integer given in file-b.php on line 2
NULL

Warning: in_array() expects parameter 2 to be array, integer given in file-c.inc on line 1
NULL

Warning: in_array() expects parameter 2 to be array, integer given in file-c.inc on line 2
NULL

Warning: in_array() expects parameter 2 to be array, integer given in file-a.pxp on line 3
NULL

Warning: in_array() expects parameter 2 to be array, integer given in output.php on line 9
NULL

The problem is that not all generator output all line informations. That
is some only get the directive for the original input file. And others
create their own code but do not start those blocks with line directives.

Case one means the second error message would be
output.php: generated file

1. <?php #line 1 "file-a.pxp"
2. include 'file-b.php'; // line 1, file-a.pxp, include errors unchanged
3. var_dump(in_array(1,1)); // line 2, file-a.pxp
4. var_dump(in_array(1,1)); // line 3, file-a.pxp
5. #line 3 "file-a.pxp"
6. var_dump(in_array(1,1)); // line 4, file-a.pxp
7. var_dump(in_array(1,1));

Now the error in line 5 is output as line 3 in file-a.pxp. It will take
you an endless amount to locate the original source. And this is exactly
what happens when you work with comments, only then you even get the
error message as output.php.

In the second case the problem is the omitted line 8 which leads to the
last error been seen as line 5 of file-a.pxp. This will make you think
either your code generator or php is broken.

Best regards,
Marcus

This has some really good implications for helping PHP users get the
line numbers more correct. For instance, from what I gather, my
template
engine can use this to dynamically generate PHP code from an XML tag
and
when the generated code fails due to some syntax error based on the
tag's attributes, If my engine included this directive then the engine
will tell them in what included template source file and on what line
they screwed up rather than them seeing an error that has no obvious
relationship whatsoever to what they did (did I get that right
Marcus?).

So, what would the code look like that fixes this issue, from the
sample posted?

It seems to me like you're still going to get an error message about
the right line number, but in the wrong file name.

Or is #file also going in with #line, so your template engine can
forge the filename for FILE to the included file? I can see that
working to solve this for you.

A file specification will also be part of the line directive. I believe
Marcus mentioned that in one of his posts.

Working backwards from generated code to source files in templates is
never fun, but solving this in PHP code instead of the template itself
seems like a case of killing a fly with a cannon.

It can't be properly solved in PHP land without hacks that are still not
as useful as the line directive.

It may make life a tiny bit easier for the experts, but I suspect
#line is going to be abused by the naive to make life hell on the
masses...

I don't think the naive will go near it. They would need someone to tell
them about it :) Of course, I'm sure it will happen, but that's why
documentation exists.

Cheers,
Rob.

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