[xdebug-general] Re: how breakpoints relate to filenames when remote debugging

On Wed, 2 May 2018, David Bradley wrote:

> >From the DBgp docs I gleaned that:
> 1) (file) breakpoints commands take a filename and a line number
> 2) file names have to be absolute paths
> 3) probably shouldn't have spaces (whoever thinks spaces in paths are a
> good idea is nuts)
> 4) may have some case sensitivity issues when crossing Windows -> linux VM
> worlds?

That's all correct.

> 5) some kind of mapping from server, debugger, and IDE views of filenames
> is required.

This is solely an IDE issue. Xdebug does not know anything about
mappings.

> Could you give the community an explanation of the steps from a user
> asking for a breakpoint to be created in an IDE, through all path
> mappings to the debugger - being careful to identify which component
> has the responsibility of mapping

The IDE needs to map. As Xdebug only runs on the server side, it has no
knowledge of the file paths on the machine where your IDE runs. And the
IDE (likely) has no idea of the paths on the machine where Xdebug runs.
It's therefore unfortunately necessary for users to configure this
mapping in their IDE. For most projects, you would only need to set the
root.

> In the general case for remote debugging the root location of the
> files in the IDE and the webserver are different names and
> inaccessible to one another (hence the term "remote").
>
> If you could also identify the canonical perspective and format of the
> filenames in the debugger (if there is one)

It's what PHP reports to Xdebug - often the absolute path name as
returned by the "realpath" system call. A PHP equivalent function of
realpath is documented at http://php.net/realpath

> Moreover (just in case this matters) URLs passed from the webserver are not
> guaranteed to map via a simple root prefix to any file name ( eg "
> https://foo/inbox" might map to
> <someroot>/<someintermediatepath>/inbox-xxx.php) - this would mean web
> URLs are not relevant for breakpoints

That's correct. Web URLs have no relation to setting breakpoints.

> Hopefully with this information I will be able to figure out what my
> IDE is supposed to be doing and configure it correctly according to
> some methodology rather than from random posts of desperate developers

You can also have a look at the log files that Xdebug makes if you
configure xdebug.remote_log
(https://xdebug.org/docs/all_settings#remote_log) — it will show you
exactly which commands the IDE sets, which should allow you to see
whether it does something wrong with file path roots for example.

cheers,
Derick

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