[plt-dev] Re: planet compilation not happening for recursive requires

On Thu, Feb 12, 2009 at 5:05 AM, Robby Findler
<robby at eecs.northwestern.edu> wrote:

> I believe that the first problem is traceable to resolver.ss, where a
> new namespace is created before setup plt is called, with this funny
> comment:
>
>           ;; oh man is this a bad hack!
>           (parameterize ([current-namespace (make-namespace)])
>             (let ([ipp (dynamic-require 'setup/plt-single-installer
>                                         'install-planet-package)])
>               (ipp path the-dir (list owner (pkg-spec-name pkg)
>                                       extra-path maj min))))))
>

Yeah, this has been in planet since the beginning, and it's always
bothered me. Unfortunately I never figured out how to get rid of it.
In fact, IIRC, you're actually the person who suggested I do this when
I discovered the problem for which it's the solution :) Last time it
cropped up was in a thread from October 2007 called "can't install
typed-scheme 2.0 due to namespace-attach-module error". I wrote:

;; ---

I vaguely remember writing the code in question, which is:

 ;; oh man is this a bad hack!
 (parameterize ((current-namespace (make-namespace)))
   (let ([ipp (dynamic-require '(lib "plt-single-installer.ss"
"setup") 'install-planet-package)])
     (ipp path the-dir (list owner (pkg-spec-name pkg) extra-path maj min))))

This is used to compile the package, and (IIRC) has existed like this
since the first version of planet. I believe the point of doing this
strange and terrible thing was to allow what would otherwise be a
cyclic module loading dependency, and sure enough if I change this to
a normal old require I get an error message when I attempt to run
setup-plt:

dhcp-164-32:~/tmp/web-root/servlets/speeddating jacobm$ setup-plt
setup-plt: bootstrapping from source...
standard-module-name-resolver: cycle in loading at
#<path:/Users/jacobm/svn/plt/collects/mzlib/cm.ss>:
(#<path:/Users/jacobm/svn/plt/collects/mzlib/cm.ss>
#<path:/Users/jacobm/svn/plt/collects/syntax/modresolve.ss>
#<path:/Users/jacobm/svn/plt/collects/planet/resolver.ss>
#<path:/Users/jacobm/svn/plt/collects/setup/plt-single-installer.ss>
#<path:/Users/...

 === context ===
/Users/jacobm/svn/plt/collects/setup/setup.ss:59:20: loop


Digging a bit, it appears that the cycle is real as opposed to one
caused by unnecessary grouping of procedures. It goes like this:
1. The compilation manager needs to turn require-lines into paths.
2. The function that turns require-lines into paths (that's the
modresolve thing) needs to resolve planet package require specs to
filenames.
3. The planet resolver needs to be able to set up a package in the
course of its resolution process, because that's the entire point of
planet existing.
4. The setup procedure needs to use the compilation manager to compile packages.

I believe the above hack was intended to allow me to create this cycle.

;; ---

-jacob