Tcl Source Code

Any command imported (namespace import) from a script that has been auto_loaded fails if used in conjunction with the Iwidgets package.

This is true for 8.5 and 8.6

Consider the following two procs:

src.tcl --------------------------------------
namespace eval src {
    proc a {} {return "alpha"}
    proc b {} {return "beta"}
    proc etc {} {return "..."}
    namespace export a b
}


dst.tcl -------------------------------------------
package require Iwidgets

lappend ::auto_path [file dirname [info script]]
puts $::auto_path

namespace eval dst {
    namespace import ::src::*
    proc c {} {return "Charlie"}
    puts "[a] [b] [c]"
}

use mk to create a tcl index and run dst.

The result "a" is an invalid command.

Next: comment the package require.

=> alpha beta charlie


Now, consider the mods to dst.tcl - namespace import commented.

dst.tcl ----------------------------------
package require Iwidgets

lappend ::auto_path [file dirname [info script]]
puts $::auto_path

namespace eval dst {
    #namespace import ::src::*
    proc c {} {return "Charlie"}
    puts "[::src::a] [::src::b] [c]"
}

=> alpha beta charlie

I looked. I tried. I will not fix this.

Itcl breaks Tcl's built-in hackery to try
to make the snapshot-oriented command
[namespace import] "Do What You Mean" in
combination with the "delay until the last
minute" scheme of the built-in
auto-loader.  Choose one or the other,
magical imports of autoloaded commands or
use of the Itcl package, but you cannot have both.

Accommodating this was a dumb idea to
begin with.  [namespace import] has
snapshot semantics.  That's documented.
So create commands before you attempt
to [namespace import] them.  You cannot
make water that is not wet.  You cannot
take a snapshot of something that hasn't
yet been brought into existence.

Beyond that, give serious contemplation
to ditching all use of Tcl's built-in
auto-load system completely.  It's ancient,
not well-maintained, and the case for it
is very hard to make anymore.  If you can
make the case, you can make your own
stub-powered auto-loading scheme that works
better in every way than this relic.

As a workaround to the trouble reported in
the ticket, you could remove the
definition of [::auto_import] found in
the itcl.tcl file installed as part of
your Itcl installation.  That will avoid
the bug associated with this ticket, but
I have no idea what impact that may have
on the internal expectations of Itcl.
Test suite doesn't care, but only a fool
thinks the Itcl test suite is comprehensive.

That workaround is what I would adapt if
I had confidence it would not upset 
established Itcl uses.  At this point
though, the only winning move is not to play.

Itcl replaces the [::auto_import] with its own customized
version.

The customized approach adds another layer of indirection.
On [namespace import] all indexed auto-load-able commands
have stub-versions created, which will then only invoke
the actual auto-loading when the are called.

The problem with this is that it misses the
[namespace export] command that takes place when the
actual auto-loading [source]s the implementation.
With out an enabling [namespace export], the
[namespace import] fails to get the auto-loaded
command.

This is so broken, I cannot imagine anyone wishing
for this, but since I'm not an Itcl user it's hard
to say with any confidence.

Same ticket in the Tk tracker.