TIP #207: Add a -namespace Option to [interp invokehidden]

From: Joe Mistachkin (joe_at_mistachkin.com)
Date: 07/08/04 

Date: Thu, 8 Jul 2004 16:55:41 +0000 (UTC)

 TIP #207: ADD A -NAMESPACE OPTION TO [INTERP INVOKEHIDDEN]
============================================================
 Version: $Revision: 1.1 $
 Author: Joe Mistachkin <joe_at_mistachkin.com>
 State: Draft
 Type: Project
 Tcl-Version: 8.5
 Vote: Pending
 Created: Tuesday, 29 June 2004
 URL: http://purl.org/tcl/tip/207.html
 WebEdit: http://purl.org/tcl/tip/edit/207
 Post-History:

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 ABSTRACT
==========

 This TIP proposes a /-namespace/ option for the *interp invokehidden*
 subcommand to allow hidden commands to be invoked in the specified
 namespace context in the slave interpreter.

 RATIONALE
===========

 Safe interpreters and namespaces have been useful and important
 features of Tcl since version 8.0. However, it can sometimes be
 difficult to use them together effectively. For example, while you can
 invoke a hidden command in a safe interpreter with *interp
 invokehidden*, such as *source*, you cannot specify the target
 namespace context where the command should be invoked. Using the
 *interp eval* subcommand is not an option because that, by design, does
 not allow hidden commands to be invoked. In addition, since the *interp
 invokehidden* subcommand expects a command name, *namespace eval* and
 similar constructs that would typically be used to change the target
 namespace context cannot be used.

 SPECIFICATION
===============

       *interp invokehidden* /path/ ?*-global*? ?*-namespace*
       /namespace/? ?*--*? /hiddenCmdName/ ?/arg .../?

 The *interp invokehidden* subcommand would continue to function as the
 current documentation dictates with the following notable exceptions:

     * The *-namespace* specifies the target namespace context in the
       slave interpreter where the command should be invoked.

     * The target namespace context specified by the *-namespace* option
       is created in the slave interpreter if it does not already exist.

     * If both the *-global* and *-namespace* options are present, the
       *-namespace* option is ignored.

 A *--* option (with the standard meaning) will be added as well.

 The slave-interpreter command version of *invokehidden* will be updated
 in an equivalent way.

 EXAMPLE USAGE
---------------

 The following example scripts illustrates how this feature might be
 used.

   ################################################
   # file inside.tcl
   ################################################
   
   set x "this is a test from inside [namespace current]."
   
   ################################################
   # file invoke.tcl
   ################################################
   
   set i [interp create -safe]
   set file [file join [file dirname [info script]] inside.tcl]
   
   interp invokehidden $i -namespace ::test::foo::bar source $file
   
   set result [interp eval $i [list set ::test::foo::bar::x]]
   
   # should be: "this is a test from inside ::test::foo::bar."
   puts stdout $result

 PROPOSED INTERNAL C API CHANGES
=================================

 The following additions/changes would be made to the private Tcl C API:

     * int *TclObjInvokeNamespace*(Tcl_Interp */interp/, int /objc/,
       Tcl_Obj *CONST /objv/[], Tcl_Obj *CONST /namespaceName/, int
       /flags/)

       Invokes the specified command in the namespace context specified
       by the /namespaceName/ argument. This is a new function.

     * Two new flags *TCL_INVOKE_NS_MUST_EXIST* and
       *TCL_INVOKE_NO_GLOBAL_ONLY* would be created for use with the
       *TclObjInvoke** family of functions.

       The *TCL_INVOKE_NS_MUST_EXIST* flag (used with
       *TclObjInvokeNamespace*) indicates that the caller does /not/
       want the namespace context to be created if it does not already
       exist. *The TCL_INVOKE_NO_GLOBAL_ONLY* flag (used with
       *TclObjInvoke*) inhibits the use of the *TCL_GLOBAL_ONLY* during
       command resolution.

     * static int *SlaveInvokeHidden*(Tcl_Interp */interp/, Tcl_Interp
       */slaveInterp/, int /global/, Tcl_Obj *CONST /namespaceName/, int
       /objc/, Tcl_Obj *CONST /objv/[])

       The *SlaveInvokeHidden* would be modified to accept a
       /namespaceName/ argument.

     * The *FIND_ONLY_NS* flag would be moved from /generic/tclNamesp.c/
       to /generic/tclInt.h/

 REFERENCE IMPLEMENTATION
==========================

 A reference implementation of this TIP is availble
 [<URL:http://sf.net/tracker/?func=detail&aid=981841&group_id=10894&atid=310894>].

 COPYRIGHT
===========

 This document has been placed in the public domain.

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