Implementation of TIP #381: Call Chain Introspection and Control

1 files changed, 109 insertions, 11 deletions

diff --git a/generic/tclOOBasic.c b/generic/tclOOBasic.c
index 0d38dcd..b286088 100644
--- a/generic/tclOOBasic.c
+++ b/generic/tclOOBasic.c
@@ -680,10 +680,11 @@ TclOO_Object_VarName(
 /*
  * ----------------------------------------------------------------------
  *
- * TclOONextObjCmd --
+ * TclOONextObjCmd, TclOONextToObjCmd --
  *
- *	Implementation of the [next] command. Note that this command is only
- *	ever to be used inside the body of a procedure-like method.
+ *	Implementation of the [next] and [nextto] commands. Note that these
+ *	commands are only ever to be used inside the body of a procedure-like
+ *	method.
  *
  * ----------------------------------------------------------------------
  */
@@ -723,6 +724,97 @@ TclOONextObjCmd(
     return TclNRObjectContextInvokeNext(interp, context, objc, objv, 1);
 }
 
+int
+TclOONextToObjCmd(
+    ClientData clientData,
+    Tcl_Interp *interp,
+    int objc,
+    Tcl_Obj *const *objv)
+{
+    Interp *iPtr = (Interp *) interp;
+    CallFrame *framePtr = iPtr->varFramePtr;
+    Class *classPtr;
+    CallContext *contextPtr;
+    int i;
+    Tcl_Object object;
+
+    /*
+     * Start with sanity checks on the calling context to make sure that we
+     * are invoked from a suitable method context. If so, we can safely
+     * retrieve the handle to the object call context.
+     */
+
+    if (framePtr == NULL || !(framePtr->isProcCallFrame & FRAME_IS_METHOD)) {
+	Tcl_AppendResult(interp, TclGetString(objv[0]),
+		" may only be called from inside a method", NULL);
+	Tcl_SetErrorCode(interp, "TCL", "OO", "CONTEXT_REQUIRED", NULL);
+	return TCL_ERROR;
+    }
+    contextPtr = framePtr->clientData;
+
+    /*
+     * Sanity check the arguments; we need the first one to refer to a class.
+     */
+
+    if (objc < 2) {
+	Tcl_WrongNumArgs(interp, 1, objv, "class ?arg...?");
+	return TCL_ERROR;
+    }
+    object = Tcl_GetObjectFromObj(interp, objv[1]);
+    if (object == NULL) {
+	return TCL_ERROR;
+    }
+    classPtr = ((Object *)object)->classPtr;
+    if (classPtr == NULL) {
+	Tcl_AppendResult(interp, "\"", TclGetString(objv[1]),
+		"\" is not a class", NULL);
+	return TCL_ERROR;
+    }
+
+    /*
+     * Search for an implementation of a method associated with the current
+     * call on the call chain past the point where we currently are. Do not
+     * allow jumping backwards!
+     */
+
+    for (i=contextPtr->index+1 ; i<contextPtr->callPtr->numChain ; i++) {
+	struct MInvoke *miPtr = contextPtr->callPtr->chain + i;
+
+	if (!miPtr->isFilter && miPtr->mPtr->declaringClassPtr == classPtr) {
+	    /*
+	     * Invoke the (advanced) method call context in the caller
+	     * context. Note that this is like [uplevel 1] and not [eval].
+	     */
+
+	    TclNRAddCallback(interp, RestoreFrame, framePtr, contextPtr,
+		    INT2PTR(contextPtr->index), NULL);
+	    contextPtr->index = i-1;
+	    iPtr->varFramePtr = framePtr->callerVarPtr;
+	    return TclNRObjectContextInvokeNext(interp,
+		    (Tcl_ObjectContext) contextPtr, objc, objv, 2);
+	}
+    }
+
+    /*
+     * Generate an appropriate error message, depending on whether the value
+     * is on the chain but unreachable, or not on the chain at all.
+     */
+
+    for (i=contextPtr->index ; i>=0 ; i--) {
+	struct MInvoke *miPtr = contextPtr->callPtr->chain + i;
+
+	if (!miPtr->isFilter && miPtr->mPtr->declaringClassPtr == classPtr) {
+	    Tcl_AppendResult(interp, "method implementation by \"",
+		    TclGetString(objv[1]), "\" not reachable from here",
+		    NULL);
+	    return TCL_ERROR;
+	}
+    }
+    Tcl_AppendResult(interp, "method has no non-filter implementation by \"",
+	    TclGetString(objv[1]), "\"", NULL);
+    return TCL_ERROR;
+}
+
 static int
 RestoreFrame(
     ClientData data[],
@@ -730,8 +822,12 @@ RestoreFrame(
     int result)
 {
     Interp *iPtr = (Interp *) interp;
+    CallContext *contextPtr = data[1];
 
     iPtr->varFramePtr = data[0];
+    if (contextPtr != NULL) {
+	contextPtr->index = PTR2INT(data[2]);
+    }
     return result;
 }
 
@@ -754,16 +850,17 @@ TclOOSelfObjCmd(
     Tcl_Obj *const *objv)
 {
     static const char *const subcmds[] = {
-	"caller", "class", "filter", "method", "namespace", "next", "object",
-	"target", NULL
+	"call", "caller", "class", "filter", "method", "namespace", "next",
+	"object", "target", NULL
     };
     enum SelfCmds {
-	SELF_CALLER, SELF_CLASS, SELF_FILTER, SELF_METHOD, SELF_NS, SELF_NEXT,
-	SELF_OBJECT, SELF_TARGET
+	SELF_CALL, SELF_CALLER, SELF_CLASS, SELF_FILTER, SELF_METHOD, SELF_NS,
+	SELF_NEXT, SELF_OBJECT, SELF_TARGET
     };
     Interp *iPtr = (Interp *) interp;
     CallFrame *framePtr = iPtr->varFramePtr;
     CallContext *contextPtr;
+    Tcl_Obj *result[3];
     int index;
 
 #define CurrentlyInvoked(contextPtr) \
@@ -834,7 +931,6 @@ TclOOSelfObjCmd(
 	    return TCL_ERROR;
 	} else {
 	    register struct MInvoke *miPtr = &CurrentlyInvoked(contextPtr);
-	    Tcl_Obj *result[3];
 	    Object *oPtr;
 	    const char *type;
 
@@ -862,7 +958,6 @@ TclOOSelfObjCmd(
 	    CallContext *callerPtr = framePtr->callerVarPtr->clientData;
 	    Method *mPtr = callerPtr->callPtr->chain[callerPtr->index].mPtr;
 	    Object *declarerPtr;
-	    Tcl_Obj *result[3];
 
 	    if (mPtr->declaringClassPtr != NULL) {
 		declarerPtr = mPtr->declaringClassPtr->thisPtr;
@@ -894,7 +989,6 @@ TclOOSelfObjCmd(
 	    Method *mPtr =
 		    contextPtr->callPtr->chain[contextPtr->index+1].mPtr;
 	    Object *declarerPtr;
-	    Tcl_Obj *result[2];
 
 	    if (mPtr->declaringClassPtr != NULL) {
 		declarerPtr = mPtr->declaringClassPtr->thisPtr;
@@ -928,7 +1022,6 @@ TclOOSelfObjCmd(
 	} else {
 	    Method *mPtr;
 	    Object *declarerPtr;
-	    Tcl_Obj *result[2];
 	    int i;
 
 	    for (i=contextPtr->index ; i<contextPtr->callPtr->numChain ; i++){
@@ -957,6 +1050,11 @@ TclOOSelfObjCmd(
 	    Tcl_SetObjResult(interp, Tcl_NewListObj(2, result));
 	    return TCL_OK;
 	}
+    case SELF_CALL:
+	result[0] = TclOORenderCallChain(interp, contextPtr->callPtr);
+	result[1] = Tcl_NewIntObj(contextPtr->index);
+	Tcl_SetObjResult(interp, Tcl_NewListObj(2, result));
+	return TCL_OK;
     }
     return TCL_ERROR;
 }