Initial reference implementation of TIP 712 (Add "positive" options to the subst command) with code, documentation and tests.

doc/subst.n

@@ -13,7 +13,10 @@
 .SH NAME
 subst \- Perform backslash, command, and variable substitutions
 .SH SYNOPSIS
+.nf
 \fBsubst \fR?\fB\-nobackslashes\fR? ?\fB\-nocommands\fR? ?\fB\-novariables\fR? \fIstring\fR
+\fBsubst \fR?\fB\-backslashes\fR? ?\fB\-commands\fR? ?\fB\-variables\fR? \fIstring\fR
+.fi
 .BE
 .SH DESCRIPTION
 .PP
@@ -33,6 +36,18 @@ For example, if \fB\-nocommands\fR is specified, command substitution
 is not performed:  open and close brackets are treated as ordinary characters
 with no special interpretation.
 .PP
+If any of the \fB\-backslashes\fR, \fB\-commands\fR, or
+\fB\-variables\fR are specified, then only the corresponding
+substitutions are performed. This means that the following lines are
+equivalent:
+.PP
+.CS
+\fBsubst\fR -nobackslashes -nocommands $string
+\fBsubst\fR -variables $string
+.CE
+.PP
+It is not allowed to combine positive and negated options.
+.PP
 Note that the substitution of one kind can include substitution of
 other kinds.  For example, even when the \fB\-novariables\fR option
 is specified, command substitution is performed without restriction.

generic/tclCmdMZ.c

@@ -3337,12 +3337,15 @@ TclSubstOptions(
     int *flagPtr)
 {
     static const char *const substOptions[] = {
-	"-nobackslashes", "-nocommands", "-novariables", NULL
+	"-nobackslashes", "-nocommands", "-novariables",
+	"-backslashes", "-commands", "-variables", NULL
     };
     enum {
-	SUBST_NOBACKSLASHES, SUBST_NOCOMMANDS, SUBST_NOVARS
+	SUBST_NOBACKSLASHES, SUBST_NOCOMMANDS, SUBST_NOVARS,
+	SUBST_BACKSLASHES, SUBST_COMMANDS, SUBST_VARS
     };
     int i, flags = TCL_SUBST_ALL;
+    int positive = 0, negative = 0;
 
     for (i = 0; i < numOpts; i++) {
 	int optionIndex;
@@ -3351,6 +3354,20 @@ TclSubstOptions(
 		&optionIndex) != TCL_OK) {
 	    return TCL_ERROR;
 	}
+	if (optionIndex >= SUBST_NOBACKSLASHES &&
+	    optionIndex <= SUBST_NOVARS) {
+	    negative = 1;
+	} else if (optionIndex >= SUBST_BACKSLASHES &&
+		   optionIndex <= SUBST_VARS && positive == 0) {
+	    positive = 1;
+	    /* Swap the default at the first positive switch */
+	    flags = 0;
+	}
+	if (positive && negative) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "positive and negative switches cannot be combined", -1));
+	    return TCL_ERROR;
+	}
 	switch (optionIndex) {
 	case SUBST_NOBACKSLASHES:
 	    flags &= ~TCL_SUBST_BACKSLASHES;
@@ -3361,6 +3378,15 @@ TclSubstOptions(
 	case SUBST_NOVARS:
 	    flags &= ~TCL_SUBST_VARIABLES;
 	    break;
+	case SUBST_BACKSLASHES:
+	    flags |= TCL_SUBST_BACKSLASHES;
+	    break;
+	case SUBST_COMMANDS:
+	    flags |= TCL_SUBST_COMMANDS;
+	    break;
+	case SUBST_VARS:
+	    flags |= TCL_SUBST_VARIABLES;
+	    break;
 	default:
 	    Tcl_Panic("Tcl_SubstObjCmd: bad option index to SubstOptions");
 	}
@@ -3390,7 +3416,8 @@ TclNRSubstObjCmd(
 
     if (objc < 2) {
 	Tcl_WrongNumArgs(interp, 1, objv,
-		"?-nobackslashes? ?-nocommands? ?-novariables? string");
+		"?-nobackslashes? ?-nocommands? ?-novariables? "
+		"?-backslashes? ?-commands? ?-variables? string");
 	return TCL_ERROR;
     }
 

tests/subst.test

@@ -22,10 +22,10 @@ testConstraint testbytestring [llength [info commands testbytestring]]
 
 test subst-1.1 {basics} -returnCodes error -body {
     subst
-} -result {wrong # args: should be "subst ?-nobackslashes? ?-nocommands? ?-novariables? string"}
+} -result {wrong # args: should be "subst ?-nobackslashes? ?-nocommands? ?-novariables? ?-backslashes? ?-commands? ?-variables? string"}
 test subst-1.2 {basics} -returnCodes error -body {
     subst a b c
-} -result {bad option "a": must be -nobackslashes, -nocommands, or -novariables}
+} -result {bad option "a": must be -nobackslashes, -nocommands, -novariables, -backslashes, -commands, or -variables}
 
 test subst-2.1 {simple strings} {
     subst {}
@@ -123,29 +123,57 @@ test subst-6.1 {clear the result after command substitution} -body {
 
 test subst-7.1 {switches} -returnCodes error -body {
     subst foo bar
-} -result {bad option "foo": must be -nobackslashes, -nocommands, or -novariables}
+} -result {bad option "foo": must be -nobackslashes, -nocommands, -novariables, -backslashes, -commands, or -variables}
 test subst-7.2 {switches} -returnCodes error -body {
     subst -no bar
-} -result {ambiguous option "-no": must be -nobackslashes, -nocommands, or -novariables}
+} -result {ambiguous option "-no": must be -nobackslashes, -nocommands, -novariables, -backslashes, -commands, or -variables}
 test subst-7.3 {switches} -returnCodes error -body {
     subst -bogus bar
-} -result {bad option "-bogus": must be -nobackslashes, -nocommands, or -novariables}
-test subst-7.4 {switches} {
+} -result {bad option "-bogus": must be -nobackslashes, -nocommands, -novariables, -backslashes, -commands, or -variables}
+test subst-7.4.1 {switches} {
     set x 123
     subst -nobackslashes {abc $x [expr {1 + 2}] \\\x41}
 } {abc 123 3 \\\x41}
-test subst-7.5 {switches} {
+test subst-7.4.2 {switches} {
+    set x 123
+    subst -commands -variables {abc $x [expr {1 + 2}] \\\x41}
+} {abc 123 3 \\\x41}
+test subst-7.5.1 {switches} {
     set x 123
     subst -nocommands {abc $x [expr {1 + 2}] \\\x41}
 } {abc 123 [expr {1 + 2}] \A}
-test subst-7.6 {switches} {
+test subst-7.5.2 {switches} {
+    set x 123
+    subst -backslashes -variables {abc $x [expr {1 + 2}] \\\x41}
+} {abc 123 [expr {1 + 2}] \A}
+test subst-7.6.1 {switches} {
     set x 123
     subst -novariables {abc $x [expr {1 + 2}] \\\x41}
 } {abc $x 3 \A}
+test subst-7.6.2 {switches} {
+    set x 123
+    subst -backslashes -commands {abc $x [expr {1 + 2}] \\\x41}
+} {abc $x 3 \A}
 test subst-7.7 {switches} {
     set x 123
     subst -nov -nob -noc {abc $x [expr {1 + 2}] \\\x41}
 } {abc $x [expr {1 + 2}] \\\x41}
+test subst-7.8 {switches} {
+    set x 123
+    subst -backslashes {abc $x [expr {1 + 2}] \\\x41}
+} {abc $x [expr {1 + 2}] \A}
+test subst-7.9 {switches} {
+    set x 123
+    subst -commands {abc $x [expr {1 + 2}] \\\x41}
+} {abc $x 3 \\\x41}
+test subst-7.10 {switches} {
+    set x 123
+    subst -variables {abc $x [expr {1 + 2}] \\\x41}
+} {abc 123 [expr {1 + 2}] \\\x41}
+test subst-7.11 {switches} {
+    set x 123
+    subst -ba -co -va {abc $x [expr {1 + 2}] \\\x41}
+} {abc 123 3 \A}
 
 test subst-8.1 {return in a subst} {
     subst {foo [return {x}; bogus code] bar}