fix issue #1305 - failed #untrap from doorway

Issue reported by loggersviii:  attempting #untrap from an adjacent
doorway can move the hero diagonally out of the doorway.

A followup comment by elunna pointed out that a monster's attack that
results in knockback can produce similar result.

Fixes #1305

include/extern.h

@@ -1173,6 +1173,7 @@ extern boolean in_town(coordxy, coordxy);
 extern void check_special_room(boolean);
 extern int dopickup(void);
 extern void lookaround(void);
+extern boolean doorless_door(coordxy, coordxy);
 extern boolean crawl_destination(coordxy, coordxy);
 extern int monster_nearby(void);
 extern void end_running(boolean);
@@ -3218,6 +3219,7 @@ extern void drain_en(int, boolean);
 extern int dountrap(void);
 extern int could_untrap(boolean, boolean);
 extern void cnv_trap_obj(int, int, struct trap *, boolean) NONNULLARG3;
+extern boolean into_vs_onto(int);
 extern int untrap(boolean, coordxy, coordxy, struct obj *) NO_NNARGS;
 extern boolean openholdingtrap(struct monst *, boolean *) NO_NNARGS;
 extern boolean closeholdingtrap(struct monst *, boolean *) NO_NNARGS;

src/hack.c

@@ -47,7 +47,6 @@ staticfn struct monst *monstinroom(struct permonst *, int) NONNULLARG1;
 staticfn boolean furniture_present(int, int);
 staticfn void move_update(boolean);
 staticfn int pickup_checks(void);
-staticfn boolean doorless_door(coordxy, coordxy);
 staticfn void maybe_wail(void);
 staticfn boolean water_turbulence(coordxy *, coordxy *);
 
@@ -963,7 +962,7 @@ invocation_pos(coordxy x, coordxy y)
                       && x == svi.inv_pos.x && y == svi.inv_pos.y);
 }
 
-/* return TRUE if (dx,dy) is an OK place to move;
+/* return TRUE if (ux+dx,ux+dy) is an OK place to move;
    mode is one of DO_MOVE, TEST_MOVE, TEST_TRAV, or TEST_TRAP */
 boolean
 test_move(
@@ -2749,20 +2748,8 @@ domove_core(void)
             || Hallucination)) {
         char qbuf[QBUFSZ];
         int traptype = (Hallucination ? rnd(TRAPNUM - 1) : (int) trap->ttyp);
-        boolean into = FALSE; /* "onto" the trap vs "into" */
+        boolean into = into_vs_onto(traptype);
 
-        switch (traptype) {
-        case BEAR_TRAP:
-        case PIT:
-        case SPIKED_PIT:
-        case HOLE:
-        case TELEP_TRAP:
-        case LEVEL_TELEP:
-        case MAGIC_PORTAL:
-        case WEB:
-            into = TRUE;
-            break;
-        }
         Snprintf(qbuf, sizeof qbuf, "Really %s %s that %s?",
                  u_locomotion("step"), into ? "into" : "onto",
                  defsyms[trap_to_defsym(traptype)].explanation);
@@ -3910,7 +3897,7 @@ lookaround(void)
 }
 
 /* check for a doorway which lacks its door (NODOOR or BROKEN) */
-staticfn boolean
+boolean
 doorless_door(coordxy x, coordxy y)
 {
     struct rm *lev_p = &levl[x][y];

src/trap.c

@@ -5267,6 +5267,24 @@ cnv_trap_obj(
     deltrap(ttmp);
 }
 
+/* whether moving to a trap location is moving "into" the trap or "onto" it */
+boolean
+into_vs_onto(int traptype)
+{
+    switch (traptype) {
+    case BEAR_TRAP:
+    case PIT:
+    case SPIKED_PIT:
+    case HOLE:
+    case TELEP_TRAP:
+    case LEVEL_TELEP:
+    case MAGIC_PORTAL:
+    case WEB:
+        return TRUE;
+    }
+    return FALSE;
+}
+
 /* while attempting to disarm an adjacent trap, we've fallen into it */
 staticfn void
 move_into_trap(struct trap *ttmp)
@@ -5276,9 +5294,13 @@ move_into_trap(struct trap *ttmp)
     boolean unused;
 
     bx = by = cx = cy = 0; /* lint suppression */
-    /* we know there's no monster in the way, and we're not trapped */
-    if (!Punished
-        || drag_ball(x, y, &bc, &bx, &by, &cx, &cy, &unused, TRUE)) {
+    /* we know there's no monster in the way and we're not trapped, but
+       need to make sure the move is not diagonally into or out of a
+       doorway; the sgn() calls are redundant since ttmp is adjacent */
+    if (test_move(u.ux, u.uy, sgn(x - u.ux), sgn(y - u.uy), TEST_MOVE)
+        && (!Punished
+            || drag_ball(x, y, &bc, &bx, &by, &cx, &cy, &unused, TRUE))) {
+        /* move hero and update map */
         u.ux0 = u.ux, u.uy0 = u.uy;
         /* set u.ux,u.uy and u.usteed->mx,my plus handle CLIPPING */
         u_on_newpos(x, y);
@@ -5303,6 +5325,11 @@ move_into_trap(struct trap *ttmp)
         if ((ttmp = t_at(u.ux, u.uy)) != 0)
             ttmp->tseen = 1;
         exercise(A_WIS, FALSE);
+    } else {
+        /* caller has just printed "Whoops..." so if hero is prevented from
+           moving, a followup message is needed */
+        pline("Fortunately, you don't move %s it.",
+              into_vs_onto(ttmp->ttyp) ? "into" : "onto");
     }
 }
 

src/uhitm.c

@@ -5140,6 +5140,26 @@ mhitm_knockback(
     if (rn2(6))
         return FALSE;
 
+    /* decide where the first step will place the target; not accurate
+       for being knocked out of saddle but doesn't need to be; used for
+       test_move() and for message before actual hurtle */
+    defx = u_def ? u.ux : mdef->mx;
+    defy = u_def ? u.uy : mdef->my;
+    dx = sgn(defx - (u_agr ? u.ux : magr->mx));
+    dy = sgn(defy - (u_agr ? u.uy : magr->my));
+
+    /* can't move most targets into or out of a doorway diagonally */
+    if (u_def) {
+        if (!test_move(defx, defy, dx, dy, TEST_MOVE))
+            return FALSE;
+    } else {
+        /* subset of test_move() */
+        if (IS_DOOR(levl[defx][defy].typ)
+            && (defx - magr->mx && defy - magr->my)
+            && !doorless_door(defx, defy))
+            return FALSE;
+    }
+
     /* if hero is stuck to a cursed saddle, knock the steed back */
     if (u_def && u.usteed) {
         if ((otmp = which_armor(u.usteed, W_SADDLE)) != 0 && otmp->cursed) {
@@ -5191,13 +5211,6 @@ mhitm_knockback(
         return FALSE;
     }
 
-    /* decide where the first step will place the target; not accurate
-       for being knocked out of saddle but doesn't need to be; used for
-       message before actual hurtle */
-    defx = u_def ? u.ux : mdef->mx;
-    defy = u_def ? u.uy : mdef->my;
-    dx = sgn(defx - (u_agr ? u.ux : magr->mx));
-    dy = sgn(defy - (u_agr ? u.uy : magr->my));
     /* subtly vary the message text if monster won't actually move */
     knockedhow = dismount ? "out of your saddle"
                  : will_hurtle(mdef, defx + dx, defy + dy) ? "backward"