Fix condition recursion

- Show error on home page to admins when recursion is detected
- Clear error when appropriate

src/pages/p_adminhome.php

@@ -118,6 +118,11 @@ static function print(Contact $user) {
                 }
             }
         }
+        // Condition recursion?
+        if ($conf->setting("__sf_condition_recursion") > 0)  {
+            $ml[] = MessageItem::error("<0>Self-referential search in submission field conditions");
+            $ml[] = new MessageItem(null, "<5>Some presence conditions in submission fields appear to be circularly defined. The fields involved will never appear. You should <a href=\"" . $conf->hoturl("settings", "group=subform") . "\">update the submission form settings</a> to fix this problem.", MessageSet::INFORM);
+        }
 
         if (!empty($ml)) {
             $ml[] = new MessageItem(null, "", MessageSet::WARNING);

src/paperoption.php

@@ -1,6 +1,6 @@
 <?php
 // paperoption.php -- HotCRP helper class for paper options
-// Copyright (c) 2006-2023 Eddie Kohler; see LICENSE.
+// Copyright (c) 2006-2024 Eddie Kohler; see LICENSE.
 
 class PaperOption implements JsonSerializable {
     const TITLEID = -1000;
@@ -564,7 +564,9 @@ final function test_exists(PaperInfo $prow, $use_script_expression = false) {
         } else if ($this->_exists_state !== 0) {
             return $this->_exists_state > 0;
         } else if (++$this->_recursion > 5) {
-            throw new ErrorException("Recursion in {$this->name}::test_exists [{$this->exists_if}]");
+            $this->mark_condition_recursion("exists_if");
+            $this->_exists_state = -1;
+            return false;
         } else {
             if ($use_script_expression) {
                 $x = !!($this->exists_script_expression($prow) ?? true);
@@ -582,6 +584,18 @@ final function exists_script_expression(PaperInfo $prow) {
             return $this->exists_term()->script_expression($prow, SearchTerm::ABOUT_PAPER);
         }
     }
+    private function mark_condition_recursion($name) {
+        $scr = $this->conf->setting("__sf_condition_recursion") ?? 0;
+        if ($scr < 0) {
+            $this->conf->change_setting("__sf_condition_recursion", $this->id, $name);
+        } else if ($scr === 0) {
+            $this->conf->save_setting("__sf_condition_recursion", $this->id, $name);
+        }
+        if ($scr >= 0 && !defined("HOTCRP_TESTHARNESS")) {
+            $prop = property_exists($this, $name) ? " [{$this->$name}]" : "";
+            error_log("Recursion in {$this->name}::{$name}{$prop}");
+        }
+    }
 
     /** @return ?string */
     final function editable_condition() {
@@ -607,12 +621,12 @@ final function test_editable(PaperInfo $prow) {
             $this->_editable_term = $s->full_term();
         }
         if (++$this->_recursion > 5) {
-            throw new ErrorException("Recursion in {$this->name}::test_editable");
-        } else {
-            $x = $this->_editable_term->test($prow, null);
-            --$this->_recursion;
-            return $x;
+            $this->_editable_term = new False_SearchTerm;
+            $this->mark_condition_recursion("editable_if");
         }
+        $x = $this->_editable_term->test($prow, null);
+        --$this->_recursion;
+        return $x;
     }
 
     /** @return bool */

src/settings/s_options.php

@@ -1051,6 +1051,7 @@ function store_value(Si $si, SettingValues $sv) {
                 $sv->conf->qe("insert into PaperOption (paperId, optionId, value, data, dataOverflow) values ?v", $updates);
             }
         }
+        $sv->conf->save_setting("__sf_condition_recursion", null);
         $sv->mark_invalidate_caches(["autosearch" => true]);
     }
 

src/settings/s_subfieldcondition.php

@@ -1,6 +1,6 @@
 <?php
 // settings/s_subfieldcondition.php -- HotCRP submission field conditions
-// Copyright (c) 2006-2023 Eddie Kohler; see LICENSE.
+// Copyright (c) 2006-2024 Eddie Kohler; see LICENSE.
 
 class SubFieldCondition_SettingParser extends SettingParser {
     function print(SettingValues $sv) {
@@ -34,47 +34,57 @@ function print(SettingValues $sv) {
     }
 
     /** @param SettingValues $sv
-     * @param string $siname
+     * @param int $ctr
+     * @param 'exists_if'|'editable_if' $type
      * @param PaperOption $field
-     * @param string $q
-     * @param 1|2 $status */
-    static function validate1($sv, $siname, $field, $q, $status) {
+     * @param 1|2 $status
+     * @param PaperInfo $prow */
+    static private function validate1($sv, $ctr, $type, $field, $status, $prow) {
+        $q = $type === "exists_if" ? $field->exists_condition() : $field->editable_condition();
         if ($q === null || $q === "NONE" || $q === "phase:final") {
             return;
         }
+        $siname = "sf/{$ctr}/" . ($type === "exists_if" ? "condition" : "edit_condition");
+
         $ps = new PaperSearch($sv->conf->root_user(), $q);
         foreach ($ps->message_list() as $mi) {
             $sv->append_item_at($siname, $mi);
         }
-        try {
-            $fake_prow = PaperInfo::make_placeholder($sv->conf, -1);
-            if ($ps->main_term()->script_expression($fake_prow, SearchTerm::ABOUT_PAPER) === null) {
-                $sv->msg_at($siname, "<0>Invalid search in field condition", $status);
-                $sv->inform_at($siname, "<0>Field conditions are limited to simple search keywords.");
-            }
-        } catch (ErrorException $e) {
-            $sv->msg_at($siname, "<0>Field condition is defined in terms of itself", 2);
+
+        $scr = $sv->conf->setting("__sf_condition_recursion");
+        $scrd = $sv->conf->setting_data("__sf_condition_recursion");
+        $sv->conf->change_setting("__sf_condition_recursion", -1);
+        if ($ps->main_term()->script_expression($prow, SearchTerm::ABOUT_PAPER) === null) {
+            $sv->msg_at($siname, "<0>Invalid search in field condition", $status);
+            $sv->inform_at($siname, "<0>Field conditions are limited to simple search keywords.");
+        }
+        if ($sv->conf->setting("__sf_condition_recursion") > 0
+            || ($status === 1 && $scr === $field->id && $scrd === $type)) {
+            $sv->msg_at($siname, "<0>Self-referential search in field condition", 2);
         }
+        $sv->conf->change_setting("__sf_condition_recursion", $scr, $scrd);
     }
 
     static function crosscheck(SettingValues $sv) {
         if ($sv->has_interest("sf")) {
             $opts = Options_SettingParser::configurable_options($sv->conf);
+            $prow = PaperInfo::make_placeholder($sv->conf, -1);
             foreach ($opts as $ctrz => $f) {
                 $ctr = $ctrz + 1;
-                self::validate1($sv, "sf/{$ctr}/condition", $f, $f->exists_condition(), 1);
-                self::validate1($sv, "sf/{$ctr}/edit_condition", $f, $f->editable_condition(), 1);
+                self::validate1($sv, $ctr, "exists_if", $f, 1, $prow);
+                self::validate1($sv, $ctr, "editable_if", $f, 1, $prow);
             }
         }
     }
 
     static function validate(SettingValues $sv) {
         $opts = Options_SettingParser::configurable_options($sv->conf);
         $osp = $sv->cs()->callable("Options_SettingParser");
+        $prow = PaperInfo::make_placeholder($sv->conf, -1);
         foreach ($opts as $f) {
             if (($ctr = $osp->option_id_to_ctr[$f->id] ?? null) !== null) {
-                self::validate1($sv, "sf/{$ctr}/condition", $f, $f->exists_condition(), 2);
-                self::validate1($sv, "sf/{$ctr}/edit_condition", $f, $f->editable_condition(), 2);
+                self::validate1($sv, $ctr, "exists_if", $f, 2, $prow);
+                self::validate1($sv, $ctr, "editable_if", $f, 2, $prow);
             }
         }
     }

test/t_settings.php

@@ -1868,14 +1868,17 @@ function test_sf_condition_recursion_live() {
         xassert_eqq($j[3]->id, 1);
         xassert_eqq($j[3]->name, "Brownies");
         xassert_eqq($j[3]->exists_if ?? null, null);
+        xassert_eqq($this->conf->setting("__sf_condition_recursion"), null);
 
         $j[3]->exists_if = "#foobar && !has:brownies";
         $this->conf->save_refresh_setting("options", $this->conf->setting("options") + 1, json_encode_db($j));
 
         $pa = PaperInfo::make_new($this->u_chair, null);
         $pa->set_prop("paperTags", " foobar#0");
         xassert($this->u_chair->can_view_option($pa, $this->conf->option_by_id(1)));
+        xassert_eqq($this->conf->setting("__sf_condition_recursion"), 1);
 
         $this->conf->save_refresh_setting("options", $this->conf->setting("options") + 1, $old_options);
+        $this->conf->save_setting("__sf_condition_recursion", null);
     }
 }