MDL-70909 core: add cannotmatchanyrows to capabilities join

enrol/tests/enrollib_test.php

@@ -1362,4 +1362,77 @@ class core_enrollib_testcase extends advanced_testcase {
         $durationinday = $duration / DAYSECS;
         $this->assertEquals(9, $durationinday);
     }
+
+    /**
+     * Test get_enrolled_with_capabilities_join cannotmatchanyrows attribute.
+     *
+     * @dataProvider get_enrolled_with_capabilities_join_cannotmatchanyrows_data()
+     * @param string $capability the tested capability
+     * @param bool $useprohibit if the capability must be assigned to prohibit
+     * @param int $expectedmatch expected cannotmatchanyrows value
+     * @param int $expectedcount expceted count value
+     */
+    public function test_get_enrolled_with_capabilities_join_cannotmatchanyrows(
+        string $capability,
+        bool $useprohibit,
+        int $expectedmatch,
+        int $expectedcount
+    ) {
+        global $DB, $CFG;
+
+        $this->resetAfterTest();
+
+        $course = $this->getDataGenerator()->create_course();
+        $context = context_course::instance($course->id);
+
+        $roleid = $CFG->defaultuserroleid;
+
+        // Override capability if necessary.
+        if ($useprohibit && $capability) {
+            assign_capability($capability, CAP_PROHIBIT, $roleid, $context);
+        }
+
+        // Check if we must enrol or not.
+        $this->getDataGenerator()->create_and_enrol($course, 'editingteacher');
+
+        $join = get_enrolled_with_capabilities_join($context, '', $capability);
+
+        // Execute query.
+        $sql = "SELECT COUNT(DISTINCT u.id)
+                  FROM {user} u {$join->joins}
+                 WHERE {$join->wheres}";
+        $countrecords = $DB->count_records_sql($sql, $join->params);
+
+        // Validate cannotmatchanyrows.
+        $this->assertEquals($expectedmatch, $join->cannotmatchanyrows);
+        $this->assertEquals($expectedcount, $countrecords);
+    }
+
+    /**
+     * Data provider for test_get_enrolled_with_capabilities_join_cannotmatchanyrows
+     *
+     * @return @array of testing scenarios
+     */
+    public function get_enrolled_with_capabilities_join_cannotmatchanyrows_data() {
+        return [
+            'no prohibits, no capability' => [
+                'capability' => '',
+                'useprohibit' => false,
+                'expectedmatch' => 0,
+                'expectedcount' => 1,
+            ],
+            'no prohibits with capability' => [
+                'capability' => 'moodle/course:manageactivities',
+                'useprohibit' => false,
+                'expectedmatch' => 0,
+                'expectedcount' => 1,
+            ],
+            'prohibits with capability' => [
+                'capability' => 'moodle/course:manageactivities',
+                'useprohibit' => true,
+                'expectedmatch' => 1,
+                'expectedcount' => 0,
+            ],
+        ];
+    }
 }

lib/enrollib.php

@@ -1384,6 +1384,10 @@ function is_enrolled(context $context, $user = null, $withcapability = '', $only
  * several times (e.g. as manual enrolment, and as self enrolment). You may
  * need to use a SELECT DISTINCT in your query (see get_enrolled_sql for example).
  *
+ * In case is guaranteed some of the joins never match any rows, the resulting
+ * join_sql->cannotmatchanyrows will be true. This happens when the capability
+ * is prohibited.
+ *
  * @param context $context
  * @param string $prefix optional, a prefix to the user id column
  * @param string|array $capability optional, may include a capability name, or array of names.
@@ -1393,24 +1397,27 @@ function is_enrolled(context $context, $user = null, $withcapability = '', $only
  * @param bool $onlyactive consider only active enrolments in enabled plugins and time restrictions
  * @param bool $onlysuspended inverse of onlyactive, consider only suspended enrolments
  * @param int $enrolid The enrolment ID. If not 0, only users enrolled using this enrolment method will be returned.
- * @return \core\dml\sql_join Contains joins, wheres, params
+ * @return \core\dml\sql_join Contains joins, wheres, params and cannotmatchanyrows
  */
 function get_enrolled_with_capabilities_join(context $context, $prefix = '', $capability = '', $group = 0,
         $onlyactive = false, $onlysuspended = false, $enrolid = 0) {
     $uid = $prefix . 'u.id';
     $joins = array();
     $wheres = array();
+    $cannotmatchanyrows = false;
 
     $enrolledjoin = get_enrolled_join($context, $uid, $onlyactive, $onlysuspended, $enrolid);
     $joins[] = $enrolledjoin->joins;
     $wheres[] = $enrolledjoin->wheres;
     $params = $enrolledjoin->params;
+    $cannotmatchanyrows = $cannotmatchanyrows || $enrolledjoin->cannotmatchanyrows;
 
     if (!empty($capability)) {
         $capjoin = get_with_capability_join($context, $capability, $uid);
         $joins[] = $capjoin->joins;
         $wheres[] = $capjoin->wheres;
         $params = array_merge($params, $capjoin->params);
+        $cannotmatchanyrows = $cannotmatchanyrows || $capjoin->cannotmatchanyrows;
     }
 
     if ($group) {
@@ -1420,13 +1427,14 @@ function get_enrolled_with_capabilities_join(context $context, $prefix = '', $ca
         if (!empty($groupjoin->wheres)) {
             $wheres[] = $groupjoin->wheres;
         }
+        $cannotmatchanyrows = $cannotmatchanyrows || $groupjoin->cannotmatchanyrows;
     }
 
     $joins = implode("\n", $joins);
     $wheres[] = "{$prefix}u.deleted = 0";
     $wheres = implode(" AND ", $wheres);
 
-    return new \core\dml\sql_join($joins, $wheres, $params);
+    return new \core\dml\sql_join($joins, $wheres, $params, $cannotmatchanyrows);
 }
 
 /**