(stable) Prevent typeahead sources from querying against empty tokens

Summary:
Certain unusual queries, like `[-]`, could tokenize into a list which included the empty string.

This would then convert into a query for `... LIKE "%"` which just joins the entire table.

Instead: tokenize smarter; never return the empty token; add some test cases.

Test Plan: Ran unit tests. Queried for `[[blah blah]]`, saw a reasonable query come out the other end.

Reviewers: chad

Reviewed By: chad

Subscribers: 20after4

Differential Revision: https://secure.phabricator.com/D16888

PhabricatorTypeaheadDatasourceTestCase.php

@@ -0,0 +1,39 @@
+<?php
+
+final class PhabricatorTypeaheadDatasourceTestCase
+  extends PhabricatorTestCase {
+
+  public function testTypeaheadTokenization() {
+    $this->assertTokenization(
+      'The quick brown fox',
+      array('the', 'quick', 'brown', 'fox'));
+
+    $this->assertTokenization(
+      'Quack quack QUACK',
+      array('quack'));
+
+    $this->assertTokenization(
+      '',
+      array());
+
+    $this->assertTokenization(
+      '  [ - ]  ',
+      array());
+
+    $this->assertTokenization(
+      'jury-rigged',
+      array('jury', 'rigged'));
+
+    $this->assertTokenization(
+      '[[ brackets ]] [-] ]-[ tie-fighters',
+      array('brackets', 'tie', 'fighters'));
+  }
+
+  private function assertTokenization($input, $expect) {
+    $this->assertEqual(
+      $expect,
+      PhabricatorTypeaheadDatasource::tokenizeString($input),
+      pht('Tokenization of "%s"', $input));
+  }
+
+}

src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php

@@ -141,8 +141,18 @@ abstract class PhabricatorTypeaheadDatasource extends Phobject {
       return array();
     }
 
-    $tokens = preg_split('/\s+|[-\[\]]/u', $string);
-    return array_unique($tokens);
+    $tokens = preg_split('/[\s\[\]-]+/u', $string);
+    $tokens = array_unique($tokens);
+
+    // Make sure we don't return the empty token, as this will boil down to a
+    // JOIN against every token.
+    foreach ($tokens as $key => $value) {
+      if (!strlen($value)) {
+        unset($tokens[$key]);
+      }
+    }
+
+    return array_values($tokens);
   }
 
   public function getTokens() {