diff --git a/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php b/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php
index 9e905f8cce..7c2205df46 100644
--- a/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php
+++ b/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php
@@ -1,434 +1,453 @@
 <?php
 
 final class PhabricatorTypeaheadModularDatasourceController
   extends PhabricatorTypeaheadDatasourceController {
 
   public function shouldAllowPublic() {
     return true;
   }
 
   public function handleRequest(AphrontRequest $request) {
     $request = $this->getRequest();
     $viewer = $request->getUser();
     $query = $request->getStr('q');
     $offset = $request->getInt('offset');
     $select_phid = null;
     $is_browse = ($request->getURIData('action') == 'browse');
 
     $select = $request->getStr('select');
     if ($select) {
       $select = phutil_json_decode($select);
       $query = idx($select, 'q');
       $offset = idx($select, 'offset');
       $select_phid = idx($select, 'phid');
     }
 
     // Default this to the query string to make debugging a little bit easier.
     $raw_query = nonempty($request->getStr('raw'), $query);
 
     // This makes form submission easier in the debug view.
     $class = nonempty($request->getURIData('class'), $request->getStr('class'));
 
     $sources = id(new PhutilClassMapQuery())
       ->setAncestorClass('PhabricatorTypeaheadDatasource')
       ->execute();
 
     if (isset($sources[$class])) {
       $source = $sources[$class];
-      $source->setParameters($request->getRequestData());
+
+      $parameters = array();
+
+      $raw_parameters = $request->getStr('parameters');
+      if (strlen($raw_parameters)) {
+        try {
+          $parameters = phutil_json_decode($raw_parameters);
+        } catch (PhutilJSONParserException $ex) {
+          return $this->newDialog()
+            ->setTitle(pht('Invalid Parameters'))
+            ->appendParagraph(
+              pht(
+                'The HTTP parameter named "parameters" for this request is '.
+                'not a valid JSON parameter. JSON is required. Exception: %s',
+                $ex->getMessage()))
+            ->addCancelButton('/');
+        }
+      }
+
+      $source->setParameters($parameters);
       $source->setViewer($viewer);
 
       // NOTE: Wrapping the source in a Composite datasource ensures we perform
       // application visibility checks for the viewer, so we do not need to do
       // those separately.
       $composite = new PhabricatorTypeaheadRuntimeCompositeDatasource();
       $composite->addDatasource($source);
 
       $hard_limit = 1000;
       $limit = 100;
 
       $composite
         ->setViewer($viewer)
         ->setQuery($query)
         ->setRawQuery($raw_query)
         ->setLimit($limit + 1);
 
       if ($is_browse) {
         if (!$composite->isBrowsable()) {
           return new Aphront404Response();
         }
 
         if (($offset + $limit) >= $hard_limit) {
           // Offset-based paging is intrinsically slow; hard-cap how far we're
           // willing to go with it.
           return new Aphront404Response();
         }
 
         $composite
           ->setOffset($offset)
           ->setIsBrowse(true);
       }
 
       $results = $composite->loadResults();
 
       if ($is_browse) {
         // If this is a request for a specific token after the user clicks
         // "Select", return the token in wire format so it can be added to
         // the tokenizer.
         if ($select_phid !== null) {
           $map = mpull($results, null, 'getPHID');
           $token = idx($map, $select_phid);
           if (!$token) {
             return new Aphront404Response();
           }
 
           $payload = array(
             'key' => $token->getPHID(),
             'token' => $token->getWireFormat(),
           );
 
           return id(new AphrontAjaxResponse())->setContent($payload);
         }
 
         $format = $request->getStr('format');
         switch ($format) {
           case 'html':
           case 'dialog':
             // These are the acceptable response formats.
             break;
           default:
             // Return a dialog if format information is missing or invalid.
             $format = 'dialog';
             break;
         }
 
         $next_link = null;
         if (count($results) > $limit) {
           $results = array_slice($results, 0, $limit, $preserve_keys = true);
           if (($offset + (2 * $limit)) < $hard_limit) {
             $next_uri = id(new PhutilURI($request->getRequestURI()))
               ->setQueryParam('offset', $offset + $limit)
               ->setQueryParam('q', $query)
               ->setQueryParam('raw', $raw_query)
               ->setQueryParam('format', 'html');
 
             $next_link = javelin_tag(
               'a',
               array(
                 'href' => $next_uri,
                 'class' => 'typeahead-browse-more',
                 'sigil' => 'typeahead-browse-more',
                 'mustcapture' => true,
               ),
               pht('More Results'));
           } else {
             // If the user has paged through more than 1K results, don't
             // offer to page any further.
             $next_link = javelin_tag(
               'div',
               array(
                 'class' => 'typeahead-browse-hard-limit',
               ),
               pht('You reach the edge of the abyss.'));
           }
         }
 
         $exclude = $request->getStrList('exclude');
         $exclude = array_fuse($exclude);
 
         $select = array(
           'offset' => $offset,
           'q' => $query,
         );
 
         $items = array();
         foreach ($results as $result) {
           // Disable already-selected tokens.
           $disabled = isset($exclude[$result->getPHID()]);
 
           $value = $select + array('phid' => $result->getPHID());
           $value = json_encode($value);
 
           $button = phutil_tag(
             'button',
             array(
               'class' => 'small grey',
               'name' => 'select',
               'value' => $value,
               'disabled' => $disabled ? 'disabled' : null,
             ),
             pht('Select'));
 
           $information = $this->renderBrowseResult($result, $button);
 
           $items[] = phutil_tag(
             'div',
             array(
               'class' => 'typeahead-browse-item grouped',
             ),
             $information);
         }
 
         $markup = array(
           $items,
           $next_link,
         );
 
         if ($format == 'html') {
           $content = array(
             'markup' => hsprintf('%s', $markup),
           );
           return id(new AphrontAjaxResponse())->setContent($content);
         }
 
         $this->requireResource('typeahead-browse-css');
         $this->initBehavior('typeahead-browse');
 
         $input_id = celerity_generate_unique_node_id();
         $frame_id = celerity_generate_unique_node_id();
 
         $config = array(
           'inputID' => $input_id,
           'frameID' => $frame_id,
           'uri' => (string)$request->getRequestURI(),
         );
         $this->initBehavior('typeahead-search', $config);
 
         $search = javelin_tag(
           'input',
           array(
             'type' => 'text',
             'id' => $input_id,
             'class' => 'typeahead-browse-input',
             'autocomplete' => 'off',
             'placeholder' => $source->getPlaceholderText(),
           ));
 
         $frame = phutil_tag(
           'div',
           array(
             'class' => 'typeahead-browse-frame',
             'id' => $frame_id,
           ),
           $markup);
 
         $browser = array(
           phutil_tag(
             'div',
             array(
               'class' => 'typeahead-browse-header',
             ),
             $search),
           $frame,
         );
 
         $function_help = null;
         if ($source->getAllDatasourceFunctions()) {
           $reference_uri = '/typeahead/help/'.get_class($source).'/';
 
           $parameters = $source->getParameters();
           if ($parameters) {
             $reference_uri = (string)id(new PhutilURI($reference_uri))
               ->setQueryParam('parameters', phutil_json_encode($parameters));
           }
 
           $reference_link = phutil_tag(
             'a',
             array(
               'href' => $reference_uri,
               'target' => '_blank',
             ),
             pht('Reference: Advanced Functions'));
 
           $function_help = array(
             id(new PHUIIconView())
               ->setIcon('fa-book'),
             ' ',
             $reference_link,
           );
         }
 
         return $this->newDialog()
           ->setWidth(AphrontDialogView::WIDTH_FORM)
           ->setRenderDialogAsDiv(true)
           ->setTitle($source->getBrowseTitle())
           ->appendChild($browser)
           ->setResizeX(true)
           ->setResizeY($frame_id)
           ->addFooter($function_help)
           ->addCancelButton('/', pht('Close'));
       }
 
     } else if ($is_browse) {
       return new Aphront404Response();
     } else {
       $results = array();
     }
 
     $content = mpull($results, 'getWireFormat');
     $content = array_values($content);
 
     if ($request->isAjax()) {
       return id(new AphrontAjaxResponse())->setContent($content);
     }
 
     // If there's a non-Ajax request to this endpoint, show results in a tabular
     // format to make it easier to debug typeahead output.
 
     foreach ($sources as $key => $source) {
       // See T13119. Exclude proxy datasources from the dropdown since they
       // fatal if built like this without actually being configured with an
       // underlying datasource. This is a bit hacky but this is just a
       // debugging/development UI anyway.
       if ($source instanceof PhabricatorTypeaheadProxyDatasource) {
         unset($sources[$key]);
         continue;
       }
 
       // This can happen with composite or generic sources.
       if (!$source->getDatasourceApplicationClass()) {
         continue;
       }
 
       if (!PhabricatorApplication::isClassInstalledForViewer(
         $source->getDatasourceApplicationClass(),
         $viewer)) {
         unset($sources[$key]);
       }
     }
     $options = array_fuse(array_keys($sources));
     asort($options);
 
     $form = id(new AphrontFormView())
       ->setUser($viewer)
       ->setAction('/typeahead/class/')
       ->appendChild(
         id(new AphrontFormSelectControl())
           ->setLabel(pht('Source Class'))
           ->setName('class')
           ->setValue($class)
           ->setOptions($options))
       ->appendChild(
         id(new AphrontFormTextControl())
           ->setLabel(pht('Query'))
           ->setName('q')
           ->setValue($request->getStr('q')))
       ->appendChild(
         id(new AphrontFormTextControl())
           ->setLabel(pht('Raw Query'))
           ->setName('raw')
           ->setValue($request->getStr('raw')))
       ->appendChild(
         id(new AphrontFormSubmitControl())
           ->setValue(pht('Query')));
 
     $form_box = id(new PHUIObjectBoxView())
       ->setHeaderText(pht('Token Query'))
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->setForm($form);
 
     // Make "\n" delimiters more visible.
     foreach ($content as $key => $row) {
       $content[$key][0] = str_replace("\n", '<\n>', $row[0]);
     }
 
     $table = new AphrontTableView($content);
     $table->setHeaders(
       array(
         pht('Name'),
         pht('URI'),
         pht('PHID'),
         pht('Priority'),
         pht('Display Name'),
         pht('Display Type'),
         pht('Image URI'),
         pht('Priority Type'),
         pht('Icon'),
         pht('Closed'),
         pht('Sprite'),
         pht('Color'),
         pht('Type'),
         pht('Unique'),
         pht('Auto'),
         pht('Phase'),
       ));
 
     $result_box = id(new PHUIObjectBoxView())
       ->setHeaderText(pht('Token Results (%s)', $class))
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->appendChild($table);
 
     $title = pht('Typeahead Results');
 
     $header = id(new PHUIHeaderView())
       ->setHeader($title);
 
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setFooter(array(
         $form_box,
         $result_box,
       ));
 
     return $this->newPage()
       ->setTitle($title)
       ->appendChild($view);
   }
 
   private function renderBrowseResult(
     PhabricatorTypeaheadResult $result,
     $button) {
 
     $class = array();
     $style = array();
     $separator = " \xC2\xB7 ";
 
     $class[] = 'phabricator-main-search-typeahead-result';
 
     $name = phutil_tag(
       'div',
       array(
         'class' => 'result-name',
       ),
       $result->getDisplayName());
 
     $icon = $result->getIcon();
     $icon = id(new PHUIIconView())->setIcon($icon);
 
     $attributes = $result->getAttributes();
     $attributes = phutil_implode_html($separator, $attributes);
     $attributes = array($icon, ' ', $attributes);
 
     $closed = $result->getClosed();
     if ($closed) {
       $class[] = 'result-closed';
       $attributes = array($closed, $separator, $attributes);
     }
 
     $attributes = phutil_tag(
       'div',
       array(
         'class' => 'result-type',
       ),
       $attributes);
 
     $image = $result->getImageURI();
     if ($image) {
       $style[] = 'background-image: url('.$image.');';
       $class[] = 'has-image';
     }
 
     return phutil_tag(
       'div',
       array(
         'class' => implode(' ', $class),
         'style' => implode(' ', $style),
       ),
       array(
         $button,
         $name,
         $attributes,
       ));
   }
 
 }
diff --git a/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php b/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php
index 2e369a3f67..196ad1b98b 100644
--- a/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php
+++ b/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php
@@ -1,595 +1,607 @@
 <?php
 
 /**
  * @task functions Token Functions
  */
 abstract class PhabricatorTypeaheadDatasource extends Phobject {
 
   private $viewer;
   private $query;
   private $rawQuery;
   private $offset;
   private $limit;
   private $parameters = array();
   private $functionStack = array();
   private $isBrowse;
   private $phase = self::PHASE_CONTENT;
 
   const PHASE_PREFIX = 'prefix';
   const PHASE_CONTENT = 'content';
 
   public function setLimit($limit) {
     $this->limit = $limit;
     return $this;
   }
 
   public function getLimit() {
     return $this->limit;
   }
 
   public function setOffset($offset) {
     $this->offset = $offset;
     return $this;
   }
 
   public function getOffset() {
     return $this->offset;
   }
 
   public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
     return $this;
   }
 
   public function getViewer() {
     return $this->viewer;
   }
 
   public function setRawQuery($raw_query) {
     $this->rawQuery = $raw_query;
     return $this;
   }
 
   public function getPrefixQuery() {
     return phutil_utf8_strtolower($this->getRawQuery());
   }
 
   public function getRawQuery() {
     return $this->rawQuery;
   }
 
   public function setQuery($query) {
     $this->query = $query;
     return $this;
   }
 
   public function getQuery() {
     return $this->query;
   }
 
   public function setParameters(array $params) {
     $this->parameters = $params;
     return $this;
   }
 
   public function getParameters() {
     return $this->parameters;
   }
 
   public function getParameter($name, $default = null) {
     return idx($this->parameters, $name, $default);
   }
 
   public function setIsBrowse($is_browse) {
     $this->isBrowse = $is_browse;
     return $this;
   }
 
   public function getIsBrowse() {
     return $this->isBrowse;
   }
 
   public function setPhase($phase) {
     $this->phase = $phase;
     return $this;
   }
 
   public function getPhase() {
     return $this->phase;
   }
 
   public function getDatasourceURI() {
     $uri = new PhutilURI('/typeahead/class/'.get_class($this).'/');
-    $uri->setQueryParams($this->parameters);
+    $uri->setQueryParams($this->newURIParameters());
     return (string)$uri;
   }
 
   public function getBrowseURI() {
     if (!$this->isBrowsable()) {
       return null;
     }
 
     $uri = new PhutilURI('/typeahead/browse/'.get_class($this).'/');
-    $uri->setQueryParams($this->parameters);
+    $uri->setQueryParams($this->newURIParameters());
     return (string)$uri;
   }
 
+  private function newURIParameters() {
+    if (!$this->parameters) {
+      return array();
+    }
+
+    $map = array(
+      'parameters' => phutil_json_encode($this->parameters),
+    );
+
+    return $map;
+  }
+
   abstract public function getPlaceholderText();
 
   public function getBrowseTitle() {
     return get_class($this);
   }
 
   abstract public function getDatasourceApplicationClass();
   abstract public function loadResults();
 
   protected function loadResultsForPhase($phase, $limit) {
     // By default, sources just load all of their results in every phase and
     // rely on filtering at a higher level to sequence phases correctly.
     $this->setLimit($limit);
     return $this->loadResults();
   }
 
   protected function didLoadResults(array $results) {
     return $results;
   }
 
   public static function tokenizeString($string) {
     $string = phutil_utf8_strtolower($string);
     $string = trim($string);
     if (!strlen($string)) {
       return array();
     }
 
     // NOTE: Splitting on "(" and ")" is important for milestones.
 
     $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() {
     return self::tokenizeString($this->getRawQuery());
   }
 
   protected function executeQuery(
     PhabricatorCursorPagedPolicyAwareQuery $query) {
 
     return $query
       ->setViewer($this->getViewer())
       ->setOffset($this->getOffset())
       ->setLimit($this->getLimit())
       ->execute();
   }
 
 
   /**
    * Can the user browse through results from this datasource?
    *
    * Browsable datasources allow the user to switch from typeahead mode to
    * a browse mode where they can scroll through all results.
    *
    * By default, datasources are browsable, but some datasources can not
    * generate a meaningful result set or can't filter results on the server.
    *
    * @return bool
    */
   public function isBrowsable() {
     return true;
   }
 
 
   /**
    * Filter a list of results, removing items which don't match the query
    * tokens.
    *
    * This is useful for datasources which return a static list of hard-coded
    * or configured results and can't easily do query filtering in a real
    * query class. Instead, they can just build the entire result set and use
    * this method to filter it.
    *
    * For datasources backed by database objects, this is often much less
    * efficient than filtering at the query level.
    *
    * @param list<PhabricatorTypeaheadResult> List of typeahead results.
    * @return list<PhabricatorTypeaheadResult> Filtered results.
    */
   protected function filterResultsAgainstTokens(array $results) {
     $tokens = $this->getTokens();
     if (!$tokens) {
       return $results;
     }
 
     $map = array();
     foreach ($tokens as $token) {
       $map[$token] = strlen($token);
     }
 
     foreach ($results as $key => $result) {
       $rtokens = self::tokenizeString($result->getName());
 
       // For each token in the query, we need to find a match somewhere
       // in the result name.
       foreach ($map as $token => $length) {
         // Look for a match.
         $match = false;
         foreach ($rtokens as $rtoken) {
           if (!strncmp($rtoken, $token, $length)) {
             // This part of the result name has the query token as a prefix.
             $match = true;
             break;
           }
         }
 
         if (!$match) {
           // We didn't find a match for this query token, so throw the result
           // away. Try with the next result.
           unset($results[$key]);
           break;
         }
       }
     }
 
     return $results;
   }
 
   protected function newFunctionResult() {
     return id(new PhabricatorTypeaheadResult())
       ->setTokenType(PhabricatorTypeaheadTokenView::TYPE_FUNCTION)
       ->setIcon('fa-asterisk')
       ->addAttribute(pht('Function'));
   }
 
   public function newInvalidToken($name) {
     return id(new PhabricatorTypeaheadTokenView())
       ->setValue($name)
       ->setIcon('fa-exclamation-circle')
       ->setTokenType(PhabricatorTypeaheadTokenView::TYPE_INVALID);
   }
 
   public function renderTokens(array $values) {
     $phids = array();
     $setup = array();
     $tokens = array();
 
     foreach ($values as $key => $value) {
       if (!self::isFunctionToken($value)) {
         $phids[$key] = $value;
       } else {
         $function = $this->parseFunction($value);
         if ($function) {
           $setup[$function['name']][$key] = $function;
         } else {
           $name = pht('Invalid Function: %s', $value);
           $tokens[$key] = $this->newInvalidToken($name)
             ->setKey($value);
         }
       }
     }
 
     // Give special non-function tokens which are also not PHIDs (like statuses
     // and priorities) an opportunity to render.
     $type_unknown = PhabricatorPHIDConstants::PHID_TYPE_UNKNOWN;
     $special = array();
     foreach ($values as $key => $value) {
       if (phid_get_type($value) == $type_unknown) {
         $special[$key] = $value;
       }
     }
 
     if ($special) {
       $special_tokens = $this->renderSpecialTokens($special);
       foreach ($special_tokens as $key => $token) {
         $tokens[$key] = $token;
         unset($phids[$key]);
       }
     }
 
     if ($phids) {
       $handles = $this->getViewer()->loadHandles($phids);
       foreach ($phids as $key => $phid) {
         $handle = $handles[$phid];
         $tokens[$key] = PhabricatorTypeaheadTokenView::newFromHandle($handle);
       }
     }
 
     if ($setup) {
       foreach ($setup as $function_name => $argv_list) {
         // Render the function tokens.
         $function_tokens = $this->renderFunctionTokens(
           $function_name,
           ipull($argv_list, 'argv'));
 
         // Rekey the function tokens using the original array keys.
         $function_tokens = array_combine(
           array_keys($argv_list),
           $function_tokens);
 
         // For any functions which were invalid, set their value to the
         // original input value before it was parsed.
         foreach ($function_tokens as $key => $token) {
           $type = $token->getTokenType();
           if ($type == PhabricatorTypeaheadTokenView::TYPE_INVALID) {
             $token->setKey($values[$key]);
           }
         }
 
         $tokens += $function_tokens;
       }
     }
 
     return array_select_keys($tokens, array_keys($values));
   }
 
   protected function renderSpecialTokens(array $values) {
     return array();
   }
 
 /* -(  Token Functions  )---------------------------------------------------- */
 
 
   /**
    * @task functions
    */
   public function getDatasourceFunctions() {
     return array();
   }
 
 
   /**
    * @task functions
    */
   public function getAllDatasourceFunctions() {
     return $this->getDatasourceFunctions();
   }
 
 
   /**
    * @task functions
    */
   protected function canEvaluateFunction($function) {
     return $this->shouldStripFunction($function);
   }
 
 
   /**
    * @task functions
    */
   protected function shouldStripFunction($function) {
     $functions = $this->getDatasourceFunctions();
     return isset($functions[$function]);
   }
 
 
   /**
    * @task functions
    */
   protected function evaluateFunction($function, array $argv_list) {
     throw new PhutilMethodNotImplementedException();
   }
 
 
   /**
    * @task functions
    */
   protected function evaluateValues(array $values) {
     return $values;
   }
 
 
   /**
    * @task functions
    */
   public function evaluateTokens(array $tokens) {
     $results = array();
     $evaluate = array();
     foreach ($tokens as $token) {
       if (!self::isFunctionToken($token)) {
         $results[] = $token;
       } else {
         // Put a placeholder in the result list so that we retain token order
         // when possible. We'll overwrite this below.
         $results[] = null;
         $evaluate[last_key($results)] = $token;
       }
     }
 
     $results = $this->evaluateValues($results);
 
     foreach ($evaluate as $result_key => $function) {
       $function = $this->parseFunction($function);
       if (!$function) {
         throw new PhabricatorTypeaheadInvalidTokenException();
       }
 
       $name = $function['name'];
       $argv = $function['argv'];
 
       $evaluated_tokens = $this->evaluateFunction($name, array($argv));
       if (!$evaluated_tokens) {
         unset($results[$result_key]);
       } else {
         $is_first = true;
         foreach ($evaluated_tokens as $phid) {
           if ($is_first) {
             $results[$result_key] = $phid;
             $is_first = false;
           } else {
             $results[] = $phid;
           }
         }
       }
     }
 
     $results = array_values($results);
     $results = $this->didEvaluateTokens($results);
 
     return $results;
   }
 
 
   /**
    * @task functions
    */
   protected function didEvaluateTokens(array $results) {
     return $results;
   }
 
 
   /**
    * @task functions
    */
   public static function isFunctionToken($token) {
     // We're looking for a "(" so that a string like "members(q" is identified
     // and parsed as a function call. This allows us to start generating
     // results immediately, before the user fully types out "members(quack)".
     return (strpos($token, '(') !== false);
   }
 
 
   /**
    * @task functions
    */
   protected function parseFunction($token, $allow_partial = false) {
     $matches = null;
 
     if ($allow_partial) {
       $ok = preg_match('/^([^(]+)\((.*?)\)?\z/', $token, $matches);
     } else {
       $ok = preg_match('/^([^(]+)\((.*)\)\z/', $token, $matches);
     }
 
     if (!$ok) {
       if (!$allow_partial) {
         throw new PhabricatorTypeaheadInvalidTokenException(
           pht(
             'Unable to parse function and arguments for token "%s".',
             $token));
       }
       return null;
     }
 
     $function = trim($matches[1]);
 
     if (!$this->canEvaluateFunction($function)) {
       if (!$allow_partial) {
         throw new PhabricatorTypeaheadInvalidTokenException(
           pht(
             'This datasource ("%s") can not evaluate the function "%s(...)".',
             get_class($this),
             $function));
       }
 
       return null;
     }
 
     // TODO: There is currently no way to quote characters in arguments, so
     // some characters can't be argument characters. Replace this with a real
     // parser once we get use cases.
 
     $argv = $matches[2];
     $argv = trim($argv);
     if (!strlen($argv)) {
       $argv = array();
     } else {
       $argv = preg_split('/,/', $matches[2]);
       foreach ($argv as $key => $arg) {
         $argv[$key] = trim($arg);
       }
     }
 
     foreach ($argv as $key => $arg) {
       if (self::isFunctionToken($arg)) {
         $subfunction = $this->parseFunction($arg);
 
         $results = $this->evaluateFunction(
           $subfunction['name'],
           array($subfunction['argv']));
 
         $argv[$key] = head($results);
       }
     }
 
     return array(
       'name' => $function,
       'argv' => $argv,
     );
   }
 
 
   /**
    * @task functions
    */
   public function renderFunctionTokens($function, array $argv_list) {
     throw new PhutilMethodNotImplementedException();
   }
 
 
   /**
    * @task functions
    */
   public function setFunctionStack(array $function_stack) {
     $this->functionStack = $function_stack;
     return $this;
   }
 
 
   /**
    * @task functions
    */
   public function getFunctionStack() {
     return $this->functionStack;
   }
 
 
   /**
    * @task functions
    */
   protected function getCurrentFunction() {
     return nonempty(last($this->functionStack), null);
   }
 
   protected function renderTokensFromResults(array $results, array $values) {
     $tokens = array();
     foreach ($values as $key => $value) {
       if (empty($results[$value])) {
         continue;
       }
       $tokens[$key] = PhabricatorTypeaheadTokenView::newFromTypeaheadResult(
         $results[$value]);
     }
 
     return $tokens;
   }
 
   public function getWireTokens(array $values) {
     // TODO: This is a bit hacky for now: we're sort of generating wire
     // results, rendering them, then reverting them back to wire results. This
     // is pretty silly. It would probably be much cleaner to make
     // renderTokens() call this method instead, then render from the result
     // structure.
     $rendered = $this->renderTokens($values);
 
     $tokens = array();
     foreach ($rendered as $key => $render) {
       $tokens[$key] = id(new PhabricatorTypeaheadResult())
         ->setPHID($render->getKey())
         ->setIcon($render->getIcon())
         ->setColor($render->getColor())
         ->setDisplayName($render->getValue())
         ->setTokenType($render->getTokenType());
     }
 
     return mpull($tokens, 'getWireFormat', 'getPHID');
   }
 
 }