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PhutilSymbolLoader.php
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Tue, May 7, 21:34

PhutilSymbolLoader.php
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<?php
/**
* Query and load Phutil classes, interfaces and functions.
*
* `PhutilSymbolLoader` is a query object which selects symbols which satisfy
* certain criteria, and optionally loads them. For instance, to load all
* classes in a library:
*
* ```lang=php
* $symbols = id(new PhutilSymbolLoader())
* ->setType('class')
* ->setLibrary('example')
* ->selectAndLoadSymbols();
* ```
*
* When you execute the loading query, it returns a dictionary of matching
* symbols:
*
* ```lang=php
* array(
* 'class$Example' => array(
* 'type' => 'class',
* 'name' => 'Example',
* 'library' => 'libexample',
* 'where' => 'examples/example.php',
* ),
* // ... more ...
* );
* ```
*
* The **library** and **where** keys show where the symbol is defined. The
* **type** and **name** keys identify the symbol itself.
*
* NOTE: This class must not use libphutil functions, including @{function:id}
* and @{function:idx}.
*
* @task config Configuring the Query
* @task load Loading Symbols
* @task internal Internals
*/
final class PhutilSymbolLoader {
private $type;
private $library;
private $base;
private $name;
private $concrete;
private $pathPrefix;
private $suppressLoad;
/**
* Select the type of symbol to load, either `class`, `function` or
* `interface`.
*
* @param string Type of symbol to load.
* @return this
*
* @task config
*/
public function setType($type) {
$this->type = $type;
return $this;
}
/**
* Restrict the symbol query to a specific library; only symbols from this
* library will be loaded.
*
* @param string Library name.
* @return this
*
* @task config
*/
public function setLibrary($library) {
// Validate the library name; this throws if the library in not loaded.
$bootloader = PhutilBootloader::getInstance();
$bootloader->getLibraryRoot($library);
$this->library = $library;
return $this;
}
/**
* Restrict the symbol query to a specific path prefix; only symbols defined
* in files below that path will be selected.
*
* @param string Path relative to library root, like "apps/cheese/".
* @return this
*
* @task config
*/
public function setPathPrefix($path) {
$this->pathPrefix = str_replace(DIRECTORY_SEPARATOR, '/', $path);
return $this;
}
/**
* Restrict the symbol query to a single symbol name, e.g. a specific class
* or function name.
*
* @param string Symbol name.
* @return this
*
* @task config
*/
public function setName($name) {
$this->name = $name;
return $this;
}
/**
* Restrict the symbol query to only descendants of some class. This will
* strictly select descendants, the base class will not be selected. This
* implies loading only classes.
*
* @param string Base class name.
* @return this
*
* @task config
*/
public function setAncestorClass($base) {
$this->base = $base;
return $this;
}
/**
* Restrict the symbol query to only concrete symbols; this will filter out
* abstract classes.
*
* NOTE: This currently causes class symbols to load, even if you run
* @{method:selectSymbolsWithoutLoading}.
*
* @param bool True if the query should load only concrete symbols.
* @return this
*
* @task config
*/
public function setConcreteOnly($concrete) {
$this->concrete = $concrete;
return $this;
}
/* -( Load )--------------------------------------------------------------- */
/**
* Execute the query and select matching symbols, then load them so they can
* be used.
*
* @return dict A dictionary of matching symbols. See top-level class
* documentation for details. These symbols will be loaded
* and available.
*
* @task load
*/
public function selectAndLoadSymbols() {
$map = array();
$bootloader = PhutilBootloader::getInstance();
if ($this->library) {
$libraries = array($this->library);
} else {
$libraries = $bootloader->getAllLibraries();
}
if ($this->type) {
$types = array($this->type);
} else {
$types = array(
'class',
'function',
);
}
$names = null;
if ($this->base) {
$names = $this->selectDescendantsOf(
$bootloader->getClassTree(),
$this->base);
}
$symbols = array();
foreach ($libraries as $library) {
$map = $bootloader->getLibraryMap($library);
foreach ($types as $type) {
if ($type == 'interface') {
$lookup_map = $map['class'];
} else {
$lookup_map = $map[$type];
}
// As an optimization, we filter the list of candidate symbols in
// several passes, applying a name-based filter first if possible since
// it is highly selective and guaranteed to match at most one symbol.
// This is the common case and we land here through `__autoload()` so
// it's worthwhile to micro-optimize a bit because this code path is
// very hot and we save 5-10ms per page for a very moderate increase in
// complexity.
if ($this->name) {
// If we have a name filter, just pick the matching name out if it
// exists.
if (isset($lookup_map[$this->name])) {
$filtered_map = array(
$this->name => $lookup_map[$this->name],
);
} else {
$filtered_map = array();
}
} else if ($names !== null) {
$filtered_map = array();
foreach ($names as $name => $ignored) {
if (isset($lookup_map[$name])) {
$filtered_map[$name] = $lookup_map[$name];
}
}
} else {
// Otherwise, start with everything.
$filtered_map = $lookup_map;
}
if ($this->pathPrefix) {
$len = strlen($this->pathPrefix);
foreach ($filtered_map as $name => $where) {
if (strncmp($where, $this->pathPrefix, $len) !== 0) {
unset($filtered_map[$name]);
}
}
}
foreach ($filtered_map as $name => $where) {
$symbols[$type.'$'.$name] = array(
'type' => $type,
'name' => $name,
'library' => $library,
'where' => $where,
);
}
}
}
if (!$this->suppressLoad) {
$caught = null;
foreach ($symbols as $symbol) {
try {
$this->loadSymbol($symbol);
} catch (Exception $ex) {
$caught = $ex;
}
}
if ($caught) {
// NOTE: We try to load everything even if we fail to load something,
// primarily to make it possible to remove functions from a libphutil
// library without breaking library startup.
throw $caught;
}
}
if ($this->concrete) {
// Remove 'abstract' classes.
foreach ($symbols as $key => $symbol) {
if ($symbol['type'] == 'class') {
$reflection = new ReflectionClass($symbol['name']);
if ($reflection->isAbstract()) {
unset($symbols[$key]);
}
}
}
}
return $symbols;
}
/**
* Execute the query and select matching symbols, but do not load them. This
* will perform slightly better if you are only interested in the existence
* of the symbols and don't plan to use them; otherwise, use
* @{method:selectAndLoadSymbols}.
*
* @return dict A dictionary of matching symbols. See top-level class
* documentation for details.
*
* @task load
*/
public function selectSymbolsWithoutLoading() {
$this->suppressLoad = true;
$result = $this->selectAndLoadSymbols();
$this->suppressLoad = false;
return $result;
}
/**
* Select symbols matching the query and then instantiate them, returning
* concrete objects. This is a convenience method which simplifies symbol
* handling if you are only interested in building objects.
*
* If you want to do more than build objects, or want to build objects with
* varying constructor arguments, use @{method:selectAndLoadSymbols} for
* fine-grained control over results.
*
* This method implicitly restricts the query to match only concrete
* classes.
*
* @param list<wild> List of constructor arguments.
* @return map<string, object> Map of class names to constructed objects.
*/
public function loadObjects(array $argv = array()) {
$symbols = $this
->setConcreteOnly(true)
->setType('class')
->selectAndLoadSymbols();
$objects = array();
foreach ($symbols as $symbol) {
$objects[$symbol['name']] = newv($symbol['name'], $argv);
}
return $objects;
}
/* -( Internals )---------------------------------------------------------- */
/**
* @task internal
*/
private function selectDescendantsOf(array $tree, $root) {
$result = array();
if (empty($tree[$root])) {
// No known descendants.
return array();
}
foreach ($tree[$root] as $child) {
$result[$child] = true;
if (!empty($tree[$child])) {
$result += $this->selectDescendantsOf($tree, $child);
}
}
return $result;
}
/**
* @task internal
*/
private function loadSymbol(array $symbol_spec) {
// Check if we've already loaded the symbol; bail if we have.
$name = $symbol_spec['name'];
$is_function = ($symbol_spec['type'] == 'function');
if ($is_function) {
if (function_exists($name)) {
return;
}
} else {
if (class_exists($name, false) || interface_exists($name, false)) {
return;
}
}
$lib_name = $symbol_spec['library'];
$where = $symbol_spec['where'];
$bootloader = PhutilBootloader::getInstance();
$bootloader->loadLibrarySource($lib_name, $where);
// Check that we successfully loaded the symbol from wherever it was
// supposed to be defined.
$load_failed = null;
if ($is_function) {
if (!function_exists($name)) {
$load_failed = 'function';
}
} else {
if (!class_exists($name, false) && !interface_exists($name, false)) {
$load_failed = 'class/interface';
}
}
if ($load_failed !== null) {
$lib_path = phutil_get_library_root($lib_name);
throw new PhutilMissingSymbolException(
$name,
$load_failed,
pht(
'The symbol map for library "%s" (at "%s") claims this symbol '.
'(of type "%s") is defined in "%s", but loading that source file '.
'did not cause the symbol to become defined.',
$lib_name,
$lib_path,
$load_failed,
$where));
}
}
}

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