hhvm/hhvm-autoload

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Language:Hack

Type:composer-plugin

v3.3.0 2021-07-13 16:10 UTC

README

The autoloader for autoloading classes, enums, functions, typedefs, and constants on HHVM.

Usage

  1. Add an hh_autoload.json file (see section below)
  2. composer require hhvm/hhvm-autoload
  3. Require the autoload file from your entrypoint functions using require_once (__DIR__ . '(/..)(repeat as needed)/vendor/autoload.hack');
  4. Call Facebook\AutolaodMap\initialize() to register the autoloader with hhvm.
  5. To re-generate the map, run vendor/bin/hh-autoload, composer dump-autoload, or any other command that generates the map

Configuration (hh_autoload.json)

A minimal configuration file is:

{
  "roots": [ "src/" ]
}

This will look for autoloadable definitions in src/, and also look in vendor/. Projects in vendor/ are only processed if they also contain a hh_autoload.json file.

Previously we also supported projects without hh_autoload.json by simulating Composer's autoload behavior, but we no longer do because that mostly applied to PHP files which HHVM can no longer parse.

The following settings are optional:

  • "extraFiles": ["file1.hack"] - files that should not be autoloaded, but should be require()ed by vendor/autoload.hack. This should be needed much less frequently than under Composer
  • "includeVendor": false - do not include vendor/ definitions in vendor/autoload.hack
  • "devRoots": [ "path/", ...] - additional roots to only include in dev mode, not when installed as a dependency.
  • "relativeAutoloadRoot": false - do not use a path relative to __DIR__ for autoloading. Instead, use the path to the folder containing hh_autoload.json when building the autoload map.
  • "failureHandler:" classname<Facebook\AutoloadMap\FailureHandler> - use the specified class to handle definitions that aren't the Map. Defaults to none.
  • "devFailureHandler": classname<Facebook\AutoloadMap\FailureHandler> - use a different handler for development environments. Defaults to the same value as failureHandler.
  • "parser:" any of [ext-factparse]" - select a parser to use, but there is only one valid option. Defaults to a sensible parser.
  • "useFactsIfAvailable": false - use ext-facts (HH\Facts...) to back Facebook\AutoloadMap\Generated\map() instead of a codegenned dict. See Use with HH\Facts for more information about this mode.

Use In Development (Failure Handlers)

When you add, remove, or move definitions, there are several options available:

  • run composer dump-autoload to regenerate the map
  • run vendor/bin/hh-autoload to regenerate the map faster
  • specify devFailureHandler as Facebook\AutoloadMap\HHClientFallbackHandler
  • specify a custom subclass of Facebook\AutoloadMap\FailureHandler
  • use a filesystem monitor such as watchman to invoke one of the above commands when necessary

Facebook\AutoloadMap\HHClientFallbackHandler is probably the most convenient for Hack development.

For performance reasons, failure handler methods will not be invoked for namespaced functions or constants that have the same name as one in the global namespace. You will need to re-generate the map if you make changes to functions or constants that are affected by this restriction.

HHClientFallbackHandler

If you are working in Hack, this handler will remove the need to manually rebuild the map in almost all circumstances.

It asks hh_client for definitions that aren't in the map, and has the following additional behaviors:

  • it is disabled if the CI, CONTINUOUS_INTEGRATION, or TRAVIS environment variables are set to a Truthy value; this is because it is not a recommended approach for production environments, and you probably want your automated testing environment to reflect production
  • results are cached in both APC and a file in vendor/, if vendor/ is writable

You can override these behaviors in a subclass.

Custom Handlers

Information you may need is available from:

  • Facebook\AutoloadMap\Generated\build_id(): this is unique ID regenerated every time the map is rebuilt; it includes the date, time, and a long random hex string. If your failure handler has a cache, it most likely should be invalidated when this changes, for example, by including it in the cache key.
  • Facebook\AutoloadMap\Generated\map(): the autoload map
  • Facebook\AutoloadMap\Generated\root(): the directory containing the project root, i.e. the parent directory of vendor/

Use with HH\Facts

HHVM 4.109 introduced ext-facts and ext-watchman. Unlike the static pre-built autoloader which is built into a repo authoratative build, this native autoloader works incrementally and is suitable for autoloading in your development environment. For more information about setting up this autoloader, see the blog post for hhvm 4.109.

When using a native autoloader (either the repo auth or ext-facts autoloader), you do not need hhvm-autoload to require classes/functions/types/constants at runtime. If you (and your vendor dependencies) do not call any functions in the Facebook\AutoloadMap namespace, other than Facebook\AutoloadMap\initialize(), you don't need hhvm-autoload anymore. In that case, you could drop this dependency and remove the calls to initialize(). If you are using other functions, like Facebook\AutoloadMap\Generated\map(), you'd still need the vendor/autoload.hack file that hhvm-autoload generates.

Hhvm-autoload supports outputting a vendor/autoload.hack file which forwards all queries to ext-facts. Facebook\AutoloadMap\Generated\map_uncached() will always be up to date in this mode, since HH\Facts is always up to date. Facebook\AutoloadMap\Generated\map() is memoized (within a request), since some code may rely on getting the same result from multiple calls. You can enable this mode by adding "useFactsIfAvailable": true to the hh_autoload.json config file. Hhvm-autoload will emit a shim file instead of a full map. This option is ignored if HH\Facts\enabled() returns false, or when --no-facts is passed to vendor/bin/hh-autoload. We recommend passing --no-facts when building for production (specifically repo auth mode). Returning a hardcoded dict is faster than asking HH\Facts.

Important to note. Autoloading with a native autoloader does not respect hh_autoload.json. The repo auth autoloader allows any code to use any symbol. The facts autoloader honors the configuration in .hhvmconfig.hdf instead. Make sure that the configuration in hh_autoload.json and .hhvmconfig.hdf match.

How It Works

  • A parser (FactParse) provides a list of all Hack definitions in the specified locations
  • This is used to generate something similar to a classmap, except including other kinds of definitions
  • The map is provided to HHVM with HH\autoload_set_paths()
  • If a native autoloader is registered, this autoloader will intentionally not register itself. So calling Facebook\AutoloadMap\initialize() in repo auth mode or when the facts based autoloader is registered is a noop.

Contributing

We welcome GitHub issues and pull requests - please see CONTRIBUTING.md for details.

License

hhvm-autoload is MIT-licensed.