Extracting FBTs

We provide collect-fbts as a utility for collecting strings.

php ./vendor/bin/fbt collect-fbts --path=./path/to/fbt/ --src=./path/to/project/

Options:

name	default	description
--src=[path]	none	The directory where you want to scan usages of fbt in php files.
--path=[path]	none	Cache storage path for source strings
--fbt-common-path=[path]	none	Optional path to the common strings module. This is a map from {[text]: [description]}.

⚠️ Unlike Facebook's version of fbt, we primarily collect <fbt> & translate strings during script execution.

Writing to the standard output

Without --path, the collected strings are written as JSON to the standard output instead of .source_strings.json. The files and directories to scan are given as arguments, and the source code is read from the standard input when no file is given. Progress and errors are written to the standard error output.

php ./vendor/bin/fbt collect-fbts --pretty ./path/to/project/ > source_strings.json
echo '<?php fbt("Hello", "greeting");' | php ./vendor/bin/fbt collect-fbts

name	default	description
--packager=text|phrase|both|none	text	text outputs hashToLeaf, phrase outputs the hash_key and hash_code of the callsite instead, both outputs both, none outputs neither
--hash-module=md5|tiger	md5	Hash module of hashToLeaf
--terse	no	Leave out jsfbt (only hashes, texts and descriptions)
--pretty	no	Pretty print the JSON output
--gen-outer-token-name	no	Add the outer token name of inner strings to the phrases (see the generateOuterTokenName option)
--gen-fbt-nodes	no	Add the fbt element nodes of the callsites to the output (fbtElementNodes)
--options=[a,b]	none	Extra options allowed on fbt callsites (see the extraOptions option)
--fbt-common-path=[path]	none	Optional path to the common strings module

The command exits with code 1 when some callsites couldn't be collected.

Upon successful execution, the output of the /your/path/to/fbt/.source_strings.json will be in the following format (the same as the output of collectFbt of Facebook's fbt):

{
  "phrases": [
    {
      "hashToLeaf": {
        "<hash>": {"text": "<text>", "desc": "<description>"},
        ...
      },
      "filepath": "<path of the file>",
      "line_beg": <line>,
      "line_end": <line>,
      "author": "<author>",
      "project": "<project>",
      "jsfbt": {
        "t": <leaf> | <table of leaves>,
        "m": <metadata>
      }
    }
  ],
  "childParentMappings": {
    "<childIdx>": <parentIdx>
  }
}

A leaf is an object of the form {"desc": "...", "text": "...", "tokenAliases": {...}}, and a table is a (nested) object whose keys are string variations (e.g. *, _1 for plurals, enum keys, genders, …) and whose values are leaves or tables:

{
  "t": {
    "*": {"desc": "plural example", "text": "{number} photos"},
    "_1": {"desc": "plural example", "text": "1 photo"}
  },
  "m": [{"token": "number", "type": 2, "singular": true}]
}

Inner strings of HTML elements nested in an fbt (e.g. <a>Learn more</a>) are collected as separate phrases, and childParentMappings links them to their enclosing phrase. The enclosing phrase refers to them with a token like {=Learn more}, and tokenAliases maps these tokens to their runtime aliases (e.g. {"=Learn more": "=m3"}).

phrases here represents all the source information we need to process and produce an fbt::_(...) callsite's final payload. When combined with corresponding translations to each hashToLeaf entry we can produce the translated payloads fbt::_() expects.

When it comes to moving from source text to translations, what is most pertinent is the hashToLeaf payload containing all relevant texts and descriptions with their identifying hash. You can choose md5 or tiger hash module. It defaults to md5 (encoded in base64 by default, see the md5_digest option).

A note on hashes

In the FBT framework, there are 2 main places we uses hashes for identification: text and fbt callsite. The hashToLeaf mapping above represents the hash of the text and its description. This is used when building the translated payloads.

The hash of the callsite (defaulting to jenkins hash) is used to look up the payload in FbtTranslations. This is basically the hash of the object you see in jsfbt.t.

See Translating FBTs for getting your translations in the right format.