Document the new workflow for Dart code obfuscation on Flutter #3827
Description
( See also #1567 )
As of Flutter v1.15.18 the information in https://github.com/flutter/flutter/wiki/Obfuscating-Dart-Code is out of date. We've stabilized the feature and made source code obfuscation stable, and it is supported by iOS and Android builds with the --obfuscate and --split-debug-info options.
The existing documentation for these features:
--split-debug-info=</project-name/v1.2.3/> In a release build, this flag reduces application size by storing Dart program
symbols in a separate file on the host rather than in the application. The value
of the flag should be a directory where program symbol files can be stored for
later use. These symbol files contain the information needed to symbolize Dart
stack traces. For an app built with this flag, the 'flutter symbolize' command
with the right program symbol file is required to obtain a human readable stack
trace.
--[no-]obfuscate In a release build, this flag removes identifiers and replaces them with
randomized values for the purposes of source code obfuscation. This flag must
always be combined with "--split-debug-info" option, the mapping between the
values and the original identifiers is stored in the symbol map created in the
specified directory. For an app built with this flag, the 'flutter symbolize'
command with the right program symbol file is required to obtain a human readable
stack trace.
Because all identifiers are renamed, methods like Object.runtimeType,
Type.toString, Enum.toString, Stacktrace.toString, Symbol.toString (for constant
symbols or those generated by runtime system) will return obfuscated results. Any
code or tests that rely on exact names will break.
These two flags must be combined in order to use obfuscation. split-debug-info should be a directory where flutter can output debug files.
We also need to document the functionality of --split-debug-info separately, since this can also reduce code size fairly dramatically.