The generate-symbols.js task runs JSDoc on source files. Because this takes a long time (13s) to run on the whole library, the resulting symbols file includes additional metadata to make it possible to do incremental symbol generation on subsequent runs. The 'path' and 'extends' metadata for a symbol are used to determine what needs to be regenerated.
This runs JSDoc with the "symbols" config, providing a list of source files that have been changed since the previous run. The output is used to generate a symbols.json metadata file containing all exportable symbols info. A separate task will be run to generate the exports.js file. These same metadata files will be used by a build tool.
