tree 33667120ee5c5dd5657d718594269c9ca9547df5
parent f9bd630375efb21f00e28f6671cc9ab257b0c85d
author Scott Graham <scottmg@chromium.org> 1605735839 -0800
committer Commit Bot <commit-bot@chromium.org> 1605904693 +0000

Support `format --read-tree=json`

Allows roundtripping to json and back with `gn format --dump-tree=json
a.gn` and then `gn format --read-tree=json a.gn`. The preexisting
.json format is not the most pleasant to work with, but this does at
least allow for programmatic editing of the gn files with knowledge of
structure, going beyond naive string replacement.

For example, a python script to change `deps` inside `source_sets` from
`=` to `+=` to support a BUILDCONFIG.gn change:
https://gist.github.com/sgraham/bd9ffee312f307d5f417019a9c0f0777

The .json format was extended slightly, mostly to include location
information which is necessary to faithfully roundtrip including
whitespace. If the input .gn is formatted by `gn format`, then it can
roundtrip to json without change. This was confirmed by running
--dump-tree=json => --read-tree=json on all .gn and .gni files in both
the Fuchsia and Chromium trees
(https://gist.github.com/sgraham/bc561f19cd354746dd2469103e1f97d4), as
well as by adding a roundtrip step to the formatter tests in-repo.

Change-Id: Ie10bbbcb32b8184400ca9bb1f6ab63e5ca9c89e7
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/10700
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>