9296136fa6
To achieve this, while preserving flags-team approvals for never-expiring flags, this change: 1) Adds //chrome/browser/flag-never-expire-list.json, which contains a JSON list of names of flags that are permitted to never expire; 2) Adds AboutFlagsTest.OnlyPermittedFlagsNeverExpire, which asserts that the flags listed in flag-metadata.json with expiry_milestone -1 are a subset of the flags named in flag-never-expire-list.json; 3) Updates the //chrome/browser OWNERS file to make * the owner of flag-metadata.json and to make flags-team the owners of flag-never-expire-list.json. 4) Updates the flag ownership documentation to mention flag-never-expire-list.json. Bug: 897809 Change-Id: I691b85d73274b6798924b2069ef9e77e29b4a991 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1512613 Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org> Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org> Reviewed-by: Avi Drissman <avi@chromium.org> Cr-Commit-Position: refs/heads/master@{#639504}
86 lines
4.1 KiB
Markdown
86 lines
4.1 KiB
Markdown
# Chrome Flag Ownership
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ellyjones@ / avi@
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[TOC]
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## TL;DR / What Do I Need To Do?
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Look through
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[`chrome/browser/flag-metadata.json`](https://cs.chromium.org/chromium/src/chrome/browser/flag-metadata.json?sq=package:chromium&q=flag-metadata.json&g=0&l=1)
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for flags that your team added, maintains, or cares about. For each such flag
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you find, either:
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- **If it is still in use:** add entries to the owners list (see the comment at
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the top of the file) and set an appropriate expiration milestone;
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- **If it is not in use:** delete it from `kFeatureEntries` in
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[`chrome/browser/about_flags.cc`](https://cs.chromium.org/chromium/src/chrome/browser/about_flags.cc?sq=package:chromium&g=0&l=1319).
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Remember to file a cleanup bug to remove code paths that become dead. It is
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not necessary to delete the corresponding entry in `flag-metadata.json` as it
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will be cleaned up for you in the future.
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All existing flags have been set to expire in M76 (~6 months from now). At that
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time, every flag with no owners will be hardcoded to behave as though it was
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always its default value and will be removed from the `chrome://flags` UI.
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## Wait, What Are You Doing?
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Presently, Chrome has approximately 600 entries in `chrome://flags`, many of
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which are obsolete and unused, but each of which represents configuration
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surface that is exposed to users and to QA. Worse, obsolete flags often prevent
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removal of legacy code paths that are not used in the field but are still
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reachable via a flag setting.
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To deal with that, we are moving Chrome towards a model where `chrome://flags`
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entries are what they were originally intended to be: temporary, experimental
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options. Each flag must have a set owner who can keep track of whether or when
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that flag should expire and an express time by which it will expire, either
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because the feature it controls will have become default-enabled or because the
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feature it controls will have been cancelled.
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Note that this change only affects `chrome://flags` entries, not features
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controlled via
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[`FeatureList`](https://cs.chromium.org/chromium/src/base/feature_list.h?q=FeatureList&sq=package:chromium&g=0&l=92)
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(commonly used to run Finch trials) or command-line switches.
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## I Don't Want My Flag To Expire!
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Some flags do not control UI features, but rather are commonly-used debugging
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controls, such as `ignore-gpu-blacklist`. For these flags, see the instructions
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at the head of `flag-metadata.json`. Please be very judicious about
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never-expiring flags, since they represent ongoing engineering, test and support
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burden. The flags team will probably only approve your non-expiring flag if:
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- You regularly ask users or developers to change its value for
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debugging/support purposes
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- You have been doing so for at least six months
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- You don't plan to stop doing so any time soon
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If you have a non-expiring flag, the flags team requires a comment in the json
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file as to the rationale that it be non-expiring. A quick sentence or two will
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be fine. Yes, we are aware that, technically, JSON files can't have comments.
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Don't worry about it. You'll also need to add your flag to the permitted list in
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[`chrome/browser/flag-never-expire-list.json`](https://cs.chromium.org/chromium/src/chrome/browser/flag-never-expire-list.json?sq=package:chromium&q=flag-never-expire-list.json&g=0&l=1)
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which will require approval from the flags team.
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## What Should My Expiry Be?
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A good rule of thumb is that your flag should expire one milestone after you
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expect your feature to have launched to stable. In other words, if your feature
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will be 100% enabled on Stable in M74, your flag should be marked as expiring in
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M75.
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Please do not stress about the expiration date. The purpose of the expiration
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milestone is to let us remove *abandoned* flags. Pick a reasonable milestone by
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which you'll be done with the flag; you can always adjust it later if your
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schedule changes.
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## I Have Other Questions
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Please get in touch with
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[`flags-dev@chromium.org`](https://groups.google.com/a/chromium.org/forum/#!forum/flags-dev).
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If you feel like you need to have a Google-internal discussion for some reason,
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there's also
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[`chrome-flags@`](https://groups.google.com/a/google.com/forum/#!forum/chrome-flags).
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