When opening this bug, it was assumed that there are no uses of IDBMutableFile/IDBFileHandle, but it turned out that this was only true for the beta channel. We we need to officially deprecate it, check the telemetry and also figure out what to do with existing databases which contain data for it (cf. https://bugzilla.mozilla.org/show_bug.cgi?id=1338603#c3).

Andrew, I tried to do this at some point, but got too tied up in trying to remove as much as I could and hence deep in the weeds of MutableFile/File/Blob stuff. It might be worth someone removing just enough of this to remove DOMRequest, which is the real reason I was poking at it....

Hey Simon, given the apparent need to file bug 1639550 and the extremely low usage numbers for these APIs (2 pings for 24M samples on beta 83), I suggest we go ahead and remove these. For safety we could disable them on Nightly/Beta for one or two cycles first and we should email an intent to unship to dev-platform, but other than that I don't think there's anything needed here. What do you think?

We discussed about this recently. It seems we might want to implement NativeIO (https://github.com/fivedots/nativeio-explainer) which is very similar to our SimpleDB internal API.
NativeIO would be a good replacement for MutableFile/FileHandle (However, we don't have any concrete plans nor a timeline for that yet).
So yes, we can start the process of disabling it.

That looks interesting, though I don't think we necessarily need replacements for features that didn't get adopted and in general we should be removing features that are proprietary to Firefox as they are a maintenance burden for us and a potential web compatibility problem.

https://hg.mozilla.org/mozilla-central/rev/035a9b3d4547

DOMRequest is only used by IDBMutableFile/FileHandle, maybe it should be removed together?

Depends on D159730

Depends on D159731

Depends on D159732

The only use was in IDBDatabase::CreateMutableFile which is removed in part 1.

Depends on D159733

Of course this class should be removed, this is just to make it progressive.

Depends on D159734

Depends on D159856

Depends on D159891

Depends on D160383

Depends on D160384

Landing some initial part of this to prevent bitrotting. Technically it causes intermediate state where IDL interfaces are still exposed while the functions to construct them are removed. But it should be okay as this pref has been disabled for a while and zero people are using it per the telemetry.

https://hg.mozilla.org/mozilla-central/rev/65fd33247185
https://hg.mozilla.org/mozilla-central/rev/07211e8132e4
https://hg.mozilla.org/mozilla-central/rev/6f6882b65188

Backed out for causing build bustages on ActorsParent.cpp.

• Push with failures

• Failure log for Bb builds Also affectes Hazard builds.

• Backout link

[task 2023-02-22T22:55:40.893Z] 22:55:40     INFO -  gmake[4]: Entering directory '/builds/worker/workspace/obj-build/dom/indexedDB'
[task 2023-02-22T22:55:40.893Z] 22:55:40     INFO -  /builds/worker/fetches/sccache/sccache /builds/worker/fetches/gcc/bin/g++ --sysroot /builds/worker/fetches/sysroot-x86_64-linux-gnu -std=gnu++17 -isystem /builds/worker/fetches/sysroot-x86_64-linux-gnu/usr/include/c++/7.5.0 -isystem /builds/worker/fetches/sysroot-x86_64-linux-gnu/usr/include/x86_64-linux-gnu/c++/7.5.0 -isystem /builds/worker/fetches/sysroot-x86_64-linux-gnu/usr/include/x86_64-linux-gnu -isystem /builds/worker/fetches/sysroot-x86_64-linux-gnu/usr/include -o ActorsParent.o -c  -I/builds/worker/workspace/obj-build/dist/stl_wrappers -I/builds/worker/workspace/obj-build/dist/system_wrappers -include /builds/worker/checkouts/gecko/config/gcc_hidden.h -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-strong -DDEBUG=1 -DOS_POSIX=1 -DOS_LINUX=1 -DMOZ_HAS_MOZGLUE -DMOZILLA_INTERNAL_API -DIMPL_LIBXUL -DSTATIC_EXPORTABLE_JS_API -I/builds/worker/checkouts/gecko/dom/indexedDB -I/builds/worker/workspace/obj-build/dom/indexedDB -I/builds/worker/workspace/obj-build/ipc/ipdl/_ipdlheaders -I/builds/worker/checkouts/gecko/ipc/chromium/src -I/builds/worker/checkouts/gecko/dom/base -I/builds/worker/checkouts/gecko/dom/storage -I/builds/worker/checkouts/gecko/ipc/glue -I/builds/worker/checkouts/gecko/third_party/sqlite3/src -I/builds/worker/checkouts/gecko/xpcom/build -I/builds/worker/workspace/obj-build/dist/include -I/builds/worker/workspace/obj-build/dist/include/nspr -I/builds/worker/workspace/obj-build/dist/include/nss -DMOZILLA_CLIENT -include /builds/worker/workspace/obj-build/mozilla-config.h -D_GLIBCXX_USE_CXX11_ABI=0 -fno-sized-deallocation -fno-aligned-new -fno-exceptions -fPIC -fno-rtti -ffunction-sections -fdata-sections -fno-exceptions -fno-math-errno -pthread -pipe -gdwarf-4 -freorder-blocks -Os -fno-omit-frame-pointer -funwind-tables -Werror -Wall -Wempty-body -Wignored-qualifiers -Wpointer-arith -Wsign-compare -Wtype-limits -Wunreachable-code -Wno-invalid-offsetof -Wno-error=deprecated -Wduplicated-cond -Wimplicit-fallthrough -Wlogical-op -Wno-error=maybe-uninitialized -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=free-nonheap-object -Wformat -Wformat-overflow=2 -Wno-psabi -fno-strict-aliasing -ffp-contract=off  -MD -MP -MF .deps/ActorsParent.o.pp   /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp
[task 2023-02-22T22:55:40.894Z] 22:55:40    ERROR -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:9410:6: error: 'void mozilla::dom::indexedDB::{anonymous}::Database::NoteInactiveMutableFile()' defined but not used [-Werror=unused-function]
[task 2023-02-22T22:55:40.895Z] 22:55:40     INFO -   void Database::NoteInactiveMutableFile() {
[task 2023-02-22T22:55:40.895Z] 22:55:40     INFO -        ^~~~~~~~
[task 2023-02-22T22:55:40.895Z] 22:55:40    ERROR -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:9402:6: error: 'void mozilla::dom::indexedDB::{anonymous}::Database::NoteActiveMutableFile()' defined but not used [-Werror=unused-function]
[task 2023-02-22T22:55:40.895Z] 22:55:40     INFO -   void Database::NoteActiveMutableFile() {
[task 2023-02-22T22:55:40.896Z] 22:55:40     INFO -        ^~~~~~~~
[task 2023-02-22T22:55:40.896Z] 22:55:40    ERROR -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:3840:1: error: 'static mozilla::dom::indexedDB::{anonymous}::ObjectStoreAddOrPutRequestOp::StoredFileInfo mozilla::dom::indexedDB::{anonymous}::ObjectStoreAddOrPutRequestOp::StoredFileInfo::CreateForMutableFile(mozilla::SafeRefPtr<mozilla::dom::indexedDB::FileInfo<mozilla::dom::indexedDB::DatabaseFileManager> >)' defined but not used [-Werror=unused-function]
[task 2023-02-22T22:55:40.896Z] 22:55:40     INFO -   ObjectStoreAddOrPutRequestOp::StoredFileInfo::CreateForMutableFile(
[task 2023-02-22T22:55:40.896Z] 22:55:40     INFO -   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
[task 2023-02-22T22:55:40.897Z] 22:55:40     INFO -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp: In member function 'virtual nsresult mozilla::dom::indexedDB::{anonymous}::DatabaseMaintenance::Run()':
[task 2023-02-22T22:55:40.898Z] 22:55:40  WARNING -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:13577:3: warning: 'maintenanceAction' may be used uninitialized in this function [-Wmaybe-uninitialized]
[task 2023-02-22T22:55:40.898Z] 22:55:40     INFO -     switch (maintenanceAction) {
[task 2023-02-22T22:55:40.898Z] 22:55:40     INFO -     ^~~~~~
[task 2023-02-22T22:55:40.899Z] 22:55:40     INFO -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:13570:21: note: 'maintenanceAction' was declared here
[task 2023-02-22T22:55:40.899Z] 22:55:40     INFO -     MaintenanceAction maintenanceAction;
[task 2023-02-22T22:55:40.899Z] 22:55:40     INFO -                       ^~~~~~~~~~~~~~~~~
[task 2023-02-22T22:55:40.903Z] 22:55:40  WARNING -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:13563:18: warning: 'databaseIsOk' may be used uninitialized in this function [-Wmaybe-uninitialized]
[task 2023-02-22T22:55:40.903Z] 22:55:40     INFO -     if (NS_WARN_IF(!databaseIsOk)) {
[task 2023-02-22T22:55:40.903Z] 22:55:40     INFO -                    ^
[task 2023-02-22T22:55:40.904Z] 22:55:40     INFO -  /builds/worker/checkouts/gecko/dom/indexedDB/ActorsParent.cpp:13557:8: note: 'databaseIsOk' was declared here
[task 2023-02-22T22:55:40.904Z] 22:55:40     INFO -     bool databaseIsOk;
[task 2023-02-22T22:55:40.904Z] 22:55:40     INFO -          ^~~~~~~~~~~~
[task 2023-02-22T22:55:40.905Z] 22:55:40     INFO -  cc1plus: all warnings being treated as errors
[task 2023-02-22T22:55:40.906Z] 22:55:40    ERROR -  gmake[4]: *** [/builds/worker/checkouts/gecko/config/rules.mk:669: ActorsParent.o] Error 1
[task 2023-02-22T22:55:40.906Z] 22:55:40     INFO -  gmake[4]: Leaving directory '/builds/worker/workspace/obj-build/dom/indexedDB'

Huh, it seems GCC is better at detecting dead code 🙂

https://hg.mozilla.org/mozilla-central/rev/af5a18ddc6e3
https://hg.mozilla.org/mozilla-central/rev/42a6fb62ca2e
https://hg.mozilla.org/mozilla-central/rev/08540aeb1905
https://hg.mozilla.org/mozilla-central/rev/410e053fee55
https://hg.mozilla.org/mozilla-central/rev/06df2ac13e2a
https://hg.mozilla.org/mozilla-central/rev/1f1abbf1f07d
https://hg.mozilla.org/mozilla-central/rev/ec09f5de38b4

FF112 docs work for this can be tracked in https://github.com/mdn/content/issues/25360 (it is largely complete).