[lazerg]

Summary:

When a Props constructor reads a key that isn't the next one in the prepared order, RawPropsParser::at walked the cursor round keys_ one key at a time until it hit it. That happens on every parse for props that extend ViewProps and read one of View's keys again (width, backgroundColor, ...), costing up to one comparison per registered key. The parser already keeps nameToIndex_ for preparse, so now a miss on the next key looks the key up there and moves the cursor to its index. In-order reads are unchanged.

A key that was never seen while preparing now returns nullptr in release builds too, instead of looping forever.

Fixes #59759

Changelog:

[GENERAL] [CHANGED] - Props parsing looks up props read out of order by name instead of scanning every key

Test Plan:

Built RawPropsTest.cpp (minus the Hermes test) against this change with Homebrew folly/gtest on macOS: all tests pass in debug. In a release build, reading an unknown key returns nullptr with this change and hangs on main.

A small benchmark with a 100-key Props struct that re-reads two keys after the in-order pass, 200k parses in release: 222 ms on main, 191 ms with this change.

scripts/clang-format is clean. Not run on a device.

[meta-codesync]

@javache has imported this pull request. If you are a Meta employee, you can view this in D129355825.