Before this change, if a user toggled a FEATURE_foo variable, we only
recomputed the value for dependent features who's CONDITION would break
with the new value. If the CONDITION was not broken, the dependent
feature value would remain unchanged.
For example if FEATURE_developer_build was OFF, and the user
toggled it to ON, the FEATURE_private_tests value would remain OFF,
because OFF is a valid value for private_tests' CONDITION.
But we would like FEATURE_private_tests to become ON if we toggled
FEATURE_developer_build to ON.
To address this case, we need to recompute features who's dependent
feature values have changed.
The algorithm introduced by this change is:
- keep track of initial dirty features, aka track when FEATURE_foo is
different from QT_FEATURE_foo. We expect FEATURE_foo to be the
variable that a user toggles in the cache file or an IDE.
- when evaluating feature values, collect feature dependencies from
the various expressions given to options like CONDITION, AUTODETECT
- if any feature dependency is marked dirty, reset the feature value
to its auto-computed value and mark the reset feature as dirty
- repeat for all feature evaluations
Because feature evaluation is eagerly recursive, we will successfully
reset all features that need resetting.
To ensure against unforeseen breakages, allow disabling this behavior
by configuring with -DQT_NO_FEATURE_AUTO_RESET=ON
Adjust some of the messages to contain more details.
Note that the pre-existing behavior of resetting feature values when
the condition can't be satisfied, stays. For example if
FEATURE_developer_build is OFF and FEATURE_private_tests is manually
toggled to ON, it will reset to OFF
because its condition can't be satisfied (developer_build is still
OFF).
Amends 61943aefd6
[ChangeLog][Build System] The build system will now try to recompute
configure features when dependent feature values are toggled by the
user.
Pick-to: 6.6
Fixes: QTBUG-96936
Task-number: QTBUG-85962
Task-number: QTBUG-112957
Task-number: QTBUG-116209
Change-Id: Ib627f3675df8a3b08f4936cdc9c51f2d6e15f58c
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
65e04162d1