options should be available for certain model outputs and script
algorithm outputs
We do this by swapping the test for non-file based output support
from checking only the algorithm's provider to instead checking
on a parameter-by-parameter basis.
This is done in order to support models. For models, depending
on what child algorithm a model output is based off, an individual
model may or may not have support for non-file based outputs. E.g
a model may generate outputs from a native qgis alg (supporting
these outputs) AND an output from a GDAL alg (with no support
for these outputs). In this case we need to enable or disable
the ui controls for non-file based outputs on an individual
output basis.
For scripts (for now) we blindly just say all outputs support
non-file based formats. This is going to be the case most of
the time, since scripts will usually be written using PyQGIS
API. For the exceptions (e.g. scripts which call other algs
like GDAL algs) we probably should add some way for the script
to indicate whether an individual output supports this, but
for now we just say they all do.
Fixes#17949
Since it's much more useful. Also add a prompt for layer name, so that
you can save the results of an algorithm into an existing geopackage
without wiping existing layers.
...instead of embedding in output destination file selector. Otherwise
Qt downgrades the file picker to the Qt basic file picker, instead of
the native OS file picker. Which is a huge downgrade and barely
functional for users.
Also remember last selected file format
Since these expressions were only evaluated immediately, it led to
confusing behavior for users who were expecting that the expression
would be applied per-feature.
Given that expressions can be directly entered into spin boxes, we already
have a way of users evaluating simple calculations for numeric
parameters at least.
I don't think there's a strong enough use case for needing to
calculate string results to leave the confusing expression builder
option in place.
This should be re-evaluated when we add UI support for dynamic
parameters (which are already supported in the backend), where
expressions are evaluated per-feature.
Fixes#17267
This allows optional outputs (such as null geometry features detected
by the Remove Null Geometries algorithm) to be skipped by default
when desirable.
The previous naming was too easily confused with processing outputs.
Rename them to QgsProcessingParameterFileDestination, etc... to
make it clearer what they are used for.
Also fix some UX issues with the panel in folder, such as
correctly remembering/restoring last used folders, defaulting
to home dir, don't clear value when canceling while browsing
This adds a lot of flexibility to algorithms, as it makes output
sinks truely optional. For instance, the various "Extract by..."
algorithms could add a new optional sink for features which
'fail' the extraction criteria. This effectively allows these
algorithms to become feature 'routers', directing features onto
other parts of a model depending on whether they pass or fail
the test.
But in this situation we don't always care about these failing
features, and we don't want to force them to always be fetched
from the provider. By making the outputs truely optional,
the algorithm can tweak its logic to either fetch all features
and send them to the correct output, or only fetch
matching features from the provider in the first place (a big
speed boost).
