Densify by interval always resorts to default value if field is given

[lukasvd]

Describe the bug
QGIS 3.10.1 > Vector geometry > Densify by interval
The tool works properly when a direct value is given. When a field type is given, it always resorts to the default value of 1,0.

How to Reproduce
Open the tool. Select a layer with linestrings which has attributes/fields. Click on the "data defined override" button and select a field. In my case it is a field of type double called "ps_width". When the job has run the log shows that the script tried to use the field ('INTERVAL' : QgsProperty.fromExpression('"ps_width"'). The value of the field is 2,8. The value used for the calculations is still 1,0 (the default)

QGIS and OS versions

[nyalldawson]

Does it work if the field value is "2.8" (using . as decimal separator)

[lukasvd]

Hi Nyall, In the attribute table I can't use a dot for real/double. It changes it back. I did make a string field with value "2.8", that didn't work.

…

On Wed, Dec 18, 2019 at 11:34 PM Nyall Dawson ***@***.***> wrote: Does it work if the field value is "2.8" (using . as decimal separator) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#33470?email_source=notifications&email_token=AAPTKJZBHLYO4CHC5CK3AYDQZKQQ7A5CNFSM4J4SX7H2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEHHXDZY#issuecomment-567243239>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAPTKJ53XBDITLZEEW5VSNDQZKQQ7ANCNFSM4J4SX7HQ> .

[agiudiceandrea]

@nyalldawson @m-kuhn It could be due to

QGIS/src/analysis/processing/qgsalgorithmdensifygeometriesbyinterval.cpp

Lines 94 to 99 in 73f707e

	double interval = mInterval;
	if ( mDynamicInterval )
	interval = mIntervalProperty.valueAsDouble( context.expressionContext(), interval );
	if ( feature.hasGeometry() )
	modifiedFeature.setGeometry( feature.geometry().densifyByDistance( mInterval ) );

where modifiedFeature.setGeometry( feature.geometry().densifyByDistance( mInterval ) ) should be modifiedFeature.setGeometry( feature.geometry().densifyByDistance( interval ) )
It's probably an oversight in 9fec8ed (#8923).

[nyalldawson]

Right - good solving! Can you open a pr?