fix pasting features into vector layer from clipboard (fix #21154)

[alexbruy]

Description

There are two layers (in my tests this is 1 shapefile and 1 geopackage). They have different tables, but the shapefile table is just a subset of the GPKG one meaning that the shape has columns with the same name and type of the GPKG. Copy/pasting from the SHP to GPKG results in only a few attributes to be copied.

Looks like this happens because QgsVectorLayerUtils::matchAttributesToFields() updates feature attributes while fields stay untouched. Later untouched fields are used to create attribute map for pasted feature leading to the data loss.

Not sure that this is proper fix.

Checklist

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[gioman]

@alexbruy this is possibly an unreported issue (possibly even a regression), anyway I confirm the bug and will test the patch asap.

[gioman]

This will fix the now reported issue https://issues.qgis.org/issues/21154

[m-kuhn]

@alexbruy thanks for tackling this, I think I've run into this too in the past.
Sidenote: the fix #xyz comment will need to go to a commit message (git commit --am && git push -f)

[gioman]

@alexbruy thanks for tackling this, I think I've run into this too in the past.

Hi all, can anyone review this? To me seems to work ok.

[m-kuhn]

Looking at this now...

[gioman]

Looking at this now...

@m-kuhn thanks!

[gioman]

Is there any problem holding this from merging?

[luipir]

Is there any problem holding this from merging?

IMHO it's up to @alexbruy to merge. review has been already done

[m-kuhn]

As said, I'll have a look at it soon, I'm working on this area currently. I'd be happy if you could hold back till the end of the week.

[gioman]

ah ok, sorry, I just wanted to have this merged sooner than later to allow a wider testing on master (I know several users affected by this bug).

[m-kuhn]

ok, let's merge it for testing, I can also proceed with the updated codebase ;)

[gioman]

Hi there,
I just noticed this https://issues.qgis.org/issues/21304 and as it affects only master I was guessing if this could possibly be related. I guess I can compile 3.4 with this patch and check... I'll let you know.

[m-kuhn]

That's the issue which I was investigating and already existed in master before this patch. Are you sure this works in 3.4?

[gioman]

That's the issue which I was investigating and already existed in master before this patch

ok, so is unrelated

Are you sure this works in 3.4?

yes, just tested (3.4.4 from osgeo4w) and linux.

[luipir]

Hi there,
I just noticed this https://issues.qgis.org/issues/21304 and as it affects only master I was guessing if this could possibly be related. I guess I can compile 3.4 with this patch and check... I'll let you know.

I do not think is related... the differente between feature.fields() and feature.attributes() is that the first is static the second not, but has been already parsed from clipboard