QGIS » QGIS Application

See this thread:
https://lists.osgeo.org/pipermail/qgis-developer/2017-July/049234.html

In short:

Even when selecting 'Check extension' in "Settings/Options/Data Sources/Data source handling/Scan for valid
items in the browser dock" GDAL is used to test if QGIS is able to open certain files in the directories seen in the Browser(widget).

Even though GDAL reports that the file is not openable, the files are still visible in the browser.

From that thread:

Ah indeed you're right, even if we only check by extension, then we end up still opening the file with GDALOpen :-)

"
So we should have either :
- do only extension checking and defer the call to
https://github.com/qgis/QGIS/blob/master/src/providers/gdal/qgsgdaldataitems.cpp#L43 as late as possible. But I'm not sure if that's doable. I am merely discovering this piece of code
- or do extension checking as a pre-filter, but try GDALOpen() to ensure then that the file is a valid candidate. Would seem a more reasonable approach.
"

Another option would be to introduce an icon for each layer type (raster, vector etc) which is 'grayed out' like 'not enabled' to show that: "It is possible that we can open it, but there is also a chance that we fail". For all those cases where the Identify() is not conclusive, OR where the actual opening of the file/connection is just too expensive/complex.