fromWKT should fail if neither EMPTY or coordinates are supplied

[qgib]

Author Name: Johannes Kroeger (Johannes Kroeger)
Original Redmine Issue: 20754
Affected QGIS version: 3.5(master)
Redmine category:geometry

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QGIS allows geometries to be created using a string like "GeometryType" without either specifying the coordinates or EMPTY.

http://www.opengeospatial.org/standards/sfa defines for example for a POINT:

<empty set> ::= EMPTY

<point text> ::= <empty set> | <left paren> <point> <right
paren>

So "Point" would not be ok. QGIS however, does allow and produce weird stuff...

>>> for type in "POINT", "LINESTRING", "POLYGON", "GEOMETRYCOLLECTION", "MULTIPOINT":
>>>   g = QgsGeometry.fromWkt(type)
>>>   print(type)
>>>   print(g)
>>>   print(g.asWkt())
POINT
<QgsGeometry: >

LINESTRING
<QgsGeometry: LineString ()>
LineString ()
POLYGON
<QgsGeometry: >

GEOMETRYCOLLECTION
<QgsGeometry: GeometryCollection ()>
GeometryCollection ()
MULTIPOINT
<QgsGeometry: MultiPoint ()>
MultiPoint ()

Related #22604

[qgib]

Author Name: Jürgen Fischer (@jef-n)

---

• description was changed from QGIS allows geometries to be created using a string like "GeometryType" without either specifying the coordinates or EMPTY.

http://www.opengeospatial.org/standards/sfa defines for example for a POINT:

 ::= EMPTY

 ::=  |   

So "Point" would not be ok. QGIS however, does allow and produce weird stuff...

for type in "POINT", "LINESTRING", "POLYGON", "GEOMETRYCOLLECTION", "MULTIPOINT":
g = QgsGeometry.fromWkt(type)
print(type)
print(g)
print(g.asWkt())
POINT
<QgsGeometry: >

LINESTRING
<QgsGeometry: LineString ()>
LineString ()
POLYGON
<QgsGeometry: >

GEOMETRYCOLLECTION
<QgsGeometry: GeometryCollection ()>
GeometryCollection ()
MULTIPOINT
<QgsGeometry: MultiPoint ()>
MultiPoint ()

Also see https://issues.qgis.org/issues/14640 to QGIS allows geometries to be created using a string like "GeometryType" without either specifying the coordinates or EMPTY.

http://www.opengeospatial.org/standards/sfa defines for example for a POINT:

 ::= EMPTY

 ::=  |   

So "Point" would not be ok. QGIS however, does allow and produce weird stuff...

>>> for type in "POINT", "LINESTRING", "POLYGON", "GEOMETRYCOLLECTION", "MULTIPOINT":
>>>   g = QgsGeometry.fromWkt(type)
>>>   print(type)
>>>   print(g)
>>>   print(g.asWkt())
POINT


LINESTRING

LineString ()
POLYGON


GEOMETRYCOLLECTION

GeometryCollection ()
MULTIPOINT

MultiPoint ()

Related #22604

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

---

I don't think there's an issue here. By design, QGIS' WKT parser is very forgiving and is designed to accept many types of invalid WKT strings, converting them wherever possible to actual geometries.

POINT
<QgsGeometry: >

<QgsGeometry: > is a null geometry, so that's correct -- we can't convert the string "point" to a meaningful geometry.

LINESTRING
<QgsGeometry: LineString ()>
LineString ()

This looks correct - we've been forgiving and interpreted the string as an empty linestring (ignoring the issue that .asWkt() should return "LineString EMPTY" here -- that's a different issue).

POLYGON
<QgsGeometry: >

In this case we haven't been able to parse the invalid WKT -- without even an exterior ring there's nothing here, so the returned geometry is null.

GEOMETRYCOLLECTION
<QgsGeometry: GeometryCollection ()>
GeometryCollection ()

Again, looks correct to me -- we've been forgiving and interpreted this as an empty geometry collection.

MULTIPOINT
<QgsGeometry: MultiPoint ()>
MultiPoint ()

Same again -- we've interpreted as an empty multipoint.

---

• status_id was changed from Open to Feedback

[qgib]

Author Name: Loïc BARTOLETTI (@lbartoletti)

---

related issues #27019 and #28573

[qgib]

Author Name: Giovanni Manghi (@gioman)

---

Nyall Dawson wrote:

I don't think there's an issue here.

Nyall should this be closed?

[lbartoletti]

Fixed in #9645