[Processing] Various algorithms: "DeprecationWarning: QgsField constructor is deprecated"

[agiudiceandrea]

What is the bug or the crash?

The following warning are printed in the "Python warning" tab of the Log Messages panel when the "Check validity" (qgis:checkvalidity) processing algorithm (and probably many other ones) is executed:

2024-06-28T08:49:49     WARNING    warning:C:\OSF9FA~1/apps/qgis/./python/plugins\processing\algs\qgis\CheckValidity.py:137: DeprecationWarning: QgsField constructor is deprecated
              invalid_fields.append(QgsField('_errors', QVariant.String, 'string', 255))
             
             traceback: File "C:\OSF9FA~1/apps/qgis/./python/plugins\processing\algs\qgis\CheckValidity.py", line 122, in processAlgorithm
              return self.doCheck(
              File "C:\OSF9FA~1/apps/qgis/./python/plugins\processing\algs\qgis\CheckValidity.py", line 137, in doCheck
              invalid_fields.append(QgsField('_errors', QVariant.String, 'string', 255))
             
2024-06-28T08:49:49     WARNING    warning:C:\OSF9FA~1/apps/qgis/./python/plugins\processing\algs\qgis\CheckValidity.py:143: DeprecationWarning: QgsField constructor is deprecated
              error_fields.append(QgsField('message', QVariant.String, 'string', 255))
             
             traceback: File "C:\OSF9FA~1/apps/qgis/./python/plugins\processing\algs\qgis\CheckValidity.py", line 122, in processAlgorithm
              return self.doCheck(
              File "C:\OSF9FA~1/apps/qgis/./python/plugins\processing\algs\qgis\CheckValidity.py", line 143, in doCheck
              error_fields.append(QgsField('message', QVariant.String, 'string', 255))

Steps to reproduce the issue

1. execute the "Check validity" processing algorithm

Versions

QGIS version
3.38.0-Grenoble
QGIS code revision
37aa618
Qt version
5.15.13
Python version
3.12.4
GDAL/OGR version
3.9.0
PROJ version
9.4.0
EPSG Registry database version
v11.004 (2024-02-24)
GEOS version
3.12.2-CAPI-1.18.2
SQLite version
3.45.1
PDAL version
2.6.3
PostgreSQL client version
16.2
SpatiaLite version
5.1.0
QWT version
6.2.0
QScintilla2 version
2.14.1
OS version
Windows 10 Version 1903

Active Python plugins
db_manager
0.1.20
grassprovider
2.12.99
MetaSearch
0.3.6
processing
2.12.99

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

Related to #57272.

[mbukowski]

I experienced very similar behaviour for instance when running qgis:exportaddgeometrycolumns algorithm
file: ./python/plugins\processing\algs\qgis\ExportGeometryInfo.py:106
file: ./python/plugins\processing\algs\qgis\ExportGeometryInfo.py:107

This piece of code is still using old QGSField constructor