Fix unreleased regression related to 78d563c, that caused GDAL's test_gdalwarp_lib_135 test to fail

Author: rouault

src/iso19111/operation/singleoperation.cpp

@@ -297,7 +297,9 @@ bool CoordinateOperation::isPROJInstantiable(
     }
     for (const auto &gridDesc :
          gridsNeeded(databaseContext, considerKnownGridsAsAvailable)) {
-        if (!gridDesc.available) {
+        // Grid name starting with @ are considered as optional.
+        if (!gridDesc.available &&
+            (gridDesc.shortName.empty() || gridDesc.shortName[0] != '@')) {
             return false;
         }
     }

test/cli/testvarious

@@ -1247,6 +1247,13 @@ echo 39 -3 0 | PROJ_DISPLAY_PROGRAM_NAME=NO PROJ_DATA=tmp_dir PROJ_DEBUG=2 $EXE
 
 rm -rf tmp_dir
 
+echo "##############################################################" >> ${OUT}
+echo "Test cs2cs grid missing with @gridname" >> ${OUT}
+
+$EXE +proj=longlat +datum=WGS84 +units=m +geoidgrids=@i_dont_exist.tif +vunits=m +no_defs +type=crs +to EPSG:4979 >> ${OUT} <<EOF
+2 49 0
+EOF
+
 echo "##############################################################" >> ${OUT}
 echo "Test Similarity Transformation (example from EPSG Guidance Note 7.2)" >> ${OUT}
 #

test/cli/tv_out.dist

@@ -607,6 +607,9 @@ cannot initialize transformation
 cause: File not found or invalid
 program abnormally terminated
 ##############################################################
+Test cs2cs grid missing with @gridname
+49dN	2dE 0.000
+##############################################################
 Test Similarity Transformation (example from EPSG Guidance Note 7.2)
 300000 4500000	299905.060	4499796.515 0.000
 ##############################################################