ECC-1792: GRIB: headers_only cloning does not work as expected after changing geography

src/grib_accessor_class_latitudes.cc

@@ -221,6 +221,13 @@ static int value_count(grib_accessor* a, long* len)
     }
     *len = size;
 
+    // See ECC-1792
+    // Give priority to the Grid Section (rather than the Data Section)
+    long numberOfDataPoints = 0;
+    if (grib_get_long(h, "numberOfDataPoints", &numberOfDataPoints) == GRIB_SUCCESS) {
+        *len = numberOfDataPoints;
+    }
+
     if (self->distinct) {
         ret = get_distinct(a, &val, len);
         if (ret != GRIB_SUCCESS)

src/grib_accessor_class_longitudes.cc

@@ -196,6 +196,13 @@ static int value_count(grib_accessor* a, long* len)
     }
     *len = size;
 
+    // See ECC-1792
+    // Give priority to the Grid Section (rather than the Data Section)
+    long numberOfDataPoints = 0;
+    if (grib_get_long(h, "numberOfDataPoints", &numberOfDataPoints) == GRIB_SUCCESS) {
+        *len = numberOfDataPoints;
+    }
+
     if (self->distinct) {
         ret = get_distinct(a, &val, len);
         if (ret != GRIB_SUCCESS)

src/grib_iterator_class_gen.cc

@@ -193,12 +193,21 @@ static int init(grib_iterator* iter, grib_handle* h, grib_arguments* args)
     if ((err = grib_get_long_internal(h, s_numPoints, &numberOfPoints)) != GRIB_SUCCESS)
         return err;
 
-    if (numberOfPoints != dli) {
-        grib_context_log(h->context, GRIB_LOG_ERROR, "Geoiterator: %s != size(%s) (%ld!=%ld)",
-                         s_numPoints, s_rawData, numberOfPoints, dli);
-        return GRIB_WRONG_GRID;
+    // See ECC-1792. If we don't want to decode the Data Section, we should not do a check
+    // to see if it is consistent with the Grid Section
+    if (iter->flags & GRIB_GEOITERATOR_NO_VALUES) {
+        // Iterator's number of values taken from the Grid Section
+        iter->nv = numberOfPoints;
+    } else {
+        // Check for consistency between the Grid and Data Sections
+        if (numberOfPoints != dli) {
+            grib_context_log(h->context, GRIB_LOG_ERROR, "Geoiterator: %s != size(%s) (%ld!=%ld)",
+                             s_numPoints, s_rawData, numberOfPoints, dli);
+            return GRIB_WRONG_GRID;
+        }
+        iter->nv = dli;
     }
-    iter->nv = dli;
+
     if (iter->nv == 0) {
         grib_context_log(h->context, GRIB_LOG_ERROR, "Geoiterator: size(%s) is %ld", s_rawData, dli);
         return GRIB_WRONG_GRID;

tests/CMakeLists.txt

@@ -266,6 +266,7 @@ if( HAVE_BUILD_TOOLS )
         grib_ecc-1425
         grib_ecc-1467
         grib_ecc-1764
+        grib_ecc-1792
         grib_sub_hourly
         grib_set_bytes
         grib_set_force

tests/grib_ecc-1792.sh

@@ -0,0 +1,57 @@
+#!/bin/sh
+# (C) Copyright 2005- ECMWF.
+#
+# This software is licensed under the terms of the Apache Licence Version 2.0
+# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+# 
+# In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
+# virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
+#
+
+. ./include.ctest.sh
+
+REDIRECT=/dev/null
+
+label="grib_ecc-1792_test"
+tempGrib=temp.$label.grib
+tempFilt=temp.$label.filt
+tempLog=temp.$label.log
+tempRef=temp.$label.ref
+
+sample_grib2=$ECCODES_SAMPLES_PATH/GRIB2.tmpl
+
+# Create a message with its Data Section out-of-sync with its Grid
+${tools_dir}/grib_set -s numberOfValues=2 $sample_grib2 $tempGrib
+grib_check_key_equals $tempGrib numberOfDataPoints 496
+
+# grib_get_data should fail
+set +e
+${tools_dir}/grib_get_data $tempGrib > $tempLog 2>&1
+status=$?
+set -e
+[ $status -ne 0 ]
+grep "Grid description is wrong" $tempLog
+
+# Just getting lats and lons; no need for Data Section to be in-sync
+cat >$tempFilt<<EOF
+    print "latitudes  = [latitudes]";
+    print "longitudes = [longitudes]";
+    print "distinctLatitudes  = [distinctLatitudes]";
+    print "distinctLongitudes  = [distinctLongitudes]";
+EOF
+${tools_dir}/grib_filter -o $tempGrib $tempFilt $tempGrib
+
+# latLonValues does require Data Section to be in-sync
+cat >$tempFilt<<EOF
+    print "[latLonValues]";
+EOF
+set +e
+${tools_dir}/grib_filter -o $tempGrib $tempFilt $tempGrib > $tempLog 2>&1
+status=$?
+set -e
+[ $status -ne 0 ]
+grep "Grid description is wrong" $tempLog
+
+
+# Clean up
+rm -f $tempGrib $tempFilt $tempLog $tempRef