proj_create_crs_to_crs(): emit a debug message if the best transformation cannot be used / cs2cs: add a --only-best=no switch

docs/source/apps/cs2cs.rst

@@ -14,7 +14,7 @@ Synopsis
     | **cs2cs** [**-eEfIlrstvwW** [args]]
     |           [[--area <name_or_code>] | [--bbox <west_long,south_lat,east_long,north_lat>]]
     |           [--authority <name>] [--3d]
-    |           [--accuracy <accuracy>] [--only-best] [--no-ballpark]
+    |           [--accuracy <accuracy>] [--only-best[=yes|=no]] [--no-ballpark]
     |           ([*+opt[=arg]* ...] [+to *+opt[=arg]* ...] | {source_crs} {target_crs})
     |           file ...
 
@@ -167,15 +167,17 @@ The following control parameters can appear in any order:
     `south_lat` and `north_lat` in the [-90,90]. `west_long` is generally lower than
     `east_long`, except in the case where the area of interest crosses the antimeridian.
 
-.. option:: --only-best
+.. option:: --only-best[=yes|=no]
 
     .. versionadded:: 9.2.0
 
-    Error out if the best transformation, known of PROJ, and usable by PROJ if
-    all grids known and usable by PROJ were accessible, cannot be used.
-    Best transformation should be understood as the transformation returned by
-    :cpp:func:`proj_get_suggested_operation` if all known grids were
-    accessible (either locally or through network).
+    If set to yes, error out if the best transformation, known of PROJ, and
+    usable by PROJ if all grids known and usable by PROJ were accessible,
+    cannot be used.
+    Best transformation should be understood as the most accurate transformation
+    available among all relevant for the point to transform, and if all known
+    grids required to perform such transformation were accessible (either locally
+    or through network).
 
 .. option:: --no-ballpark
 

src/4D_api.cpp

@@ -348,7 +348,8 @@ similarly, but prefers the 2D resp. 3D interfaces if available.
             if( res.xyzt.x != HUGE_VAL ) {
                 return res;
             }
-            else if( P->errorIfBestTransformationNotAvailable ) {
+            else if( P->errorIfBestTransformationNotAvailable ||
+                     P->ctx->warnIfBestTransformationNotAvailable ) {
                 std::string msg("Attempt to use coordinate operation ");
                 msg += alt.name;
                 msg += " failed.";
@@ -367,8 +368,18 @@ similarly, but prefers the 2D resp. 3D interfaces if available.
                         msg += " is not available.";
                     }
                 }
-                pj_log(P->ctx, PJ_LOG_ERROR, msg.c_str());
-                return res;
+                if( P->ctx->warnIfBestTransformationNotAvailable )
+                {
+                    msg += " This might become an error in a future PROJ major release. "
+                           "Set the ONLY_BEST option to YES or NO. "
+                           "This warning will no longer be emitted (for the current context).";
+                    P->ctx->warnIfBestTransformationNotAvailable = false;
+                }
+                pj_log(P->ctx,
+                       P->errorIfBestTransformationNotAvailable ? PJ_LOG_ERROR : PJ_LOG_DEBUG,
+                       msg.c_str());
+                if( P->errorIfBestTransformationNotAvailable )
+                    return res;
             }
             if( iRetry == N_MAX_RETRY ) {
                 break;
@@ -1939,6 +1950,7 @@ PJ  *proj_create_crs_to_crs_from_pj (PJ_CONTEXT *ctx, const PJ *source_crs, cons
                 return nullptr;
             }
         } else if ((value = getOptionValue(*iter, "ONLY_BEST="))) {
+            ctx->warnIfBestTransformationNotAvailable = false;
             if( ci_equal(value, "yes") )
                 errorIfBestTransformationNotAvailable = true;
             else if( ci_equal(value, "no") )
@@ -1996,7 +2008,9 @@ PJ  *proj_create_crs_to_crs_from_pj (PJ_CONTEXT *ctx, const PJ *source_crs, cons
         ctx, operation_ctx, PROJ_SPATIAL_CRITERION_PARTIAL_INTERSECTION);
     proj_operation_factory_context_set_grid_availability_use(
         ctx, operation_ctx,
-        (errorIfBestTransformationNotAvailable || proj_context_is_network_enabled(ctx)) ?
+        (errorIfBestTransformationNotAvailable ||
+         ctx->warnIfBestTransformationNotAvailable ||
+         proj_context_is_network_enabled(ctx)) ?
             PROJ_GRID_AVAILABILITY_KNOWN_AVAILABLE:
             PROJ_GRID_AVAILABILITY_DISCARD_OPERATION_IF_MISSING_GRID);
 
@@ -2018,7 +2032,7 @@ PJ  *proj_create_crs_to_crs_from_pj (PJ_CONTEXT *ctx, const PJ *source_crs, cons
     ctx->forceOver = forceOver;
 
     const int old_debug_level = ctx->debug_level;
-    if( errorIfBestTransformationNotAvailable )
+    if( errorIfBestTransformationNotAvailable || ctx->warnIfBestTransformationNotAvailable )
         ctx->debug_level = PJ_LOG_NONE;
     PJ* P = proj_list_get(ctx, op_list, 0);
     ctx->debug_level = old_debug_level;
@@ -2031,7 +2045,8 @@ PJ  *proj_create_crs_to_crs_from_pj (PJ_CONTEXT *ctx, const PJ *source_crs, cons
         ctx->forceOver = false;
 
         if( P != nullptr &&
-            errorIfBestTransformationNotAvailable &&
+            (errorIfBestTransformationNotAvailable ||
+             ctx->warnIfBestTransformationNotAvailable) &&
             !proj_coordoperation_is_instantiable(ctx, P) )
         {
             std::string msg("Attempt to use coordinate operation ");
@@ -2052,13 +2067,22 @@ PJ  *proj_create_crs_to_crs_from_pj (PJ_CONTEXT *ctx, const PJ *source_crs, cons
                     msg += " is not available.";
                 }
             }
-            pj_log(ctx, PJ_LOG_ERROR, msg.c_str());
+            if( ctx->warnIfBestTransformationNotAvailable )
+            {
+                msg += " This might become an error in a future PROJ major release."
+                       "Set the ONLY_BEST option to YES or NO. "
+                       "This warning will no longer be emitted (for the current context).";
+                ctx->warnIfBestTransformationNotAvailable = false;
+            }
+            pj_log(ctx,
+                   errorIfBestTransformationNotAvailable ? PJ_LOG_ERROR : PJ_LOG_DEBUG,
+                   msg.c_str());
         }
 
         return P;
     }
 
-    if( errorIfBestTransformationNotAvailable )
+    if( errorIfBestTransformationNotAvailable || ctx->warnIfBestTransformationNotAvailable )
         ctx->debug_level = PJ_LOG_NONE;
     auto preparedOpList = pj_create_prepared_operations(ctx, source_crs, target_crs,
                                                    op_list);

src/apps/cs2cs.cpp

@@ -79,7 +79,7 @@ static const char *usage =
     "%s\nusage: %s [-dDeEfIlrstvwW [args]]\n"
     "              [[--area name_or_code] | [--bbox west_long,south_lat,east_long,north_lat]]\n"
     "              [--authority {name}] [--3d]\n"
-    "              [--accuracy {accuracy}] [--only-best] [--no-ballpark]\n"
+    "              [--accuracy {accuracy}] [--only-best[=yes|=no]] [--no-ballpark]\n"
     "              [+opt[=arg] ...] [+to +opt[=arg] ...] [file ...]\n";
 
 static double (*informat)(const char *,
@@ -419,6 +419,7 @@ int main(int argc, char **argv) {
     const char* authority = nullptr;
     double accuracy = -1;
     bool allowBallpark = true;
+    bool onlyBestSet = false;
     bool errorIfBestTransformationNotAvailable = false;
     bool promoteTo3D = false;
 
@@ -486,9 +487,15 @@ int main(int argc, char **argv) {
         else if (strcmp(*argv, "--no-ballpark") == 0 ) {
             allowBallpark = false;
         }
-        else if (strcmp(*argv, "--only-best") == 0 ) {
+        else if (strcmp(*argv, "--only-best") == 0 ||
+                 strcmp(*argv, "--only-best=yes") == 0 ) {
+            onlyBestSet = true;
             errorIfBestTransformationNotAvailable = true;
         }
+        else if (strcmp(*argv, "--only-best=no") == 0 ) {
+            onlyBestSet = true;
+            errorIfBestTransformationNotAvailable = false;
+        }
         else if (strcmp(*argv, "--3d") == 0 ) {
             promoteTo3D = true;
         }
@@ -898,8 +905,13 @@ int main(int argc, char **argv) {
     if( !allowBallpark ) {
         options.push_back("ALLOW_BALLPARK=NO");
     }
-    if( errorIfBestTransformationNotAvailable ) {
-        options.push_back("ONLY_BEST=YES");
+    if( onlyBestSet ) {
+        if( errorIfBestTransformationNotAvailable ) {
+            options.push_back("ONLY_BEST=YES");
+        }
+        else {
+            options.push_back("ONLY_BEST=NO");
+        }
     }
     options.push_back(nullptr);
     transformation = proj_create_crs_to_crs_from_pj(nullptr, src, dst,

src/ctx.cpp

@@ -150,6 +150,7 @@ pj_ctx::pj_ctx(const pj_ctx& other) :
     lastFullErrorMessage(std::string()),
     last_errno(0),
     debug_level(other.debug_level),
+    warnIfBestTransformationNotAvailable(other.warnIfBestTransformationNotAvailable),
     logger(other.logger),
     logger_app_data(other.logger_app_data),
     cpp_context(other.cpp_context ? other.cpp_context->clone(this) : nullptr),

src/proj_internal.h

@@ -695,6 +695,7 @@ struct pj_ctx{
     std::string lastFullErrorMessage{}; // used by proj_context_errno_string
     int     last_errno = 0;
     int     debug_level = PJ_LOG_ERROR;
+    bool warnIfBestTransformationNotAvailable = true; /* to remove in PROJ 10? */
     void    (*logger)(void *, int, const char *) = nullptr;
     void    *logger_app_data = nullptr;
     struct projCppContext* cpp_context = nullptr; /* internal context for C++ code */

test/cli/testvarious

@@ -1089,6 +1089,20 @@ $EXE --only-best NTF RGF93 -E >>${OUT} 2>&1 <<EOF
 49 2 0
 EOF
 
+echo "##############################################################" >> ${OUT}
+echo "Test cs2cs (grid missing)" >> ${OUT}
+#
+$EXE EPSG:4326+3855 EPSG:4979 -E >>${OUT} 2>&1 <<EOF
+49 2 0
+EOF
+
+echo "##############################################################" >> ${OUT}
+echo "Test cs2cs --only-best=no  (grid missing)" >> ${OUT}
+#
+$EXE --only-best=no EPSG:4326+3855 EPSG:4979 -E >>${OUT} 2>&1 <<EOF
+49 2 0
+EOF
+
 echo "##############################################################" >> ${OUT}
 echo "Test cs2cs --only-best (grid missing)" >> ${OUT}
 #
@@ -1096,6 +1110,13 @@ $EXE --only-best EPSG:4326+3855 EPSG:4979 -E >>${OUT} 2>&1 <<EOF
 49 2 0
 EOF
 
+echo "##############################################################" >> ${OUT}
+echo "Test cs2cs --only-best=yes (grid missing)" >> ${OUT}
+#
+$EXE --only-best=yes EPSG:4326+3855 EPSG:4979 -E >>${OUT} 2>&1 <<EOF
+49 2 0
+EOF
+
 echo "##############################################################" >> ${OUT}
 echo "Test cs2cs --only-best (grid missing)" >> ${OUT}
 #

test/cli/tv_out.dist

@@ -532,10 +532,20 @@ program abnormally terminated
 Test cs2cs --only-best (working)
 49 2 0	48d59'59.756"N	1d59'57.4"E 0.000
 ##############################################################
+Test cs2cs (grid missing)
+49 2 0	49dN	2dE 0.000
+##############################################################
+Test cs2cs --only-best=no  (grid missing)
+49 2 0	49dN	2dE 0.000
+##############################################################
 Test cs2cs --only-best (grid missing)
 Attempt to use coordinate operation Inverse of WGS 84 to EGM2008 height (1) failed. Grid us_nga_egm08_25.tif is not available.
 49 2 0	*	* inf
 ##############################################################
+Test cs2cs --only-best=yes (grid missing)
+Attempt to use coordinate operation Inverse of WGS 84 to EGM2008 height (1) failed. Grid us_nga_egm08_25.tif is not available.
+49 2 0	*	* inf
+##############################################################
 Test cs2cs --only-best (grid missing)
 Attempt to use coordinate operation NAD27 to NAD83 (7) failed. Grid us_noaa_nadcon5_nad27_nad83_1986_conus.tif is not available.
 40 -100 0	*	* inf