Merge pull request #1616 from OSGeo/backport-1614-to-6.2

[Backport 6.2] Fixes related to #1597

4 files changed, 62 insertions, 9 deletions

diff --git a/docs/source/development/migration.rst b/docs/source/development/migration.rst
index 00e251c3..e22d7b16 100644
--- a/docs/source/development/migration.rst
+++ b/docs/source/development/migration.rst
@@ -117,7 +117,8 @@ Function mapping from old to new API
 +---------------------------------------+-------------------------------------------------+
 | pj_inv3                               | :c:func:`proj_trans`                            |
 +---------------------------------------+-------------------------------------------------+
-| pj_transform                          | :c:func:`proj_create_crs_to_crs` +              |
+| pj_transform                          | :c:func:`proj_create_crs_to_crs`                |
+|                                       | or :c:func:`proj_create_crs_to_crs_from_pj` +   |
 |                                       | (:c:func:`proj_normalize_for_visualization` +)  |
 |                                       | :c:func:`proj_trans`,                           |
 |                                       | :c:func:`proj_trans_array` or                   |
@@ -155,6 +156,31 @@ Function mapping from old to new API
 | pj_get_release                        | :c:func:`proj_info`                             |
 +---------------------------------------+-------------------------------------------------+
 
+
+Backward incompatibilities
+###############################################################################
+
+Access to the proj_api.h is still possible but requires to define the
+``ACCEPT_USE_OF_DEPRECATED_PROJ_API_H`` macro.
+
+The emulation of the now deprecated ``+init=epsg:XXXX`` syntax in PROJ 6 is not
+fully compatible with previous versions.
+
+In particular, when used with the ``pj_transform()`` function, no datum shift term
+(``towgs84``, ``nadgrids``, ``geoidgrids``) will be added during the expansion of the
+``+init=epsg:XXXX`` string to ``+proj=YYYY ....``. If you still uses ``pj_transform()``
+and want datum shift to be applied, then you need to provide a fully expanded
+string with appropriate ``towgs84``, ``nadgrids`` or ``geoidgrids`` terms to ``pj_init()``.
+
+To use the ``+init=epsg:XXXX`` syntax with :c:func:`proj_create` and then
+:c:func:`proj_create_crs_to_crs`, ``proj_context_use_proj4_init_rules(ctx, TRUE)``
+or the ``PROJ_USE_PROJ4_INIT_RULES=YES`` environment variable must have been
+previously set. In that context, datum shift will be researched. However they
+might be different than with PROJ 4 or PROJ 5, since a "late-binding" approach
+will be used (that is trying to find as much as possible the most direct
+transformation between the source and target datum), whereas PROJ 4 or PROJ 5
+used an "early-binding" approach consisting in always going to EPSG:4326 / WGS 84.
+
 ================================================================================
 Version 4 to 5 API Migration
 ================================================================================
diff --git a/src/iso19111/factory.cpp b/src/iso19111/factory.cpp
index 0f6790c0..60083455 100644
--- a/src/iso19111/factory.cpp
+++ b/src/iso19111/factory.cpp
@@ -1000,9 +1000,11 @@ bool DatabaseContext::lookForGridInfo(const std::string &projFilename,
     if (d->pjCtxt() == nullptr) {
         d->setPjCtxt(pj_get_default_ctx());
     }
+    int errno_before = proj_context_errno(d->pjCtxt());
     gridAvailable =
         pj_find_file(d->pjCtxt(), projFilename.c_str(), &fullFilename[0],
                      fullFilename.size() - 1) != 0;
+    proj_context_errno_set(d->pjCtxt(), errno_before);
     fullFilename.resize(strlen(fullFilename.c_str()));
 
     auto res =
diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 25d122af..ebccf78b 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -8313,10 +8313,13 @@ CRSNNPtr PROJStringParser::Private::buildProjectedCRS(
     } else if (step.name == "somerc") {
         mapping =
             getMapping(EPSG_CODE_METHOD_HOTINE_OBLIQUE_MERCATOR_VARIANT_B);
-        step.paramValues.emplace_back(Step::KeyValue("alpha", "90"));
-        step.paramValues.emplace_back(Step::KeyValue("gamma", "90"));
-        step.paramValues.emplace_back(
-            Step::KeyValue("lonc", getParamValue(step, "lon_0")));
+        if (!hasParamValue(step, "alpha") && !hasParamValue(step, "gamma") &&
+            !hasParamValue(step, "lonc")) {
+            step.paramValues.emplace_back(Step::KeyValue("alpha", "90"));
+            step.paramValues.emplace_back(Step::KeyValue("gamma", "90"));
+            step.paramValues.emplace_back(
+                Step::KeyValue("lonc", getParamValue(step, "lon_0")));
+        }
     } else if (step.name == "krovak" &&
                ((getParamValue(step, "axis") == "swu" && iAxisSwap < 0) ||
                 (iAxisSwap > 0 &&
@@ -8756,10 +8759,17 @@ PROJStringParser::createFromPROJString(const std::string &projString) {
             if (!file_found) {
                 auto obj = createFromUserInput(stepName, d->dbContext_, true);
                 auto crs = dynamic_cast<CRS *>(obj.get());
-                if (crs &&
-                    (d->steps_[0].paramValues.empty() ||
-                     (d->steps_[0].paramValues.size() == 1 &&
-                      d->getParamValue(d->steps_[0], "type") == "crs"))) {
+
+                bool hasSignificantParamValues = false;
+                for (const auto &kv : d->steps_[0].paramValues) {
+                    if (!((kv.key == "type" && kv.value == "crs") ||
+                          kv.key == "no_defs")) {
+                        hasSignificantParamValues = true;
+                        break;
+                    }
+                }
+
+                if (crs && !hasSignificantParamValues) {
                     PropertyMap properties;
                     properties.set(IdentifiedObject::NAME_KEY,
                                    d->title_.empty() ? crs->nameStr()
diff --git a/test/unit/test_io.cpp b/test/unit/test_io.cpp
index 7930ff53..0eed2d15 100644
--- a/test/unit/test_io.cpp
+++ b/test/unit/test_io.cpp
@@ -7800,6 +7800,10 @@ TEST(io, projparse_somerc) {
     EXPECT_TRUE(wkt.find("\"Northing at projection centre\",5") !=
                 std::string::npos)
         << wkt;
+
+    auto wkt1 = crs->exportToWKT(
+        WKTFormatter::create(WKTFormatter::Convention::WKT1_GDAL).get());
+    EXPECT_TRUE(wkt1.find("EXTENSION") == std::string::npos) << wkt1;
 }
 
 // ---------------------------------------------------------------------------
@@ -8637,6 +8641,17 @@ TEST(io, projparse_init) {
     }
 
     {
+        // Test that +no_defs +type=crs have no effect
+        auto obj = createFromUserInput("+init=epsg:4326 +no_defs +type=crs",
+                                       dbContext, true);
+        auto crs = nn_dynamic_pointer_cast<GeographicCRS>(obj);
+        ASSERT_TRUE(crs != nullptr);
+
+        auto wkt = crs->exportToWKT(WKTFormatter::create().get());
+        EXPECT_TRUE(wkt.find("GEODCRS[\"WGS 84\"") == 0) << wkt;
+    }
+
+    {
         // EPSG:3040 is normally northing-easting order, but in compatibillity
         // mode it will be easting-northing
         auto obj =