createFromWkt(): be tolerant to missing scale_factor parameter (fixes #1700)

This is invalid WKT, but GDAL 2.4 used to accept it and make a reasonable
use of it...

Currently we default it to 0 which is non sensical. Better use 1 as GDAL 2.4
did, and emit a warning.

Other fix: proj_create_from_wkt() was documented to operate by default in
non-strict validation mode, but it was actually in strict mode. So do as
documented.

2 files changed, 38 insertions, 2 deletions

diff --git a/test/unit/test_c_api.cpp b/test/unit/test_c_api.cpp
index 7fd0e742..0a860d1f 100644
--- a/test/unit/test_c_api.cpp
+++ b/test/unit/test_c_api.cpp
@@ -231,7 +231,8 @@ TEST_F(CApi, proj_create_from_wkt) {
             "    PRIMEM[\"Greenwich\",0],\n"
             "    UNIT[\"degree\",0.0174532925199433]]",
             nullptr, nullptr, nullptr);
-        EXPECT_EQ(obj, nullptr);
+        ObjectKeeper keeper(obj);
+        EXPECT_NE(obj, nullptr);
     }
     {
         PROJ_STRING_LIST warningList = nullptr;
@@ -244,7 +245,8 @@ TEST_F(CApi, proj_create_from_wkt) {
             "    PRIMEM[\"Greenwich\",0],\n"
             "    UNIT[\"degree\",0.0174532925199433]]",
             nullptr, &warningList, &errorList);
-        EXPECT_EQ(obj, nullptr);
+        ObjectKeeper keeper(obj);
+        EXPECT_NE(obj, nullptr);
         EXPECT_EQ(warningList, nullptr);
         proj_string_list_destroy(warningList);
         EXPECT_NE(errorList, nullptr);
diff --git a/test/unit/test_io.cpp b/test/unit/test_io.cpp
index 488638a4..8b6b315f 100644
--- a/test/unit/test_io.cpp
+++ b/test/unit/test_io.cpp
@@ -1174,6 +1174,40 @@ TEST(wkt_parse, wkt1_Mercator_1SP_with_latitude_origin_0) {
 
 // ---------------------------------------------------------------------------
 
+TEST(wkt_parse, wkt1_Mercator_1SP_without_scale_factor) {
+    // See https://github.com/OSGeo/PROJ/issues/1700
+    auto wkt = "PROJCS[\"unnamed\",\n"
+               "    GEOGCS[\"WGS 84\",\n"
+               "        DATUM[\"unknown\",\n"
+               "            SPHEROID[\"WGS84\",6378137,298.257223563]],\n"
+               "        PRIMEM[\"Greenwich\",0],\n"
+               "        UNIT[\"degree\",0.0174532925199433]],\n"
+               "    PROJECTION[\"Mercator_1SP\"],\n"
+               "    PARAMETER[\"central_meridian\",0],\n"
+               "    PARAMETER[\"false_easting\",0],\n"
+               "    PARAMETER[\"false_northing\",0],\n"
+               "    UNIT[\"Meter\",1],\n"
+               "    AXIS[\"Easting\",EAST],\n"
+               "    AXIS[\"Northing\",NORTH]]";
+    WKTParser parser;
+    parser.setStrict(false).attachDatabaseContext(DatabaseContext::create());
+    auto obj = parser.createFromWKT(wkt);
+    EXPECT_TRUE(!parser.warningList().empty());
+
+    auto crs = nn_dynamic_pointer_cast<ProjectedCRS>(obj);
+    ASSERT_TRUE(crs != nullptr);
+    auto got_wkt = crs->exportToWKT(
+        WKTFormatter::create(WKTFormatter::Convention::WKT1_GDAL).get());
+    EXPECT_TRUE(got_wkt.find("PARAMETER[\"scale_factor\",1]") !=
+                std::string::npos)
+        << got_wkt;
+    EXPECT_EQ(crs->exportToPROJString(PROJStringFormatter::create().get()),
+              "+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +units=m "
+              "+no_defs +type=crs");
+}
+
+// ---------------------------------------------------------------------------
+
 TEST(wkt_parse, wkt1_krovak_south_west) {
     auto wkt =
         "PROJCS[\"S-JTSK / Krovak\","