PROJJSON export: for a Projected CRS, add an explicit type=Geographic…

…CRS/GeodeticCRS members to the base_crs member

This can make consumption/validation of PROJJSON easier. This doesn't
affect forward/backward compatibility as the importer is tolerant about
presence or absence of base_crs.type, and the schema too.

docs/source/specifications/projjson.rst

@@ -504,6 +504,7 @@ The EPSG:32631 / "WGS 84 / UTM zone 31N" projected CRS can be expressed as
         "type": "ProjectedCRS",
         "name": "WGS 84 / UTM zone 31N",
         "base_crs": {
+            "type": "GeographicCRS",
             "name": "WGS 84",
             "datum": {
                 "type": "GeodeticReferenceFrame",
@@ -623,6 +624,12 @@ The EPSG:32631 / "WGS 84 / UTM zone 31N" projected CRS can be expressed as
         }
     }
 
+
+.. note::
+
+    The ``type`` member of the ``base_crs`` member was omitted in PROJ export of PROJJSON
+    prior to PROJ 9.6.
+
 CompoundCRS
 +++++++++++
 

src/iso19111/crs.cpp

@@ -4533,7 +4533,6 @@ void ProjectedCRS::_exportToJSON(
 
     writer->AddObjKey("base_crs");
     formatter->setAllowIDInImmediateChild();
-    formatter->setOmitTypeInImmediateChild();
     baseCRS()->_exportToJSON(formatter);
 
     writer->AddObjKey("conversion");

test/unit/test_io.cpp

@@ -15133,8 +15133,14 @@ TEST(json_import, projected_crs) {
     auto obj = createFromUserInput(json, nullptr);
     auto pcrs = nn_dynamic_pointer_cast<ProjectedCRS>(obj);
     ASSERT_TRUE(pcrs != nullptr);
-    EXPECT_EQ(pcrs->exportToJSON(&(JSONFormatter::create()->setSchema("foo"))),
-              json);
+    std::string got_json =
+        pcrs->exportToJSON(&(JSONFormatter::create()->setSchema("foo")));
+    const char *typeGeogCRS = "    \"type\": \"GeographicCRS\",\n";
+    const auto posTypeGeogCRS = got_json.find(typeGeogCRS);
+    EXPECT_TRUE(posTypeGeogCRS != std::string::npos) << got_json;
+    got_json = got_json.substr(0, posTypeGeogCRS) +
+               got_json.substr(posTypeGeogCRS + strlen(typeGeogCRS));
+    EXPECT_STREQ(got_json.c_str(), json);
 }
 
 // ---------------------------------------------------------------------------
@@ -15363,8 +15369,14 @@ TEST(json_import, projected_crs_with_geocentric_base) {
     auto pcrs = nn_dynamic_pointer_cast<ProjectedCRS>(obj);
     ASSERT_TRUE(pcrs != nullptr);
     EXPECT_TRUE(pcrs->baseCRS()->isGeocentric());
-    EXPECT_EQ(pcrs->exportToJSON(&(JSONFormatter::create()->setSchema("foo"))),
-              json);
+    std::string got_json =
+        pcrs->exportToJSON(&(JSONFormatter::create()->setSchema("foo")));
+    const char *typeGeodCRS = "    \"type\": \"GeodeticCRS\",\n";
+    const auto posTypeGeodCRS = got_json.find(typeGeodCRS);
+    EXPECT_TRUE(posTypeGeodCRS != std::string::npos) << got_json;
+    got_json = got_json.substr(0, posTypeGeodCRS) +
+               got_json.substr(posTypeGeodCRS + strlen(typeGeodCRS));
+    EXPECT_STREQ(got_json.c_str(), json);
 }
 
 // ---------------------------------------------------------------------------
@@ -16153,6 +16165,7 @@ TEST(json_import, concatenated_operation) {
         "    \"type\": \"ProjectedCRS\",\n"
         "    \"name\": \"GDA94 / Vicgrid\",\n"
         "    \"base_crs\": {\n"
+        "      \"type\": \"GeographicCRS\",\n"
         "      \"name\": \"GDA94\",\n"
         "      \"datum\": {\n"
         "        \"type\": \"GeodeticReferenceFrame\",\n"
@@ -17371,6 +17384,7 @@ TEST(json_import, derived_projected_crs) {
                 "    \"type\": \"ProjectedCRS\",\n"
                 "    \"name\": \"WGS 84 / UTM zone 31N\",\n"
                 "    \"base_crs\": {\n"
+                "      \"type\": \"GeographicCRS\",\n"
                 "      \"name\": \"WGS 84\",\n"
                 "      \"datum\": {\n"
                 "        \"type\": \"GeodeticReferenceFrame\",\n"