PROJBasedOperation: write it as a conformant CONVERSION WKT, and make it parsed appropriately on the reading side

5 files changed, 47 insertions, 43 deletions

diff --git a/include/proj/internal/coordinateoperation_internal.hpp b/include/proj/internal/coordinateoperation_internal.hpp
index d8c091d0..8428b8bf 100644
--- a/include/proj/internal/coordinateoperation_internal.hpp
+++ b/include/proj/internal/coordinateoperation_internal.hpp
@@ -252,8 +252,7 @@ class PROJBasedOperation : public SingleOperation {
     gridsNeeded(const io::DatabaseContextPtr &databaseContext) const override;
 
   protected:
-    PROJBasedOperation(const OperationMethodNNPtr &methodIn,
-                       const std::vector<GeneralParameterValueNNPtr> &values);
+    PROJBasedOperation(const OperationMethodNNPtr &methodIn);
 
     void _exportToPROJString(io::PROJStringFormatter *formatter)
         const override; // throw(FormattingException)
@@ -261,6 +260,7 @@ class PROJBasedOperation : public SingleOperation {
     INLINED_MAKE_SHARED
 
   private:
+    std::string projString_{};
     io::IPROJStringExportablePtr projStringExportable_{};
     bool inverse_ = false;
 };
diff --git a/src/iso19111/coordinateoperation.cpp b/src/iso19111/coordinateoperation.cpp
index 47f10392..cc212314 100644
--- a/src/iso19111/coordinateoperation.cpp
+++ b/src/iso19111/coordinateoperation.cpp
@@ -11788,33 +11788,22 @@ PROJBasedOperation::~PROJBasedOperation() = default;
 
 // ---------------------------------------------------------------------------
 
-PROJBasedOperation::PROJBasedOperation(
-    const OperationMethodNNPtr &methodIn,
-    const std::vector<GeneralParameterValueNNPtr> &values)
-    : SingleOperation(methodIn) {
-    setParameterValues(values);
-}
+PROJBasedOperation::PROJBasedOperation(const OperationMethodNNPtr &methodIn)
+    : SingleOperation(methodIn) {}
 
 // ---------------------------------------------------------------------------
 
-static const std::string PROJSTRING_PARAMETER_NAME("PROJ string");
-
 PROJBasedOperationNNPtr PROJBasedOperation::create(
     const util::PropertyMap &properties, const std::string &PROJString,
     const crs::CRSPtr &sourceCRS, const crs::CRSPtr &targetCRS,
     const std::vector<metadata::PositionalAccuracyNNPtr> &accuracies) {
-    auto parameter = OperationParameter::create(util::PropertyMap().set(
-        common::IdentifiedObject::NAME_KEY, PROJSTRING_PARAMETER_NAME));
     auto method = OperationMethod::create(
         util::PropertyMap().set(common::IdentifiedObject::NAME_KEY,
-                                "PROJ-based operation method"),
-        std::vector<OperationParameterNNPtr>{parameter});
-    std::vector<GeneralParameterValueNNPtr> values;
-    values.push_back(OperationParameterValue::create(
-        parameter, ParameterValue::create(PROJString)));
-    auto op =
-        PROJBasedOperation::nn_make_shared<PROJBasedOperation>(method, values);
+                                "PROJ-based operation method: " + PROJString),
+        std::vector<GeneralOperationParameterNNPtr>{});
+    auto op = PROJBasedOperation::nn_make_shared<PROJBasedOperation>(method);
     op->assignSelf(op);
+    op->projString_ = PROJString;
     if (sourceCRS && targetCRS) {
         op->setCRSs(NN_NO_CHECK(sourceCRS), NN_NO_CHECK(targetCRS), nullptr);
     }
@@ -11826,21 +11815,11 @@ PROJBasedOperationNNPtr PROJBasedOperation::create(
 
 // ---------------------------------------------------------------------------
 
-static const std::string
-    APPROX_PROJSTRING_PARAMETER_NAME("(Approximte) PROJ string");
-
 PROJBasedOperationNNPtr PROJBasedOperation::create(
     const util::PropertyMap &properties,
     const io::IPROJStringExportableNNPtr &projExportable, bool inverse,
     const crs::CRSNNPtr &sourceCRS, const crs::CRSNNPtr &targetCRS,
     const std::vector<metadata::PositionalAccuracyNNPtr> &accuracies) {
-    auto parameter = OperationParameter::create(util::PropertyMap().set(
-        common::IdentifiedObject::NAME_KEY, APPROX_PROJSTRING_PARAMETER_NAME));
-    auto method = OperationMethod::create(
-        util::PropertyMap().set(common::IdentifiedObject::NAME_KEY,
-                                "PROJ-based operation method"),
-        std::vector<OperationParameterNNPtr>{parameter});
-    std::vector<GeneralParameterValueNNPtr> values;
 
     auto formatter = io::PROJStringFormatter::create();
     if (inverse) {
@@ -11852,11 +11831,14 @@ PROJBasedOperationNNPtr PROJBasedOperation::create(
     }
     auto projString = formatter->toString();
 
-    values.push_back(OperationParameterValue::create(
-        parameter, ParameterValue::create(projString)));
-    auto op =
-        PROJBasedOperation::nn_make_shared<PROJBasedOperation>(method, values);
+    auto method = OperationMethod::create(
+        util::PropertyMap().set(common::IdentifiedObject::NAME_KEY,
+                                "PROJ-based operation method (approximate) : " +
+                                    projString),
+        std::vector<GeneralOperationParameterNNPtr>{});
+    auto op = PROJBasedOperation::nn_make_shared<PROJBasedOperation>(method);
     op->assignSelf(op);
+    op->projString_ = projString;
     op->setCRSs(sourceCRS, targetCRS, nullptr);
     op->setProperties(
         addDefaultNameIfNeeded(properties, "PROJ-based coordinate operation"));
@@ -11882,8 +11864,7 @@ CoordinateOperationNNPtr PROJBasedOperation::inverse() const {
     auto formatter = io::PROJStringFormatter::create();
     formatter->startInversion();
     try {
-        formatter->ingestPROJString(
-            parameterValue(PROJSTRING_PARAMETER_NAME)->stringValue());
+        formatter->ingestPROJString(projString_);
     } catch (const io::ParsingException &e) {
         throw util::UnsupportedOperationException(
             std::string("PROJBasedOperation::inverse() failed: ") + e.what());
@@ -11938,8 +11919,7 @@ void PROJBasedOperation::_exportToPROJString(
     }
 
     try {
-        formatter->ingestPROJString(
-            parameterValue(PROJSTRING_PARAMETER_NAME)->stringValue());
+        formatter->ingestPROJString(projString_);
     } catch (const io::ParsingException &e) {
         throw io::FormattingException(
             std::string("PROJBasedOperation::exportToPROJString() failed: ") +
diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 13a8f236..5be02ffe 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -4252,8 +4252,20 @@ BaseObjectNNPtr WKTParser::Private::build(const WKTNodeNNPtr &node) {
     }
 
     if (ci_equal(name, WKTConstants::CONVERSION)) {
-        return util::nn_static_pointer_cast<BaseObject>(
-            buildConversion(node, UnitOfMeasure::METRE, UnitOfMeasure::DEGREE));
+        auto conv =
+            buildConversion(node, UnitOfMeasure::METRE, UnitOfMeasure::DEGREE);
+
+        if (conv->nameStr() == "PROJ-based coordinate operation" &&
+            starts_with(conv->method()->nameStr(),
+                        "PROJ-based operation method: ")) {
+            auto projString = conv->method()->nameStr().substr(
+                strlen("PROJ-based operation method: "));
+            return util::nn_static_pointer_cast<BaseObject>(
+                PROJBasedOperation::create(PropertyMap(), projString, nullptr,
+                                           nullptr, {}));
+        }
+
+        return util::nn_static_pointer_cast<BaseObject>(conv);
     }
 
     if (ci_equal(name, WKTConstants::CONCATENATEDOPERATION)) {
diff --git a/test/unit/test_io.cpp b/test/unit/test_io.cpp
index 2b5eeffc..43b74fd8 100644
--- a/test/unit/test_io.cpp
+++ b/test/unit/test_io.cpp
@@ -2280,6 +2280,20 @@ TEST(wkt_parse, COORDINATEOPERATION) {
 
 // ---------------------------------------------------------------------------
 
+TEST(wkt_parse, conversion_proj_based) {
+
+    auto wkt = "CONVERSION[\"PROJ-based coordinate operation\",\n"
+               "    METHOD[\"PROJ-based operation method: +proj=merc\"]]";
+
+    auto obj = WKTParser().createFromWKT(wkt);
+    auto transf = nn_dynamic_pointer_cast<SingleOperation>(obj);
+    ASSERT_TRUE(transf != nullptr);
+    EXPECT_EQ(transf->exportToPROJString(PROJStringFormatter::create().get()),
+              "+proj=merc");
+}
+
+// ---------------------------------------------------------------------------
+
 TEST(wkt_parse, CONCATENATEDOPERATION) {
 
     auto transf_1 = Transformation::create(
diff --git a/test/unit/test_operation.cpp b/test/unit/test_operation.cpp
index d3f05548..bdadd830 100644
--- a/test/unit/test_operation.cpp
+++ b/test/unit/test_operation.cpp
@@ -4099,8 +4099,7 @@ TEST(operation, PROJ_based) {
 
     EXPECT_EQ(conv->exportToWKT(WKTFormatter::create().get()),
               "CONVERSION[\"PROJ-based coordinate operation\",\n"
-              "    METHOD[\"PROJ-based operation method\"],\n"
-              "    PARAMETER[\"PROJ string\",\"+proj=merc\"]]");
+              "    METHOD[\"PROJ-based operation method: +proj=merc\"]]");
 
     EXPECT_EQ(conv->inverse()->exportToPROJString(
                   PROJStringFormatter::create().get()),
@@ -4135,8 +4134,7 @@ TEST(operation, PROJ_based_empty) {
 
     EXPECT_EQ(conv->exportToWKT(WKTFormatter::create().get()),
               "CONVERSION[\"PROJ-based coordinate operation\",\n"
-              "    METHOD[\"PROJ-based operation method\"],\n"
-              "    PARAMETER[\"PROJ string\",\"\"]]");
+              "    METHOD[\"PROJ-based operation method: \"]]");
 
     EXPECT_THROW(
         conv->exportToWKT(