ISO19111: remove PROJ.5 specific format for CRS (refs #1214)

As discussed in https://github.com/OSGeo/proj.4/issues/1214#issuecomment-452084720,
the introduction of a new PROJ.5 format to export CRS using pipeline/unitconvert/axisswap
as an attempt of improving the PROJ.4 format used by GDAL and other products is
likely a dead-end since it is still lossy in many aspects and can cause confusion
with coodinate operations.

Consequently the PROJ_5 convention will be identical to PROJ_4 for CRS export.

Note: on the import side, I've kept the code that could parse unitconvert and
axisswap when building a CRS definition from a pipeline. It is there as a hidden
feature as it was kind of a tear to remove that code in case it might still be
useful...

1 files changed, 17 insertions, 4 deletions

diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index cfccd70f..13a8f236 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -4596,15 +4596,19 @@ IPROJStringExportable::~IPROJStringExportable() = default;
 
 std::string IPROJStringExportable::exportToPROJString(
     PROJStringFormatter *formatter) const {
+    const bool bIsCRS = dynamic_cast<const crs::CRS *>(this) != nullptr;
+    if (bIsCRS) {
+        formatter->setCRSExport(true);
+    }
     _exportToPROJString(formatter);
-    if (formatter->getAddNoDefs() &&
-        formatter->convention() ==
-            io::PROJStringFormatter::Convention::PROJ_4 &&
-        dynamic_cast<const crs::CRS *>(this)) {
+    if (formatter->getAddNoDefs() && bIsCRS) {
         if (!formatter->hasParam("no_defs")) {
             formatter->addParam("no_defs");
         }
     }
+    if (bIsCRS) {
+        formatter->setCRSExport(false);
+    }
     return formatter->toString();
 }
 //! @endcond
@@ -4673,6 +4677,7 @@ struct PROJStringFormatter::Private {
     bool useETMercForTMercSet_ = false;
     bool addNoDefs_ = true;
     bool coordOperationOptimizations_ = false;
+    bool crsExport_ = false;
 
     std::string result_{};
 
@@ -5311,6 +5316,14 @@ void PROJStringFormatter::ingestPROJString(
 
 // ---------------------------------------------------------------------------
 
+void PROJStringFormatter::setCRSExport(bool b) { d->crsExport_ = b; }
+
+// ---------------------------------------------------------------------------
+
+bool PROJStringFormatter::getCRSExport() const { return d->crsExport_; }
+
+// ---------------------------------------------------------------------------
+
 void PROJStringFormatter::startInversion() {
     PROJStringFormatter::Private::InversionStackElt elt;
     elt.startIter = d->steps_.end();