PROJStringFormatter: make startInversion/stopInversion properly deal with omit_fwd/omit_inv

2 files changed, 30 insertions, 0 deletions

diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index b57d1de5..c704e1c1 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -7156,6 +7156,12 @@ void PROJStringFormatter::stopInversion() {
     // the current end of steps
     for (auto iter = startIter; iter != d->steps_.end(); ++iter) {
         iter->inverted = !iter->inverted;
+        for (auto &paramValue : iter->paramValues) {
+            if (paramValue.key == "omit_fwd")
+                paramValue.key = "omit_inv";
+            else if (paramValue.key == "omit_inv")
+                paramValue.key = "omit_fwd";
+        }
     }
     // And reverse the order of steps in that range as well.
     std::reverse(startIter, d->steps_.end());
diff --git a/test/unit/test_io.cpp b/test/unit/test_io.cpp
index 9fefaf9b..15ab8706 100644
--- a/test/unit/test_io.cpp
+++ b/test/unit/test_io.cpp
@@ -6867,6 +6867,30 @@ TEST(io, projstringformatter_optim_hgridshift_vgridshift_hgridshift_inv) {
                   "+step +proj=pop +v_1 +v_2");
     }
 
+    // Test omit_fwd->omit_inv when inversing the pipeline
+    {
+        auto fmt = PROJStringFormatter::create();
+        fmt->startInversion();
+        fmt->ingestPROJString("+proj=hgridshift +grids=foo +omit_fwd");
+        fmt->stopInversion();
+
+        EXPECT_EQ(fmt->toString(),
+                  "+proj=pipeline "
+                  "+step +inv +proj=hgridshift +grids=foo +omit_inv");
+    }
+
+    // Test omit_inv->omit_fwd when inversing the pipeline
+    {
+        auto fmt = PROJStringFormatter::create();
+        fmt->startInversion();
+        fmt->ingestPROJString("+proj=hgridshift +grids=foo +omit_inv");
+        fmt->stopInversion();
+
+        EXPECT_EQ(fmt->toString(),
+                  "+proj=pipeline "
+                  "+step +inv +proj=hgridshift +grids=foo +omit_fwd");
+    }
+
     // Variant with first hgridshift inverted, and second forward
     {
         auto fmt = PROJStringFormatter::create();