CRS::_isEquivalentTo(): be tolerant to different order of PROJ step options (fixes #2886)

4 files changed, 91 insertions, 4 deletions

diff --git a/include/proj/io.hpp b/include/proj/io.hpp
index 47703442..235688cb 100644
--- a/include/proj/io.hpp
+++ b/include/proj/io.hpp
@@ -460,6 +460,8 @@ class PROJ_GCC_DLL PROJStringFormatter {
     PROJ_INTERNAL void setLegacyCRSToCRSContext(bool legacyContext);
     PROJ_INTERNAL bool getLegacyCRSToCRSContext() const;
 
+    PROJ_INTERNAL PROJStringFormatter &setNormalizeOutput();
+
     PROJ_INTERNAL const DatabaseContextPtr &databaseContext() const;
 
     PROJ_INTERNAL Convention convention() const;
diff --git a/src/iso19111/crs.cpp b/src/iso19111/crs.cpp
index 731bf7f9..b7d57767 100644
--- a/src/iso19111/crs.cpp
+++ b/src/iso19111/crs.cpp
@@ -1394,6 +1394,7 @@ bool SingleCRS::baseIsEquivalentTo(
         return false;
     }
 
+    // Check datum
     if (criterion == util::IComparable::Criterion::STRICT) {
         const auto &thisDatum = d->datum;
         const auto &otherDatum = otherSingleCRS->d->datum;
@@ -1428,10 +1429,36 @@ bool SingleCRS::baseIsEquivalentTo(
         }
     }
 
-    return d->coordinateSystem->_isEquivalentTo(
-               otherSingleCRS->d->coordinateSystem.get(), criterion,
-               dbContext) &&
-           getExtensionProj4() == otherSingleCRS->getExtensionProj4();
+    // Check coordinate system
+    if (!(d->coordinateSystem->_isEquivalentTo(
+            otherSingleCRS->d->coordinateSystem.get(), criterion, dbContext))) {
+        return false;
+    }
+
+    // Now compare PROJ4 extensions
+
+    const auto &thisProj4 = getExtensionProj4();
+    const auto &otherProj4 = otherSingleCRS->getExtensionProj4();
+
+    if (thisProj4.empty() && otherProj4.empty()) {
+        return true;
+    }
+
+    if (!(thisProj4.empty() ^ otherProj4.empty())) {
+        return true;
+    }
+
+    // Asks for a "normalized" output during toString(), aimed at comparing two
+    // strings for equivalence.
+    auto formatter1 = io::PROJStringFormatter::create();
+    formatter1->setNormalizeOutput();
+    formatter1->ingestPROJString(thisProj4);
+
+    auto formatter2 = io::PROJStringFormatter::create();
+    formatter2->setNormalizeOutput();
+    formatter2->ingestPROJString(otherProj4);
+
+    return formatter1->toString() == formatter2->toString();
 }
 
 // ---------------------------------------------------------------------------
diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 1f193559..24201ee1 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -7436,6 +7436,7 @@ struct PROJStringFormatter::Private {
     bool crsExport_ = false;
     bool legacyCRSToCRSContext_ = false;
     bool multiLine_ = false;
+    bool normalizeOutput_ = false;
     int indentWidth_ = 2;
     int indentLevel_ = 0;
     int maxLineLength_ = 80;
@@ -7535,6 +7536,17 @@ const std::string &PROJStringFormatter::toString() const {
     d->result_.clear();
 
     auto &steps = d->steps_;
+
+    if (d->normalizeOutput_) {
+        // Sort +key=value options of each step in lexicographic order.
+        for (auto &step : steps) {
+            std::sort(step.paramValues.begin(), step.paramValues.end(),
+                      [](const Step::KeyValue &a, const Step::KeyValue &b) {
+                          return a.key < b.key;
+                      });
+        }
+    }
+
     for (auto iter = steps.begin(); iter != steps.end();) {
         // Remove no-op helmert
         auto &step = *iter;
@@ -8689,6 +8701,19 @@ bool PROJStringFormatter::getLegacyCRSToCRSContext() const {
 
 // ---------------------------------------------------------------------------
 
+/** Asks for a "normalized" output during toString(), aimed at comparing two
+ * strings for equivalence.
+ *
+ * This consists for now in sorting the +key=value option in lexicographic
+ * order.
+ */
+PROJStringFormatter &PROJStringFormatter::setNormalizeOutput() {
+    d->normalizeOutput_ = true;
+    return *this;
+}
+
+// ---------------------------------------------------------------------------
+
 const DatabaseContextPtr &PROJStringFormatter::databaseContext() const {
     return d->dbContext_;
 }
diff --git a/test/unit/test_crs.cpp b/test/unit/test_crs.cpp
index a1838896..987ffe1b 100644
--- a/test/unit/test_crs.cpp
+++ b/test/unit/test_crs.cpp
@@ -6726,4 +6726,37 @@ TEST(crs, projected_is_equivalent_to_with_proj4_extension) {
     // Check equivalence of the CRS from PROJ.4 and WKT
     EXPECT_TRUE(crs1->isEquivalentTo(crs_from_wkt.get(),
                                      IComparable::Criterion::EQUIVALENT));
+
+    ASSERT_TRUE(crs_from_wkt != nullptr);
+    // Same as above but with different option order
+    const auto obj2 = PROJStringParser().createFromPROJString(
+        "+proj=omerc +lat_0=50 +no_rot +alpha=50.0 +a=6378144.0 +b=6356759.0 "
+        "+lon_0=8.0 +type=crs");
+    const auto crs2 = nn_dynamic_pointer_cast<ProjectedCRS>(obj2);
+    ASSERT_TRUE(crs2 != nullptr);
+
+    // Check equivalence of the 2 PROJ.4 based CRS
+    EXPECT_TRUE(
+        crs1->isEquivalentTo(crs2.get(), IComparable::Criterion::EQUIVALENT));
+
+    // Without +no_rot --> no PROJ.4 extension
+    const auto objNoRot = PROJStringParser().createFromPROJString(
+        "+proj=omerc +lat_0=50 +alpha=50.0 +a=6378144.0 +b=6356759.0 "
+        "+lon_0=8.0 +type=crs");
+    const auto crsNoRot = nn_dynamic_pointer_cast<ProjectedCRS>(objNoRot);
+    ASSERT_TRUE(crsNoRot != nullptr);
+    EXPECT_FALSE(crs1->isEquivalentTo(crsNoRot.get(),
+                                      IComparable::Criterion::EQUIVALENT));
+    EXPECT_FALSE(crsNoRot->isEquivalentTo(crs1.get(),
+                                          IComparable::Criterion::EQUIVALENT));
+
+    // Change alpha value
+    const auto objDifferent = PROJStringParser().createFromPROJString(
+        "+proj=omerc +lat_0=50 +alpha=49.0 +no_rot +a=6378144.0 +b=6356759.0 "
+        "+lon_0=8.0 +type=crs");
+    const auto crsDifferent =
+        nn_dynamic_pointer_cast<ProjectedCRS>(objDifferent);
+    ASSERT_TRUE(crsDifferent != nullptr);
+    EXPECT_FALSE(crs1->isEquivalentTo(crsDifferent.get(),
+                                      IComparable::Criterion::EQUIVALENT));
 }