From f28d36cee9ec099ae5fea3873988204a7ebda520 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Wed, 6 Oct 2021 19:26:09 +0200
Subject: CRS::_isEquivalentTo(): be tolerant to different order of PROJ step
 options (fixes #2886)

---
 src/iso19111/io.cpp | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'src/iso19111/io.cpp')

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_;
 }
-- 
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