Merge pull request #554 from peterstace/fix_bug_in_envelope_transform_xy

Fix bug in Envelope's TransformXY method

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
     - name: cmpgeos
       run: make cmpgeos
     - name: Convert coverage to lcov
-      uses: jandelgado/gcov2lcov-action@v1.0.2
+      uses: jandelgado/gcov2lcov-action@v1.0.9
       with:
         infile: coverage.out
         outfile: coverage.lcov

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## v0.45.1
+
+2023-09-29
+
+- Fixes a bug in `Envelope`'s `TransformXY` method, where (depending on the
+  transform) invariants in the newly created `Envelope` value would be
+  violated.
+
 ## v0.45.0
 
 2023-09-29

geom/type_envelope.go

@@ -279,7 +279,12 @@ func (e Envelope) TransformXY(fn func(XY) XY) Envelope {
 	if !ok {
 		return Envelope{}
 	}
-	return newUncheckedEnvelope(fn(min), fn(max))
+	u := fn(min)
+	v := fn(max)
+	return newUncheckedEnvelope(
+		XY{fastMin(u.X, v.X), fastMin(u.Y, v.Y)},
+		XY{fastMax(u.X, v.X), fastMax(u.Y, v.Y)},
+	)
 }
 
 // AsBox converts this Envelope to an rtree.Box.

geom/type_envelope_test.go

@@ -572,6 +572,16 @@ func TestEnvelopeTransformXY(t *testing.T) {
 	}
 }
 
+func TestEnvelopeTransformBugFix(t *testing.T) {
+	// Reproduces a bug where a transform that alters which coordinates are min
+	// and max causes a malformed envelope.
+	env := twoPtEnv(1, 2, 3, 4)
+	got := env.TransformXY(func(in XY) XY {
+		return XY{-in.X, -in.Y}
+	})
+	expectEnvEq(t, got, twoPtEnv(-3, -4, -1, -2))
+}
+
 func BenchmarkEnvelopeTransformXY(b *testing.B) {
 	input := twoPtEnv(1, 2, 3, 4)
 	b.ResetTimer()

geom/util_test.go

@@ -209,11 +209,7 @@ func expectEnvEq(t testing.TB, got, want Envelope) {
 		ExactEquals(got.Max().AsGeometry(), want.Max().AsGeometry()) {
 		return
 	}
-	t.Errorf(
-		"\ngot:  %v\nwant: %v\n",
-		got.AsGeometry().AsText(),
-		want.AsGeometry().AsText(),
-	)
+	t.Errorf("\ngot:  %v\nwant: %v", got, want)
 }
 
 func expectSequenceEq(t testing.TB, got, want Sequence) {

go.mod

@@ -2,4 +2,6 @@ module github.com/peterstace/simplefeatures
 
 go 1.17
 
+retract v0.45.0 // Due to bug: https://github.com/peterstace/simplefeatures/pull/554
+
 require github.com/lib/pq v1.1.1