Add methods to check geometry type and convert simultaneously

CHANGELOG.md

@@ -1,5 +1,24 @@
 # Changelog
 
+## Unreleased
+
+- **Breaking change**: Renames the `AsFoo` methods of the Geometry type to
+  `MustAsFoo` (where `Foo` is a concrete geometry type such as `Point`). This
+  follows the go convention that methods and functions prefixed with Must may
+  panic if preconditions are not met. Note that there's no change in behaviour
+  here, it's simply a rename (these methods previously panicked). Users may
+  resolve this breaking change by just updating the names of any `AsFoo`
+  methods they are calling to `MustAsFoo`.
+
+- **Breaking change**: Adds new methods named `AsFoo` to the Geometry type.
+  These methods have the signature `AsFoo() (Foo, bool)`. The boolean return
+  value indicates if the conversion was successful or not. These methods are
+  useful because they allow concrete geometries to be extracted from a Geometry
+  value, with the concrete type for the `Is` and `As` call only specified once.
+  Users now just have to call `AsFoo`, and can then check the flag. This helps
+  to eliminate the class of bugs there the type specified with `IsFoo`
+  erroneously differs from the type specified by `AsFoo`.
+
 ## v0.33.1
 
 __Special thanks to Albert Teoh for contributing to this release.__

geom/accessor_test.go

@@ -7,18 +7,18 @@ import (
 )
 
 func TestPointAccessorNonEmpty(t *testing.T) {
-	xy, ok := geomFromWKT(t, "POINT(1 2)").AsPoint().XY()
+	xy, ok := geomFromWKT(t, "POINT(1 2)").MustAsPoint().XY()
 	expectBoolEq(t, ok, true)
 	expectXYEq(t, xy, XY{1, 2})
 }
 
 func TestPointAccessorEmpty(t *testing.T) {
-	_, ok := geomFromWKT(t, "POINT EMPTY").AsPoint().XY()
+	_, ok := geomFromWKT(t, "POINT EMPTY").MustAsPoint().XY()
 	expectBoolEq(t, ok, false)
 }
 
 func TestLineStringAccessor(t *testing.T) {
-	ls := geomFromWKT(t, "LINESTRING(1 2,3 4,5 6)").AsLineString()
+	ls := geomFromWKT(t, "LINESTRING(1 2,3 4,5 6)").MustAsLineString()
 	seq := ls.Coordinates()
 	pt12 := xyCoords(1, 2)
 	pt34 := xyCoords(3, 4)
@@ -47,7 +47,7 @@ func TestLineStringAccessor(t *testing.T) {
 }
 
 func TestLineStringEmptyAccessor(t *testing.T) {
-	ls := geomFromWKT(t, "LINESTRING EMPTY").AsLineString()
+	ls := geomFromWKT(t, "LINESTRING EMPTY").MustAsLineString()
 	seq := ls.Coordinates()
 	emptyPoint := geomFromWKT(t, "POINT EMPTY")
 
@@ -68,7 +68,7 @@ func TestLineStringEmptyAccessor(t *testing.T) {
 }
 
 func TestLineStringAccessorWithDuplicates(t *testing.T) {
-	ls := geomFromWKT(t, "LINESTRING(1 2,3 4,3 4,5 6)").AsLineString()
+	ls := geomFromWKT(t, "LINESTRING(1 2,3 4,3 4,5 6)").MustAsLineString()
 	seq := ls.Coordinates()
 	pt12 := xyCoords(1, 2)
 	pt34 := xyCoords(3, 4)
@@ -88,7 +88,7 @@ func TestLineStringAccessorWithDuplicates(t *testing.T) {
 }
 
 func TestLineStringAccessorWithMoreDuplicates(t *testing.T) {
-	ls := geomFromWKT(t, "LINESTRING(1 2,1 2,3 4,3 4,3 4,5 6,5 6)").AsLineString()
+	ls := geomFromWKT(t, "LINESTRING(1 2,1 2,3 4,3 4,3 4,5 6,5 6)").MustAsLineString()
 	seq := ls.Coordinates()
 	pt12 := xyCoords(1, 2)
 	pt34 := xyCoords(3, 4)
@@ -111,7 +111,7 @@ func TestLineStringAccessorWithMoreDuplicates(t *testing.T) {
 }
 
 func TestPolygonAccessor(t *testing.T) {
-	poly := geomFromWKT(t, "POLYGON((0 0,5 0,5 3,0 3,0 0),(1 1,2 1,2 2,1 2,1 1),(3 1,4 1,4 2,3 2,3 1))").AsPolygon()
+	poly := geomFromWKT(t, "POLYGON((0 0,5 0,5 3,0 3,0 0),(1 1,2 1,2 2,1 2,1 1),(3 1,4 1,4 2,3 2,3 1))").MustAsPolygon()
 	outer := geomFromWKT(t, "LINESTRING(0 0,5 0,5 3,0 3,0 0)")
 	inner0 := geomFromWKT(t, "LINESTRING(1 1,2 1,2 2,1 2,1 1)")
 	inner1 := geomFromWKT(t, "LINESTRING(3 1,4 1,4 2,3 2,3 1)")
@@ -125,7 +125,7 @@ func TestPolygonAccessor(t *testing.T) {
 }
 
 func TestMultiPointAccessor(t *testing.T) {
-	mp := geomFromWKT(t, "MULTIPOINT((4 5),(2 3),(8 7))").AsMultiPoint()
+	mp := geomFromWKT(t, "MULTIPOINT((4 5),(2 3),(8 7))").MustAsMultiPoint()
 	pt0 := geomFromWKT(t, "POINT(4 5)")
 	pt1 := geomFromWKT(t, "POINT(2 3)")
 	pt2 := geomFromWKT(t, "POINT(8 7)")
@@ -139,7 +139,7 @@ func TestMultiPointAccessor(t *testing.T) {
 }
 
 func TestMultiLineStringAccessors(t *testing.T) {
-	mls := geomFromWKT(t, "MULTILINESTRING((1 2,3 4,5 6),(7 8,9 10,11 12))").AsMultiLineString()
+	mls := geomFromWKT(t, "MULTILINESTRING((1 2,3 4,5 6),(7 8,9 10,11 12))").MustAsMultiLineString()
 	ls0 := geomFromWKT(t, "LINESTRING(1 2,3 4,5 6)")
 	ls1 := geomFromWKT(t, "LINESTRING(7 8,9 10,11 12)")
 
@@ -151,7 +151,7 @@ func TestMultiLineStringAccessors(t *testing.T) {
 }
 
 func TestMultiPolygonAccessors(t *testing.T) {
-	polys := geomFromWKT(t, "MULTIPOLYGON(((0 0,0 1,1 0,0 0)),((2 0,2 1,3 0,2 0)))").AsMultiPolygon()
+	polys := geomFromWKT(t, "MULTIPOLYGON(((0 0,0 1,1 0,0 0)),((2 0,2 1,3 0,2 0)))").MustAsMultiPolygon()
 	poly0 := geomFromWKT(t, "POLYGON((0 0,0 1,1 0,0 0))")
 	poly1 := geomFromWKT(t, "POLYGON((2 0,2 1,3 0,2 0))")
 
@@ -163,7 +163,7 @@ func TestMultiPolygonAccessors(t *testing.T) {
 }
 
 func TestGeometryCollectionAccessors(t *testing.T) {
-	geoms := geomFromWKT(t, "GEOMETRYCOLLECTION(POLYGON((0 0,0 1,1 0,0 0)),POLYGON((2 0,2 1,3 0,2 0)))").AsGeometryCollection()
+	geoms := geomFromWKT(t, "GEOMETRYCOLLECTION(POLYGON((0 0,0 1,1 0,0 0)),POLYGON((2 0,2 1,3 0,2 0)))").MustAsGeometryCollection()
 	geom0 := geomFromWKT(t, "POLYGON((0 0,0 1,1 0,0 0))")
 	geom1 := geomFromWKT(t, "POLYGON((2 0,2 1,3 0,2 0))")
 

geom/alg_convex_hull.go

@@ -80,7 +80,7 @@ func convexHullPointSet(g Geometry) []XY {
 	switch {
 	case g.IsGeometryCollection():
 		var points []XY
-		c := g.AsGeometryCollection()
+		c := g.MustAsGeometryCollection()
 		n := c.NumGeometries()
 		for i := 0; i < n; i++ {
 			points = append(
@@ -90,24 +90,24 @@ func convexHullPointSet(g Geometry) []XY {
 		}
 		return points
 	case g.IsPoint():
-		xy, ok := g.AsPoint().XY()
+		xy, ok := g.MustAsPoint().XY()
 		if !ok {
 			return nil
 		}
 		return []XY{xy}
 	case g.IsLineString():
-		cs := g.AsLineString().Coordinates()
+		cs := g.MustAsLineString().Coordinates()
 		n := cs.Length()
 		points := make([]XY, n)
 		for i := 0; i < n; i++ {
 			points[i] = cs.GetXY(i)
 		}
 		return points
 	case g.IsPolygon():
-		p := g.AsPolygon()
+		p := g.MustAsPolygon()
 		return convexHullPointSet(p.ExteriorRing().AsGeometry())
 	case g.IsMultiPoint():
-		m := g.AsMultiPoint()
+		m := g.MustAsMultiPoint()
 		n := m.NumPoints()
 		points := make([]XY, 0, n)
 		for i := 0; i < n; i++ {
@@ -118,7 +118,7 @@ func convexHullPointSet(g Geometry) []XY {
 		}
 		return points
 	case g.IsMultiLineString():
-		m := g.AsMultiLineString()
+		m := g.MustAsMultiLineString()
 		var points []XY
 		n := m.NumLineStrings()
 		for i := 0; i < n; i++ {
@@ -130,7 +130,7 @@ func convexHullPointSet(g Geometry) []XY {
 		}
 		return points
 	case g.IsMultiPolygon():
-		m := g.AsMultiPolygon()
+		m := g.MustAsMultiPolygon()
 		var points []XY
 		numPolys := m.NumPolygons()
 		for i := 0; i < numPolys; i++ {

geom/alg_distance.go

@@ -103,21 +103,21 @@ func Distance(g1, g2 Geometry) (float64, bool) {
 func extractXYsAndLines(g Geometry) ([]XY, []line) {
 	switch g.Type() {
 	case TypePoint:
-		return g.AsPoint().asXYs(), nil
+		return g.MustAsPoint().asXYs(), nil
 	case TypeLineString:
-		return nil, g.AsLineString().asLines()
+		return nil, g.MustAsLineString().asLines()
 	case TypePolygon:
-		return nil, g.AsPolygon().Boundary().asLines()
+		return nil, g.MustAsPolygon().Boundary().asLines()
 	case TypeMultiPoint:
-		return g.AsMultiPoint().asXYs(), nil
+		return g.MustAsMultiPoint().asXYs(), nil
 	case TypeMultiLineString:
-		return nil, g.AsMultiLineString().asLines()
+		return nil, g.MustAsMultiLineString().asLines()
 	case TypeMultiPolygon:
-		return nil, g.AsMultiPolygon().Boundary().asLines()
+		return nil, g.MustAsMultiPolygon().Boundary().asLines()
 	case TypeGeometryCollection:
 		var allXYs []XY
 		var allLines []line
-		g.AsGeometryCollection().walk(func(child Geometry) {
+		g.MustAsGeometryCollection().walk(func(child Geometry) {
 			xys, lns := extractXYsAndLines(child)
 			allXYs = append(allXYs, xys...)
 			allLines = append(allLines, lns...)

geom/alg_dump_test.go

@@ -119,7 +119,7 @@ func TestDumpMultiPoint(t *testing.T) {
 	} {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			want := geomsFromWKTs(t, tc.wantOutputWKT)
-			got := upcastPoints(geomFromWKT(t, tc.inputWKT).AsMultiPoint().Dump())
+			got := upcastPoints(geomFromWKT(t, tc.inputWKT).MustAsMultiPoint().Dump())
 			expectGeomsEq(t, got, want)
 		})
 	}
@@ -153,7 +153,7 @@ func TestDumpMultiLineString(t *testing.T) {
 	} {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			want := geomsFromWKTs(t, tc.wantOutputWKT)
-			got := upcastLineStrings(geomFromWKT(t, tc.inputWKT).AsMultiLineString().Dump())
+			got := upcastLineStrings(geomFromWKT(t, tc.inputWKT).MustAsMultiLineString().Dump())
 			expectGeomsEq(t, got, want)
 		})
 	}
@@ -179,7 +179,7 @@ func TestDumpMultiPolygon(t *testing.T) {
 	} {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			want := geomsFromWKTs(t, tc.wantOutputWKT)
-			got := upcastPolygons(geomFromWKT(t, tc.inputWKT).AsMultiPolygon().Dump())
+			got := upcastPolygons(geomFromWKT(t, tc.inputWKT).MustAsMultiPolygon().Dump())
 			expectGeomsEq(t, got, want)
 		})
 	}
@@ -213,7 +213,7 @@ func TestDumpGeometryCollection(t *testing.T) {
 	} {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			want := geomsFromWKTs(t, tc.wantOutputWKT)
-			got := geomFromWKT(t, tc.inputWKT).AsGeometryCollection().Dump()
+			got := geomFromWKT(t, tc.inputWKT).MustAsGeometryCollection().Dump()
 			expectGeomsEq(t, got, want)
 		})
 	}

geom/alg_exact_equals.go

@@ -83,19 +83,19 @@ func (c exactEqualsComparator) geometriesEq(g1, g2 Geometry) bool {
 	}
 	switch typ := g1.Type(); typ {
 	case TypePoint:
-		return c.pointsEq(g1.AsPoint(), g2.AsPoint())
+		return c.pointsEq(g1.MustAsPoint(), g2.MustAsPoint())
 	case TypeMultiPoint:
-		return c.multiPointsEq(g1.AsMultiPoint(), g2.AsMultiPoint())
+		return c.multiPointsEq(g1.MustAsMultiPoint(), g2.MustAsMultiPoint())
 	case TypeLineString:
-		return c.lineStringsEq(g1.AsLineString(), g2.AsLineString())
+		return c.lineStringsEq(g1.MustAsLineString(), g2.MustAsLineString())
 	case TypeMultiLineString:
-		return c.multiLineStringsEq(g1.AsMultiLineString(), g2.AsMultiLineString())
+		return c.multiLineStringsEq(g1.MustAsMultiLineString(), g2.MustAsMultiLineString())
 	case TypePolygon:
-		return c.polygonsEq(g1.AsPolygon(), g2.AsPolygon())
+		return c.polygonsEq(g1.MustAsPolygon(), g2.MustAsPolygon())
 	case TypeMultiPolygon:
-		return c.multiPolygonsEq(g1.AsMultiPolygon(), g2.AsMultiPolygon())
+		return c.multiPolygonsEq(g1.MustAsMultiPolygon(), g2.MustAsMultiPolygon())
 	case TypeGeometryCollection:
-		return c.geometryCollectionsEq(g1.AsGeometryCollection(), g2.AsGeometryCollection())
+		return c.geometryCollectionsEq(g1.MustAsGeometryCollection(), g2.MustAsGeometryCollection())
 	default:
 		panic("unknown geometry type: " + typ.String())
 	}