Log a warning if MBTiles is missing format metadata [#167] (#168)

pmtiles/convert.go

@@ -251,6 +251,11 @@ func convertMbtiles(logger *log.Logger, input string, output string, deduplicate
 			mbtilesMetadata = append(mbtilesMetadata, stmt.ColumnText(1))
 		}
 	}
+
+	if !mbtilesMetadataHasFormat(mbtilesMetadata) {
+		logger.Println("WARNING: MBTiles metadata is missing format information. Update this with: INSERT INTO metadata (name, value) VALUES ('format', 'png')")
+	}
+
 	header, jsonMetadata, err := mbtilesToHeaderJSON(mbtilesMetadata)
 
 	if err != nil {
@@ -558,6 +563,15 @@ func parseCenter(center string) (int32, int32, uint8, error) {
 	return int32(centerLon * E7), int32(centerLat * E7), uint8(centerZoom), nil
 }
 
+func mbtilesMetadataHasFormat(mbtilesMetadata []string) bool {
+	for i := 0; i < len(mbtilesMetadata); i += 2 {
+		if mbtilesMetadata[i] == "format" {
+			return true
+		}
+	}
+	return false
+}
+
 func mbtilesToHeaderJSON(mbtilesMetadata []string) (HeaderV3, map[string]interface{}, error) {
 	header := HeaderV3{}
 	jsonResult := make(map[string]interface{})

pmtiles/convert_test.go

@@ -176,6 +176,11 @@ func TestMbtiles(t *testing.T) {
 	assert.True(t, ok)
 }
 
+func TestMbtilesMissingFormat(t *testing.T) {
+	assert.False(t, mbtilesMetadataHasFormat([]string{"version", "1.0"}))
+	assert.True(t, mbtilesMetadataHasFormat([]string{"format", "png"}))
+}
+
 func TestMbtilesMissingBoundsCenter(t *testing.T) {
 	header, _, err := mbtilesToHeaderJSON([]string{
 		"name", "test_name",