Fix for bug affecting -polygons and -mosaic

src/commands/mapshaper-mosaic.mjs

@@ -5,6 +5,7 @@ import cmd from '../mapshaper-cmd';
 import { stop } from '../utils/mapshaper-logging';
 import { DataTable } from '../datatable/mapshaper-data-table';
 import { MosaicIndex } from '../polygons/mapshaper-mosaic-index';
+import { getArcPresenceTest } from '../paths/mapshaper-path-utils';
 
 cmd.mosaic = function(layers, dataset, opts) {
   var lyr = layers[0];
@@ -13,6 +14,8 @@ cmd.mosaic = function(layers, dataset, opts) {
   }
   requirePolygonLayer(lyr);
   var nodes = addIntersectionCuts(dataset, opts);
+  // ignore arcs that don't belong to this layer
+  nodes.setArcFilter(getArcPresenceTest(lyr.shapes, nodes.arcs));
   var mosaicIndex = new MosaicIndex(lyr, nodes, {flat: false});
   var mosaicShapes = mosaicIndex.mosaic;
   var records2;

src/commands/mapshaper-polygons.mjs

@@ -7,6 +7,7 @@ import { requirePolylineLayer } from '../dataset/mapshaper-layer-utils';
 import cmd from '../mapshaper-cmd';
 import { message, stop } from '../utils/mapshaper-logging';
 import geom from '../geom/mapshaper-geom';
+import { getArcPresenceTest } from '../paths/mapshaper-path-utils';
 
 cmd.polygons = function(layers, dataset, opts) {
   layers.forEach(requirePolylineLayer);
@@ -46,6 +47,8 @@ function createPolygonLayerFromRings(lyr, dataset) {
 
 function createPolygonLayer(lyr, dataset, opts) {
   var nodes = closeUndershoots(lyr, dataset, opts);
+  // ignore arcs that don't belong to this layer
+  nodes.setArcFilter(getArcPresenceTest(lyr.shapes, nodes.arcs));
   var data = buildPolygonMosaic(nodes);
   return {
     geometry_type: 'polygon',

src/topology/mapshaper-nodes.mjs

@@ -16,11 +16,16 @@ export function NodeCollection(arcs, filter) {
       nn = arcData.nn,
       xx = arcData.xx,
       yy = arcData.yy,
-      nodeData;
+      nodeData,
+      globalFilter;
 
   // Accessor function for arcs
   Object.defineProperty(this, 'arcs', {value: arcs});
 
+  this.setArcFilter = function(f) {
+    globalFilter = f;
+  };
+
   this.toArray = function() {
     var chains = getNodeChains(),
         flags = new Uint8Array(chains.length),
@@ -99,17 +104,19 @@ export function NodeCollection(arcs, filter) {
   //    Returned ids lead into the node (as opposed to outwards from it)
   // An optional filter function receives the directed id (positive or negative)
   //    of each connected arc and excludes arcs for which the filter returns false.
-  //    The filter is also applied to the initial arc; if false, no arcs are returned.
+  //    // removed: The filter is also applied to the initial arc; if false, no arcs are returned.
   //
-  this.getConnectedArcs = function(arcId, filter) {
+  this.getConnectedArcs = function(arcId, localFilter) {
     var ids = [];
-    var filtered = !!filter;
     var nextId = nextConnectedArc(arcId);
-    if (filtered && !filter(arcId)) {
-      // return ids;
+    // kludge: return empty result if arc fails global test
+    // ... applying the local filter causes tests to fail
+    if (globalFilter && !globalFilter(arcId)) {
+      return [];
     }
     while (nextId != arcId) {
-      if (!filtered || filter(nextId)) {
+      // if (!filtered || filter && filter(nextId) ) {
+      if ((!localFilter || localFilter(nextId)) && (!globalFilter || globalFilter(nextId))) {
         ids.push(nextId);
       }
       nextId = nextConnectedArc(nextId);