Add new function to allow ID modification

docs/CONFIGURATION.md

@@ -128,6 +128,8 @@ Note that this is not compatible with the `combine_xxx` settings to reduce tiles
 
 If you need to include OSM object types as well, you can use the `OsmType()` function in your `process.lua` script.
 
+It is possible to override the original OSM ID using the function `ModifyId(newId)`.
+
 ## Lua processing reference
 
 Your Lua file can supply these functions for tilemaker to call:
@@ -163,6 +165,7 @@ To do that, you use these methods:
 * `Attribute(key,value,minzoom)`: add an attribute to the most recently written layer. Argument `minzoom` is optional, use it if you do not want to write the attribute on lower zoom levels.
 * `AttributeNumeric(key,value,minzoom)`, `AttributeInteger(key,value,minzoom)`, `AttributeBoolean(key,value,minzoom)`: for numeric (floating-point), integer and boolean columns.
 * `Id()`: get the OSM ID of the current object.
+* `ModifyId(newId)`: replace the ID of the current object with newId.
 * `OsmType()`: get the OSM type of the current object.
 * `IsClosed()`: returns true if the current object is a closed area.
 * `IsMultiPolygon()`: returns true if the current object is a multipolygon.

include/osm_lua_processing.h

@@ -197,6 +197,7 @@ class OsmLuaProcessing {
 	void LayerAsCentroid(const std::string &layerName, kaguya::VariadicArgType nodeSources);
 
 	// Set attributes in a vector tile's Attributes table
+	void ModifyId(const int newId);
 	void Attribute(const std::string &key, const protozero::data_view val, const char minzoom);
 	void AttributeNumeric(const std::string &key, const double val, const char minzoom);
 	void AttributeBoolean(const std::string &key, const bool val, const char minzoom);

src/osm_lua_processing.cpp

@@ -188,6 +188,7 @@ bool rawIsMultiPolygon() { return osmLuaProcessing->IsMultiPolygon(); }
 double rawArea() { return osmLuaProcessing->Area(); }
 double rawLength() { return osmLuaProcessing->Length(); }
 kaguya::optional<std::vector<double>> rawCentroid(kaguya::VariadicArgType algorithm) { return osmLuaProcessing->Centroid(algorithm); }
+void rawModifyId(const int newId) { return osmLuaProcessing->ModifyId(newId); }
 void rawLayer(const std::string& layerName, bool area) { return osmLuaProcessing->Layer(layerName, area); }
 void rawLayerAsCentroid(const std::string &layerName, kaguya::VariadicArgType nodeSources) { return osmLuaProcessing->LayerAsCentroid(layerName, nodeSources); }
 void rawMinZoom(const double z) { return osmLuaProcessing->MinZoom(z); }
@@ -267,6 +268,7 @@ OsmLuaProcessing::OsmLuaProcessing(
 	luaState["Centroid"] = &rawCentroid;
 	luaState["Layer"] = &rawLayer;
 	luaState["LayerAsCentroid"] = &rawLayerAsCentroid;
+	luaState["ModifyId"] = &rawModifyId;
 	luaState["Attribute"] = kaguya::overload(
 			[](const std::string &key, const protozero::data_view val) { osmLuaProcessing->Attribute(key, val, 0); },
 			[](const std::string &key, const protozero::data_view val, const char minzoom) { osmLuaProcessing->Attribute(key, val, minzoom); }
@@ -922,6 +924,11 @@ void OsmLuaProcessing::removeAttributeIfNeeded(const string& key) {
 	outputKeys.push_back(key);
 }
 
+// Force a new ID
+void OsmLuaProcessing::ModifyId(const int newId) {
+    originalOsmID = static_cast<int64_t>(newId);
+}
+
 // Set attributes in a vector tile's Attributes table
 void OsmLuaProcessing::Attribute(const string &key, const protozero::data_view val, const char minzoom) {
 	if (outputs.size()==0) { ProcessingError("Can't add Attribute if no Layer set"); return; }