feat: addEdge now edge properties if their type is defined

Author: JesusTheHun

graph.spec-d.ts

@@ -1,5 +1,5 @@
 import { describe, expectTypeOf, it } from 'vitest';
-import { Graph } from "./src/index.js";
+import { Graph } from './src/index.js';
 
 /**
  * Those tests are not run. Their sole purpose is to test the types.
@@ -16,7 +16,7 @@ describe('graph types', () => {
     const g = new Graph<string, { type: 'foo' | 'bar' }>();
     const props = g.getEdgeProperties('a', 'b');
 
-    expectTypeOf(props).toEqualTypeOf<{ type: 'foo' | 'bar'}>();
+    expectTypeOf(props).toEqualTypeOf<{ type: 'foo' | 'bar' }>();
   });
 
   it('should only accept nodes of the given type', () => {
@@ -33,5 +33,24 @@ describe('graph types', () => {
 
     // @ts-expect-error Wrong properties type
     g.setEdgeProperties('a', 'b', { type: 'nope' });
-  })
-});
+  });
+
+  it('should require edge properties if LinkProps is defined', () => {
+    const g = new Graph<string, { type: string }>();
+
+    g.addEdge('a', 'b', undefined, { type: 'foo' });
+    g.addEdge('a', 'b', 1, { type: 'foo' });
+
+    // @ts-expect-error
+    g.addEdge('a', 'b', 1);
+  });
+
+  it('should not allow edge properties if LinkProps is never', () => {
+    const g = new Graph<string>();
+    g.addEdge('a', 'b');
+    g.addEdge('a', 'b', 1);
+
+    // @ts-expect-error Graph<string, never> does not allow edge properties
+    g.addEdge('a', 'b', 1, 'notAllowed');
+  });
+});

src/Graph.ts

@@ -2,7 +2,7 @@ import { invariant } from './invariant.js';
 import { EdgeWeight, SerializedInput } from './types.js';
 import { deserializeGraph } from './utils/deserializeGraph.js';
 
-export class Graph<Node = string, LinkProps = unknown> {
+export class Graph<Node = string, LinkProps = never> {
   /**
    * The adjacency list of the graph.
    */
@@ -135,7 +135,14 @@ export class Graph<Node = string, LinkProps = unknown> {
    * Adds an edge from the `source` node to `target` node.
    * This method will create the nodes if they were not already added.
    */
-  addEdge(source: Node, target: Node, weight?: EdgeWeight, linkProps?: LinkProps): this {
+  addEdge(
+    source: Node,
+    target: Node,
+    ...opts: [LinkProps] extends [never]
+      ? [weight?: EdgeWeight]
+      : [weight: EdgeWeight | undefined, linkProps: LinkProps]
+  ): this {
+    const [weight, linkProps] = opts;
     this.addNode(source);
     this.addNode(target);
     const adjacentNodes = this.adjacent(source);

src/utils/cloneGraph.ts

@@ -11,7 +11,7 @@ export function cloneGraph<Node, LinkProps>(
 
   for (let [source, targets] of graph.edges.entries()) {
     targets.forEach((target) => {
-      clone.addEdge(source, target);
+      clone.addEdge.apply(clone, [source, target] as never);
 
       const edgeWeight = graph.edgeWeights.get(source)?.get(target);
 

src/utils/deserializeGraph.ts

@@ -11,7 +11,7 @@ export function deserializeGraph<Node, LinkProps>(
   });
 
   data.links.forEach((link) => {
-    g.addEdge(link.source, link.target, link.weight);
+    g.addEdge.apply(g, [link.source, link.target, link.weight, link.props] as never);
   });
 
   return g;