VertexAttributes func caching last values

[davemcphee]

Calling AddVertex() with VertexAttribute() functions will sometimes cache the last value on all vertices. I've been unable to reproduce this via your unit tests, but this shows the issue:

package main

import (
	"bytes"
	"fmt"
	"github.com/dominikbraun/graph"
	"github.com/dominikbraun/graph/draw"
)

var (
	hashingFunction = func(d someVertex) string { return d.Name }
	redVertexAttr   = graph.VertexAttributes(map[string]string{"color": "red"})
	dotBuffer       bytes.Buffer
)

type someVertex struct {
	Name string
}

func main() {

	g := graph.New(hashingFunction, graph.Directed())

	for i, name := range []string{"foo", "bar", "baz"} {
		vertex := someVertex{Name: name}

		label := fmt.Sprintf("%s [%d]", name, i)
		fmt.Printf("adding someVertex{Name: %s} with label %s\n", name, label)

		_ = g.AddVertex(
			vertex,
			redVertexAttr,
			graph.VertexAttribute("label", label),
		)

		// read the new vertex back
		newVertex, newVertexProps, _ := g.VertexWithProperties(vertex.Name)
		fmt.Printf("new Vertex %s: %#v\nProps: %#v\n\n", vertex.Name, newVertex, newVertexProps)
	}

        fmt.Println("Here be issues:")

	fooVertex, fooProps, _ := g.VertexWithProperties("bar")
	fmt.Printf("Vertex bar: %#v\n", fooVertex)
	fmt.Printf("Vertex bar properties: %#v\n", fooProps)

	if dotErr := draw.DOT(g, &dotBuffer); dotErr != nil {
		panic(dotErr)
	}

	fmt.Printf("\n%s", dotBuffer.String())
}

---

adding someVertex{Name: foo} with label foo [0]
new Vertex foo: main.someVertex{Name:"foo"}
Props: graph.VertexProperties{Attributes:map[string]string{"color":"red", "label":"foo [0]"}, Weight:0}

adding someVertex{Name: bar} with label bar [1]
new Vertex bar: main.someVertex{Name:"bar"}
Props: graph.VertexProperties{Attributes:map[string]string{"color":"red", "label":"bar [1]"}, Weight:0}

adding someVertex{Name: baz} with label baz [2]
new Vertex baz: main.someVertex{Name:"baz"}
Props: graph.VertexProperties{Attributes:map[string]string{"color":"red", "label":"baz [2]"}, Weight:0}

Here be issues:
Vertex bar: main.someVertex{Name:"bar"}
Vertex bar properties: graph.VertexProperties{Attributes:map[string]string{"color":"red", "label":"baz [2]"}, Weight:0}

strict digraph {


        "baz" [ color="red", label="baz [2]",  weight=0 ];

        "foo" [ color="red", label="baz [2]",  weight=0 ];

        "bar" [ color="red", label="baz [2]",  weight=0 ];

}

Each vertices' Attributes map contains the Attributes of the last created vertex. Am I creating these VertexProperties functions incorrectly, or mis-using them?

[tzq0301]

Attributes map of all VertexProperties share the same map declared in the line of:

    redVertexAttr   = graph.VertexAttributes(map[string]string{"color": "red"})

This was a bug of the library, and I fixed it in PR #179, cc. @dominikbraun