RenderFilename() does not work as expected

[GavinB-hpe]

I had some code that used

if err := g.RenderFilename(mycontext, graph, graphviz.PNG, imagepath); err != nil {
    log.Fatal(err)
}

This used to work, generating an image in imagepath as expected.

However re-running this code for the first time for a while (and after an update to the latest version) the code no longer works. There is no error - but no file is created.

If I replace with

fl, err := os.Create(imagepath)
if err != nil {
    log.Fatal(err)
}
defer fl.Close()
if err := g.Render(mycontext, graph, graphviz.PNG, fl); err != nil {
    log.Fatal(err)
}

Then the code works as expected - an image file is created.

My expectation is that RenderFilename should render to a file and leave that file available.

[GavinB-hpe]

go version go1.23.1 linux/amd64

github.com/goccy/go-graphviz v0.2.1

[goccy]

@GavinB-hpe Thank you for your reporting. But RenderFilename function works on my side, so could you provide a full reproducible code example ?

[chrissexton]

I see this as well on MacOS. the RenderFilename function works if the file already exists. It fails silently otherwise. I can touch the file and then see the contents updated.

package main

import (
	"context"
	"github.com/goccy/go-graphviz"
	"log"
)

func main() {
	ctx := context.Background()
	g, err := graphviz.New(ctx)

	// Assume this is a valid graphviz file:
	graph, err := graphviz.ParseFile("MathSci.dot")
	checkErr(err)

	// Works:
	
	//f, err := os.Create("out.png")
	//checkErr(err)
	//defer f.Close()
	//err = g.Render(ctx, graph, graphviz.PNG, f)
	//checkErr(err)

	// Does not work unless the file already exists:
	
	err = g.RenderFilename(ctx, graph, graphviz.PNG, "out.png")
	checkErr(err) // no error will be reported, but no file will exist
}

func checkErr(err error) {
	if err != nil {
		log.Fatal(err)
	}
}

Running the program:

$ go version
go version go1.23.1 darwin/arm64
$ ls -l out.png
ls: out.png: No such file or directory
$ go run main.go 
$ ls -l out.png
ls: out.png: No such file or directory
$ touch out.png
$ ls -l out.png
-rw-r--r--  1 cws  staff  0 Oct 25 10:04 out.png
$ go run main.go 
$ ls -l out.png
-rw-r--r--  1 cws  staff  72624 Oct 25 10:04 out.png

[goccy]

I've fixed this problem with v0.2.8 ! Thank you for your reporting.