Hash not unique

[jmooring]

With the exception of my comment, below is a verbatim copy of https://github.com/terrastruct/d2/blob/master/docs/examples/lib/1-d2lib/d2lib.go:

d2lib.go

package main

import (
	"context"
	"os"
	"path/filepath"

	"oss.terrastruct.com/d2/d2graph"
	"oss.terrastruct.com/d2/d2layouts/d2dagrelayout"
	"oss.terrastruct.com/d2/d2lib"
	"oss.terrastruct.com/d2/d2renderers/d2svg"
	"oss.terrastruct.com/d2/d2themes/d2themescatalog"
	"oss.terrastruct.com/d2/lib/log"
	"oss.terrastruct.com/d2/lib/textmeasure"
	"oss.terrastruct.com/util-go/go2"
)

// Remember to add if err != nil checks in production.
func main() {
	ruler, _ := textmeasure.NewRuler()
	layoutResolver := func(engine string) (d2graph.LayoutGraph, error) {
		return d2dagrelayout.DefaultLayout, nil
	}
	renderOpts := &d2svg.RenderOpts{
		Pad:     go2.Pointer(int64(5)),
		ThemeID: &d2themescatalog.GrapeSoda.ID,
	}
	compileOpts := &d2lib.CompileOptions{
		LayoutResolver: layoutResolver,
		Ruler:          ruler,
	}
	ctx := log.WithDefault(context.Background())
	diagram, _, _ := d2lib.Compile(ctx, "x -> y", compileOpts, renderOpts)

	// jmooring
	//
	// At this point diagram.Config is nil. Then we call d2svg.Render, which
	// calls diagram.HashID(), which calls diagram.Bytes(), which builds a byte
	// slice that includes diagram.Config if isn't nil.
	//
	// The result is that our hash is not unique when the same diagram markup
	// is rendered with different options in the same HTML file. This causes,
	// for example, one diagram to take on another diagram's style.

	out, _ := d2svg.Render(diagram, renderOpts)
	_ = os.WriteFile(filepath.Join("out.svg"), out, 0o600)
}

I suppose we could manually populate diagram.Config at this point, but it seems like that should have happened already.

[alixander]

It shouldn't be nil after d2lib.Compile?: https://github.com/alixander/d2/blob/4c74a05705a16a613bb11fb00a1b0b460d82b074/d2lib/d2.go#L80

I can also inspect the hash of the resulting diagram on playground (using DOM inspector) with and without some config, and see that it's different.

https://play.d2lang.com/?script=KkssKrZSqOZSUEgx0k3Oz0vLTIdwFRRKMlJzU3UzU6wUjA0MuBQUarlquSoUdO0UKrkAAQAA__8%3D&

[jmooring]

I just tested this again with 4c74a05. Please run this example:

package main

import (
	"context"
	"fmt"
	"os"
	"path/filepath"

	"oss.terrastruct.com/d2/d2graph"
	"oss.terrastruct.com/d2/d2layouts/d2dagrelayout"
	"oss.terrastruct.com/d2/d2lib"
	"oss.terrastruct.com/d2/d2renderers/d2svg"
	"oss.terrastruct.com/d2/d2themes/d2themescatalog"
	"oss.terrastruct.com/d2/lib/log"
	"oss.terrastruct.com/d2/lib/textmeasure"
	"oss.terrastruct.com/util-go/go2"
)

// Remember to add if err != nil checks in production.
func main() {
	ruler, _ := textmeasure.NewRuler()
	layoutResolver := func(engine string) (d2graph.LayoutGraph, error) {
		return d2dagrelayout.DefaultLayout, nil
	}
	renderOpts := &d2svg.RenderOpts{
		Pad:     go2.Pointer(int64(5)),
		ThemeID: &d2themescatalog.GrapeSoda.ID,
	}
	compileOpts := &d2lib.CompileOptions{
		LayoutResolver: layoutResolver,
		Ruler:          ruler,
	}

	ctx := log.WithDefault(context.Background())

	diagram, _, _ := d2lib.Compile(ctx, "x -> y", compileOpts, renderOpts)
	fmt.Printf("%+v\n", diagram.Config) // prints <nil>
	out, _ := d2svg.Render(diagram, renderOpts)
	_ = os.WriteFile(filepath.Join("grape_soda.svg"), out, 0o600)

	renderOpts.ThemeID = &d2themescatalog.EarthTones.ID

	diagram, _, _ = d2lib.Compile(ctx, "x -> y", compileOpts, renderOpts)
	fmt.Printf("%+v\n", diagram.Config) // prints <nil>
	out, _ = d2svg.Render(diagram, renderOpts)
	_ = os.WriteFile(filepath.Join("earth_tones.svg"), out, 0o600)
}

Both the resulting SVG files have class .d2-1706184380. That's fine when they're individual files, but not when they're embedded in the same HTML file.

Also note that in the above, fmt.Printf("%+v\n", diagram.Config) prints <nil>.

If I manually set diagram.Config ...

	diagram, _, _ := d2lib.Compile(ctx, "x -> y", compileOpts, renderOpts)
	fmt.Printf("%+v\n", diagram.Config) // prints <nil>
	diagram.Config = &d2target.Config{
		ThemeID: &d2themescatalog.GrapeSoda.ID,
	}
	out, _ := d2svg.Render(diagram, renderOpts)
	_ = os.WriteFile(filepath.Join("grape_soda.svg"), out, 0o600)

	renderOpts.ThemeID = &d2themescatalog.EarthTones.ID

	diagram, _, _ = d2lib.Compile(ctx, "x -> y", compileOpts, renderOpts)
	fmt.Printf("%+v\n", diagram.Config) // prints <nil>
	diagram.Config = &d2target.Config{
		ThemeID: &d2themescatalog.EarthTones.ID,
	}
	out, _ = d2svg.Render(diagram, renderOpts)
	_ = os.WriteFile(filepath.Join("earth_tones.svg"), out, 0o600)

...the classes in the two files are different, as they should be.

[alixander]

Oh I see now.

That config being nil is expected, as it represents config defined in the DSL.

But changing the render opts should've resulted in a different diagram hash. Fixed here: #2314

Thank you for reporting!