[Feature Request]: Expose ability to update snapshot via the API

[wagoodman]

🚀 Feature Proposal

It would be great to be able to update snapshots more programmatically:

	cfg := snaps.WithConfig(snaps.Update(true))
	cfg.MatchSnapshot(t, myTestSubject)

In this way you could have other test conditions / mechanisms that enforce when a snapshot can and should be updated.

Motivation

Today we use the flag package which hooks nicely into the standard test utils:

package spdxjson

import (
	"flag"
	"testing"
)

var updateSnapshot = flag.Bool("update-spdx-json-snapshot", false, "update the *.golden files for spdx-json encoders")

func Test_Something(t *testing.T) {
	...
	if *updateSnapshot {
		// do something...
	}
	...
}

Which can be used like so:

go test ./path/to/package -update-spdx-json-snapshot

See:

• https://github.com/anchore/syft/blob/44e54802380f949a1476c25c1b48c5e3488e89bc/syft/formats/internal/testutils/snapshot.go#L45-L63
• https://github.com/anchore/syft/blob/44e54802380f949a1476c25c1b48c5e3488e89bc/syft/formats/spdxjson/encoder_test.go#L10

This has the nice quality that:

• just by running tests as usual you cannot write out a snapshot
• you can continually update a snapshot without needing to scope the go test command with the correct env var while developing on a narrow feature that isn't stable yet

Example

Combining the motivation and the feature request:

package spdxjson

import (
	"flag"
	"testing"
)

var updateSnapshot = flag.Bool("update-spdx-json-snapshot", false, "update the *.golden files for spdx-json encoders")

func Test_Something(t *testing.T) {
	...
	cfg := snaps.WithConfig(snaps.Update(*updateSnapshot))
	cfg.MatchSnapshot(t, myTestSubject)
	...
}

In which case the flags are the only way to update snapshot files.

[gkampitakis]

hey 👋 thanks a lot for opening this issue. I really like this idea. I created a draft pr to support this. I am thinking that the priority should be CI > snaps.Update > UPDATE_SNAPS . So if running on a CI the snaps won't update and will fail. wdyt ?

[gkampitakis]

Have added this on #78 please tell me if that works for you. Again thanks for opening this issue.