imagefilter: add SupportedOutputFormats

[schuellerf]

Convenience function for concise help output

(This is based on #1166 and #1167)

The last commit could be split off, it's not directly related to the implementation of SupportedOutputFormats just extends the tests

[mvo5]

Thank you! I like the idea of having the SupportedOutputFormats() helper. Some suggestions for the implementation inline.

[mvo5]

Quick drive-by:

1. the PR description should follow the convention: module: change (e.g. imagefilter: add SupportedOutputFormats)
2. Rebasing this on top of main and dropping the diff for the "short" output would most likely get this merged much quicker as I feel "short" output will need some more design/discussion but this here is very nice and straightforward.

[mvo5]

You can drop the rename commit, the export_test.go change in the next commit should do what you need and the package <pkg>_test is a common (and deliberate) pattern used here.

[mvo5]

Sorry, I realize this was a rather terse comment. Please just drop the first commit (and I personally would just squash 2+3 [edit: sorry, totally fine to keep]) and then with this diff:

diff --git a/pkg/imagefilter/formatter_test.go b/pkg/imagefilter/formatter_test.go
index 2a4f2ab8c..5bc7e105f 100644
--- a/pkg/imagefilter/formatter_test.go
+++ b/pkg/imagefilter/formatter_test.go
@@ -107,8 +107,8 @@ func TestResultsFormatter(t *testing.T) {
 }
 
 func TestSupportedOutputFormats(t *testing.T) {
-       formatters := SupportedOutputFormats()
-       assert.Len(t, formatters, len(supportedFormatterMap))
+       formatters := imagefilter.SupportedOutputFormats()
+       assert.Len(t, formatters, len(imagefilter.SupportedFormatterMap))
        assert.Contains(t, formatters, "text")
        assert.Contains(t, formatters, "json")
        assert.Contains(t, formatters, "shell")
@@ -116,7 +116,7 @@ func TestSupportedOutputFormats(t *testing.T) {
 }
 
 func TestResultsFormatterError(t *testing.T) {
-       fmter, err := NewResultsFormatter(OutputFormat("unsupported"))
+       fmter, err := imagefilter.NewResultsFormatter(imagefilter.OutputFormat("unsupported"))
        assert.Error(t, err)
        assert.Nil(t, fmter)
 }

things should be fine.

[supakeen]

Two notes:

1. We normally don't use Hungarian notation; e.g. writing the type (Map) in the variable name and personally I don't like it.
2. The behavior here is slightly different because all key lookups now return the same instance of a formatter. Since formatters don't keep state (right now) this might be OK, just wanted to write it down as it's a behavioral change I think?

[supakeen]

Just a question; but maps.Keys returns an iterator. Which part of this function turns that into a slice, is it the return or the sort.Strings?

[mvo5]

This is a bit of a funny one, the new "maps" package in 1.23 does return an iterator but the compat package golang.org/x/exp/maps (that we need to use as we are not on 1.23 yet) just returns a []string slice. We can keep the compat maps until it gets removed and then we either port to iterators or just implement our own .Keys() (its trivial enough).

[supakeen]

I think we should test the sorted-ness here as well as it seems like an important feature of the SupportedOutputFormats function :)

[supakeen]

Some minor questions and bits.

[supakeen]

the PR description should follow the convention: module: change (e.g. imagefilter: add SupportedOutputFormats)

I noticed the commits are now prefixed with the full package path instead of the module name. I don't know how I feel about this :)