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cmd: validate: restructure filtering to use filter functions

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This lets us modernise the filtering logic a little bit, and also allows
us to configure which filters we wish to apply (a future patch will
move some of the filtering done in the top-level go-mtree package to the
cmd/validate package).

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
This commit is contained in:
Aleksa Sarai 2025-09-16 18:36:14 +10:00
parent f0d9d5891f
commit ae454c4a6f
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GPG key ID: 2897FAD2B7E9446F
1 changed files with 49 additions and 42 deletions
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91
cmd/gomtree/cmd/validate.go
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@ -362,11 +362,15 @@ func validateAction(c *cli.Context) error {
if err != nil {
return err
}
if res != nil {
if isTarSpec(specDh) || c.String("tar") != "" {
res = filterMissingKeywords(res)
}
// Apply filters.
var filters []deltaFilterFn
if isTarSpec(specDh) || c.String("tar") != "" {
filters = append(filters, tarKeywordFilter)
}
res = filterDeltas(res, filters...)
if len(res) > 0 {
out := formatFunc(res)
if _, err := os.Stdout.Write([]byte(out)); err != nil {
return err
@ -430,48 +434,51 @@ func isDirEntry(e mtree.Entry) bool {
return false
}
// filterMissingKeywords is a fairly annoying hack to get around the fact that
// tar archive manifest generation has certain unsolveable problems regarding
// certain keywords. For example, the size=... keyword cannot be implemented
// for directories in a tar archive (which causes Missing errors for that
// keyword).
//
// This function just removes all instances of Missing errors for keywords.
// This makes certain assumptions about the type of issues tar archives have.
// Only call this on tar archive manifest comparisons.
func filterMissingKeywords(diffs []mtree.InodeDelta) []mtree.InodeDelta {
newDiffs := []mtree.InodeDelta{}
loop:
for _, diff := range diffs {
if diff.Type() == mtree.Modified {
// We only apply this filtering to directories.
// NOTE: This will probably break if someone drops the size keyword.
if isDirEntry(*diff.Old()) || isDirEntry(*diff.New()) {
// If this applies to '.' then we just filter everything
// (meaning we remove this entry). This is because note all tar
// archives include a '.' entry. Which makes checking this not
// practical.
if diff.Path() == "." {
continue
}
// tarKeywordFilter is a filter for diffs produced where one half is a tar
// archive. tar archive manifests do not have a "size" key associated with
// directories (due to limitations in manifest generation for tar archives) and
// so any deltas due to size missing should be removed.
func tarKeywordFilter(delta *mtree.InodeDelta) bool {
if delta.Path() == "." {
// Not all tar archives include a root entry so we should skip that
// entry if we run into a diff that claims there is an issue with
// it.
return false
}
if delta.Type() != mtree.Modified {
return true
}
// Strip out "size" entries for directory entries.
if isDirEntry(*delta.Old()) || isDirEntry(*delta.New()) {
keys := delta.DiffPtr()
*keys = slices.DeleteFunc(*keys, func(kd mtree.KeyDelta) bool {
return kd.Name() == "size"
})
}
return true
}
// Only filter out the size keyword.
keys := diff.DiffPtr()
*keys = slices.DeleteFunc(*keys, func(kd mtree.KeyDelta) bool {
return kd.Name() == "size"
})
// If there are no key deltas left after filtering, the entry
// should be filtered out entirely.
if len(*keys) == 0 {
continue loop
}
type deltaFilterFn func(*mtree.InodeDelta) bool
// filterDeltas takes the set of deltas generated by mtree and applies the
// given set of filters to it.
func filterDeltas(deltas []mtree.InodeDelta, filters ...deltaFilterFn) []mtree.InodeDelta {
filtered := make([]mtree.InodeDelta, 0, len(deltas))
next:
for _, delta := range deltas {
for _, filter := range filters {
if !filter(&delta) {
continue next
}
}
// If we got here, append to the new set.
newDiffs = append(newDiffs, diff)
// Some filters might modify the entry to remove keyword deltas --
// if there are no deltas left then we should skip the entry entirely.
if delta.Type() == mtree.Modified && len(delta.Diff()) == 0 {
continue next
}
filtered = append(filtered, delta)
}
return newDiffs
return filtered
}
// isTarSpec returns whether the spec provided came from the tar generator.