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filters: add basic pattern matching for label keys i.e --filter label=<pattern> #12295

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merged 1 commit into from
Nov 18, 2021
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filters: add basic pattern matching for label keys i.e --filter label=<pattern> #12295

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25 changes: 24 additions & 1 deletion pkg/util/filters.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"encoding/json"
"fmt"
"net/http"
"regexp"
"strings"
"time"

Expand Down Expand Up @@ -94,6 +95,28 @@ func PrepareFilters(r *http.Request) (*map[string][]string, error) {
return &filterMap, nil
}

func wildCardToRegexp(pattern string) string {
var result strings.Builder
for i, literal := range strings.Split(pattern, "*") {
// Replace * with .*
if i > 0 {
result.WriteString(".*")
}
// Quote any regular expression meta characters in the
// literal text.
result.WriteString(regexp.QuoteMeta(literal))
}
return result.String()
}

func matchPattern(pattern string, value string) bool {
if strings.Contains(pattern, "*") {
result, _ := regexp.MatchString(wildCardToRegexp(pattern), value)
return result
}
return false
}

Comment on lines +112 to +119
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does it need to handle only *?

Perhaps you could use filepath.Match?

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Yes I think that would be much better. otherwise you might end up with more regex failures.

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@flouthoc flouthoc Nov 15, 2021 •
edited
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I thought of it first but we want to match label keys where filepath.Match does not works for cases like. Filepath is very restricted to matching valid path. However my idea was to match for patterns.

This fails with filepath.Match and few more cases.

fmt.Println(filepath.Match("/home/c*", "/home/catch/foo"))

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how does Docker do it?

If Docker doesn't do it, could we just use a regex here?

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@flouthoc flouthoc Nov 15, 2021 •
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I don't think docker does it. This was a new feature request. Afaik people mostly use pipe and grep with docker for that.

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I tend to agree that a regex is better - it's definitely more complicated but attempting to treat labels as a path seems very fragile?

Besides, Podman does absolutely no standardization of label formats, so there's neither guarantee nor obligation for labels to include slashes as separators.

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@giuseppe I think regex like regexp.MatchString("hello", key) would match all keys starting with hello so --filter label= becomes hard to use. But I'll try it out.

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My problem with regex is almost no human beings understand it and it has a lot more symbols.
People understand globing , well at least () a lot better then (.)

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Docker has a very small documentation but it only talks about * in examples https://docs.docker.com/engine/reference/commandline/images/#filtering . We could do a regex but lot of tests would need to be readjusted.

https://kliushnikov.medium.com/filtering-docker-images-5eb5aee358df

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Nvm found a fix also confirmed with @giuseppe I'll amend the PR.

// MatchLabelFilters matches labels and returns true if they are valid
func MatchLabelFilters(filterValues []string, labels map[string]string) bool {
outer:
Expand All @@ -106,7 +129,7 @@ outer:
filterValue = ""
}
for labelKey, labelValue := range labels {
if labelKey == filterKey && (filterValue == "" || labelValue == filterValue) {
if ((labelKey == filterKey) || matchPattern(filterKey, labelKey)) && (filterValue == "" || labelValue == filterValue) {
continue outer
}
}
Expand Down
11 changes: 11 additions & 0 deletions test/e2e/volume_ls_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,17 @@ var _ = Describe("Podman volume ls", func() {
Expect(len(session.OutputToStringArray())).To(Equal(2))
})

It("podman ls volume filter with a key pattern", func() {
session := podmanTest.Podman([]string{"volume", "create", "--label", "helloworld=world", "myvol2"})
session.WaitWithDefaultTimeout()
Expect(session).Should(Exit(0))

session = podmanTest.Podman([]string{"volume", "ls", "--filter", "label=hello*"})
session.WaitWithDefaultTimeout()
Expect(session).Should(Exit(0))
Expect(len(session.OutputToStringArray())).To(Equal(2))
})

It("podman ls volume with JSON format", func() {
session := podmanTest.Podman([]string{"volume", "create", "myvol"})
session.WaitWithDefaultTimeout()
Expand Down