From ec6cfbaaaccbe695d3c091c45e13ea0211baacd8 Mon Sep 17 00:00:00 2001
From: sh0rez <me@shorez.de>
Date: Mon, 10 Aug 2020 17:50:54 +0200
Subject: [PATCH] feat(cli): support negative filters

Output filtering (`-t`) now supports excluding objects, by prepending an
exlamation mark (`!`) before the regular expression
---
 docs/docs/targets.md        | 11 +++++++++
 pkg/process/filter.go       | 46 ++++++++++++++++++++++++++++++++++++-
 pkg/process/process_test.go |  9 ++++++++
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/docs/docs/targets.md b/docs/docs/targets.md
index 6b8edb253..e8fdb270e 100644
--- a/docs/docs/targets.md
+++ b/docs/docs/targets.md
@@ -78,3 +78,14 @@ apiVersion: apps/v1
 kind: Deployment
 # ...
 ```
+
+## Excluding
+
+Sometimes it may be desirably to exclude a single object, instead of including all others.
+
+To do so, prepend the regular expression with an exclamation mark (`!`), like so:
+
+```bash
+# filter out all Deployments
+$ tk show . -t '!deployment/.*'
+```
diff --git a/pkg/process/filter.go b/pkg/process/filter.go
index 8e8d7e79b..6b2b8c5d7 100644
--- a/pkg/process/filter.go
+++ b/pkg/process/filter.go
@@ -9,12 +9,16 @@ import (
 )
 
 // Filter returns all elements of the list that match at least one expression
+// and are not ignored
 func Filter(list manifest.List, exprs Matchers) manifest.List {
 	out := make(manifest.List, 0, len(list))
 	for _, m := range list {
 		if !exprs.MatchString(m.KindName()) {
 			continue
 		}
+		if exprs.IgnoreString(m.KindName()) {
+			continue
+		}
 		out = append(out, m)
 	}
 	return out
@@ -26,7 +30,13 @@ type Matcher interface {
 	MatchString(string) bool
 }
 
+// Ignorer is like matcher, but for explicitely ignoring resources
+type Ignorer interface {
+	IgnoreString(string) bool
+}
+
 // Matchers is a collection of multiple expressions.
+// A matcher may also implement Ignorer to explicitely ignore fields
 type Matchers []Matcher
 
 // MatchString returns whether at least one expression (OR) matches the string
@@ -38,6 +48,18 @@ func (e Matchers) MatchString(s string) bool {
 	return b
 }
 
+func (e Matchers) IgnoreString(s string) bool {
+	b := false
+	for _, exp := range e {
+		i, ok := exp.(Ignorer)
+		if !ok {
+			continue
+		}
+		b = b || i.IgnoreString(s)
+	}
+	return b
+}
+
 // RegExps is a helper to construct Matchers from regular expressions
 func RegExps(rs []*regexp.Regexp) Matchers {
 	xprs := make(Matchers, 0, len(rs))
@@ -50,11 +72,20 @@ func RegExps(rs []*regexp.Regexp) Matchers {
 func StrExps(strs ...string) (Matchers, error) {
 	exps := make(Matchers, 0, len(strs))
 	for _, raw := range strs {
-		s := fmt.Sprintf(`(?i)^%s$`, raw)
+		// trim exlamation mark, not supported by regex
+		s := fmt.Sprintf(`(?i)^%s$`, strings.TrimPrefix(raw, "!"))
+
+		// create regexp matcher
+		var exp Matcher
 		exp, err := regexp.Compile(s)
 		if err != nil {
 			return nil, ErrBadExpr{err}
 		}
+
+		// if negative (!), invert regex behaviour
+		if strings.HasPrefix(raw, "!") {
+			exp = NegMatcher{exp: exp}
+		}
 		exps = append(exps, exp)
 	}
 	return exps, nil
@@ -76,3 +107,16 @@ type ErrBadExpr struct {
 func (e ErrBadExpr) Error() string {
 	return fmt.Sprintf("%s.\nSee https://tanka.dev/output-filtering/#regular-expressions for details on regular expressions.", strings.Title(e.inner.Error()))
 }
+
+// NexMatcher is a matcher that inverts the original behaviour
+type NegMatcher struct {
+	exp Matcher
+}
+
+func (n NegMatcher) MatchString(s string) bool {
+	return true
+}
+
+func (n NegMatcher) IgnoreString(s string) bool {
+	return n.exp.MatchString(s)
+}
diff --git a/pkg/process/process_test.go b/pkg/process/process_test.go
index 5014b3805..cf0461593 100644
--- a/pkg/process/process_test.go
+++ b/pkg/process/process_test.go
@@ -64,6 +64,15 @@ func TestProcess(t *testing.T) {
 				`DePlOyMeNt/GrAfAnA`,
 			),
 		},
+		{
+			name: "targets-negative",
+			deep: testDataDeep().Deep,
+			flat: manifest.List{
+				testDataDeep().Flat[".app.web.frontend.nodejs.express.service"],
+				testDataDeep().Flat[".app.namespace"],
+			},
+			targets: MustStrExps(`!deployment/.*`),
+		},
 		{
 			name: "unwrap-list",
 			deep: loadFixture("list").Deep,