From 8c2de64182b72463cb12f08fba7407ec6838f000 Mon Sep 17 00:00:00 2001
From: Pranav Gaikwad <pgaikwad@redhat.com>
Date: Thu, 28 Sep 2023 14:54:43 -0400
Subject: [PATCH] :sparkles: add short-circuit filter label

Signed-off-by: Pranav Gaikwad <pgaikwad@redhat.com>
---
 docs/labels.md               | 11 ++++++-----
 engine/labels/labels.go      | 16 ++++++++++++++++
 engine/labels/labels_test.go | 18 ++++++++++++++++++
 3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/docs/labels.md b/docs/labels.md
index 023dd357..3755ffa9 100644
--- a/docs/labels.md
+++ b/docs/labels.md
@@ -29,14 +29,15 @@ labels:
 - "konveyor.io/key"
 ```
 
-## Reserved Labels
+## Rule Labels
 
-The analyzer defines some labels that have special meaning. Here is a list of all such labels:
+Analyzer defines some labels that are commonly used to express known pieces of information about a rule:
 
-- `konveyor.io/source`: Identifies source technology a rule or a ruleset applies to.
-- `konveyor.io/target`: Identifies target technology a rule or a ruleset applies to.
+- `konveyor.io/source`: Identifies source technology a rule or a ruleset applies to. The value can be a string with optional version range at the end e.g. "eap", "eap6", "eap7-" etc.
+- `konveyor.io/target`: Identifies target technology a rule or a ruleset applies to. The value can be a string with optional version range at the end e.g. "eap", "eap6", "eap8+" etc.
+- `konveyor.io/selector`: Defines rule disposition with respect to the [rule label selector](#rule-label-selector). A value of `always` indicates that the rule will always be included irrespective of the label selector, while a value of `never` indicates that the rule will always be excluded.
 
-## Label Selector
+### Rule Label Selector
 
 The analyzer CLI takes `--label-selector` as an option. It is a string expression that supports logical AND, OR and NOT operations. It can be used to filter-in/filter-out rules based on labels.
 
diff --git a/engine/labels/labels.go b/engine/labels/labels.go
index 68144a9f..048cecb3 100644
--- a/engine/labels/labels.go
+++ b/engine/labels/labels.go
@@ -10,6 +10,13 @@ import (
 	"github.com/hashicorp/go-version"
 )
 
+const (
+	// a selector label takes precedance over any other label when matching
+	SelectorLabel = "konveyor.io/selector"
+	SelectAlways  = "always"
+	SelectNever   = "never"
+)
+
 const (
 	LabelValueFmt      = "^[a-zA-Z0-9]([-a-zA-Z0-9. ]*[a-zA-Z0-9+-])?$"
 	LabelPrefixFmt     = "^(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])?$"
@@ -33,6 +40,15 @@ func AsString(key, value string) string {
 
 func (l *LabelSelector[T]) Matches(v T) (bool, error) {
 	ruleLabels, _ := ParseLabels(v.GetLabels())
+	if val, ok := ruleLabels[SelectorLabel]; ok &&
+		val != nil && len(val) > 0 {
+		switch val[0] {
+		case SelectAlways:
+			return true, nil
+		case SelectNever:
+			return false, nil
+		}
+	}
 	expr := getBooleanExpression(l.expr, ruleLabels)
 	val, err := l.language.Evaluate(expr, nil)
 	if err != nil {
diff --git a/engine/labels/labels_test.go b/engine/labels/labels_test.go
index 697ee4d7..1b0e7315 100644
--- a/engine/labels/labels_test.go
+++ b/engine/labels/labels_test.go
@@ -360,6 +360,24 @@ func Test_ruleSelector_Matches(t *testing.T) {
 			},
 			want: true,
 		},
+		{
+			name: "rule has a explicit selector=always label",
+			expr: "konveyor.io/source=test",
+			ruleLabels: []string{
+				"konveyor.io/selector=always",
+				"konveyor.io/source=noTest", // this should make the selector not match, but 'always' selector takes precedance
+			},
+			want: true,
+		},
+		{
+			name: "rule has a explicit selector=never label",
+			expr: "konveyor.io/source=test",
+			ruleLabels: []string{
+				"konveyor.io/selector=never",
+				"konveyor.io/source=test", // this should make the selector match, but 'never' selector takes precedance
+			},
+			want: false,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {